Are Omega-3 fatty acids from supplements absorbed and useful? How about nuts?

My sister is going through nutrition class, and was informed that fish oil supplements are useless. In the same conversation, nuts were also said to be unabsorbed by the body. Understandable concerned, she asked me what I thought.

The first question is whether fish oil supplements are absorbed by the body. But this question is perhaps secondary to the idea that fish oil supplements are useless. Intravenous fatty acid supplementation shortens hospital stays, prolongs life, and helps patients heal. (study here) So the real question is whether we have definitive evidence that fish oil supplements do something when taken.

As there are many fish oil studies with variable results, clinicians rely on professional statisticians to compile the studies and give us a summary.

  • For cardiovascular disease, there were few direct studies and they did not show a significant effect (study here).
  • But studies judging platelet aggregation showed that fish oil significantly helped sick patients (no change for health patients)(study here).
  • Patients with chronic heart failure had significantly improved heart function after taking fish oil supplements (study here)
  • Patients with rheumatoid arthritis had significantly less pain (less use of pain medication) on fish oil supplementation. (study here)

So can we conclude that the statement “fish oil supplements are useless” is false? I think that hundreds of studies show that fish oil may benefit some patients some of the time. To claim fish oil is good for everyone is equally false, and it is likely that the instructor was using hyperbole to make the point that healthy students would be better served to eat fish over a lifetime. I would have to agree.

The quality of fish oil supplements varies widely. A study of different supplements on the market found that over 70% of the supplements on the market did not contain the claimed amount of fish oil. So consumers working on their own have a less than one in three chance of getting a decent supplement. (study here)

As to nuts not absorbing and being useless, I’m afraid that’s just wrong. Diets high in nuts have been shown to help control weight compared to control diets. “Compared with control diets, diets enriched with nuts did not increase body weight, body mass index, or waist circumference.” (study here) In type 2 diabetics: “Pooled analyses show that tree nuts improve glycemic control in individuals with type 2 diabetes” (study here) In metabolic syndrome: “modest decreases in triglycerides and fasting blood glucose with no adverse effects” (study here) But is this simply because the nuts are wonderful fiber? No. Necessary compounds are absorbed from nuts. In this study of dialysis patients, their bodies absorbed selenium until they were no longer deficient, then allowed levels to drop over time. (study here)

My sense is that as I have learned more about nutrition the less and less likely I am to make absolute statements about what should and shouldn’t be eaten. Given our genetic polymorphisms and varied detoxification speeds, it is likely that each of us needs to individualize our dietary intake. While that may see like nutritional relativism, it is not. Very few nutritionally educated individuals will argue that eating what comes through your car window is preferable to anything that can be purchased in the periphery of your grocery store. It is that dichotomy, fast food vs. real food, that becomes the nutritional common ground. Let us focus on that, rather than picking apart where on the periphery one purchases one’s meals.


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