Current “Healthy” Salt Recommendations Still Too High

A recent review of research shows that the recommended amount of salt in the diet may not lower risk of high blood pressure (hypertension), heart attack, and stroke as much as previously thought, according to Hypertension (2003;42:1093–9). This review suggests that more drastic salt reductions may be needed to protect people from these health risks.

Sodium, a mineral nutrient found in nearly all foods, exists in a balance with potassium that is critical for the normal functioning of every living cell. Eating unprocessed fruits, vegetables, meat, and fish provides all the sodium the body needs (about 500 mg a day). Most people, however, get far more than they need due to the salt (sodium chloride) added during the processing or cooking of foods, and at the table. In fact, added salt is responsible for an estimated 95% of our sodium consumption.

Excessive sodium intake unfavorably shifts the potassium-to-sodium balance and can lead to hypertension. Hypertension is the most common cardiovascular disease worldwide and increases the risk of suffering a heart attack or stroke. The average daily intake of salt varies in different parts of the world from 6 to 18 grams. The World Health Organization recommends restricting daily salt intake to 5 grams or less, and authorities in the United States recommend 6 grams or less. Studies have shown that salt restriction lowers blood pressure, and suggest that blood pressure will continue to drop as salt intake diminishes.

The new review of the research on salt intake and blood pressure analyzed the results from 28 controlled studies involving a total of 2,954 people. Only studies that lasted at least four weeks and in which daily salt intake was reduced by at least 2.4 grams were included. The combined results were used to calculate the amount that blood pressure would be expected to drop for any given reduction in salt intake. For example, this analysis predicted that a 3-gram reduction in daily salt intake would reduce systolic blood pressure (the upper number in a blood pressure reading) by 3.6 mm Hg and diastolic blood pressure (the bottom number in a blood pressure reading) by 1.9 mm Hg in people with hypertension. It was predicted that a 6-gram reduction in daily salt intake would lower systolic and diastolic pressures by 7.1 and 3.9 mm Hg, respectively, and a 9-gram reduction would lower systolic and diastolic pressures by 10.7 and 5.8 mm Hg, respectively, in people with hypertension. In people with normal blood pressure, the predicted trend was similar but less pronounced.

Two of the controlled studies comparing the effects of different levels of salt intake reduction were analyzed separately. These studies found a similar but more pronounced trend: they predicted that 3-, 6-, and 9-gram reductions in daily salt intake would lower systolic/diastolic pressures by 5.4/3.0, 10.6/6.0, and 16.3/9.1 mm Hg, respectively, in people with hypertension.

The results of this review suggest that large reductions in salt intake might indeed lower blood pressure enough to significantly reduce the risk of heart attack and stroke, but that current dietary recommendations may not be low enough. Large and long-term studies examining the real effect of very low salt intake on blood pressure and incidence of heart attack and stroke are needed. Public health recommendations should be adjusted based on the findings of such studies.

Maureen Williams, ND, received her bachelor’s degree from the University of Pennsylvania and her Doctorate of Naturopathic Medicine from Bastyr University in Seattle, WA. She has a private practice in Quechee, VT, and does extensive work with traditional herbal medicine in Guatemala and Honduras. Dr. Williams is a regular contributor to Healthnotes Newswire.

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