Diet and fertility: Omega 3s are the best fats for women

Omega 3s are increasingly emerging as valuable allies of female fertility. The findings of a recent study, published in The American Journal of Clinical Nutrition, shine a spotlight on their positive impact on fecundability, highlighting the importance of acting on the Omega 6/Omega 3 ratio to increase the likelihood of conceiving within a single month of trying.

Infertility and subfertility – the inability to conceive after 12 months of regular unprotected intercourse – are a challenge for millions of couples worldwide. Fortunately, medical treatments are available, but they are often demanding both psychophysically and financially; moreover, their success is not always guaranteed.

This is why research into lifestyle changes that can promote fertility is in constant ferment. Nutrition is undoubtedly one of the areas where researchers are most active, and among the nutrients most studied for their potential impact on reproductive health are polyunsaturated fats (PUFAs, PolyUnsaturated Fatty Acids).

Within this category, however, not all fats are the same. And between Omega 6 and Omega 3, the latter are in all likelihood the type most decisive for reproductive success.

The role of polyunsaturated Omega 3 and Omega 6 fats in reproduction

Reflecting on the role of Omega 3s in the body helps to understand why they are so important for reproduction too.

The precursors of active polyunsaturated fats must be obtained through diet, because the human body cannot synthesise them. These are linoleic acid (LA, the parent of the Omega 6 family) and alpha-linolenic acid (ALA, the parent of the Omega 3 family).

Moreover, since the ability to convert ALA into the active Omega 3s EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) is very low (also because of competition with Omega 6 for the enzymes needed to process linoleic acid), it is preferable to also take preformed EPA and DHA.

Omega 3 and Omega 6 are the precursors for the synthesis of prostaglandins, signalling molecules that regulate fundamental processes such as ovulation, embryo implantation and sperm function.

In addition, Omega 3s act as anti-inflammatory mediators, counteracting the potential pro-inflammatory effects of an excess of Omega 6.

Finally, in women, Omega 3s perform specific functions:

• in endometrial receptivity, supporting the uterine environment and making it more suitable for implantation;
• in the fluidity of cell membranes, promoting their integrity – a critical factor for oocyte quality and fertilisation.

Omega 3 and female fertility: the role in fecundability

In 2025, Mireille C Schipper and colleagues at the University Medical Center in Rotterdam, the Netherlands, published in The American Journal of Clinical Nutrition the results of a prospective population-based study (named the Generation R Next Study) aimed at analysing the association between periconceptional intake of Omega 3 and Omega 6 and fecundability and fertility in men and women.

The study involved 830 women and 651 men, revealing a clear correlation between a high intake of total Omega 3 and greater fecundability. Conversely, in women with a higher Omega 3 intake a lower risk of subfertility was observed.

Specifically, the analysis showed that the strongest positive effects come from the intake of DHA and ALA. The former is an Omega 3 of marine origin; its main source is oily fish (such as sardines and anchovies). ALA, on the other hand, is found in plant sources such as seeds and nuts. The fact that both are associated with a greater probability of conception suggests that the winning strategy for women may be to obtain Omega 3 from a combination of different sources.

The importance of the Omega 6/Omega 3 ratio

Another key finding of the research by Schipper and colleagues is that it is not only how much Omega 3 you take in that matters, but also its ratio to Omega 6. Indeed, a lower Omega 6/Omega 3 ratio was significantly associated with better fecundability.

Although Omega 6 is necessary for the production of steroid hormones in the ovary, an excess of it (typical of modern Western diets) can exacerbate inflammatory states and oxidative stress, and this could have negative effects on reproductive functions.

For this reason, reducing the intake of pro-inflammatory Omega 6 in favour of Omega 3, which tends to have anti-inflammatory properties, appears to be an important clinical recommendation for women who wish to become pregnant.

Fish: not all of it is the same

Despite the clear association between Omega 3 and fertility, in the cited study the association between fertility and total fish intake (the main source of EPA and DHA), although present, was not statistically significant.

This lack of significance could depend on the presence in fish of environmental contaminants such as mercury and polychlorinated biphenyls (PCBs), which could dampen the benefits of Omega 3.

This suggests that, for women, the quality and source of the fish are crucial. The advice that seems to emerge is to favour species with a low mercury content, such as smaller ones (for example sardines and anchovies).

On the other hand, whereas in men nuts (especially peanuts) were associated with significant benefits for reproductive functions – probably due to other components, such as selenium, folate and arginine, rather than to PUFAs alone – in women a high consumption of nuts and seeds was sometimes associated with a slight trend towards an increased risk of subfertility.

This effect reflects the high Omega 6 content of some of these foods which, if not balanced by Omega 3 sources, could alter the optimal Omega 6/Omega 3 ratio.

Gender differences in recommendations

The data from the Generation R Next Study confirm that Omega 3s are the fats best suited to supporting female fertility. Their ability to modulate inflammation, improve uterine receptivity and promote faster conception makes them fundamental pillars of periconceptional nutrition.

Promoting a diet rich in these fats represents a safe, natural and potentially transformative intervention for couples wishing to embark on the path to parenthood. However, the nutritional strategy should not be limited to a generic increase in ‘good’ fats, but should focus specifically on increasing DHA and ALA and on reducing the Omega 6/Omega 3 ratio.

One of the most relevant conclusions of the research is the need for gender-specific dietary interventions:

• for women, the main focus seems to be increasing the intake of Omega 3 (DHA and ALA), together with balancing the ratio with Omega 6, in order to modulate the inflammatory environment;
• for men, the regular consumption of nuts and seeds would be recommended, regardless of total PUFA intake, to increase sperm quality and fecundability through mechanisms apparently linked to protection from oxidative stress and improvement of vascular function.

To increase DHA and EPA, women can eat 2–3 servings per week of low-mercury fish; highly purified Omega 3 supplements are a valuable aid in reaching this goal.

They can instead increase ALA with walnuts and flaxseeds, being careful, however, not to exceed the total Omega 6 load.

To optimise the Omega 6/Omega 3 ratio it is advisable to reduce the use of vegetable oils that are excessively rich in Omega 6 (such as large amounts of sunflower oil).

References

Schipper MC, Jaddoe VW, Bekkers EL, Mulders AG, Gaillard R. Dietary intake of polyunsaturated fatty acids, their food sources and fertility in females and males: a preconception prospective population-based cohort study. Am J Clin Nutr. 2025 Jun;121(6):1354-1364. doi: 10.1016/j.ajcnut.2025.04.006