The first really health conscious decision I made was to cut as much salt as possible out of my diet. I gave up Cheerios and Alpha-Bits, the cereals I had eaten for close to 50 years, because of their high salt content. I learned to treat salt-shakers as if they had skull-and-crossbones on them (poison.)
After cutting back my salt intake I now find many prepared foods, especially soups, too salty.
I learned early on that salt in the diet leads to hypertension (high blood pressure.) Here’s some recent research on the topic:
How Much Salt Is Safe?
An increasing body of evidence indicates that we should reduce the amount of salt in our diet. The American Medical Association (AMA), the American Heart Association (AHA), the American Dietetic Association (ADA), and the National Institutes of Health have begun a campaign to cut the salt intake of Americans by one-half. The AMA is even pushing the Food and Drug Administration to withdraw salt’s designation as “safe,” according to UCLA's Healthy Years.
“The consequences of too much salt are hypertension, or high blood pressure, which increases the risk of a stroke or heart attack,” says Amy Schnabel, MS, RD, Clinical Nutrition Manager at the UCLA Medical Center. Ninety percent of Americans will develop hypertension unless they take steps to prevent it. Two studies reported in the April 19, 2007 issue of the British Medical Journal showed that people who cut back on the amount of salt in their diets by 25-35 percent could reduce their risk of cardiovascular disease by as much as 25 percent and lower their mortality rates by 20 percent.
Where’s the salt?_Identifying products that are high in salt is a good place to start. (For the record, table salt is sodium chloride and is 40 percent sodium by weight.) One problem in finding salt content is that excessive amounts are present in many products generally considered to be healthy. Just one cup of canned soup can contain more than 50 percent of the FDA recommended allowance of 2,400 mg a day, equivalent to one teaspoon (The Institute of Medicine recommends even less—1,500 mg per day). A serving of lasagna at a restaurant can put you over your sodium allowance in one meal.
“The biggest misconception about sodium intake is that many people think that, by removing the salt shaker from the dinner table, they aren't eating salt,” adds Schnabel. “What they may not know is that as much as 80 percent of dietary sodium comes from eating out and from packaged and processed foods. The average American consumes 4,000 to 6,000 milligrams of salt per day. It is used for taste, to preserve foods, and provide texture. About 12 percent of the sodium in our diets comes from adding salt and sodium-containing condiments to what we cook and eat. Even some drugs (antacids, for example) have high amount of sodium.
How Much is Too Much?_We need salt to maintain a balance of body fluids, to transmit nerve signals, and for muscles to function properly. But we don’t need as much as most people are getting. Here are some examples of foods and their sodium content:_2 large scrambled eggs = 342 mg _1 slice luncheon meat = 350 mg__ cup canned green beans = 177 mg_4-inch oatbran bagel = 451 mg_1-ounce pretzel = 486__ cup vanilla ice cream = 53 mg
How Much is Not Enough?_With age and the presence of chronic illnesses, the body may not process sodium the way it once did; for some people, that can result in hyponatremia—low blood sodium. Other contributing factors are pain medications, antidepressants, and diuretics, as well as an underactive thyroid, heart or kidney failure, cirrhosis, dehydration, and Addison’s disease. The symptoms of hyponatremia include nausea, headaches, confusion, lethargy, and loss of consciousness. The only way it can be diagnosed is by a blood test, so you must see a doctor to get an accurate diagnosis. If low blood sodium is found, you may be advised to temporarily reduce fluid intake, but the condition will ultimately be treated by determining and correcting the underlying problem.
How to Cut Back_There is no shortage of advice out there on how to reduce salt intake. The AHA says to start by choosing fresh, frozen, or canned foods that don’t have added salts. Do the same for nuts, seeds, dried beans, peas, and lentils. Limit salty snacks. (If salt is in the top four ingredients listed on the label, it’s too salty.) Avoid adding salt and canned vegetables to homemade dishes. Select fat-free or low-fat milk, low-sodium cheese, and low-fat yogurt. When eating out, ask for dishes prepared without salt. Use spices and herbs instead of salt to enhance taste. At home, put down the saltshaker and step away.
If you are younger, don’t have high blood pressure, and are generally healthy, eat reasonably, enjoy your meals, and don’t worry too much (yet) about salt intake. But if you are older or African-American, or if you have either hypertension or diabetes, take the low-sodium (1,500-2,400 mg) approach to what you eat. Eating salty foods is more habit than nutritional necessity, and habits can be changed—at any age.
What You Can Do_Identify foods that have a high sodium content._Limit daily sodium intake to between 1,500 and 2,400 milligrams._Ask for unsalted dishes when eating out._Season your food at home with herbs and spices rather than salt._Remove salt from recipes when possible._Don’t put the saltshaker on your dining table.
Consuming a little less salt could mean fewer deaths
Study highlights:
• A moderate decrease in daily salt intake could benefit the U.S. population and reduce the rates of heart disease and deaths.
• All segments of the U.S. population would be expected to benefit, with the largest health benefits experienced by African Americans who are more likely to have hypertension and whose blood pressure may be more sensitive to salt.
For every gram of salt that Americans reduce in their diets daily, a quarter of a million fewer new heart disease cases and over 200,000 fewer deaths would occur over a decade, researchers said at the American Heart Association’s 49th Annual Conference on Cardiovascular Disease Epidemiology and Prevention.
These results were derived from a validated computer-simulation of heart disease among U.S. adults.
“A very modest decrease in the amount of salt — hardly detectable in the taste of food — can have dramatic health benefits for the U.S.,” said Kirsten Bibbins-Domingo, Ph.D., M.D., M.A.S., lead author of the study and an assistant professor of Medicine and of Epidemiology at the University of California, San Francisco. “It was a surprise to see the magnitude of the impact on the population, given the very small reductions in salt that we were modeling.”
A 3-gram–a-day reduction in salt intake (about 1200 mg of sodium) would result in 6 percent fewer cases of new heart disease, 8 percent fewer heart attacks, and 3 percent fewer deaths. Even larger health benefits are projected for African Americans, who are more likely to have high blood pressure and whose blood pressure may be more sensitive to salt. Among African Americans, new heart disease cases would be reduced by 10 percent, heart attacks by 13 percent and deaths by 6 percent.
For years, ample evidence has linked salt intake to high blood pressure and heart disease. Yet, salt consumption among Americans has risen by 50 percent and blood pressure has risen by nearly the same amount since the 1970s, according to researchers.
Currently, Americans eat 9-12 grams of salt per day (or 3600-4800 mg of sodium. This amount is far in excess than recommended by most health organizations (5-6 grams/day of salt or 2000-2400 mg sodium). Each gram of salt contains 0.4 grams of sodium.
