We continue to be bombarded by studies claiming to have discovered the miracle diet that unlocks the mystery of weight control. Is any of this knowledge, or is it all just marketing hype? When society looks back on today’s research in the future, will our nutritional breakthroughs seem equivalent to pre-germ theory in medieval medicine? While we do seem to be homing in on what our bodies need for optimal health, the most promising recent development in nutritional science has been in the field of nutrigenomics, the study of the interaction of genetics and nutrition. Scientists are coming to understand that the elusive search for the magic diet has proved futile because both genetic and environmental factors cause diets to affect each of us differently. One nutritional guideline doesn’t fit all.
In a recent Time cover blazing the title “What to Eat Now,” celebrity physician Mehmet Oz compiles a mini-handbook of current nutritional gospel. He marvels that throughout most of human history, our existence rode out waves of famine and plenty. Yet today’s seemingly infinite availability of food, a would-be miracle to our ancestors, has paradoxically resulted in possibly the first generation to live shorter lives than their parents, secondary to medical complications of obesity (Miller, 2012). Dr. Oz acknowledges the plethora of diets on the market today, each one promising a successful formula that other diets lack. But now, he says, we know more than ever about the science of nutrition.
Among these discoveries are some that counter conventional wisdom. Oz redeems the tainted reputations of such foods as eggs, whole milk, nuts, chocolate, and coffee, whose nutritional values are worth the calorie content when eaten in moderation. Fat, he advises, is by no means to be avoided; in fact, monounsaturated and polyunsaturated fats have been shown to lower bad cholesterol and raise good cholesterol levels in the blood. Even some forms of saturated fat, such as coconut oil, may offer health benefits.
Some of Dr. Oz’s observations:
- Only a small minority have a real problem with blood cholesterol levels after eating high-cholesterol foods. Doctors now endorse one egg per day as a good source of protein.
- Fat free items compensate for the loss of taste by adding more salt, sugar, and thickeners. People who eat fat-free foods not only get extra doses of these unhealthy ingredients, they also don’t get the satiety-inducing effects of fat, thus inducing them to eat more overall.
- Despite fad diets’ claims, two people may follow identical diets with radically different results. (Nutrigenomics, the link between genes and diet, has burgeoned in the past few years, with UNC’s Nutrition Research Institute emerging as a leader in the field.)
- High fiber foods slow digestion and make you feel fuller longer.
- Exercise is very important. The CDC recommends 150 minutes of moderate aerobic activity per week for adults. It is important to remember that we also shouldn’t overestimate the caloric benefit of exercise: a muffin as a reward after a workout negates all the calories you’ve burned.
Dr. Oz’s article has received largely positive reviews from scientific critics. The website “Science Based Medicine” endorsed it as offering a “rational, science-based perspective” (Hall 2012). It represents a well-written, comprehensive overview of the timely dietary advice backed by solid scientific research.
But Oz’s cursory acknowledgement of the caveat that identical diets may affect two people differently forces readers to take even his advice with the proverbial grain of salt. His mention of our increasing understanding of the science of nutrition emerges most clearly in the expanding field of nutrigenomics. A 2003 study found that the link between genes and nutrition occurs in two ways: the environment (usually food availability) affects gene expression, and an individual’s genetic make up affects how certain nutrients are metabolized. These adaptations are a vestige of a human society constantly at risk of famine; today, faced with food abundance, these protections may be harmful.
A number of recent studies have shed light on the link between genetics and environment in determining risk for obesity. Meirhaeghe et al. (1999) found that male carriers of the Gln27Gln genotype were at increased risk of overweight only when they were not physically active, thus suggesting that an environmental trigger—sedentary lifestyle—incited the expression of a gene that increased susceptibility to obesity. Additionally, Corella et al. (2005) found that, given the same low-calorie diet for one year, subjects homozygotic for a G allele lost more weight than those carrying an A allele. Qi and Cho (2007) compile a comprehensive list of such studies, all demonstrating how a specific environment can change genes’ potential contribution to obesity.
TIME’s riveting photo essay, “Around the World in 80 Diets”, presents visual examples of nutrigenomics in action. It displays a day’s worth of food in various places across the world. Many of these diets defy contemporary Western nutritional advice, including that of Dr. Oz. Rice, potatoes, and white breads, especially, are staples around the globe. While many of these international diets contained far more calories than recommended—an Iranian baker, for one, eats 4900 calories per day, mostly of his own bread—none of them are overweight. One American subject, by contrast, is 468 pounds and relegated to a 1600-calorie-per-day diet in preparation for bariatric surgery.
The juxtaposition of these two pieces reveals that while the developed world has made breakthroughs in nutritional knowledge, these newly established “facts” do not represent the only means of establishing a healthy weight. As nutrigenomics suggests, varying levels of physical activity and food availability affect individual gene expression, thereby influencing weight. Millions of people in developing countries live active lifestyles and maintain a healthy weight by eating foods that fly in the face of Oz’s assertions. In addition to probing contemporary scientific research on nutrition and its interaction with genetics, we may do well to integrate a global perspective when establishing a dietary model.
Hall, H. (Sep 13, 2012). TIME Magazine, What to Eat, Dr. Oz, and Supplements. Retrieved from http://www.sciencebasedmedicine.org/index.php/time-magazine-dr-oz-what-to-eat-and-supplements/
Miller, A.M. (May 4, 2012). Largely preventable health conditions hamper U.S. Retrieved from http://www.georgiahealthnews.com/2012/05/largely-preventable-health-conditions-hamper-u-s/
By: Cora Wilen