RETHINKING THE OMEGA-6 TO OMEGA-3 RATIO: BALANCE VS. ADEQUACY

By Mark Messina, PhD, MS

Research published beginning in the early 1990s led to a consensus within the field of nutrition that the dietary ratio of omega-6 to omega-3 polyunsaturated fatty acids (PUFAs) was a measure of diet quality. The essential PUFAs linoleic acid (LA) and alpha-linolenic acid (ALA) are the primary dietary omega-6 and omega-3 PUFAs. It was hypothesized that a high LA to ALA ratio induces a pro-inflammatory state through LA’s conversion to arachidonic acid and subsequent eicosanoid production. However, a large amount of clinical and observational research suggests there are several reasons to doubt how useful the omega-6 to omega-3 ratio really is. 

Not only does LA intake have little to no bearing on blood or tissue levels of arachidonic acid,¹ but some of the eicosanoid mediators produced from this fatty acid are anti-inflammatory.² LA intake may still affect the conversion of ALA into the long-chain omega-3 PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are linked to various health benefits. Since LA and ALA share a single set of enzymes for elongation, they compete for access. However, while increasing ALA intake does increase circulating and tissue levels of EPA,^3-10 there is little increase in DHA levels because the endogenous conversion of EPA into DHA is so minimal.¹¹ For example, one study found that decreasing the LA content of the diet from 7.4% of energy, which approximates current U.S. intake, to 2.4% of energy (which is barely sufficient to avoid deficiency of this fatty acid) led to a 33% increase in EPA but only a 9% increase in DHA.¹² Since both longer chain omega-3 fatty acids are beneficial, the small increase in DHA would hardly justify such a dramatic dietary change, even if such a change were feasible. Furthermore, higher LA intake is associated with a range of health benefits, including lowering circulating cholesterol levels and risk of coronary artery disease.¹³

Practical Guidance for Patients and Clients

Since both omega-6 and omega-3 fatty acids offer health benefits, the focus should be on consuming adequate amounts of each. In the U.S., omega-6 fatty acid intake is optimal with nutritional recommendations, but omega-3 fatty acid is lacking. Omega-3 fatty acids are found in certain types of fish such as salmon and mackerel and supplements derived from these fish. For vegetarians, omega-3 fatty acid supplements derived from algae are available.

REFERENCES

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