“It’s clear that we need to lower salt intake, but individuals find it hard to make substantial cuts because most salt comes from processed foods, not from the salt shaker,” Bibbins-Domingo said. “Our study suggests that the food industry and those who regulate it could contribute substantially to the health of the nation by achieving even small reductions in the amount of salt in these processed foods.”
To estimate the benefit of making small reductions in salt intake, the investigators used the Coronary Heart Disease Policy Model, a computer simulation of heart disease in the U.S. adult population. The model can be used to evaluate the impact of policy changes on the health of the nation, and has previously been used to project the future of heart disease in the United States given the current rate of childhood obesity, Bibbins-Domingo said.
The researchers used the model to estimate the impact of an immediate reduction of daily salt intake by 0–6 grams on the incidence of cardiovascular disease and deaths between 2010–2019. In that period, the model suggests that more than 800,000 life-years could be saved for each gram of salt lowered. Larger reductions would have greater benefits, with a 6 gram reduction resulting in 1.4 million fewer heart disease cases, 1.1 million fewer deaths and over 4 million life-years saved.
Because the majority of salt in the diet comes from prepared and packaged foods, the results of the study reveal the need for regulatory changes or voluntary actions by the food industry to make achievable changes in heart health, Bibbins-Domingo said.
The researchers are planning to assess the cost-effectiveness of various interventions already being used to reduce salt consumption in other countries, including industry collaborations, regulations and labeling changes.
Eating less salt could prevent cardiovascular disease
Long-term effects of dietary sodium reduction on cardiovascular disease outcomes: observational follow-up of the trials of hypertension prevention__
People who significantly cut back on the amount of salt in their diet could reduce their chances of developing cardiovascular disease by a quarter.__
Researchers in Boston also found a reduction in salt intake could lower the risk of death from cardiovascular disease by up to a fifth.__
Cardiovascular disease refers to the group of diseases linked to the heart or arteries, for example a stroke or heart disease. While there is already a substantial body of evidence showing that cutting back on salt lowers blood pressure, studies showing subsequent levels of cardiovascular disease in the population have been limited and inconclusive.__
This research provides some of the strongest objective evidence to date that lowering the amount of salt in the diet reduces the long term risk of future cardiovascular disease, say the authors of the report.__
Researchers followed up participants from two trials completed in the nineties which had been conducted to analyse the effect that reducing salt in the diet had on blood pressure.__
All the participants had high-normal blood pressure (pre-hypertension). They were therefore at greater risk of developing cardiovascular disease. 744 people took part in the first Trial of Hypertension Prevention which was completed in 1990, 2382 in the second, which ended in 1995. In both trials participants reduced their sodium intake by approximately 25% - 35% alongside a control group who didn’t cut back on their salt intake.__
Detailed information about cardiovascular and other health problems was sought from participants in the earlier trials. As part of this researchers found that participants who had cut back on salt during the trials tended to stick to a lower salt diet compared to those who had been in the control group. In total the researchers obtained information from 2415 (77.3%) participants, 200 of whom had reported some sort of cardiovascular problem.__
The reduction in the risk of developing cardiovascular problems as a result of the sodium reduction intervention was substantial. The results showed these pre-hypertensive individuals were 25% less likely to develop cardiovascular problems over the course of the 10-15 years post-trial. There was also a 20% lower mortality rate. This risk reduction was evident in each trial.__
To the authors knowledge this study is the first and only study of sufficient size and duration to assess the effects of a low salt diet on cardiovascular problems based on randomised trial data. It provides unique evidence that lowering salt in the diet might prevent cardiovascular disease.
Salt reduction may offer cardioprotective effects beyond blood pressure reduction
New study in American Journal of Clinical Nutrition
A study published in the February 2009 issue of the American Journal of Clinical Nutrition shows that salt reduction may offer cardioprotective effects beyond blood pressure reduction. The study was led by Kacie Dickinson of Flinders University, South Australia.
"Reducing your salt intake provides more benefit than a decrease in blood pressure," said ASN Spokesperson Mary Ann Johnson, PhD. The study by Dickinson et al provides "further evidence of the importance of decreasing sodium intake to improve blood vessel health and reduce the risk of cardiovascular disease, one of the leading causes of disability and death in the U.S. These researchers showed that sodium reduction is beneficial for people who have normal blood pressure and those who are overweight or obese, and the benefits start in just a few weeks." Johnson added, "Regardless of one's body weight or blood pressure, sodium reduction offers many health benefits."
UI study suggests salt might be 'nature's antidepressant'
Most people consume far too much salt, and a University of Iowa researcher has discovered one potential reason we crave it: it might put us in a better mood.
UI psychologist Kim Johnson and colleagues found in their research that when rats are deficient in sodium chloride, common table salt, they shy away from activities they normally enjoy, like drinking a sugary substance or pressing a bar that stimulates a pleasant sensation in their brains.
"Things that normally would be pleasurable for rats didn't elicit the same degree of relish, which leads us to believe that a salt deficit and the craving associated with it can induce one of the key symptoms associated with depression," Johnson said.
The UI researchers can't say it is full-blown depression because several criteria factor into such a diagnosis, but a loss of pleasure in normally pleasing activities is one of the most important features of psychological depression. And, the idea that salt is a natural mood-elevating substance could help explain why we're so tempted to over-ingest it, even though it's known to contribute to high blood pressure, heart disease and other health problems.
Past research has shown that the worldwide average for salt intake per individual is about 10 grams per day, which is greater than the U.S. Food and Drug Administration recommended intake by about 4 grams, and may exceed what the body actually needs by more than 8 grams.
Johnson, who holds appointments in psychology and integrative physiology in the College of Liberal Arts and Sciences and in pharmacology in the Carver College of Medicine, published a review of these findings in the July issue of the journal "Physiology & Behavior" with Michael J. Morris and Elisa S. Na, UI graduate students. In addition to reporting their own findings, the authors reviewed others' research on the reasons behind salt appetite.
High levels of salt are contained in everything from pancakes to pasta these days, but once upon a time, it was hard to come by. Salt consumption and its price skyrocketed around 2000 B.C. when it was discovered as a food preservative. Roman soldiers were paid in salt; the word salary is derived from the Latin for salt. Even when mechanical refrigeration lessened the need for salt in the 19th century, consumption continued in excess because people liked the taste and it had become fairly inexpensive. Today, 77 percent of our salt intake comes from processed and restaurant foods, like frozen dinners and fast food.
