|Deck of a slave ship|
Originally published May 17, 2007
WHEN Oprah Winfrey talks, people listen - about 8 million every day. Which is why a recent Ask Dr. Oz segment on "Oprah" is so troubling. An audience member asked: "Why do I sweat so much?" After explaining that excessive sweating can result from a thyroid condition, body toxins or hypertension, Dr. Mehmet Oz turned to Winfrey to ask: "Do you know why African Americans have high blood pressure?"
Winfrey replied studiously: "African Americans who survived [the slave trade's Middle Passage] were those who could hold more salt in their body." To which Dr. Oz rejoiced: "That's perfect!"
Far from it. Though well-intentioned, Winfrey's answer last month effectively lent her credibility, star power and billion-dollar brand to a dubious theory known as the "slavery hypothesis."
This speculates that the disproportionately high hypertension rate among African Americans today is an evolutionary byproduct of the slave trade. Proponents argue that slaves who survived the food and water deprivation, dysentery and vomiting endemic on this grueling voyage had a genetic predisposition to retaining sodium. This is believed to have loaded the African American gene pool with genes favoring salt retention, which in turn generates high blood pressure. In short: Black Americans' hypertension rates are nearly twice as high as whites' because, as Winfrey and Oz tell it, that's just the way they are.
Few scientific theories have been so thoroughly discredited. Since it was first popularized by Dr. Clarence Grim in 1988, there has been absolutely no biomedical data supporting the slavery hypothesis as a legitimate scientific conclusion. In fact, only one supporting peer-reviewed article has been published, and it has been soundly refuted. For a physician to casually discuss this on a nationally syndicated talk show (wearing scrubs, no less) as if it is medical fact is at best misleading and at worst pop-culture medical malpractice.
The slavery hypothesis is questionable at face value. The theory's proponents argue that the Middle Passage created what population geneticists call a "bottleneck," in which a drastic event - such as genocide or, in this example, forced migration - leads to a selection process in which the survivors share a hereditary trait that was necessary to live. But most experts in the field don't buy it. Although predisposition to salt retention may have advantaged some individual slaves, other factors - such as new selective pressures in North America and mating with non-Africans - would have increased genetic variability, not constricted today's African American population to one common hypertension gene.
Also important is the fact that no contemporary West African population suffers from rampant hypertension. Historical records suggest that Africans' overall mortality during the Middle Passage was about 13%. For a bottleneck theory to hold up, the alleged "salt sensitive gene" would have had to play a significant role for the roughly 87% that survived, implying that this gene was relatively common among enslaved West Africans.
But if that were so, a sizable number of today's West Africans would similarly exhibit hypertension as their own salt consumption increased in modern times. This has not been the case. Epidemiologist Dr. Richard Cooper has shown, for example, that the prevalence of hypertension among Nigerians is significantly lower than white Americans, while Germans and Finns have a higher prevalence than black Americans. Surely, much more is going on here than genes.
Like a game of whack-a-mole, the slavery hypothesis keeps popping up in the media, popular culture and even medical texts no matter how many times it is slammed down. It has come to symbolize the incessant way in which unfounded biological theories of racial difference continue to thrive despite significant evidence to the contrary.
Countless studies show that stressful environments and situations raise blood pressure. And few things are as consistently stressful as being black. By almost every measurable social category - such as income, infant mortality, education, incarceration rates and employment - blacks fare poorly, making everyday life a constant struggle. Only a buried-head ostrich would say that racial discrimination does not play a role in many African Americans' poor health.
What's so pernicious about this "bad gene" theory is that it attributes current health disparities to actions taken nearly four centuries ago, when the more relevant issue may very well be what is happening today. Reducing health disparities to genes obscures more sensible conversations about the contemporary nature of discrimination, how it affects minority health and how best to improve health outcomes.
Racial disparities in health are real. But a bit of caution should be exercised when playing the gene card to explain them.
This is not to say that genetic research has no value to minority healthcare. Rather, in a world with finite resources, it's regrettable that we continue to invest millions of research dollars - and valuable public air time -looking for genes to explain racial disparities in health, when so many causes lie simply in how we treat one another.
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