The paper, published in the journal Biology Letters, showed an, “experimental reduction in the level of omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) in the diet of guppies (Poecilia reticulata) depresses a male's share of paternity when sperm compete for fertilisation, confirming that the currently observed trend for reduced n-3 LC-PUFA in western diets has important implications for individual reproductive fitness”.
Jon Evans, one of the sexual selection researchers behind the paper, told NutraIngredients the paper was the first to link omega-3 to male reproductive success in the context of sexual selection, and one of only a handful of studies to show a direct fertility effect.
The scientists from the University of Western Australia randomly fed the 60 guppies, aged three months at the start of the trials, diets with similar levels of saturated fatty acids and identical quantities of base ingredients, but differing added lipid content. Half the fish were fed omega-3 enriched feed (12.9% content) while the others were fed a reduced diet (1.8% content) once daily six days a week for a period of three months.
Results revealed an average of 7.92 offspring per fish ‘family’, with the reduced omega-3 males siring significantly less offspring that their enriched rivals. Each group consisted of two rival males on different diets and three females. Body size was also tracked, but did not differ significantly.
Building fertility research
Evans said evidence that omega-3s influence reproduction was “actually somewhat limited”, with most studies linking the dietary intake of these essential fatty acids to traits linked – or thought to be linked – to fertility.
“As far as we are aware, only one other study has linked diet quality to ejaculate performance in sperm competition, and that was a study showing interactive effects of carotenoid and vitamin E on sperm competitiveness in insects.”
He said the question of what implications such findings had for humans was more complex, with links being clearly speculative given the differences in reproductive norms.
“Yes we know about health benefits of food that are rich in omega-3s [e.g. oily fish], but as far as I am aware there is limited evidence linking these essential fatty acids to fertility traits, and of course we can only speculate [for humans] on the role of omega-3s in influencing the competitiveness of sperm when they compete for fertilisations i.e. when ejaculates from two or more men compete directly for fertilisation of a woman's ova.”