I was a week away from returning home from a year’s visiting professorship in Japan, when a routine lab test discovered that I was suffering from kidney failure. The doctor tilted his head, studying me for a moment with a puzzled look on his face. “What’s odd,” he said in unambiguous but accented English, was that I appeared asymptomatic. And in truth before I had walked into his office, I would have characterized myself as enjoying the best health I had in years – feeling energetic from exercising more, eating lots of fish, but staying away from sodium-traps like miso soup and tsukemono (Japanese pickles). Within a week I was back in Texas, stumbling into my primary care physician’s office, nauseous and dizzy. But as it turned out, the new lab reports declared that my kidneys were functioning normally, although the test results had the same numerical values as the earlier Japanese one. As for the symptoms, that was a function of staying up all night surfing the Internet with near hysterical fervor, using such keywords as “kidney disease,” “kidney failure,” and “dialysis,” while pigging out on Haagen-Dazs strawberry ice cream.
In scouring this latest lab report I noticed something I had never before paid attention to. In the upper left hand corner under gender and age, my physician had checked off “African-American” for a box marked “race.” No such adjustment was made in the Japanese lab report, because that society is fairly homogeneous. Before, I might have felt queasy about medical practitioners taking note of such distinctions, but not now. For that designation had just saved me from being mistakenly hooked to a dialysis machine with two fully-functioning kidneys.
So, what might account for the differing range of values among ethnic groups in terms of what constitutes healthy kidneys? As an applied historian, who has spent years researching the West African landscape, and comparing its oral traditions to manuscripts from ancient Timbuktu and other Islamized areas, I have long noted subtle ecological differences in ancestral environments. For instance, my West African ancestors who were brought to America as slaves, were subsistence farmers who toiled in the blazing heat of the tropics, while inhabiting one of the most sodium-deficient regions on the planet. Over the course of millennia, these West African farmers evolved “miracle kidneys” in order to survive blistering heat in a region that was nearly a thousand miles or so inland of the briny, salinated waters of the Atlantic coast. But once enslaved West Africans became immersed in the sodium-saturated environment of America, salt-sensitive high blood pressure skyrocketed along with kidney disease. In the case of healthy African-Americans, there was so much confusion in the medical community that they were even misdiagnosed as having kidney disease. Medical researchers saw the necessity of recalibrating the range of values for normal kidney as a function of ancestry.
As multi-ethnic America has embraced the etiquette of colorblindness, there is one arena where the making of racial distinctions can be lifesaving. And that is the field of public health. However this classifying of subpopulations should not be confused with bogus efforts to distinguish so-called racial differences in intelligence as presented in the 1994 bestseller, The Bell Curve, or by the measuring of skulls or sexual organs, which were popular scholarly endeavors during the period after slavery. The term “race” should be seen for what it is -- a short-hand way of identifying “ancestry.” Since 99% of American blacks come from the same salt-deficient region of the African continent, calling this group “black” is a convenience, even though it would be dangerous to lump them in the same pot as coastal Africans, for whom the briny waters of the Atlantic Ocean provided infinite amounts of dietary salt.
While medical researchers are still arguing over the merits of a low-sodium diet for treating high blood pressure among whites, there is no disagreement within the medical community as to the dangers of a high sodium diet for African-Americans. The latest dietary guidelines released by the U.S. Department of Agriculture and the Department of Health and Human Services in January 2011 state that the maximum daily salt level for Americans should be 2500 milligrams a day. However it is important to remember that this is not a universal value. Most medical research now says that for African-Americans to avoid elevated blood pressure and the kidney disease it triggers, their maximum daily consumption of sodium should be closer to 1,500 milligrams/day.
In instances where the nutritional needs of a particular ancestral group is dramatically different from the norm of people of Northern European ancestry, it is simply not enough to note it in laboratory reports and articles in obscure medical journals. Those values should be spelled out on nutritional labels for all to see. The United States has come a long way, now taking for granted the fact that a black man now sits in the Oval Office. The next vital step in our societal maturation will be learning to celebrate the universality of our humanness without poisoning one another on account of medically-proven ancestral differences.