Fish Consumption Slows Narrowing of Arteries in Postmenopausal Diabetic Women

Heart disease is a slow process, taking years for the lesions that develop in the lining of coronary arteries to expand and narrow the diameter of arteries, eventually restricting blood flow. The gradual narrowing of the arteries is called stenosis. The presence of diabetes, particularly type 2 diabetes, aggravates the development of heart disease and most diabetics succumb to heart disease rather than to diabetes itself.
 

Because the consumption of fish and long-chain omega-3 fatty acids (n-3 LC-PUFAs) is associated with lower risk of cardiac mortality in both non-diabetic and diabetic subjects, the potential effect of fish oil on the progression of atherosclerosis has been of considerable interest. Some, but not all, studies that have examined the effect of fish oil consumption on stenosis and restenosis following angioplasty (the removal of plaques from arteries) have reported slower progression of the disease. To monitor the disease, investigators use X-rays that provide a picture of the arterial vessels and atherosclerotic lesions. The technique is called angiography. This approach permits the direct measurement of arterial diameter over time.

A team of investigators from Finland and two sites in the United States examined the progress of atherosclerosis in postmenopausal women, aged an average of 65 years, who participated in the Estrogen Replacement and Atherosclerosis Trial. 42% of the women were classified as having diabetes. Angiographic measurements were taken at baseline and after three years. Fish consumption was assessed from food frequency questionnaires that specified three types of fish: tuna, dark fish, and other. The first two categories were grouped together and fish consumption was expressed as servings a week.

Previous findings from this study indicated that estrogen therapy alone or with progesterone did not affect the progression of atherosclerosis in these women. In this report, artery diameter and percent stenosis were measured and analyzed according to frequency of fish consumption, type of fish consumed, and diabetic status, with adjustment for multiple confounding variables. At baseline, women who ate two or more servings of fish a week had a higher educational level and healthier lifestyle, as reflected in more strenuous physical activity and higher consumption of carotene. Diabetic women who ate two or more servings of any fish per week had smaller minimum artery diameter and significantly greater percent stenosis than non-diabetic women and diabetic subjects who ate less than two servings of fish per week.

After three years, combined analysis of the angiographic measures from all subjects indicated that consumption of two or more servings of any fish per week was associated with significantly less arterial narrowing compared with women who ate less than two fish servings per week(P=0.02). The percent increase in stenosis was significantly less in these subjects (P<0.001) and the number of new lesions significantly lower. In subgroup analysis, diabetic women who consumed any fish twice or more per week had significantly less increase in stenosis than diabetic women who ate fish less often.

The observation that significant slowing of atherosclerosis was related to the type of fish consumed strongly suggests that n-3 LC-PUFAs are involved in these changes. The strength of the effect of fatty fish consumption in postmenopausal diabetic women, who are at substantially increased risk of heart disease, lends urgency to the need for well designed intervention studies in diabetic subjects. As an editorial by William E. Connor pointed out, the predominant risk factors for coronary artery disease – smoking, hypertension, hyperlipidemia, obesity, diabetes, and low physical activity – must still be dealt with. Meanwhile, more enthusiastic encouragement of all diabetics to increase their fatty fish consumption might prolong their lives.

Erkkila AT, Lichtenstein AH, Mozaffarian D, Herrington DM. Fish intake is associated with a reduced progression of coronary artery atherosclerosis in postmenopausal women with coronary artery disease. Am J Clin Nutr 2004;80:626-632.

Connor WE. Will the dietary intake of fish prevent atherosclerosis in diabetic women? Am J Clin Nutr 2004;80:535-536.