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INTERMAP: Sodium-BP relationship unaffected by other dietary factors
Micro- and macronutrients that influence BP only modestly offset the association between sodium and BP, according to a study published in Hypertension.
“Regularly consuming excessive amounts of sodium, derived mainly from commercially processed food products, is an important factor in the development of the elevated blood pressure patterns,” Jeremiah Stamler, MD, professor emeritus of preventive medicine (epidemiology) at Northwestern University Feinberg School of Medicine, said in a press release. “To prevent and control the ongoing epidemic of prehypertension and hypertension, the salt content in the food supply must be reduced significantly.”
Researchers analyzed data from 4,680 participants aged 40 to 59 years from China, Japan, the United Kingdom and the United States (n = 2,195 U.S. citizens) from the INTERMAP trial. Participants attended four clinical visits, in which height, weight and BP were measured, urine samples were collected and dietary data were obtained. Medical and demographic data such as alcohol intake, smoking status, physical activity and history of CVD were collected by an interviewer-administered questionnaire.
Twenty-four-hour urinary sodium excretion was related to urinary sodium/potassium in the entire group (partial correlation = 0.5) and in participants from the United States (partial correlation = 0.53; P < .001). In the group from the United States, a 2-standard deviation increase in 24-hour urinary sodium excretion (118.74 mmol per 24 hours) was linked to an increased systolic BP of 3.73 mm Hg (95% CI, 2.45-5.01).
The relationship between sodium and BP persisted after controlling for 12 vitamins, 10 macronutrients, 18 dietary amino acids and seven minerals, in addition to age, sex, ethnicity/race and socioeconomic strata.
The relationship between sodium and BP was weakened after controlling for BMI in 16-cell cross-classification analyses. This was not seen in the relationship between sodium/potassium and BP.
A significant positive relationship between BP and urinary sodium was seen in participants with normal weight or obesity. This relationship was weaker in those with overweight.
The intake of potassium reduced the relationship between sodium and BP in higher levels of 24-hour sodium excretion, but not lower levels.
“The prevention and control of the adverse influences of dietary Na (salt) and Na/K on BP require major reductions in population-wide levels of salt intake,” Stamler and colleagues wrote. “They cannot be accomplished only by substituting other dietary/lifestyle measures, however useful, including the DASH-type diet. Because the majority of salt ingested by Americans and the populations of many other countries comes from commercially prepared products, sizable reductions by the food industry in the salt content of their products are essential efforts to control the epidemic of raised BP worldwide.” – by Darlene Dobkowski
Disclosures: Stamler reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.