Question: Where did the belief that too much salt in the diet causes high blood pressure originate?
Dr. Brownstein's Answer:
The big push for salt restriction came after a widely publicized 1984 study called “Intersalt.” This study examined more than 10,000 subjects at 52 locations in 39 countries.
Researchers looked at the relationship between blood pressure and electrolyte excretion in urine. A higher salt intake results in larger amounts of sodium excreted in the urine.
At the end of the study, four (out of 52) of the population centers had significantly reduced the salt in their diets. In these four centers, the subjects showed significantly lowered blood pressure, and their blood pressure did not increase with age.
Researchers and academics seized on these results as the “smoking gun” that associated salt with high blood pressure. The Intersalt study made headlines across the country. As a result of the publicity, more propaganda was thrown around, and
Americans were told to use less and less salt. However, when I looked at Intersalt, I was stunned by the data — and how the researchers had chosen to interpret it.
The problem arises from the four population centers that demonstrated the blood pressure–lowering effects with reduced salt
intake. These four centers were nonacculturated populations — or, in layman’s terms, primitive peoples. The centers included the Yanomami and Xingu tribes in Brazil, as well as one indigenous tribe in Kenya and another in New Guinea.
The subjects from each of these populations had an extremely low intake of sodium as well as a very low intake of alcohol. They also had no obesity in their populations. It is well known that obesity and alcohol abuse can lead to hypertension.
Across the other 48 centers studied in Intersalt, no correlation could be drawn between salt intake and hypertension. Therefore, using this study to draw the conclusion that all people need to lower their salt intake is ridiculous.
The only real conclusion that can be drawn from Intersalt is that if you live in the jungle in a nonacculturated population, a low salt intake is associated with a lowered blood pressure. Unfortunately, for the great majority of the world population, that finding simply doesn’t apply.