Evolution might have played an important part in the human hankering for salt. Humans evolved from creatures that lived in salty ocean water. Once on land, the body continued to need sodium and chloride because minerals play key roles in allowing fluids to pass in and out of cells, and in helping nerve cells transfer information throughout the brain and body. But as man evolved in the hot climate of Africa, perspiration robbed the body of sodium. Salt was scarce because our early ancestors ate a veggie-rich diet and lived far from the ocean.
"Most of our biological systems require sodium to function properly, but as a species that didn't have ready access to it, our kidneys evolved to become salt misers," Johnson said.
Behavior also came to play a key role in making sure we have enough salt on board. Animals like us come equipped with a taste system designed to detect salt and a brain that remembers the location of salt sources -- like salt licks in a pasture. A pleasure mechanism in the brain is activated when salt is consumed.
So the body needs salt and knows how to find it and how to conserve it. But today scientists are finding evidence that it's an abused, addictive substance -- almost like a drug.
One sign of addiction is using a substance even when it's known to be harmful. Many people are told to reduce sodium due to health concerns, but they have trouble doing so because they like the taste and find low-sodium foods bland.
Another strong aspect of addiction is the development of intense cravings when drugs are withheld. Experiments by Johnson and colleagues indicate similar changes in brain activity whether rats are exposed to drugs or salt deficiency.
"This suggests that salt need and cravings may be linked to the same brain pathways as those related to drug addiction and abuse," Johnson said.
Application of Lower Sodium Intake Recommendations to Adults --- United States, 1999--2006
In 2005--2006, an estimated 29% of U.S. adults had hypertension (i.e., high blood pressure), and another 28% had prehypertension (1). Hypertension increases the risk for heart disease and stroke (2), the first and third leading causes of death in the United States (3). Greater consumption of sodium can increase the risk for hypertension (4). The main source of sodium in food is salt (sodium chloride [NaCl]); uniodized salt is 40% sodium by weight. In 2005--2006, the estimated average intake of sodium among persons in the United States aged >2 years was 3,436 mg/day (5). In 2005, the U.S. Department of Health and Human Services and U.S. Department of Agriculture recommended that adults in the United States should consume no more than 2,300 mg/day of sodium (equal to approximately 1 tsp of salt), but those in specific groups (i.e., all persons with hypertension, all middle-aged and older adults, and all blacks) should consume no more than 1,500 mg/day of sodium (6). To estimate the proportion of the adult population for whom the lower sodium recommendation is applicable, CDC analyzed data from the National Health and Nutrition Examination Survey (NHANES) for the period 1999--2006. The results indicated that, in 2005--2006, the lower sodium recommendation was applicable to 69.2% of U.S. adults. Consumers and health-care providers should be aware of the lower sodium recommendation, and health-care providers should inform their patients of the evidence linking greater sodium intake to higher blood pressure.
NHANES is an ongoing series of cross-sectional surveys on health and nutrition designed to be nationally representative of the noninstitutionalized, U.S. civilian population by using a complex, multistage probability design. All NHANES surveys include a household interview followed by a detailed physical examination, including blood pressure tests.* Data from four NHANES survey periods (1999--2000, 2001--2002, 2003--2004, and 2005--2006) were used to estimate the percentages of U.S. adults in the three risk groups for whom lower sodium intake of <1,500 mg/per day was recommended in 2005.† To represent the three risk groups, three nonoverlapping populations were defined for the analysis: all adults aged >20 years with hypertension, all adults aged >40 years without hypertension, and blacks aged 20--39 years without hypertension (6). Participants first were categorized as having hypertension or not having hypertension, using an average of two or more blood pressure measurements (87% of the sample had three or more measurements). Hypertension was defined as having systolic blood pressure of >140 mm Hg, or diastolic blood pressure of >90 mm Hg, or taking antihypertension medication; prehypertension was defined as systolic blood pressure of 120--139 mm Hg or diastolic blood pressure of 80--89 mm Hg, and not taking antihypertension medication. Overall for the four survey periods, 22% of participants with hypertension had normal blood pressure readings but were categorized with hypertension because they self-reported taking antihypertension medication. Percentage estimates and 95% confidence intervals (CIs) were calculated using statistical software to account for nonresponse and complex sampling design. The significance of linear trend across survey periods was determined by using orthogonal polynomial coefficients calculated recursively.
Overall in 2005--2006, 69.2% of U.S. adults aged >20 years (approximately 145.5 million persons) met the criteria for the risk groups recommended for lower sodium consumption of <1,500 mg/day. Among adults aged >20 years, 30.6% were found to have hypertension; 34.4% did not have hypertension but were aged >40 years, and 4.2% did not have hypertension but were black and aged 20--39 years (Table). The overall percentage of persons in these risk groups increased significantly over the four NHANES study periods: 64.4% in 1999--2000, 67.4% in 2001--2002, 69.0% in 2003--2004, and 69.2% in 2005--2006 (p for linear trend = 0.05) (Table).
Reported by: C Ayala, PhD, EV Kuklina, MD, PhD, J Peralez, MPH, NL Keenan, PhD, DR Labarthe, MD, PhD, Div for Heart Disease and Stroke Prevention, National Center for Chronic Disease Prevention and Health Promotion, CDC.
Editorial Note:
Although the federal dietary guidelines were published 4 years ago, the percentage of U.S. residents to whom the lower sodium recommendation is applicable has never been reported. The findings in this report indicate that, using 2005--2006 NHANES data, the maximum daily sodium consumption of 1,500 mg recommended in 2005 applied to nearly 70% of U.S. residents aged >20 years. If the recommendation had been in effect during 1999--2006, the percentage of persons for whom it applied would have increased from 64.4% in 1999--2000 to 69.2% in 2005--2006. Previous NHANES results have indicated that the average daily sodium intake among persons in the United States aged >2 years increased from 3,329 mg in 2001--2002 to 3,436 mg in 2005--2006 (5), exceeding in each period even the higher sodium intake limit of 2,300 mg/day recommended in 2005.
Sodium reduction is recommended for persons with hypertension and as a first line of intervention for persons with prehypertension (2). Public health actions to reduce sodium intake likely will include 1) reducing the sodium content of processed foods; 2) encouraging consumption of more low-sodium foods, such as fruits and vegetables; and 3) providing more relevant information about sodium in food labeling. A randomized trial showed that the perceived pleasantness of highly salted food was based on dietary habit and that this perception could be changed by gradual reduction of dietary intake of sodium (7). The current daily percentage value for sodium in the nutrition facts panel of packaged foods is based on a previous federal guideline of 2,400 mg/day and is likely to mislead the majority of consumers, for whom the 1,500 mg/day limit is applicable. In addition, health-care professionals can counsel all patients regarding dietary salt intake and recommend that they adopt an eating plan such as the Dietary Approaches to Stop Hypertension Diet, which is reduced in sodium and rich in potassium and calcium (8) and has been shown to decrease blood pressure among persons with and without hypertension.
