Why is There Debate Over Sodium?

January 12, 2016

Some scientists are expressing doubt about whether sodium is as harmful to our health as it is often conveyed. As health and wellness professionals, you may be wondering how to interpret the evolving science around sodium, especially when there are inconsistencies in the data and how it is interpreted.

Dr. Robert Heaney, a renowned endocrinologist and researcher provides perspective on sodium and links to disease risk in an article in the March/April issue of Nutrition Today (continuing education credits are available for health professionals). The full article and accompanying commentary are worth a read. Here are some of the key points for consideration:

“It is important to keep in mind that the ultimate physiological purpose of sodium intake is precisely the maintenance of blood pressure.” An adequate amount of sodium is needed by the body to maintain blood volume and perfusion of the kidneys. Always making sodium the bad guy fails to recognize its physiological need and is not supported by scientific evidence.

“It is, in a sense, reassuring to note that sodium is thus like most other nutrients in that there is potential harm at both extremes of intake.” The body has (homeostatic) defense mechanisms to protect it from too high or too low sodium consumption. For example, when sodium consumption in an adult of average weight drops below 3,000 mg/day, the renin-angiotensin-aldosterone system is engaged to conserve sodium losses in urine and sweat. And when a person consumes too much sodium, salt receptors on the tongue “flip” to create an aversion to salty foods. What an example of the body’s wisdom!

“Blood pressure reduction is a reasonable proxy for health outcomes in hypertensive individuals on high sodium intakes, but it simply does not track health outcomes in people with normal blood pressure [normotensive individuals] at average or below average sodium intakes.” The 2004/2005 Dietary Reference Intakes (DRIs) from the Institute of Medicine (IOM) are the basis for current sodium recommendations, but did not evaluate the risk of lowering sodium consumption in people with normal blood pressure. In 2013 an IOM task force was convened in part to rectify this omission, but also to review evidence on the effect of sodium consumption on several health outcomes.

The IOM 2013 report concluded that “studies on health outcomes are inconĀ­sistent in quality and insufficient in quantity to determine that sodium intakes below 2,300 mg/ day either increase or decrease the risk of heart disease, stroke, or all-cause mortality in the genĀ­eral U.S. population.” As the commentators to the Heaney paper noted, more research is needed to clearly determine the effect of lowering sodium from 2,300 to 1,500 mg/day on health.

According to Dr. Heaney, the “right” amount of sodium for an individual is the amount that requires the least adaptation or compensation by homeostatic mechanisms of the body. Using that criteria, Heaney said sodium consumption between 3,000 and 5,000 mg/day seems optimal.

While the research continues to unfold and be evaluated, as health and wellness professionals providing guidance, lowering sodium consumption continues to be a recommended strategy for helping to lower blood pressure in hypertensive patients. Other advice includes the latest evidence-based guidelines for blood pressure control which emphasize the importance of lifestyle modifications such as a healthy diet, weight maintenance and regular exercise to improve blood pressure and potentially reduce medication needs in those with high blood pressure.

Additionally, when helping people manage blood pressure, remember that the DASH eating pattern has been shown to be particularly effective. Rich in fiber, calcium, potassium and magnesium, the DASH plan is low in fat and emphasizes fruit, vegetables, low-fat and fat-free milk, yogurt and cheese, and whole grains.