Paul Jaminet recently discussed the link between high DHA and cancer, which complements his earlier post on the risks of fish oil pills versus eating fish.
(There are similar posts, but none that I found which directly address these specific issues; sorry in advance if I missed them.)
What does everyone think: are fish oil pills safe and effective sources of n-3? They might oxidize too easily. And they might make high doses too easy to consume.
Regarding the former concern, the common approach is to crack a pill open and smell it to see if it has turned rancid. As an aside, I wonder if the cardiac issues are caused by rancid pills that could be screened in this manner, or if their toxicity manifests in a manner that is harder to detect and preempt.
I think that there are too many confounders to make a comprehensive statement. My workplace was actually hired seven years ago by the federal government to do the systematic review on omega-3 and health outcomes. Unfortunately, I wasn't here back then, but there are some important things I gathered:
1) Study results conflict for several legitimate reasons. For example, baseline omega-3 intakes differed depending on geography.
2) Subgroups were not adequately analyzed. In other words, subgroups were analyzed but were not large enough to attain the power to detect a potential difference between groups.
3) There is **ABSOLUTELY NO ATTENTION PAID TO OXIDATION** in most studies.
4) There is little attention paid to the balance of other fatty acids, which can be antagonistic or synergistic with omega 3.
Point number 3 is critical. Old fish oil is much worse than new fish oil. Light/air/heat have effects. Sardines canned in water are more oxidzed than sardines canned in olive oil, because of something to do with the aqueous/lipid barrier.
If you take fish oil, it might be good to take a look at where your fish oil brand rates with regards to oxidative products. Here is the most comprehensive database I've run into:
Denise Minger just weighed in on this one as a guest blog on Mark's Daily Apple:
While she concedes that fish oil supplementation isn't necessarily a health Mecca...
A bad diet plus fish oil is still a bad diet. And given the oxidation-prone nature of all polyunsaturated fats, a massive intake of omega-3’s – despite their brilliance in moderation – could potentially do more harm than good.
...she concludes that the study itself is flawed, however, because of confounding variables like the fact that low-fat diets also boost serum DHA levels independent of DHA consumption.
Check out this intervention study from 2001, which measured changes is serum fatty acids after feeding folks either a low fat (20% of calories) or high fat (45% of calories) diet. Although the low-fat dieters didn’t get any special omega-3 boost, the levels in their blood rose disproportionately by the end of the trial. The study concluded that “Consumption of a low fat diet alters fatty acid patterns in a manner similar to that observed with feeding of (n-3) long-chain fatty acids.” In other words, fat restriction caused blood levels of omega-3 fats to resemble that of seafood lovers.
Do you still take Fish Oil? 12 Answers