In humans, just two “essential fatty acids” are not produced by the body and must come from external sources such as diet or supplements. One, linoleic acid (LA), is an omega-6 fatty acid, while the other, alpha-linolenic acid (ALA), is an omega-3 fatty acid. Omega-3 fats generally come from fatty fish as well as chia and flax seeds and walnuts. Omega-6 fatty acids typically come from vegetable oils, sunflower seeds, walnuts, and pumpkin seeds. Both are also available in supplement forms.
The value of omega-3 fats, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), has been well established in reducing the risk of heart disease and may also be associated with reduced risk of breast cancer, improved cognitive function, and lower dementia risk. These fats appear to reduce inflammation, reduce the risk of blood clots, and lower triglyceride levels, according to Harvard Medical School.
The role of omega-6 fatty acids, however, has been a topic of continuing controversy. On the plus side, the omega-6 fats appear to help keep good and bad cholesterol in a favorable balance. The conversion of LA into arachidonic acid raised concerns. Arachidonic acid provides the foundation for molecules that increase inflammation, vasoconstriction, and blood clots—as well as those that fight inflammation and blood clots.
A meta-analysis of 30 studies from 13 countries recently published in Circulation could be the final word on omega-6 fatty acids and cardiovascular disease. The pooled global analysis included 15,198 cardiovascular events in 68,659 participants. Follow-up ranged from 2.5 to 31.9 years.
The researchers found higher levels of LA were associated with a 7% lower risk of total cardiovascular disease, 22% reduction in risk of cardiovascular mortality, and 12% reduction in risk of ischemic stroke. Higher arachidonic acid levels did not increase risk of cardiovascular events and, at the top quintile, reduced risk of cardiovascular disease. The authors concluded, “These results support a favorable role for LA in CVD prevention.”
Several studies have examined whether the ratio of omega-6 to omega-3 affects overall health or whether just having more of these essential fatty acids would be helpful. The European Food Safety Authority has taken the latter position, concluding that “simply increasing the amount of ALA, EPA and DHA in the diet would achieve the desired increase in levels of these fatty acids in the body’s tissues.”
The National Academy of Medicine established the adequate intake level of omega-3s as 1.6 g per day for men and 1.1 g per day for women, except for those who are pregnant or nursing who should have 1.4 g and 1.3 g per day, respectively.
For omega-6 fatty acids, the adequate intake levels peak at 17 g per day for men between the ages of 19 and 50 years and drop to 14 g per day at age 51 years. Pregnant and breastfeeding women should consume 13 g per day, while women aged 19 to 50 years should have 12 g and those over age 51 years should have 11 g per day.
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