The findings in this report are subject to at least one limitation. NHANES data are restricted to the noninstitutionalized population, excluding persons who reside in long-term care facilities or correctional facilities. Inclusion of these populations likely would increase the percentage of the population for whom the recommended 1,500 mg/day sodium limit is applicable.
The World Health Organization has set a global target for maximum intake of salt for adults at 5 g/day (i.e., 2,000 mg/day of sodium) or lower if specified by national targets, such as the recommendation in the United States (9). Eleven countries in the European Union have agreed to reduce salt intake by 16% over the next 4 years (10). In the United States, Healthy People 2010 calls for increasing to 95% the proportion of adults with high blood pressure who are taking action (e.g., reducing sodium intake) to help control their blood pressure (objective 12-11). Recent examples of public health strategies to reduce sodium consumption include a New York City campaign to reduce sodium content in restaurant and processed foods.§
References
Ostchega Y, Yoon SS, Hughes J, Louis T. Hypertension awareness, treatment, and control---continued disparities in adults: United States, 2005--2006. NCHS data brief no. 3. Hyattsville, MD: National Center for Health Statistics; 2008. Available at http://www.cdc.gov/nchs/data/databriefs/db03.pdf
Chobanian AV, Bakris GL, Black HR, et al; National Heart, Lung, and Blood Institute Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure; National High Blood Pressure Education Program Coordinating Committee. The seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: the JNC 7 report. JAMA 2003;289:2560--71.
Kung HC, Hoyert DL, Xu JQ, Murphy SL. Deaths: final data for 2005. Natl Vital Stat Rep 2008;56(10).
Institute of Medicine. Dietary reference intakes for water, potassium, sodium chloride, and sulfate. 1st ed. Washington, DC: The National Academies Press; 2004. Available at http://books.nap.edu/openbook.php?record_id=10925&page=r1.
US Department of Agriculture, Agricultural Research Service. What we eat in America. Available at http://www.ars.usda.gov/services/docs.htm?docid=15044.
US Department of Health and Human Services, US Department of Agriculture. Dietary guidelines for Americans 2005. 6th ed. Washington, DC: US Department of Health and Human Services, US Department of Agriculture; 2005. Available at http://www.health.gov/dietaryguidelines/dga2005/document/pdf/dga2005.pdf.
Blais CA, Pangborn RM, Borhani NO, Ferrell MF, Prineas RJ, Laing B. Effect of dietary sodium restriction on taste responses to sodium chloride: a longitudinal study. Am J Clin Nutr 1986;44:232--43.
Appel LJ, Brands MW, Daniels SR, Karanja N, Elmer PJ, Sacks FM; American Heart Association. Dietary approaches to prevent and treat hypertension: a scientific statement from the American Heart Association. Hypertension 2006;47:296--308.
World Health Organization. Reducing salt intake in populations: report of a WHO forum and technical meeting, 5--7 October 2006, Paris, France. Geneva, Switzerland: World Health Organization; 2007. Available at http://www.who.int/dietphysicalactivity/reducingsaltintake_EN.pdf.
He FJ, MacGregor GA. A comprehensive review on salt and health and current experience of worldwide salt reduction programmes. J Hum Hypertens 2008. Available at http://www.nature.com/jhh/journal/vaop/ncurrent/abs/jhh2008144a.html.
* Additional information available at http://www.cdc.gov/nchs/data/nhanes/databriefs/calories.pdf.
† The recommendation was based on dietary reference intakes published by the Institute of Medicine (4).
§ Information available at http://www.nyc.gov/html/doh/html/cardio/cardio-salt-initiative.shtml.
Potassium Offsets Sodium
Most people know that too much sodium from foods can increase blood pressure.
A new study suggests that people trying to lower their blood pressure should also boost their intake of potassium, which has the opposite effect to sodium.
Researchers found that the ratio of sodium-to-potassium in subjects' urine was a much stronger predictor of cardiovascular disease than sodium or potassium alone.
"There isn't as much focus on potassium, but potassium seems to be effective in lowering blood pressure and the combination of a higher intake of potassium and lower consumption of sodium seems to be more effective than either on its own in reducing the risk of cardiovascular disease," said Dr. Paul Whelton, senior author of the study in the January 2009 issue of the Archives of Internal Medicine. Whelton is an epidemiologist and president and CEO of Loyola University Health System.
Researchers determined average sodium and potassium intake during two phases of a study known as the Trials of Hypertension Prevention. They collected 24-hour urine samples intermittently during an 18-month period in one trial and during a 36-month period in a second trial. The 2,974 study participants initially aged 30-to-54 and with blood pressure readings just under levels considered high, were followed for 10-15 years to see if they would develop cardiovascular disease. Whelton was national chair of the Trials of Hypertension Prevention.
Those with the highest sodium levels in their urine were 20 percent more likely to suffer strokes, heart attacks or other forms of cardiovascular disease compared with their counterparts with the lowest sodium levels. However this link was not strong enough to be considered statistically significant.
By contrast, participants with the highest sodium-to-potassium ratio in urine were 50 percent more likely to experience cardiovascular disease than those with the lowest sodium-to-potassium ratios. This link was statistically significant.
Most previous studies of the relationship between sodium or potassium and cardiovascular disease have had to rely on people’s recall or record of what foods they eat to estimate their level of sodium consumption. This is a less precise measure of sodium intake than urine samples. In addition, many have been cross-sectional rather than follow-up studies.
The new study "is a quantum leap in the quality of the data compared to what we have had before," Whelton said.
Whelton was a member of a recent Institute of Medicine panel that set dietary recommendations for salt and potassium. The panel said healthy 19-to-50 year-old adults should consume no more than 2,300 milligrams of sodium per day -- equivalent to one teaspoon of table salt. More than 95 percent of American men and 75 percent of American women in this age range exceed this amount.
To lower blood pressure and blunt the effects of salt, adults should consume 4.7 grams of potassium per day unless they have a clinical condition or medication need that is a contraindication to increased potassium intake. Most American adults aged 31-to-50 consume only about half as much as recommended in the Institute of Medicine report. Changes in diet and physical activity should be under the supervision of a health care professional.
