Study Questions Sodium Role in Hypertension

A new study suggests that contrary to current belief, low-sodium diets can carry a higher risk of heart disease.

Researchers at Boston University School of Medicine used data from 2,632 normotensive subjects (30-64 years of age) participating in the Framingham Offspring Study in order to examine the effect of sodium on systolic blood pressure (SBP) and diastolic blood pressure (DBP). Detailed dietary records and mineral intake were collected over six days, and analyzed using mixed models to calculate mean SBP and DBP levels over 16 years of follow-up. Confounding factors included age, sex, education, height, physical activity, cigarette smoking, and alcohol intake.

The researchers found that contrary to expectations, dietary sodium intake was not positively associated with SBP and DBP, but exactly the opposite; study participants who consumed less than 2,500 milligrams of sodium per day had higher blood pressures than participants who consumed higher amounts of sodium. They also found that those who had higher intakes of potassium, calcium, and magnesium exhibited lower blood pressure over the long term. And those with a higher combined intake of sodium (3,717 mg/day) and potassium (3,211 mg/day) had the lowest blood pressure. The study was presented at the Experimental Biology 2017 meeting, held during April 2017 in Chicago (IL, USA).

“These long-term data from the Framingham Study provide no support for lowering sodium intakes among healthy adults to below 2.3 grams per day, as recommended,” said lead author and study presenter Lynn Moore, DSc, an associate professor of medicine at BUMC. “Our findings add to growing evidence that current recommendations for sodium intake may be misguided. We saw no evidence that a diet lower in sodium had any long-term beneficial effects on blood pressure.”

“This study does support the finding of a clear inverse association between potassium, magnesium, and calcium and blood pressure change over time,” concluded Dr. Moore. “I hope that this research will help refocus the current dietary guidelines for Americans on the importance of increasing intakes of foods rich in potassium, calcium, and magnesium for the purpose of maintaining a healthy blood pressure.”

Current U.S. Dietary Guidelines recommend limiting sodium intake to 2.3 g/day for healthy individuals under the age of 50, while adults over age 50 as well as all African-Americans, and anyone with high blood pressure, diabetes, or chronic kidney disease (CKD) is advised to limit sodium intake to 1.5 g/day. Very limited evidence is available to support these recommendations, and recent studies have called these guidelines into question and identified the need to consider the intakes of other minerals in relation to blood pressure regulation.