In the world of research there has always been a special place for studies involving twins. The special nature of twin studies involves an ability to determine the role of genetics. If genetics overshadow other factors, identical twins should have similar results in a research study since they share the same genes. If other factors are less important than genetics, identical twins should show different results.
Researchers based at the Emory University School of Medicine put the Mediterranean diet up against this twin test by selecting almost 300 twins and measuring their adherence to this way of eating. As a primary research question, they asked whether it would matter how closely each twin followed the Mediterranean diet: Would their health be the same because they were twins, or would the Mediterranean diet be more powerful than their genetics?
As a measurement of health, the researchers chose blood levels of glutathione, a key antioxidant nutrient. Glutathione is a well-researched marker for levels of oxidative stress in the body. Oxidative stress simply means lack of protection in the body from damage to cells and tissue by certain kinds of oxygen-containing molecules. As a primary antioxidant, glutathione helps protect against oxidative stress. (In this study, glutathione was measured in a ratio called GSH/GSSG, comparing the amount of reduced to oxidized glutathione.)
Twins were found to differ in their levels of oxidative stress, and these differences matched up well with a twin's level of adherence to the Mediterranean diet. When one twin stepped up his or her adherence to the Mediterranean diet (in comparison to the other twin) by eating a modestly higher amount of appropriate foods, his or her glutathione score went up by an average of 10%. In other words, the Mediterranean diet passed the twin test! It seems that genetic inheritance was not strong enough to overshadow the health benefits of a Mediterranean way of eating.
It's not surprising to us that a Mediterranean diet was associated with less oxidative stress in this twin study. It's hard to image a selection of foods richer in antioxidants, including the wealth of flavonoids and carotenoids found in the fruits and vegetables that are at the foundation of a Mediterranean-style eating plan. It's the same antioxidant richness that you will find in the World's Healthiest Foods and the Healthiest Way of Eating.
Dai J, Jones DP, Goldberg J et al. Association between adherence to the = Mediterranean diet and oxidative stress. The American Journal of Clinical Nutrition 2008, Vol. 88, Iss. 5; pp. 1364-1370.