Aspiring to fatherhood? Go NUTS! Walnuts, that is. A recent study published in the Biology of Reproduction suggests that healthy men routinely consuming a Western-style diet may be able to improve their sperm health by eating 75 grams of walnuts – a bit more than half a cup – daily.
Scientists at the University of California, Los Angeles (UCLA) discovered that after 12 weeks, young men who ate walnuts daily had improved sperm structure, vitality and motility – key components in male fertility – whereas those who avoided tree nuts altogether saw no such change.
‘The positive finding of walnuts on sperm may be a result of their unique nutrient profile. Walnuts are the only nuts that are an excellent source of alpha-linolenic acid (ALA) – the plant-based omega-3 fatty acid, which some studies of male infertility have linked to better sperm quality and development’, said Wendie Robbins lead author and post-doctoral researcher of the UCLA Fielding School of Public Health.
The scientists wrote that polyunsaturated fatty acids (PUFAs) such as omega-3 fatty acids – which, in the Western diet, are mostly obtained from fish, fish oil supplements, flax seed, and tree nuts – ‘play critical roles in sperm maturation and membrane function’ according to animal and human studies. And this study shows that the higher amounts of dietary ALA provided by the walnuts correlate with fewer abnormal sperm chromosomes which can result in genetic abnormalities such as Down syndrome.
In addition to ALA, walnuts are rich in omega-6 fatty acids, antioxidants, and micronutrients like folic acid. These nutrients, which Robbins thinks may work together synergistically, are believed to be important to male fertility.
This study was partly funded by the California Walnut Commission. The researchers recruited 117 men aged 21 to 35. The subjects were non-smokers, ate a typical Western diet and had no known history of infertility. 58 participants were randomly assigned to the control group and continued their normal diet but avoided tree nuts while the other 59 were requested to add 75 grams of whole-shelled English walnuts to their usual daily diet.
The researchers settled on 75 grams per day as previous studies have shown that this dose of walnuts was sufficient to raise blood levels of fatty acids and lower cholesterol levels but not enough to cause weight gain in the young men. The walnuts were eaten straight from the supplied snack packs or added to cereal, salad or yoghurt.
After 12 weeks, only the walnut group had significantly increased blood levels of omega-6 and omega-3 fatty acids. Their sperm also showed improvements in concentration, vitality, motility, and shape.
About 20 percent of the subjects showed low sperm counts, although they had not been diagnosed as infertile. Robbins reported that these men’s sperm improved the most after consuming walnuts on a daily basis for 3 months.
However, the scientists emphasised that more research is required to determine whether eating walnuts can actually improve chances of fathering children for men experiencing fertility issue.
Robbins et al (2012) Walnuts improve semen quality in men consuming a Western-style diet: randomized control dietary intervention trial. Biol Reprod. 87(4):101.