New research on twins shows that genetics plays a predominate role in differences in cholesterol levels between people. However, a person’s diet also is significantly associated with cholesterol level independent of inherited factors.

Identical twins who differed the most in their dietary intake had corresponding differences in blood cholesterol measures, showing that the association between diet and cholesterol levels was independent of genetic factors, say Jeanne M. McCaffery and Michael F. Pogue-Geile, who conducted the research in the Department of Psychology at the University of Pittsburgh.

This is the first research in twins to demonstrate an environmental association between diet and cholesterol, according to the study published in the September issue of Health Psychology.

"Because [identical] twins share all their genes, differences between [identical] co-twins, and the correlations of these differences seen here must be attributable to environmental effects of some nature," they say.

The researchers recruited 204 pairs of same-sex twins from the Pittsburgh area to participate in the study. Blood samples were drawn and subjects were instructed to keep a food diary over a three-day period. Subjects ranged in age from 18 to 30.

The researchers also found that identical twins displayed more similarities in cholesterol levels than were seen in fraternal twins, who do not have all of the same genes. This shows that there are important genetic factors that account for variation in cholesterol levels. In fact, genetic factors accounted for the majority of differences in cholesterol levels among these young adults.

Controlling for this variation due to genetic factors allowed the researchers to show that factors such as fat and calorie intake also have an environmental association with total cholesterol, high-density lipoprotein and low-density lipoprotein levels, although this accounts for a smaller proportion of the differences among individuals.

While the results of this study are consistent with recommendations for changes in caloric and fat intake, it was based on existing associations in the community and did not attempt to alter dietary habits. Therefore, the nature of this study does not directly address the effects of dietary changes on cholesterol lowering, says Pogue-Geile.

Jeanne M. McCaffery currently works at Centers for Behavioral and Preventive Medicine at Brown Medical School.

The study was supported with funding from the National Heart, Lung and Blood Institute, the National Institute of Diabetes and Digestive and Kidney Diseases, and the National Institutes of Mental Health.

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Health Psychology is the official, peer-reviewed research journal of the Division of Health Psychology (Division 38), American Psychological Association. For information about the journal, contact Arthur Stone, Ph.D., at (631) 632-8833.