Some prominent experts say there’s no reason to worry about getting too much omega-6 in your diet. But Nutrition Diva finds far too much evidence to ignore.
Then again, you might also recall a podcast I did a couple years ago on how to find reliable sources of nutrition information in which I stated that:
“A good scientist is eager to abandon any position that’s been proven false, no matter how strongly he might have held or argued that position previously.”
So, in the interests of trying to live up to my own standards, I decided to review the evidence on this question and decide whether I needed to revise my position.
Plenty of Data to Support the Importance Omega Ratio
Although you’d never have guessed it based on Dr. Willett’s dismissive statement, it turns out that there have been dozens of studies in the last few years aimed specifically at determining whether the ratio of omega-3 to omega-6 matters—everything from studies that looked at cells in petri dishes, to studies involving lab rats, to controlled studies involving humans as well as meta-analyses of large dietary intake datasets.
To be sure, many of these studies found no relationship between the omega ratio of the diet and various health outcomes. For example, it turns out the ratio of omega-6 and omega-3 in a mother’s diet does not change the amount or distribution of fat in her baby. Good to know.
On the other hand, there was evidence that women who had a high ratio of omega-6 to omega-3 in their diets were more likely to suffer from post-partum depression. A high omega-6 to omega-3 ratio was also associated increased risk of breast cancer in premenopausal women and—in a different study—with increased inflammation and fatigue in cancer survivors. Higher intake of omega-6 relative to omega-3 was also linked to an increased risk of macular degeneration, which is the leading cause of blindness in those over 55. The “high ratio” in most of these studies, by the way, is the ratio typical of the standard American diet.
With all these human studies, it seems like overkill to mention the study which found that a high intake of omega-6 promoted obesity in lab rats, an effect that was prevented when the ratio was adjusted by adding omega-3s to the mix. I also found a study linking a high ratio of omega-6 to increased inflammation in humans as well as a detailed analysis of multiple dietary intervention trials by scientists at the National Institutes of Health. The authors of that analysis—prominent scientists in their own right—concluded that advising people to replace saturated fats with PUFAs without regard to the ratio of omega-6 to omega-3 “may actually increase the risks of CHD and death.”