Your brain on fish oil — good thing?

Study results publicized last week suggest that fish oil supplements have a positive affect on mental cognition and brain size in older people.  While I think it’s exciting stuff, there are a few qualifications that need to be considered before we all jump to the conclusion that any old fish oil supplement will prevent Alzheimer’s Disease or any other form of dementia or cognitive decline with age.

The 5 year study looked at cognitive function in over 800 subjects, of which 117 reported using fish oil supplements.  The researchers did not investigate what brand or dose they were taking.  Every 6 months, subjects were tested for measures of cognitive function, as well as brain MRIs.  One other key factors that was not measured: diet.

The diet choices of those 800+ people could complicate results.  One likely scenario is that people who decide to take fish oil supplements are especially health conscious, and eat healthier diets than non-fish-oil subjects.  They might take other supplements that could help with brain function, and might also be more conscientious about exercise, known to help with health in general.  They might also eat more fish, like salmon.  Some percent of the non-fish oil subjects might eat particularly unbalanced diets, perhaps for many years.  That could leave them more susceptible to ill effects on brain function, regardless of fish oil.  So fish oil supplement use might just be a sign of healthy lifestyle.

Nevertheless, it’s interesting to note that the fish oil supplement users who started the study with no signs of dementia had better cognitive function and maintained larger brain volume throughout the 5 year period.  This suggests that at least one of the beneficial effects of fish oil might be maintenance of brain volume.  A study that provided subjects with specific doses of fish oil or placebo, perhaps varying the amounts of EPA and DHA, would help clarify exactly what is going on.  Then blood levels of omega-3 fats can be compared to dose of supplement and to results of cognitive function tests, to better understand what amount of omega-3 provides the most benefit.

This study is good news, but it’s not proof that fish oil/omega-3 supplements will prevent Alzheimer’s Disease or dementia.  The study that proves that hasn’t been done.

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