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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.

http://perfecthealthdiet.com/?p=3287

http://perfecthealthdiet.com/?p=55

Reference: http://www.sciencedaily.com/releases/2011/04/110425135643.htm

http://www.ncbi.nlm.nih.gov/pubmed/12571649?dopt=AbstractPlus

(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.

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3 Answers

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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:

http://www.ifosprogram.com/ifos/ConsumerReport.aspx

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Could you post a reference to the claim that sardines canned in spring water are more oxidized than ones canned in olive oil. I was under the impression that the ones in spring water were safer because the ones canned in olive oil could potentially have oxidized olive oil. – ROB Apr 29 2011 at 3:15
ROB- luckily, it's not a claim. I nabbed the finding from a paper on pubmed, and will try to find it again in two shakes. – Kamal♦ Apr 29 2011 at 3:51
Here you go...pubs.acs.org/doi/abs/10.1021/jf970587%2B – Kamal♦ Apr 29 2011 at 3:53
Thanks Kamal. Guess I'll buy them in olive oil now. – ROB Apr 29 2011 at 14:08
I actually was not swayed enough to switch to the olive oil ones, since that adds a considerable amount of omega-6. But overall, who knows which is better? – Kamal♦ Apr 29 2011 at 14:17
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Oxidized fish oil is bad. Saying you should not take fish oil is more crazy

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Dr. K, I do not take fish oils or supplements of any kind. I do eat salmon once a week (2 days in a row w/leftovers) and the occasional can of sardines in evo. Not to hog the original posters question but, why should I supplement? – L. Peltier Apr 29 2011 at 2:33
If you eat a lot of fish have insulin levels below 3 a HbA1c below 4.7 I think you're ok on you're own. Only groups of people who routinely fit that profile are old school inuits and okinoweans. You also want your TG below 40 and US-CRP as close to zero as possible. I eat extremely clean like you and I still take nine grams a day as supplement The reason? I want my biomarkers optimal because even with my diet I can't keep my omega 6/3 index at one to one – The Quilt Apr 29 2011 at 12:31
Dr. K- do you take nine grams of fish oil in addition to eating fish on a regular/semiregular basis? I'm wondering if that would put you at under one to one. – Kamal♦ Apr 29 2011 at 13:12
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Denise Minger just weighed in on this one as a guest blog on Mark's Daily Apple:

http://www.marksdailyapple.com/fish-oil-prostate-cancer/

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.

Hmmmm.

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