Good potassium sources include fruits, vegetables, dairy foods and fish. Foods that are especially rich in potassium include potatoes and sweet potatoes, fat-free milk and yogurt, tuna, lima beans, bananas, tomato sauce and orange juice. Potassium also is available in supplements.
After cutting back my salt intake I now find many prepared foods, especially soups, too salty.
I learned early on that salt in the diet leads to hypertension (high blood pressure.) Here’s some recent research on the topic:
How Much Salt Is Safe?
An increasing body of evidence indicates that we should reduce the amount of salt in our diet. The American Medical Association (AMA), the American Heart Association (AHA), the American Dietetic Association (ADA), and the National Institutes of Health have begun a campaign to cut the salt intake of Americans by one-half. The AMA is even pushing the Food and Drug Administration to withdraw salt’s designation as “safe,” according to UCLA's Healthy Years.
“The consequences of too much salt are hypertension, or high blood pressure, which increases the risk of a stroke or heart attack,” says Amy Schnabel, MS, RD, Clinical Nutrition Manager at the UCLA Medical Center. Ninety percent of Americans will develop hypertension unless they take steps to prevent it. Two studies reported in the April 19, 2007 issue of the British Medical Journal showed that people who cut back on the amount of salt in their diets by 25-35 percent could reduce their risk of cardiovascular disease by as much as 25 percent and lower their mortality rates by 20 percent.
Where’s the salt?_Identifying products that are high in salt is a good place to start. (For the record, table salt is sodium chloride and is 40 percent sodium by weight.) One problem in finding salt content is that excessive amounts are present in many products generally considered to be healthy. Just one cup of canned soup can contain more than 50 percent of the FDA recommended allowance of 2,400 mg a day, equivalent to one teaspoon (The Institute of Medicine recommends even less—1,500 mg per day). A serving of lasagna at a restaurant can put you over your sodium allowance in one meal.
“The biggest misconception about sodium intake is that many people think that, by removing the salt shaker from the dinner table, they aren't eating salt,” adds Schnabel. “What they may not know is that as much as 80 percent of dietary sodium comes from eating out and from packaged and processed foods. The average American consumes 4,000 to 6,000 milligrams of salt per day. It is used for taste, to preserve foods, and provide texture. About 12 percent of the sodium in our diets comes from adding salt and sodium-containing condiments to what we cook and eat. Even some drugs (antacids, for example) have high amount of sodium.
How Much is Too Much?_We need salt to maintain a balance of body fluids, to transmit nerve signals, and for muscles to function properly. But we don’t need as much as most people are getting. Here are some examples of foods and their sodium content:_2 large scrambled eggs = 342 mg _1 slice luncheon meat = 350 mg__ cup canned green beans = 177 mg_4-inch oatbran bagel = 451 mg_1-ounce pretzel = 486__ cup vanilla ice cream = 53 mg
How Much is Not Enough?_With age and the presence of chronic illnesses, the body may not process sodium the way it once did; for some people, that can result in hyponatremia—low blood sodium. Other contributing factors are pain medications, antidepressants, and diuretics, as well as an underactive thyroid, heart or kidney failure, cirrhosis, dehydration, and Addison’s disease. The symptoms of hyponatremia include nausea, headaches, confusion, lethargy, and loss of consciousness. The only way it can be diagnosed is by a blood test, so you must see a doctor to get an accurate diagnosis. If low blood sodium is found, you may be advised to temporarily reduce fluid intake, but the condition will ultimately be treated by determining and correcting the underlying problem.
How to Cut Back_There is no shortage of advice out there on how to reduce salt intake. The AHA says to start by choosing fresh, frozen, or canned foods that don’t have added salts. Do the same for nuts, seeds, dried beans, peas, and lentils. Limit salty snacks. (If salt is in the top four ingredients listed on the label, it’s too salty.) Avoid adding salt and canned vegetables to homemade dishes. Select fat-free or low-fat milk, low-sodium cheese, and low-fat yogurt. When eating out, ask for dishes prepared without salt. Use spices and herbs instead of salt to enhance taste. At home, put down the saltshaker and step away.
If you are younger, don’t have high blood pressure, and are generally healthy, eat reasonably, enjoy your meals, and don’t worry too much (yet) about salt intake. But if you are older or African-American, or if you have either hypertension or diabetes, take the low-sodium (1,500-2,400 mg) approach to what you eat. Eating salty foods is more habit than nutritional necessity, and habits can be changed—at any age.
What You Can Do_Identify foods that have a high sodium content._Limit daily sodium intake to between 1,500 and 2,400 milligrams._Ask for unsalted dishes when eating out._Season your food at home with herbs and spices rather than salt._Remove salt from recipes when possible._Don’t put the saltshaker on your dining table.
Consuming a little less salt could mean fewer deaths
Study highlights:
• A moderate decrease in daily salt intake could benefit the U.S. population and reduce the rates of heart disease and deaths.
• All segments of the U.S. population would be expected to benefit, with the largest health benefits experienced by African Americans who are more likely to have hypertension and whose blood pressure may be more sensitive to salt.
For every gram of salt that Americans reduce in their diets daily, a quarter of a million fewer new heart disease cases and over 200,000 fewer deaths would occur over a decade, researchers said at the American Heart Association’s 49th Annual Conference on Cardiovascular Disease Epidemiology and Prevention.
These results were derived from a validated computer-simulation of heart disease among U.S. adults.
“A very modest decrease in the amount of salt — hardly detectable in the taste of food — can have dramatic health benefits for the U.S.,” said Kirsten Bibbins-Domingo, Ph.D., M.D., M.A.S., lead author of the study and an assistant professor of Medicine and of Epidemiology at the University of California, San Francisco. “It was a surprise to see the magnitude of the impact on the population, given the very small reductions in salt that we were modeling.”
A 3-gram–a-day reduction in salt intake (about 1200 mg of sodium) would result in 6 percent fewer cases of new heart disease, 8 percent fewer heart attacks, and 3 percent fewer deaths. Even larger health benefits are projected for African Americans, who are more likely to have high blood pressure and whose blood pressure may be more sensitive to salt. Among African Americans, new heart disease cases would be reduced by 10 percent, heart attacks by 13 percent and deaths by 6 percent.
For years, ample evidence has linked salt intake to high blood pressure and heart disease. Yet, salt consumption among Americans has risen by 50 percent and blood pressure has risen by nearly the same amount since the 1970s, according to researchers.
Currently, Americans eat 9-12 grams of salt per day (or 3600-4800 mg of sodium. This amount is far in excess than recommended by most health organizations (5-6 grams/day of salt or 2000-2400 mg sodium). Each gram of salt contains 0.4 grams of sodium.
