Omega-6 fats for the prevention and treatment of cardiovascular diseases

Review question

We considered randomized trials (participants had an equal chance to receive any intervention), which studied the effect of increased omega-6 fat intake on mortality and cardiovascular diseases (CVD), including. heart attacks and strokes.

Relevance

Omega-6 fats are needed by the body, we get them from food. They are important for the formation of energy (metabolism), healthy bones, skin and hair. Many foods, especially vegetable oils and nuts, contain omega-6 fats. Omega-6 fats include linoleic acid (LK), gamma-linolenic acid (GLA), dihomo-gamma-linolenic acid (DGLA) and arachidonic acid (AK).

Some evidence suggests that increased intake of omega-6 fats with reduced consumption of saturated fats (animal, meat and cheese) can reduce the incidence of coronary heart disease. In contrast, there are concerns that high levels of omega-6 fats may worsen the cardiovascular risk by increasing inflammation. In general, there is no convincing evidence of the benefits or harm of omega-6 fats in cardiovascular diseases or other conditions.

Characteristics of research

The evidence in this review is relevant for May 2017. We found 19 studies involving 6461 adults. In these studies, the effects of high omega-6 fat intake on cardiovascular diseases and mortality were evaluated. We found that the three trials were highly trustworthy (they had a good design, and, therefore, reliable evidence). Studies were conducted in North America, Asia, Europe and Australia. Eight of them were funded only by national or charity agencies. Participants consumed more omega-6 fats or maintained a normal level from 1 to 8 years.

Main results

We have found that increased intake of omega-6 fats may slightly affect mortality or cardiovascular events or not affect them, as well as reduce the risk of heart attacks (evidence of poor quality). Evidence was weakened by design research problems, a small number of events, a low number of participants from developing countries and women.

Evidence suggests that increased intake of omega-6 fats lowers blood cholesterol levels (high-quality evidence), does little or no effect on body weight, taking into account growth (evidence of moderate quality), and only slightly or not at all affects high-density triglyceride levels (HDL, "good" cholesterol) and low-density lipoprotein (LDL, "bad" cholesterol, evidence of poor quality).