Eureka!
Survival of the sickest
By Queena Lee-Chua
Philippine Daily Inquirer
First Posted 00:48:00 01/19/2008
MANILA, Philippines—I spent last Christmas immersed in a provocative book titled “Survival of the Sickest,” written by Sharon Moalem of New York’s Mount Sinai School of Medicine. A researcher in the cutting-edge fields of neurogenetics and evolutionary medicine, Moalem believes that many of the diseases today once evolved to help our ancestors combat epidemics or just plain survive.
For instance, Moalam states that diabetes, which is such a killer now, started to help our forefathers survive the sudden cold of an ice age about 13,000 years ago. “Faced with year-round frigid temperatures, their insulin supply slowed, allowing their blood sugar to rise somewhat,” Moalam says. Experiments show that when blood sugar rises, the freezing point of blood becomes lower, which means that blood needs a colder temperature to freeze.
“They urinated frequently, to keep internal water levels low,” Moalem continues. “Suppose these people used their brown fat to burn the oversupply of sugar in their blood to create heat. [This might have given them] enough of an advantage over other humans, especially if the spike in sugar was only temporary, to make it more likely that they would survive long enough to reach reproductive age.”
Moalem cites evidence to support his theory. One, the wood frog uses high blood sugar to keep itself from freezing in the winter. Two, rats exposed to cold temperatures become resistant to their own insulin; in short, they become diabetic. Three, in cold areas, more diabetics are diagnosed in colder months (between November and February) than in the hotter months (between June and September) and in fact, children are most often diagnosed with Type 1 diabetes in the fall season.
Also, a study of more than 250,000 American veterans who are diabetic revealed that their blood sugar levels increased in the cold months and dropped in summer.
“Diabetes,” says Moalem, “has some deep connection to the cold.”
Fine, that was then, but diabetes now kills rather than helps. Why? Today, most diabetics have little brown fat and little exposure to constant cold. So they have no use and no outlet for the sugar accumulating in their blood. Diabetes has now become a disease.
Hypertension, slave trade
Statistics show that African-Americans have rates of high blood pressure almost double that of other Americans. Why? Perhaps diet, but many non-African Americans also eat junk food and fatty stuff. Perhaps genetics, maybe Africans really have genes for hypertension. But no, Blacks living in Africa do not have the same rates of high blood pressure as blacks in America.
Moalem gives another startling explanation. Salt can raise blood pressure, and research has shown that indeed, Africans are especially sensitive to this. But what caused this? Moalem’s answer: the slave trade.
“When Africans were taken to America against their will by slave traders, they were transported under horrible conditions—they usually weren’t fed or even given sufficient amounts of water,” Moalem says. “Their death rate was very high. It’s possible that those with a natural propensity to retain high levels of salt had a better chance to survive—the extra salt helped them maintain enough water to avoid fatal dehydration.”
The capacity to retain extra salt helped the Africans then, but now, with the modern American diet too high in fat and salt, African-Americans sadly have increased rates of high blood pressure.
Moalem gives many other examples of today’s deadly diseases, which our ancestors needed in ages past. The book also provides a lot of interesting theories, such as how tanning salons can help lower cholesterol, how iron overload helped people survive the plague, and why the common cold is a nuisance but will most likely never be really dangerous.
“Survival of the Sickest” is engaging, witty and fascinating. Highly recommended not only for doctors and health care providers, but also for all of us who want to understand our health and ourselves.
“Survival of the Sickest” by Sharon Moalem (William Morrow, 2007) is available in Powerbooks.
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