“It’s clear that we need to lower salt intake, but individuals find it hard to make substantial cuts because most salt comes from processed foods, not from the salt shaker,” Bibbins-Domingo said. “Our study suggests that the food industry and those who regulate it could contribute substantially to the health of the nation by achieving even small reductions in the amount of salt in these processed foods.”
To estimate the benefit of making small reductions in salt intake, the investigators used the Coronary Heart Disease Policy Model, a computer simulation of heart disease in the U.S. adult population. The model can be used to evaluate the impact of policy changes on the health of the nation, and has previously been used to project the future of heart disease in the United States given the current rate of childhood obesity, Bibbins-Domingo said.
The researchers used the model to estimate the impact of an immediate reduction of daily salt intake by 0–6 grams on the incidence of cardiovascular disease and deaths between 2010–2019. In that period, the model suggests that more than 800,000 life-years could be saved for each gram of salt lowered. Larger reductions would have greater benefits, with a 6 gram reduction resulting in 1.4 million fewer heart disease cases, 1.1 million fewer deaths and over 4 million life-years saved.
Because the majority of salt in the diet comes from prepared and packaged foods, the results of the study reveal the need for regulatory changes or voluntary actions by the food industry to make achievable changes in heart health, Bibbins-Domingo said.
The researchers are planning to assess the cost-effectiveness of various interventions already being used to reduce salt consumption in other countries, including industry collaborations, regulations and labeling changes.
Eating less salt could prevent cardiovascular disease
Long-term effects of dietary sodium reduction on cardiovascular disease outcomes: observational follow-up of the trials of hypertension prevention__
People who significantly cut back on the amount of salt in their diet could reduce their chances of developing cardiovascular disease by a quarter.__
Researchers in Boston also found a reduction in salt intake could lower the risk of death from cardiovascular disease by up to a fifth.__
Cardiovascular disease refers to the group of diseases linked to the heart or arteries, for example a stroke or heart disease. While there is already a substantial body of evidence showing that cutting back on salt lowers blood pressure, studies showing subsequent levels of cardiovascular disease in the population have been limited and inconclusive.__
This research provides some of the strongest objective evidence to date that lowering the amount of salt in the diet reduces the long term risk of future cardiovascular disease, say the authors of the report.__
Researchers followed up participants from two trials completed in the nineties which had been conducted to analyse the effect that reducing salt in the diet had on blood pressure.__
All the participants had high-normal blood pressure (pre-hypertension). They were therefore at greater risk of developing cardiovascular disease. 744 people took part in the first Trial of Hypertension Prevention which was completed in 1990, 2382 in the second, which ended in 1995. In both trials participants reduced their sodium intake by approximately 25% - 35% alongside a control group who didn’t cut back on their salt intake.__
Detailed information about cardiovascular and other health problems was sought from participants in the earlier trials. As part of this researchers found that participants who had cut back on salt during the trials tended to stick to a lower salt diet compared to those who had been in the control group. In total the researchers obtained information from 2415 (77.3%) participants, 200 of whom had reported some sort of cardiovascular problem.__
The reduction in the risk of developing cardiovascular problems as a result of the sodium reduction intervention was substantial. The results showed these pre-hypertensive individuals were 25% less likely to develop cardiovascular problems over the course of the 10-15 years post-trial. There was also a 20% lower mortality rate. This risk reduction was evident in each trial.__
To the authors knowledge this study is the first and only study of sufficient size and duration to assess the effects of a low salt diet on cardiovascular problems based on randomised trial data. It provides unique evidence that lowering salt in the diet might prevent cardiovascular disease.
Salt reduction may offer cardioprotective effects beyond blood pressure reduction
New study in American Journal of Clinical Nutrition
A study published in the February 2009 issue of the American Journal of Clinical Nutrition shows that salt reduction may offer cardioprotective effects beyond blood pressure reduction. The study was led by Kacie Dickinson of Flinders University, South Australia.
"Reducing your salt intake provides more benefit than a decrease in blood pressure," said ASN Spokesperson Mary Ann Johnson, PhD. The study by Dickinson et al provides "further evidence of the importance of decreasing sodium intake to improve blood vessel health and reduce the risk of cardiovascular disease, one of the leading causes of disability and death in the U.S. These researchers showed that sodium reduction is beneficial for people who have normal blood pressure and those who are overweight or obese, and the benefits start in just a few weeks." Johnson added, "Regardless of one's body weight or blood pressure, sodium reduction offers many health benefits."
UI study suggests salt might be 'nature's antidepressant'
Most people consume far too much salt, and a University of Iowa researcher has discovered one potential reason we crave it: it might put us in a better mood.
UI psychologist Kim Johnson and colleagues found in their research that when rats are deficient in sodium chloride, common table salt, they shy away from activities they normally enjoy, like drinking a sugary substance or pressing a bar that stimulates a pleasant sensation in their brains.
"Things that normally would be pleasurable for rats didn't elicit the same degree of relish, which leads us to believe that a salt deficit and the craving associated with it can induce one of the key symptoms associated with depression," Johnson said.
The UI researchers can't say it is full-blown depression because several criteria factor into such a diagnosis, but a loss of pleasure in normally pleasing activities is one of the most important features of psychological depression. And, the idea that salt is a natural mood-elevating substance could help explain why we're so tempted to over-ingest it, even though it's known to contribute to high blood pressure, heart disease and other health problems.
Past research has shown that the worldwide average for salt intake per individual is about 10 grams per day, which is greater than the U.S. Food and Drug Administration recommended intake by about 4 grams, and may exceed what the body actually needs by more than 8 grams.
Johnson, who holds appointments in psychology and integrative physiology in the College of Liberal Arts and Sciences and in pharmacology in the Carver College of Medicine, published a review of these findings in the July issue of the journal "Physiology & Behavior" with Michael J. Morris and Elisa S. Na, UI graduate students. In addition to reporting their own findings, the authors reviewed others' research on the reasons behind salt appetite.
High levels of salt are contained in everything from pancakes to pasta these days, but once upon a time, it was hard to come by. Salt consumption and its price skyrocketed around 2000 B.C. when it was discovered as a food preservative. Roman soldiers were paid in salt; the word salary is derived from the Latin for salt. Even when mechanical refrigeration lessened the need for salt in the 19th century, consumption continued in excess because people liked the taste and it had become fairly inexpensive. Today, 77 percent of our salt intake comes from processed and restaurant foods, like frozen dinners and fast food.
