Male factor infertility accounts for roughly half of all couples struggling to conceive, and yet the diet-and-fertility conversation is still far more focused on women. A BBC News report summarised a nicely designed trial that put walnuts — of all things — at the centre of a sperm-health story.
What the study found
The trial recruited young healthy men and randomised them to add about 75 grams of walnuts per day to their usual diet or to maintain their usual diet unchanged, for 12 weeks. At the end, the walnut group showed improvements in several sperm parameters — motility, morphology, and vitality. The effect was modest but statistically measurable.
The leading hypothesis is that the omega-3 fatty acids in walnuts (particularly alpha-linolenic acid), combined with antioxidants and vitamin E, supported sperm membrane integrity and reduced oxidative damage during maturation.
How to use this information
A few caveats before anyone starts eating walnuts by the handful:
- The men in the trial were young and healthy. We don’t know how well the effect translates to older men, men with known fertility issues, or men with different baseline diets.
- 75 grams a day is a lot of walnuts — roughly a half-cup, around 500 calories. Substituting walnuts for other foods is different from adding them on top of an already calorie-dense diet.
- “Sperm parameters improved” is not the same as “fertility improved.” Pregnancy rates weren’t the primary endpoint. Those are a harder thing to measure.
That said, the broader message is consistent with a growing body of evidence: diet matters for male fertility. The interventions that have shown benefit in various studies share common threads — more omega-3s (nuts, fish, flax), more antioxidant-rich vegetables, lower saturated fat, lower processed meat.
The clinic’s take
For men facing fertility challenges or planning to try for a child in the coming year, diet is a reasonable lever to adjust alongside the standard advice (avoid smoking, moderate alcohol, avoid excessive heat exposure, maintain healthy weight, treat any underlying conditions). Walnuts aren’t magic, but a handful a day is low-risk and probably helpful.
If conception has been elusive for 12 months or more, or 6 months if the female partner is over 35, a formal fertility evaluation — including semen analysis — is the right step. Many causes of male infertility are treatable.