20 January 2013

The nutritional biology of human skin color

The amount of melanin found within our skin has long been a source of division for humans culturally, but anthropologist Nina Jablonski of Penn State tells the story of how human skin color unites us all biologically.

It's become one of my favorite stories to share as it relates to nutritional biology: More pigment was naturally selected because it acted as a sunscreen needed to protect against DNA damage and destruction of folate, needed for reproduction. Depigmentation was selected for when humans dispersed from Africa and into the Northern Hemisphere where they needed skin light enough to absorb sufficient UVB rays to produce vitamin D.

I first heard Jablonski discuss the nature of human skin pigmentation almost two years ago at the AAAS conference in Washington DC. Later, I discovered her TED talk, which I've posted above. It's older, but worth watching over and over again. Jablonski has a simple message: instead of using skin color to discriminate, use skin color to teach people about evolution and health.

What a Komodo dragon can teach us about energy balance

Credit: San Diego Zoo
Try telling a Komodo dragon that physical activity doesn't matter and that all one needs to do to lose weight is eat a diet lower in carbohydrates.

Meet Sunny, the obese Komodo dragon. Her San Diego Zoo keepers have put her on a strict diet based on her animal energy and metabolic requirements. She eats only mice, rats, and ground turkey mixed with vitamins and calcium. Yet, it's not enough to keep Sunny from steadily gaining weight. When in captivity, dragons are prone to obesity because of their mainly sedentary lifestyle. They do little else than sleep, bask in the sun or shade, and eat breakfast or supper.

In their native habitat of Indonesian islands, Komodo dragons are extremely active. They travel up to 10 kilometers a day, run up to 13 miles per hour, swim several kilometers from island to island, then dig or climb as they hunt. Once they capture their prey, they can eat as much as 80 percent of their body weight in a single meal. That energy they will serve to store for often days or weeks.

When I asked senior zookeeper Ken Morgan what he was doing to help get Sunny moving and losing weight, he replied that they were trying a series of enrichment programs. But getting a 200-pound dragon to do any activity at all is no easy task, he said. It takes some creativity. One enrichment program Morgan has used involves burying a ball with a dead mouse inside. Sunny picks up the scent, spends some time searching for it, then digs around before finally discovering the treasure. It's activity accomplished. These games can help Sunny burn more calories to keep weight off.

What journalists should know before writing about fructophobia

"Pick your poison" Sugars by vavroom, on Flickr

In his new book, Fat Chance, Dr. Robert Lustig argues that "sugar is more toxin than it ever was nutrient." He writes that sugar is as addictive as cocaine, that it should be regulated like tobacco, and that children should be carded before having a soda. He compares the fructose component of sugar to ethanol. "Pick your poison," he writes, arguing that fructose will "fry your liver and cause all the same diseases as does alcohol." He also challenges energy balance (calories-in-calories-out) as the dominant paradigm of understanding obesity and and argues that sugar is harmful in ways beyond the calories it provides.

With statements as controversial as these, it's no wonder that the media, who tend to crave sensationalism to obtain readers or viewers, eat them up like candy. And Dr. Lustig knows what he's doing and just what to say to elicit attention. He's no stranger to the spotlight, as Elizabeth Weil writes in her article featuring the pediatric endocrinologist. The showman-doctor also knows just how to tell a classic falling-prey-to-cruelty story. He'd have his readers believe just what they want to hear: that their weight gain is not their fault, that the great evil monster of the food industry is putting addictive "poison" in their food in the form of sugar, and that the government is standing "idly by" letting it all happen. After reading Dr. Lustig's book, it's easy to understand why readers are entertained and maybe even enraged enough to give up on sugary sodas, cheese cake, and apple pie. But are the arguments Dr. Lustig makes in the book right or wrong?