In the search for answers to the cause and the cure of the condition of hypertension, some 50 years ago North American researchers began to look for clues in other cultures. Their search led them to some startling and tantalizing discoveries. Although there is a significant hypertension problem in Canada, with at least 10 per cent of adults suffering from high blood pressure, there are areas in which the condition is even more prevalent. In Japan and Korea about half of the adult population suffers from hypertension, and as a result
the incidence of strokes is extremely high. And yet hypertension is virtually unknown among the Yanamama Indians of northern Brazil. The differences have prompted a flurry of detective work by prominent scientists in North America, and their findings are compelling.
Sample: Researchers have discovered at least 20 societies scattered throughout the world in which hypertension is, or was until recently, almost nonexistent. Moreover, in those societies, unlike Canada and other developed Western nations, blood pressure does not increase with age. Instead, it remains the same —and even declines in some cases —once an individual reaches adulthood.
Dr. Lot Page, a professor of internal medicine at Tufts University in Medford, Mass., has analysed the groups, which include Iranian nomads, Chilean mountain dwellers and various Melanesian tribes in the Solomon Islands, in an attempt to find the common physical denominators in a diverse sample of subjects. Said Page: “The thing that makes these people particularly fascinating is that they are from many different racial groups, live in many different habitats and eat different diets so that it is easy to figure out what is
common between them.”
Page concluded that all of the groups have remained in relative isolation and maintained their traditional, preindustrial culture. Their members are lean and active and do not gain weight as they grow older. At the same time, their diets, although diverse, all have a low salt content—in most cases, less than one-third of the typical North American salt consumption of about half an ounce daily—while being high in potassium. Page is convinced after analysing many possible factors that the explanation for their immunity to hypertension rests principally in their diet. He said that his theory is corroborated by the fact that the most hypertensive people in the
world—the inhabitants of the northern Japanese prefecture of Akita—also consume the greatest amount of salt, as much as IV2 ounces daily, mainly in a staple called miso, a fermented bean paste. At least one group that shares the active, preindustrial society of the nonhypertensive groups, the nomadic Qash’qai of Iran, suffers from the same level of hypertension as North Americans—but it also consumes about the same amount of salt.
Cultural variations within Canada appear to support Page’s theories that a lack of potassium (found in fruits and vegetables) in the diet may also be a critical factor in hypertension. Dr. George Fodor, associate dean of community medicine and a professor of clinical epidemiology at Memorial University of Newfoundland in St. John’s, said that his studies of the province’s outport coastal communities indicate that almost one-third of the adult inhabitants suffer from hypertension. Although their salt consumption is only a little higher than that of the average Canadian, they consume less potassium, calcium and magnesium, elements that keep the cardiovascular system in good working order. Said Fodor: “It looks like the mutual balance of sodium and potassium is important.”
Factors: But other researchers point to still other variables to explain differences in blood pressure between societies. Dr.RykWard, a geneticist and epidemiologist at the University of British Columbia in Vancouver, said that, although salt does appear to be significant, obesity, genetic makeup and other factors may also be important factors. Ward’s research points to obesity as one of the major reasons why natives of the Tokelau Islands in the South Pacific Ocean.who emigrate to urban centres in New Zealand have higher levels of blood pressure than islanders who stay at home and why their blood pressure tends to go up with age, although it remains constant among islanders who do not emigrate.
Researchers say that they do not have enough data from different parts of the world to solve the continuing mystery of blood pressure variation. However, a project that the United Nations-sponsored World Health Organization will launch this year will study blood pressure levels in the populations of 50 societies around the world and will also collect information on sodium and potassium consumption. The tantalizing differences between cultures may point researchers in the right direction at last. -PATRICIA HLUCHY
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