Evidence is growing that the risks associated with taking fish oil (or eating seafood, which is becoming increasingly more contaminated) may be greater than the benefits. The study in this post found that fish oil increased lung tumors and shortened lifespan in mice. There have also been a number of studies linking fish oil to prostate cancer.
What’s an alternative? Just eat less fat. That’s what this next study found. It was small, 10 people, but it was well controlled. It compared the effect of a low-fat diet (20% energy) to a high-fat diet (45% energy) on type of fats in the blood. The diets had the same calories and the same proportions of fatty acids (1:1:1 for poly:mono:sat).
Total Fat Intake Modifies Plasma Fatty Acid Composition in Humans, The Journal of Nutrition, February 2001
It was a crossover design, so participants ate one diet for a month, then their usual diet for a month as a wash-out, then the other diet for a month.
When they ate the low-fat diet, they had higher levels of omega-3 (n-3) fatty acids and lower levels of omega-6 fatty acids in their blood compared to the high-fat diet:
The low fat diet was associated with significantly greater total (n-3) fatty acids, 20:5(n-3) and 22:6(n-3) levels in plasma phospholipid fatty acids and cholesteryl esters.
Eicosapentaenoic acid or EPA is 20:5(n-3) and docosahexaenoic acid or DHA is 22:6(n-3).
The consumption of a low fat diet promotes an increase in the level of total and highly unsaturated long-chain (n-3) fatty acids (>C20) and a decrease in the total (n-6) content of plasma phospholipid and cholesteryl ester fatty acids. The observed modifications in phospholipid and cholesteryl ester fatty acids in response to a low fat diet are similar to those observed when (n-3) fatty acids of plant or animal origin are fed. This may explain some of the beneficial effects of low fat diets.
To repeat that next to the last sentence:
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.
So, eating a low-fat diet (20% of calories in this study) increased omega-3s in the blood similar to taking fish oil or other omega-3 fatty acid-rich food.
How can you end up with higher amounts of omega-3s, especially the longer chain EPA and DHA, if you’re not actually eating them?
This change is likely related to decreased competition for the enzymes of elongation and desaturation, with reduced total intake of 18:2(n-6) favoring elongation and desaturation of available (n-3) fatty acids.”
In a low-fat diet, there’s less omega-6 floating around to fill the slot on these enzymes, giving more omega-3s the chance to be converted to EPA and DHA.
This isn’t a new study. It’s not new knowledge – that n-6 and n-3 compete for enzymes and that the less omega-6 you take in the more long chain omega-3 you’ll make. But omega-3s are being marketed so aggresively that knowledge of this benefit (of a low-fat diet) is getting muffled and even forgotten.
If you want more EPA and DHA, eat a low fat diet.