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... see more