The Yanomamo Myth
How often have we heard the anti-salt advocates, the "so-called" experts, refer to the Intersalt study, and in particular the Yanomamo Indians of Brazil. These primitive hunter-gathering tribes are held out by these experts as prime examples of the benefits of low-salt consumption, because they do not experience any age-related increase in blood pressure.
Indeed, one of the main conclusions coming out of the study was that the Intersalt populations with low-sodium intakes had low median blood pressures, a low prevalence of hypertension and no increase in blood pressure with age. Disregarding any other factors, the experts stated that the low levels of hypertension among these tribes was the exclusive result of low-salt consumption.
Such conclusions reflects the dangers of commitment to a single focus approach to science - an approach that almost always manages to manipulate the interpretation of data in order to support a prejudged conclusion. And, not particularly surprising, all the "experts" continue to use the Yanomamo Indians as primary proof that reduced salt consumption results in an absence of hypertension.
Two out of the four low-sodium populations in the Intersalt study - the Yanomamo and Xingu Indians are of Amerindian origin. Both these populations have a complete absence or a very low frequency of the D/D genotype - a genotype that is closely associated with cardiovascular diseases and hypertension.
So, it's not low salt consumption that results in the lack of an age-related rise in blood pressure in the Yanomamo and Xingu Indians, it's their genetic makeup!
Studies in Mexican Americans suggest that diseases such as obesity, diabetes mellitus, cholesterol gall stones, and gall bladder carcinoma are more common in individuals with high Amerindian genetic background (1,2,3). On the other hand, these individuals present low risk for developing cardiovascular disease, in spite of data that show serum triglyceride concentrations to be slightly higher in this population than in Caucasians at any age (4,5). These data suggest that Amerindians are protected against developing cardiovascular diseases due to their genetic background.
An interesting fact is the different prevalence of hypertension in several states of Mexico. Thus, states with a high Amerindian genetic background, such as Puebla, Chiapas, and Oaxaca present a low prevalence of hypertension when compared to the northern states of the country Coahuila, Sonora, and Sinaloa with a low Amerindian genetic background.
These differences explain the low genetic susceptibility for cardiovascular diseases and hypertension in populations with high Amerindian background such as the Yanomamo and Xingu.
How many other myth-interpretations are the "experts" responsible for?
It is hoped the new Dietary Guidelines will not be a product of the four M's, Myth-information, Myth-interpretation, Myth-representation, and Myth-guided policies
1. Hanis, C.L., R.E. Ferrell, S.A. Barton et al., « Diabetes among Mexican Americans in Starr County, Texas," Am. J. Epidemiol, 118, 659-672, (1983). 2. Hanis, C.L., R. Chakraborty, R.E. Ferrell et al., "Individual admixture estimates: Disease associations and individual risk of diabetes and gallbladder disease among Mexican-Americans in Starr County, Texas," Am. J. Phys. Anthropol, 70, 433-441, (1986). 3. Haffner, S.M., A.K. Diehl, M.P Stern et al., "Central adiposity and gallbladder disease in Mexican Americans," Am. J. Epidemiol, 129, 587-595, (1989). 4. Weiss, K.M., R.E. Ferrell, and C.L. Hants, "A New World syndrome of metabolic diseases with a genetic and evolutionary basis," Yearbook Phys. Anthropol, 27, 153-178, (1984). 5. Mitchell, B.D., M.P. Stern, S.M. Haffner et al., "Risk factors for cardiovascular mortality in Mexican Americans and non-Hispanic whites. The San Antonio Heart Study," Am. J. Epidemlol, 131, 423-433, (1990).
