Merlin Chowkwanyun: How Oprah was taken in by a slavery myth

It seemed like just another harmless moment on daytime TV: Oprah Winfrey began an"Ask Dr. Oz" segment with the physician Mehmet Oz, and the two arrived at the subject of excessive sweating. Oz cited high blood pressure as a major cause and then asked Winfrey if she knew why black Americans experienced hypertension at disproportionate rates.

No problem so far. But then Winfrey answered Oz's question by reviving what scholars have called the"slavery hypothesis" of hypertension. Black Americans, that thesis holds, experience greater rates of hypertension today because those slaves most likely to survive the brutal journey to the New World had bodily constitutions that retained higher amounts of sodium; with more sodium, they were likelier to survive ailments related to salt- and water-deprivation that often resulted in death. But, while sodium-retention became an adaptive trait that helped many slaves survive, it also imperiled them and their descendants, since sodium is a major risk-factor for hypertension. Oz approved Winfrey's summary of her ancestors'"unique ability," in his words.

There was just one problem. The thesis is bunk. Since its heavy promotion in the 1980s by Thomas W. Wilson and Clarence Grim, the slavery hypothesis has steadily been demolished on theoretical and evidentiary grounds, most notably by the distinguished historian Philip D. Curtin in a 1992 American Journal of Public Health article. Curtin argued that Wilson and Grim had sloppily handled statistical data, made inexact citations to prior articles, and neither showed that salt was actually scarce on the voyages nor proved significant numbers of deaths had occurred due to salt depletion. Meanwhile, as Curtin also pointed out, other researchers found that blacks in other former slave societies, like much of the West Indies, did not have uniformly high hypertension. (For a thorough overview, see also epidemiologist Jay Kaufman's contribution to an excellent symposium on the new science of race.) In short, the case for salt-retention as a race-specific genetic trait is incredibly weak. But these rebuttals are not just esoteric academic arguments. Without more reflection on why they keep resurfacing, the assumptions behind the slavery hypothesis and other notions of genetic determinism will hinder racial equality, and they could even imperil people's lives.

Here's why. First, by claiming an innate link between race and a chronic health condition, the hypothesis shifts the focus away from the external factors that public health researchers have identified as contributors to hypertension. A 1996 study by Nancy Krieger and Stephen Sidney, published in the American Journal of Public Health, explored links between victim responses to racial discrimination and high blood pressure. And a report this year by the city of New York found that the percentage of fast food restaurants in overwhelmingly minority (and low-income) East and Central Harlem is four times that of the white (and wealthy) Upper East Side. Two out of three grocers in Harlem are bodegas, compared with only one of three on the Upper East Side, which also has an extra supermarket per 10,000 people. Minority neighborhoods offer diets that cause not only hypertension, but also related problems like diabetes, obesity, and other conditions.

Second, the slavery hypothesis assumes a long discredited biological basis for"races." ....