Omega-3s in the blood may boost risk of aggressive prostate cancer
eurekalert.org
eurekalert.org
Correlation isn't causation. There are literally a billion possible factors that could be responsible besides a direct relationship. Of course, the same applies to any research demonstrating the efficacy of Omega-3s, too.
This is the problem with a lot of nutrition studies: a huge number of completely false associations were and still are being invented because of an inability to control for important factors. For example, the "fiber theory" of health has turned out to be almost completely false: it appeared to be "healthy" because eating fiber meant eating fewer (digested) carbohydrates. The fiber itself did almost nothing for health.
It gets worse when massive chains of correlations are assumed to be causes. A is correlated with B, B is correlated with C, C is correlated with D, therefore A causes D. The whole mess of saturated fats, cholesterol levels, heart attacks, and heart disease is a case of this.
I guess that a paper won't get accepted in Am. J. Epidemiol without proper consideration of such correlation.
The studies generally try to control for homophilly, contagion and confounding etc.
As a reader of Mark's Daily Apple and a follower of a Paleo diet, this study surprised me. Yes, the study can be argued against, but I have a more fundamental issue: "optimizing" your diet may be impossible. The needs of the human body and the composition of nutrients/macro-nutrients in food are both wildly varying and neither was "designed", so it's possible that strategies which keep you in great health in young/middle-age will produce ill-health later on. There's little evolutionary pressure exerted by grandparents on grandkids and prostate cancer is usually a very slow growing, late stage disease, so it shouldn't be inconceivable that a young/middle-age favoring diet harms late-stagers.
That said, prostate cancer (which my father had) has a very high survival rate, so I'd happily trade a litany of conditions potentially caused by a "non-good" diet for prostate cancer caused by a "good" diet.
There is a lot of scholarly literature on the general issue,
http://scholar.google.com/scholar?q=docosahexaenoic+acid+pro...
and it will be interesting to see how the trade-offs are resolved.
http://high-fat-nutrition.blogspot.com/2011/04/prostate-canc...
"To top that off, this study derails the otherwise consistent train of research showing that DHA seems protective at best (and neutral at worst) when it comes to prostate health. In 2001, a study of over 6,000 Swedish men found that the folks eating the most fish had drastically lower rates of prostate cancer than those eating the least. Another study from New Zealand found that men with the highest DHA markers slashed their prostate cancer risk by 38% compared to the men with the lowest DHA levels. And yet another study tracking Japanese men in Japan and Brazil found that omega-3 levels in the blood were consistently linked with a reduction in prostate cancer."
(I'll keep taking my fish oil supplements until I hear something much more concrete)