This may be sound statistics--although I doubt it--but after reading stuff like this, it's no wonder the lay public gets confused and frustrated. There is a metric ton of studies indicating that omega-3 fatty acids have considerable health benefits. (A brief summary of some of the literature is here.)

But because one study, of a special population, failed to find benefits--for reasons not understood--cranking up the meta-analysis machinery yields the conclusion that there is "no evidence of a clear benefit to health".

When I get some time, I think I'll do a meta-analysis of gravity. Maybe after factoring in studies of self-levitating gurus, it'll turn out that there's "no evidence of a clear gravitational effect".

Comments

[pj]

It's not quite so simple ... the trouble is that the body is chemically complex and fatty acids that are healthy in their natural state can be converted into unhealthy forms ... the omega-3 fats appear to be healthy in moderate quantities, but they are prone to oxidation and hydrogenation, and polyunsaturated fats that have been hydrogenated or oxidized are among the unhealthiest fats known. The reactions that hydrogenate or oxidize polyunsaturated fats have rates that increase strongly with temperature. In nature, animals and plants that are typically cold, such as ocean fish, usually rely on polyunsaturated fats, while warm-blooded animals and tropical plants generally rely on saturated fats for their lipid biology. Presumably, this is to avoid long-term consequences of damage from hydrogenated or oxidized polyunsaturated fats.

So while there's little doubt that moderate intake of polyunsaturated fats can have short-term health benefits, the consequences of long-term or excessive intake may be deleterious due to such processes as lipid peroxidation and increased oxygen stress -- or even a buildup of unhealthy saturated and trans fats created by the hydrogenation or oxidation of polyunsaturated fats.

The British study you cite is extraordinarily large, 3,114, and found that polyunsaturated fats increased the risk of heart attack. Most studies include no more than a few hundred patients. In a meta-analysis the negative results of the large study could easily counterbalance thirty small studies showing positive results. Also, the British study is by no means the only one showing negative effects from intake of polyunsaturated fats.

I would have to agree with the Brits that the optimal dietary intake of omega-3 fatty acids is far from clear. Intake of omega-3 fatty acids could be beneficial in small quantities and harmful in large, or beneficial in the short-term and harmful in the long-term, or beneficial when consumed along with lipid-soluble antioxidants but harmful without such antioxidants, or beneficial if in optimal ratio with other fats such as omega-6 fatty acids but harmful in excess of an optimal ratio.

Supplementation of omega-3 fatty acids is almost certainly a bad idea, as fresh fish should provide less-oxidized fatty acids along with companion antioxidants. Even eating fresh fish, it is likely that consumption of such fish parts as the brain, liver, and thyroid, which are rich in lipid-soluble antioxidants, along with the oil-rich meat would have health benefits.

[Jake]

On the other hand, both a dietitian and my doctor told me to take Omega-3 capsules.