Twin study demonstrates correlation between Mediterranean diet and inflammation

December 20, 2007 by Benjamin A. Olenchock M.D., Ph.D.

Atlanta The link between systemic inflammation and progression of atherosclerosis is firmly established. There is some evidence that the cardiovascular benefit of adherence to a Mediterranean diet is due in part to reductions in systemic inflammation, although clinical data has been inconsistent. Investigators have analyzed the association between diet and inflammation in a large cohort of monozygotic and dizygotic twins from the Twin Heart Study. Twin studies are helpful for controlling for immeasurable genetic and environmental differences that might contribute to the variable association between diet and inflammation in previous studies.

345 middle-aged men were included in the study. Subjects were grouped into quartiles based on their responses to Mediterranean diet score (MDS). Higher MDS scores were associated with higher age, more years of education, smoking status (former smokers had high MDS while current had low MDS score), higher fasting glucose, and higher use of fish oil supplements. A multivariate analysis was performed to determine the association between MDS and circulating inflammatory markers. Covariates included potato and egg consumption, age, years of education, marital status, smoking, waist to hip ratio, physical activity, history of coronary heart disease, depression, fasting glucose, systolic blood pressure, LDL & HDL cholesterol, use of aspirin and statins.

After adjustment, higher MDS score remained associated with higher levels of IL-6 in a dose-responsive manner. For every 1-point increase in MDS, the circulating level of IL-6 decreased by 5.1% (p=0.005). C-reactive protein (CRP) levels did not correlate with MDS score after adjusting for cardiovascular risk factors. When focusing on twin pairs, this correlation was even more striking: a 1-unit decrease in MDS score was associated with a 7.7% (CI 1 to 14) decrease in circulating IL-6 levels within monozygotic pairs, however there was no correlation within dizygotic pairs. Again, no difference was observed in CRP levels.

It is interesting that IL-6 levels correlated with MDS score while CRP did not. IL-6 is an inflammatory cytokine responsible in large part for the rise in acute phase reactants like CRP. In the immunology literature, IL-6 has regained attention for its role in the development of a newly described helper T cell subset called Th17 cells. This cell population has a role in autoimmune disease and mucosal immunity. The link between diet and inflammatory markers could have an immunologic basis. The authors propose that IL-6 might be a more sensitive marker for atherosclerosis as well.

Dai J, Miller AH, Bremner JD, Goldberg J, Jones L, Shallenberger L, Buckham R, Murrah NV, Veledar E, Wilson PW, Vaccarino V. Adherence to the Mediterranean Diet Is Inversely Associated With Circulating Interleukin-6 Among Middle-Aged Men. A Twin Study. ''Circulation. 2007 Dec 17; [Epub ahead of print]''