N-3 Polyunsaturated fatty acids have been shown to have potential beneficial effects for chronic diseases including cancer, insulin resistance and cardiovascular disease. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in particular have been studied extensively, whereas substantive evidence for a biological role for the precursor, alpha-linolenic acid (ALA), is lacking. It is not enough to assume that ALA exerts effects through conversion to EPA and DHA, as the process is highly inefficient in humans. Thus, clarification of ALA's involvement in health and disease is essential, as it is the principle n-3 polyunsaturated fatty acid consumed in the North American diet and intakes of EPA and DHA are typically very low. There is evidence suggesting that ALA, EPA and DHA have specific and potentially independent effects on chronic disease. Therefore, this review will assess our current understanding of the differential effects of ALA, EPA and DHA on cancer, insulin resistance, and cardiovascular disease. Potential mechanisms of action will also be reviewed. Overall, a better understanding of the individual role for ALA, EPA and DHA is needed in order to make appropriate dietary recommendations regarding n-3 polyunsaturated fatty acid consumption.

There is growing evidence that early developmental periods may importantly influence future breast cancer risk. Also, there is great interest in the role of dietary fat in breast cancer risk, but the role of dietary fat during pubertal mammary gland development remains poorly understood. This study investigated the effect of n-3 polyunsaturated fatty acids (PUFA) using complementary dietary and genetic approaches to examine the effect of lifelong exposure of n-3 PUFA or n-6 PUFA (control) on mammary gland development and fatty acid composition. n-3 PUFA from both diet and genetics were enriched in mammary glands as early as 3 weeks of age. Parameters related to mammary gland development, including number of terminal end buds (TEB), percent coverage of ductal tree, and infiltration of TEB, were influenced by n-3 PUFA at 3 and 4 weeks of age. Overall, findings suggest that n-3 PUFA incorporation into the mammary gland early in life plays a role in the morphological development of the mammary gland during puberty.

A growing body of research suggests a linkage between pubertal mammary gland development and environmental factors such as diet as modifiers of long term breast cancer risk. Much of this research is dependent upon mouse models, which may vary between studies. However, effects may be strain dependent and further modified by diet, which has not been previously examined. Therefore, the objective of the present study was to determine whether mammary gland development differs between FVB and C57Bl/6 strains on diets containing either n-6 or n-3 polyunsaturated fats. Developmental measures related to onset of puberty and mammary gland development differed between strains. Mice fed the n-3 polyunsaturated fatty acids (PUFA) diet were shown to have lower numbers of terminal end buds, a marker of mammary gland development. This study helps to further clarify differences in development and dietary response between FVB and C57Bl/6 mice in order to more appropriately relate mammary gland research to human populations.

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