One of the most significant dietary changes we have seen in the modern-day diet is an increase in our consumption of omega-6 fats, known as linoleic acid, which are found in many vegetable oils including corn, safflower, and sunflower oil. Within the body, such fats tend to encourage inflammation, constrict blood vessels, and make the blood more likely to clot.
Omega-3 fats, on the other hand, tend to have quite the opposite effects. For optimal health, we require a balance of these two types of fat in the body.
The problem is, the rise in omega-6 intake in recent times, coupled with a general decline in omega-3 consumption, may well be causing physiological and biochemical disharmony that might be contributing to a range of disease processes including heart disease and stroke [1], Type 2 diabetes [2] and autoimmune diseases (conditions where the body's immune system reacts against its own tissues) such as rheumatoid arthritis [3].
The most recent study to explore the biological significance of a high omega-6:omega-3 ratio was published online in the journal Psychosomatic Medicine [4]. In this study, higher omega-6:omega-3 ratios were found to be associated with an increased risk of depression, and the higher the ratio, the greater the depressive symptoms tended to be. This research suggests that getting the balance between omega-6 and omega-3 in the diet may be important not just for the physical health, but mental health too.
Omega-6 fats are found most plentifully in refined vegetables oils (e.g. cooking oil), but can also be found in foods such as margarine, baked good, and snack foods. Eating less of such foods will help to prevent any surfeit of omega-6 fat in the body and brain.
Another approach, of course, is to increase intake of omega-3 fats via foods such as oily fish and walnuts and/or omega-3 containing supplements. Fish oil, cod liver oil, and flaxseed oil are all appropriate choices in this respect.
References:
1. Weber PC. Are we what we eat? Fatty acids in nutrition and in cell membranes: cell functions and disorders induced by dietary conditions. In: Fish fats and your health. Norway: Svanoy Foundation, 1989:9-18
2. Raheja BS, et al. Significance of the n-6/n-3 ratio for insulin action in diabetes. Ann N Y Acad Sci 1993; 683:258-71
3. Simopoulos AP. The importance of the ratio of omega-6:omega-3 essential fatty acids Biomed Pharmacother. 2002 56(8): 365-79
4. Kiecolt-Glaser JK, et al. Depressive Symptoms, omega-6:omega-3 Fatty Acids, and Inflammation in Older Adults. Psychosomatic Medicine 30th March 2007 [epub before print publication]
Dr John Briffa is a London-based doctor, author, and health writer with an interest in nutrition and natural medicine.
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