Evolution might have played an important part in the human hankering for salt. Humans evolved from creatures that lived in salty ocean water. Once on land, the body continued to need sodium and chloride because minerals play key roles in allowing fluids to pass in and out of cells, and in helping nerve cells transfer information throughout the brain and body. But as man evolved in the hot climate of Africa, perspiration robbed the body of sodium. Salt was scarce because our early ancestors ate a veggie-rich diet and lived far from the ocean.
"Most of our biological systems require sodium to function properly, but as a species that didn't have ready access to it, our kidneys evolved to become salt misers," Johnson said.
Behavior also came to play a key role in making sure we have enough salt on board. Animals like us come equipped with a taste system designed to detect salt and a brain that remembers the location of salt sources -- like salt licks in a pasture. A pleasure mechanism in the brain is activated when salt is consumed.
So the body needs salt and knows how to find it and how to conserve it. But today scientists are finding evidence that it's an abused, addictive substance -- almost like a drug.
One sign of addiction is using a substance even when it's known to be harmful. Many people are told to reduce sodium due to health concerns, but they have trouble doing so because they like the taste and find low-sodium foods bland.
Another strong aspect of addiction is the development of intense cravings when drugs are withheld. Experiments by Johnson and colleagues indicate similar changes in brain activity whether rats are exposed to drugs or salt deficiency.
"This suggests that salt need and cravings may be linked to the same brain pathways as those related to drug addiction and abuse," Johnson said.
Application of Lower Sodium Intake Recommendations to Adults --- United States, 1999--2006
In 2005--2006, an estimated 29% of U.S. adults had hypertension (i.e., high blood pressure), and another 28% had prehypertension (1). Hypertension increases the risk for heart disease and stroke (2), the first and third leading causes of death in the United States (3). Greater consumption of sodium can increase the risk for hypertension (4). The main source of sodium in food is salt (sodium chloride [NaCl]); uniodized salt is 40% sodium by weight. In 2005--2006, the estimated average intake of sodium among persons in the United States aged >2 years was 3,436 mg/day (5). In 2005, the U.S. Department of Health and Human Services and U.S. Department of Agriculture recommended that adults in the United States should consume no more than 2,300 mg/day of sodium (equal to approximately 1 tsp of salt), but those in specific groups (i.e., all persons with hypertension, all middle-aged and older adults, and all blacks) should consume no more than 1,500 mg/day of sodium (6). To estimate the proportion of the adult population for whom the lower sodium recommendation is applicable, CDC analyzed data from the National Health and Nutrition Examination Survey (NHANES) for the period 1999--2006. The results indicated that, in 2005--2006, the lower sodium recommendation was applicable to 69.2% of U.S. adults. Consumers and health-care providers should be aware of the lower sodium recommendation, and health-care providers should inform their patients of the evidence linking greater sodium intake to higher blood pressure.
NHANES is an ongoing series of cross-sectional surveys on health and nutrition designed to be nationally representative of the noninstitutionalized, U.S. civilian population by using a complex, multistage probability design. All NHANES surveys include a household interview followed by a detailed physical examination, including blood pressure tests.* Data from four NHANES survey periods (1999--2000, 2001--2002, 2003--2004, and 2005--2006) were used to estimate the percentages of U.S. adults in the three risk groups for whom lower sodium intake of <1,500 mg/per day was recommended in 2005.† To represent the three risk groups, three nonoverlapping populations were defined for the analysis: all adults aged >20 years with hypertension, all adults aged >40 years without hypertension, and blacks aged 20--39 years without hypertension (6). Participants first were categorized as having hypertension or not having hypertension, using an average of two or more blood pressure measurements (87% of the sample had three or more measurements). Hypertension was defined as having systolic blood pressure of >140 mm Hg, or diastolic blood pressure of >90 mm Hg, or taking antihypertension medication; prehypertension was defined as systolic blood pressure of 120--139 mm Hg or diastolic blood pressure of 80--89 mm Hg, and not taking antihypertension medication. Overall for the four survey periods, 22% of participants with hypertension had normal blood pressure readings but were categorized with hypertension because they self-reported taking antihypertension medication. Percentage estimates and 95% confidence intervals (CIs) were calculated using statistical software to account for nonresponse and complex sampling design. The significance of linear trend across survey periods was determined by using orthogonal polynomial coefficients calculated recursively.
Overall in 2005--2006, 69.2% of U.S. adults aged >20 years (approximately 145.5 million persons) met the criteria for the risk groups recommended for lower sodium consumption of <1,500 mg/day. Among adults aged >20 years, 30.6% were found to have hypertension; 34.4% did not have hypertension but were aged >40 years, and 4.2% did not have hypertension but were black and aged 20--39 years (Table). The overall percentage of persons in these risk groups increased significantly over the four NHANES study periods: 64.4% in 1999--2000, 67.4% in 2001--2002, 69.0% in 2003--2004, and 69.2% in 2005--2006 (p for linear trend = 0.05) (Table).
Reported by: C Ayala, PhD, EV Kuklina, MD, PhD, J Peralez, MPH, NL Keenan, PhD, DR Labarthe, MD, PhD, Div for Heart Disease and Stroke Prevention, National Center for Chronic Disease Prevention and Health Promotion, CDC.
Editorial Note:
Although the federal dietary guidelines were published 4 years ago, the percentage of U.S. residents to whom the lower sodium recommendation is applicable has never been reported. The findings in this report indicate that, using 2005--2006 NHANES data, the maximum daily sodium consumption of 1,500 mg recommended in 2005 applied to nearly 70% of U.S. residents aged >20 years. If the recommendation had been in effect during 1999--2006, the percentage of persons for whom it applied would have increased from 64.4% in 1999--2000 to 69.2% in 2005--2006. Previous NHANES results have indicated that the average daily sodium intake among persons in the United States aged >2 years increased from 3,329 mg in 2001--2002 to 3,436 mg in 2005--2006 (5), exceeding in each period even the higher sodium intake limit of 2,300 mg/day recommended in 2005.
Sodium reduction is recommended for persons with hypertension and as a first line of intervention for persons with prehypertension (2). Public health actions to reduce sodium intake likely will include 1) reducing the sodium content of processed foods; 2) encouraging consumption of more low-sodium foods, such as fruits and vegetables; and 3) providing more relevant information about sodium in food labeling. A randomized trial showed that the perceived pleasantness of highly salted food was based on dietary habit and that this perception could be changed by gradual reduction of dietary intake of sodium (7). The current daily percentage value for sodium in the nutrition facts panel of packaged foods is based on a previous federal guideline of 2,400 mg/day and is likely to mislead the majority of consumers, for whom the 1,500 mg/day limit is applicable. In addition, health-care professionals can counsel all patients regarding dietary salt intake and recommend that they adopt an eating plan such as the Dietary Approaches to Stop Hypertension Diet, which is reduced in sodium and rich in potassium and calcium (8) and has been shown to decrease blood pressure among persons with and without hypertension.
