|Yes, this study is about omega-3s, but it is not about the beneficial effects of fish oil.|
Kicking out another couple of grams of omega-6 fatty acids, on the other hand, had pretty intriguing effects on the body composition of the ninety-six male cross-bred (Large White£
Landrace) pigs who happened to weigh about as much as an average human being (another advangate, of swine - HED calculations are not necessary; learn more).
Did you know that pigs are opportunistic omnivores just like us and provide a better model of human metabolism than our little, furry remote cousins with the big round eyes and the long tails who are populating the laboratory cages of scientists all around the world (cf. Miller. 1987)?Lineseed or soybean - that makes all the difference
I hope you did not already start popping fish oil, while you are reading this. After all, in this case the glorified residual waste from the fishery industry did not contribute to either the health or weight loss benefits Duan et al. observed in their pigs who were fed one of the four isoenergetic diets with n6:n-3 PUFA ratios of 1:1, 2·5:1, 5:1 and 10:1 for 2 months.
|Table 1: Ingredients, nutrient and fatty acids composition of the diets the pigs received; † vitamin premix (Duan. 2013)|
So, no fish oil, just ALA
Although the allegedly more potent LC-PUFAs were missing, the changes in body composition and the overall improvement (=reduction) of the activity of the potentially pro-carcinogenic PI3K-alpha gene and the fat storage genes FATP-1 and PPAR-gamma (learn more about PPAR-gamma) were still impressive.
If you take a closer look at the data in figure 1, though, you will realize that the effects on body composition require a reduction to 2.5:1, better 1:1 to become significant.
|Figure 1: Feed conversion rate, muscle mass, adipose tissue mass, lean to fat mass ratio expressed relative to the levels of the pigs in the 5:1 n6:n3 group after 2 months on the different diets (Duan. 2013)|
Ah, I'd better not get political here, but let me point out one thing: In view of the currently available scientific evidence it borders physical injury resulting from negligence that the "guidelines" do not put an emphasis on the reduction of the the crazily high n-6:n-3 ratio of the Standard American Diet (16-17:1).
|Unlike this pig study, a previous rodent study suggests you should pick EPA over DHA over ALA for weight loss purposes (learn more)|
One thing we must not forget, though, is the fact that the beneficial changes in health and body composition were brought about by the concomittant reduction in omega-6 and increase in omega-3 fatty acids. Simply drinking a bottle of lineseed or cod liver oil everyday could thus do more harm than good, because with ~3g of oil per 100g the diet was also low in total fat and almost devoid of saturated fats and whether the same results would occur in a high fat scenario is beyond what the study at hand can tell us.
- Duan Y, Li F, Li L, Fan J, Sun X, Yin Y. n-6:n-3 PUFA ratio is involved in regulating lipid metabolism and inflammation in pigs. Br J Nutr. 2013 Aug 15:1-7. [Epub ahead of print]
- Miller ER, Ullrey DE. The pig as a model for human nutrition. Annu Rev Nutr. 1987;7:361-82. Review.