Omega-3 fatty acids and psychological health

Now that omega-3 levels can be readily measured, can fish oil be used to treat various conditions with greater success?


There’s no question that omega-3 fatty acid intake and higher omega-3 fatty acid blood levels reduce cardiovascular risk.

But can higher levels blood levels of omega-3 also make us happier? Are higher blood levels of omega-3 fatty acids associated with less depression, reduced psychological distress . . . greater happiness?

Evidence is mounting that higher intakes and higher blood levels of omega-3s are indeed associated with psychological health. Greater omega-3 intake and/or blood levels have been associated with less depression, less attention-deficit hyperactivity disorder, less suicidal behavior, less depression in bipolar illness (Su 2009).

There’s a recent addition to the conversation, a study of northern Quebec Inuits, a population previously famous for their extravagant omega-3 dietary intake.

Traditionally, Inuits consume large quantities of omega-3-rich seal, fish, caribou, and whale, consuming the entire carcass - meat and fat. However, like the rest of the world, modern Inuits have increased consumption of store-bought processed foods. More heart disease, diabetes, and depression have resulted.

A group from Laval University, Quebec, and University of Guelph, Ontario, examined the relationship between plasma EPA + DHA levels and measures of psychological distress in Quebec Inuits. This research group had previously shown that Inuits older than 50 years had twice the plasma omega-3 levels (11.5%) compared to those younger than 50 years (6.5%), reflecting the shift away from the traditional diet.

Psychological distress was measured with The Psychological Distress Index Santé-Québec Survey (PDISQS-14): the higher the score, the greater the psychological distress.

"Our main finding was that women in the second and third tertiles [thirds] of EPA+DHA concentrations in plasma PLs [phospholipids] had a 3 times lower risk of having a high-level PD [psychological distress] score than women in the lowest tertile."

The striking relationship was strongest for women, with higher EPA + DHA plasma levels associated with reduced likelihood of psychological distress. Interestingly, the tertile with the greatest distress and lowest EPA + DHA levels had a plasma level of 7.0-7.5%.

Other studies have suggested a similar relationship outside of Inuits. In the Heart and Soul Study of 987 San Francisco residents with coronary heart disease, the prevalence of depression ranged from 23% in participants in the lowest third of omega-3 RBC levels (< 3.1% of total fatty acids) to 13% in participants in the highest third (>14.3% of total fatty acids).

How do omega-3 leevls in average Americans compare? A study comparing Japanese men to Caucasian Americans showed that Japanese men had a mean plasma omega-3 level of 11.8%, while Caucasian Americans had 2.5%, reflecting the substantially different intake of fish (Iso 1989).

Does omega-3 supplementation actually reduce depression? The results have been mixed. A recent (Su 2008) small study in Chinese women suffering major depression during pregnancy showed a positive mood response over 8 weeks by supplementing 3400 mg EPA + DHA per day. A series of Israeli studies from Ben Gurion University have shown positive effects of EPA (only) supplementation in adults (2000 mg per day; Nemets 2002) and children (EPA 380 mg, DHA 180 mg per day; Nemets 2006). While several other studies have not shown any effect, an analysis of 10 studies of pooled data suggest that there are, for many, measurable effects on mood (Lin 2007).


Perhaps part of the uncertainty surrounding omega-3 supplementation is that, in many of the studies, omega-3 blood levels were not verified, nor was success or failure in treatment correlated with total omega-3 blood levels nor levels of the individual fatty acids, EPA vs. DHA.

The developing experience with omega-3 fatty acid supplementation, however, suggests that, not only will you be healthier, but probably happier, too. Now, if we could just adjust mood by omega-3 blood level . . .
 

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