A new report from the Institute of Medicine opposes the United States’s recommendation to sharply reduce sodium consumption as a way to prevent heart disease. After reviewing the scientific evidence, an expert committee concluded that sharp reductions in sodium consumption do not decrease risk of heart disease and might actually increase the risk in some populations. The committee’s findings contradict recommendations in the 2010 Dietary Guidelines for Americans, which urged all Americans to reduce sodium intake below 2,300 milligrams (mg) per day and below 1,500 mg per day for at-risk individuals, who constitute more than half of the United States population.
For more than three decades, the leading health organizations in the United States, including the American Heart Association, American Medical Association, and American Public Health Association have encouraged Americans to reduce sodium intake. These organizations reasoned that by limiting sodium consumption, blood pressure, a risk factor for heart disease, could be reduced. Based upon this idea, the United States Department of Agriculture (USDA) and Department of Human Health Services (HHS) encouraged Americans to “reduce sodium intake to less than 2,300 mg and further reduce intake to 1,500 mg among persons who are 51 years of age and older and those of any age who are African-American or have hypertension, diabetes, or chronic kidney disease.”
The dietary guidelines did not seem to match current scientific evidence. Once questions about the sodium recommendations reached a critical mass, the Centers for Disease Control and Prevention (CDC) and HHS asked the Institute of Medicine to review the current scientific evidence on sodium and heart disease risk. Here are the findings:
Finding 1: There is a positive relationship between higher levels of sodium intake and risk of heart disease. While the data has limitations and methodological errors, the committee determined that, collectively, high levels of sodium consumption are indeed correlated with risk of developing heart disease.
Finding 2: For the general population, studies are inconsistent and insufficient to determine whether lowering sodium below 2,300 mg per day increases or decreases risk of heart disease.
Finding 3: For individuals with congestive heart failure, low-sodium intake (1,840 mg per day) may increase risk of developing heart disease.
Finding 4: For prehypertensive individuals, there is some evidence suggesting benefits from reducing sodium intake down to 2,300 mg per day. However, the evidence behind this finding is limited and further studies need to be conducted.
Finding 5: There is no evidence for benefit and some evidence of negative health consequences when sodium intake is reduced to 1,500-2,300 mg per day in people with diabetes, chronic kidney disease, or pre-existing heart disease. Again, evidence behind this finding is limited and more studies are needed.
Overall Conclusion: “The committee found that the available evidence on associations between sodium intake and direct health outcomes is consistent with population-based efforts to lower excessive dietary sodium intakes, but it is not consistent with recommendations that encourage lowering of sodium in the general population to 1,500 mg per day.”
The findings of the committee indicate the major health organizations in the United States were overzealous when they encouraged Americans to drastically reduce sodium consumption. As it turns out, it might be a good thing that the American public took the recommendation with a grain of salt, as the average sodium consumption in the United States has remained around 3,400 mg per day for decades.
The committee noted that consuming too little or too much sodium seemed to increase risk of heart disease. The committee did not recommend an optimal amount of sodium per day, citing wide variations among individuals and uncertainty in the scientific literature.
Perhaps the best scientific evidence on what amount of salt is healthy comes from a 2011 observational study of nearly 30,000 individuals. The study found that individuals excreting (and thus consuming) less than 3,000 or more than 7,000 mg of sodium per day had a higher risk of heart disease than those excreting 4,000-5,990 per day. This study is not conclusive and more research is needed. Nonetheless, very high and very low salt consumption seems to be problematic.
The findings of the committee are refreshing. For decades, low-salt, low-fat dietary recommendations have pervaded in United States as the health of the American population has continued to worsen. It seems that some of the popular assumptions that have prevailed for decades are now being investigated and, in some cases, reversed. It’s essential that we continue to question old assumptions about diet and determine whether they hold up under the current scientific literature.
If individuals are avoiding most processed foods (which are often high in salt) and eating a whole food diet, adding some salt to food is likely beneficial. Personally, I prefer sea salt, which contains magnesium, potassium and other trace minerals in their natural form instead of highly processed table salt, which only contains sodium chloride and iodine.