The findings in this report are subject to at least one limitation. NHANES data are restricted to the noninstitutionalized population, excluding persons who reside in long-term care facilities or correctional facilities. Inclusion of these populations likely would increase the percentage of the population for whom the recommended 1,500 mg/day sodium limit is applicable.
The World Health Organization has set a global target for maximum intake of salt for adults at 5 g/day (i.e., 2,000 mg/day of sodium) or lower if specified by national targets, such as the recommendation in the United States (9). Eleven countries in the European Union have agreed to reduce salt intake by 16% over the next 4 years (10). In the United States, Healthy People 2010 calls for increasing to 95% the proportion of adults with high blood pressure who are taking action (e.g., reducing sodium intake) to help control their blood pressure (objective 12-11). Recent examples of public health strategies to reduce sodium consumption include a New York City campaign to reduce sodium content in restaurant and processed foods.§
References
Ostchega Y, Yoon SS, Hughes J, Louis T. Hypertension awareness, treatment, and control---continued disparities in adults: United States, 2005--2006. NCHS data brief no. 3. Hyattsville, MD: National Center for Health Statistics; 2008. Available at http://www.cdc.gov/nchs/data/databriefs/db03.pdf
Chobanian AV, Bakris GL, Black HR, et al; National Heart, Lung, and Blood Institute Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure; National High Blood Pressure Education Program Coordinating Committee. The seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: the JNC 7 report. JAMA 2003;289:2560--71.
Kung HC, Hoyert DL, Xu JQ, Murphy SL. Deaths: final data for 2005. Natl Vital Stat Rep 2008;56(10).
Institute of Medicine. Dietary reference intakes for water, potassium, sodium chloride, and sulfate. 1st ed. Washington, DC: The National Academies Press; 2004. Available at http://books.nap.edu/openbook.php?record_id=10925&page=r1.
US Department of Agriculture, Agricultural Research Service. What we eat in America. Available at http://www.ars.usda.gov/services/docs.htm?docid=15044.
US Department of Health and Human Services, US Department of Agriculture. Dietary guidelines for Americans 2005. 6th ed. Washington, DC: US Department of Health and Human Services, US Department of Agriculture; 2005. Available at http://www.health.gov/dietaryguidelines/dga2005/document/pdf/dga2005.pdf.
Blais CA, Pangborn RM, Borhani NO, Ferrell MF, Prineas RJ, Laing B. Effect of dietary sodium restriction on taste responses to sodium chloride: a longitudinal study. Am J Clin Nutr 1986;44:232--43.
Appel LJ, Brands MW, Daniels SR, Karanja N, Elmer PJ, Sacks FM; American Heart Association. Dietary approaches to prevent and treat hypertension: a scientific statement from the American Heart Association. Hypertension 2006;47:296--308.
World Health Organization. Reducing salt intake in populations: report of a WHO forum and technical meeting, 5--7 October 2006, Paris, France. Geneva, Switzerland: World Health Organization; 2007. Available at http://www.who.int/dietphysicalactivity/reducingsaltintake_EN.pdf.
He FJ, MacGregor GA. A comprehensive review on salt and health and current experience of worldwide salt reduction programmes. J Hum Hypertens 2008. Available at http://www.nature.com/jhh/journal/vaop/ncurrent/abs/jhh2008144a.html.
* Additional information available at http://www.cdc.gov/nchs/data/nhanes/databriefs/calories.pdf.
† The recommendation was based on dietary reference intakes published by the Institute of Medicine (4).
§ Information available at http://www.nyc.gov/html/doh/html/cardio/cardio-salt-initiative.shtml.
Potassium Offsets Sodium
Most people know that too much sodium from foods can increase blood pressure.
A new study suggests that people trying to lower their blood pressure should also boost their intake of potassium, which has the opposite effect to sodium.
Researchers found that the ratio of sodium-to-potassium in subjects' urine was a much stronger predictor of cardiovascular disease than sodium or potassium alone.
"There isn't as much focus on potassium, but potassium seems to be effective in lowering blood pressure and the combination of a higher intake of potassium and lower consumption of sodium seems to be more effective than either on its own in reducing the risk of cardiovascular disease," said Dr. Paul Whelton, senior author of the study in the January 2009 issue of the Archives of Internal Medicine. Whelton is an epidemiologist and president and CEO of Loyola University Health System.
Researchers determined average sodium and potassium intake during two phases of a study known as the Trials of Hypertension Prevention. They collected 24-hour urine samples intermittently during an 18-month period in one trial and during a 36-month period in a second trial. The 2,974 study participants initially aged 30-to-54 and with blood pressure readings just under levels considered high, were followed for 10-15 years to see if they would develop cardiovascular disease. Whelton was national chair of the Trials of Hypertension Prevention.
Those with the highest sodium levels in their urine were 20 percent more likely to suffer strokes, heart attacks or other forms of cardiovascular disease compared with their counterparts with the lowest sodium levels. However this link was not strong enough to be considered statistically significant.
By contrast, participants with the highest sodium-to-potassium ratio in urine were 50 percent more likely to experience cardiovascular disease than those with the lowest sodium-to-potassium ratios. This link was statistically significant.
Most previous studies of the relationship between sodium or potassium and cardiovascular disease have had to rely on people’s recall or record of what foods they eat to estimate their level of sodium consumption. This is a less precise measure of sodium intake than urine samples. In addition, many have been cross-sectional rather than follow-up studies.
The new study "is a quantum leap in the quality of the data compared to what we have had before," Whelton said.
Whelton was a member of a recent Institute of Medicine panel that set dietary recommendations for salt and potassium. The panel said healthy 19-to-50 year-old adults should consume no more than 2,300 milligrams of sodium per day -- equivalent to one teaspoon of table salt. More than 95 percent of American men and 75 percent of American women in this age range exceed this amount.
To lower blood pressure and blunt the effects of salt, adults should consume 4.7 grams of potassium per day unless they have a clinical condition or medication need that is a contraindication to increased potassium intake. Most American adults aged 31-to-50 consume only about half as much as recommended in the Institute of Medicine report. Changes in diet and physical activity should be under the supervision of a health care professional.
Good potassium sources include fruits, vegetables, dairy foods and fish. Foods that are especially rich in potassium include potatoes and sweet potatoes, fat-free milk and yogurt, tuna, lima beans, bananas, tomato sauce and orange juice. Potassium also is available in supplements.
