Walnuts, Nuts, and Sperm Quality: What the Trials Found

Most "fertility foods" lists are built on biology and observation: a nutrient is involved in sperm production, so a food rich in it gets a spot on the list. Nuts are different. They're one of the few foods that have been tested the way drugs are: by randomly assigning some men to eat them and others not to, then comparing semen samples. That makes them worth a closer look.

Contents

• The walnut trial (2012)
• The mixed-nut trial (2018)
• Both trials side by side
• What other studies add
• The limits you should know
• Why nuts might help
• How to actually do it

The walnut trial (2012)

In a trial published in Biology of Reproduction, researchers randomly assigned 117 healthy men aged 21 to 35 who ate a typical Western-style diet to one of two groups. One group added 75 grams (about 2.5 ounces) of whole shelled walnuts to their daily diet for 12 weeks. The other group kept eating normally and avoided tree nuts.

Compared with the control group, the walnut group showed improvements in sperm vitality (the share of live sperm), motility (movement) and morphology (normal shape). Blood levels of omega-3 and omega-6 fatty acids rose in the walnut group but not in the control group, and sperm levels of alpha-linolenic acid (ALA), the plant omega-3 in walnuts, went up. Higher sperm ALA was also associated with fewer sperm with abnormal chromosome numbers.

The authors' conclusion was simple: walnuts added to a Western-style diet improved sperm vitality, motility and morphology.

The mixed-nut trial (2018)

The FERTINUTS trial in Spain, published in the American Journal of Clinical Nutrition, tested a similar idea with a nut mix. It randomized 119 healthy men aged 18 to 35 on Western-style diets to add 60 grams a day of mixed walnuts, almonds and hazelnuts, or to continue their usual diet without nuts, for 14 weeks.

The nut group improved compared with controls on total sperm count, vitality, total motility, progressive motility and morphology. Sperm DNA fragmentation also fell significantly in the nut group, which the investigators suggested could partly explain the other improvements. There were no significant differences in reactive oxygen species, chromosome abnormalities or DNA methylation.

When the results were presented at the ESHRE annual meeting, the European fertility society summarized the gains as roughly 16% for sperm count, 4% for vitality, 6% for motility and 1% for morphology. The lead researcher was careful about what that meant: asked whether men trying to conceive should eat more nuts, he said, "We can't yet say that," because the study was in healthy, presumably fertile men.

If DNA fragmentation is part of your picture, our explainer on sperm DNA fragmentation covers what the test measures and what else affects it.

Both trials side by side

What other studies add

A 2023 meta-analysis

Researchers at Monash University pooled the available evidence in what they described as the first systematic review and meta-analysis on nuts and fertility in men and women, published in Advances in Nutrition. Across 223 healthy men, eating at least 60 grams of nuts a day alongside a Western-style diet was associated with improved sperm quality, though sperm concentration didn't improve in the pooled analysis. They found only two intervention studies in men and none in women, and called for more research in both.

A 2025 couples study

The best link so far between nuts and actually conceiving comes from a Dutch preconception study in the American Journal of Clinical Nutrition that followed 830 women and 651 men. In men, higher nut and seed intake was associated with higher fecundability (a higher chance of conception per cycle) and lower odds of subfertility. Interestingly, men's omega-3 intake wasn't associated with fertility, which led the authors to suggest the benefit of nuts and seeds might not come from their fats alone. In women, higher omega-3 intake, including ALA, was associated with higher fecundability. This is observational, so it can't prove cause and effect, but it points in the same direction as the trials.

The limits you should know

• Healthy volunteers, not infertile men. Both trials enrolled healthy young men, not men with abnormal semen analyses. Whether nuts help men with diagnosed problems hasn't been tested.
• Semen measures, not babies. Neither trial tracked pregnancies or live births.
• Small changes. The improvements were statistically significant but modest. Nuts aren't a treatment for male infertility.
• Industry funding. FERTINUTS was funded by the International Nut and Dried Fruit Council, an industry group. That doesn't make the results wrong, and the trial was randomized and published in a major journal, but it's worth knowing. Independent replication would strengthen the case.
• No trials in women. For female partners, the evidence is limited to observational links with omega-3 intake.

Why nuts might help

The researchers proposed several reasons, none fully proven:

• Plant omega-3s. Walnuts are rich in ALA. The NIH lists 2.57 grams of ALA in one ounce of English walnuts, more than the daily Adequate Intake for men (1.6 g) or women (1.1 g). In the walnut trial, sperm ALA rose and correlated with fewer chromosomal abnormalities.
• Less DNA damage. The mixed-nut trial found lower sperm DNA fragmentation, which could improve other sperm measures.
• Displacing other foods. In real life, nuts often replace processed snacks. Our guide to ultra-processed food and fertility explains why that swap might matter on its own.

How to actually do it

1. Aim for about 2 ounces (60 g) a day, the amount used in FERTINUTS and the threshold in the meta-analysis. A kitchen scale makes this easy the first few times; after that you'll recognize the portion by eye.
2. Swap, don't just add. Use nuts in place of a packaged snack, chips or a sweet, rather than on top of everything else.
3. Choose unsalted and unsweetened. Plain walnuts, almonds and hazelnuts are closest to what the trials tested. Honey-roasted or candied versions add sugar.
4. Make it visible. A jar on the counter or pre-portioned bags for work make daily intake far more likely.
5. Give it three months. Both trials ran 12 to 14 weeks, roughly the time it takes sperm to develop. If you're planning a repeat semen analysis, time it accordingly.
6. Do it together. Walnuts, flaxseed and chia are among the top plant ALA sources on the NIH list, and ALA intake was linked to fecundability in women in the Dutch study.

Nuts fit into a bigger eating pattern rather than replacing one. For the rest of the plate, see our male fertility diet plan, and for a practical shopping list built around foods like these, the fertility-friendly winter grocery list. If you're comparing food with supplements, our review of men's fertility supplements shows how few pills have trial evidence as direct as these nut studies. fertilestart.com's his fertility basics is a good starting point if you haven't had a semen analysis yet.

Sources

• Robbins WA, Xun L, FitzGerald LZ, Esguerra S, Henning SM, Carpenter CL. Walnuts improve semen quality in men consuming a Western-style diet: randomized control dietary intervention trial. Biol Reprod. 2012;87(4):101. PubMed 22895856
• Salas-Huetos A, Moraleda R, Giardina S, et al. Effect of nut consumption on semen quality and functionality in healthy men consuming a Western-style diet: a randomized controlled trial. Am J Clin Nutr. 2018;108(5):953–962. PubMed 30475967
• ESHRE via ScienceDaily. Regular consumption of nuts is associated with improved sperm count and quality (July 4, 2018). sciencedaily.com
• Monash University. Nuts may enhance fertility for men: study (November 22, 2023), on Cardoso B, Kellow N, et al. Advances in Nutrition. monash.edu
• Schipper MC, Jaddoe VWV, Bekkers EL, Mulders AGMGJ, Gaillard R. Dietary intake of polyunsaturated fatty acids, their food sources and fertility in females and males. Am J Clin Nutr. 2025;121(6):1354–1364. Erasmus University
• NIH Office of Dietary Supplements. Omega-3 Fatty Acids: Fact Sheet for Health Professionals. ods.od.nih.gov
• Inverse. Nut industry funding and sperm quality research (on FERTINUTS funding). inverse.com