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Healthy fats in walnuts give men a fertility boost

30 August, 2012

Natural Health News — Eating a generous handful of walnuts each day improves the vitality, motility, and morphology of sperm in healthy men aged 21 to 35, according to a new study.

Approximately 70 million couples experience subfertility or infertility worldwide, with 30-50% of these cases attributable to the male partner. Some studies have suggested that human semen quality has declined in industrialised nations, possibly due to pollution, poor lifestyle habits, and/or an increasingly Western-style diet.

Researchers at the University of California, Los Angeles decided to investigate whether increasing polyunsaturated fatty acids (PUFAs), which are critical for sperm maturation and membrane function, would increase sperm quality in men consuming a Western-style diet.

Their findings are published in the journal Biology of Reproduction.

The best sources of dietary PUFAs in a Western-style diet include fish and fish oil supplements, flax seed, and walnuts, the latter of which are rich sources of α-linolenic acid (ALA), a natural plant source of omega-3.

The team selected 117 healthy men between the ages of 21 and 35 who ate a Western-style diet and split them into two groups: one (58 men) who would avoid eating tree nuts and another (59 men) who would eat 75g (2 ½ oz, approximately 20 whole nuts) of walnuts per day. Previous studies had indicated that 75g of walnuts would be a dose at which blood lipid levels would change, but at which healthy young men would not gain weight.

Before the experiment began and then again 12 weeks later, the men’s semen quality was analysed according to conventional parameters of male fertility, including sperm concentration, vitality, motility, morphology, and chromosome abnormalities.

After 12 weeks, the team found no significant changes in body-mass index, body weight, or activity level in either group. The men consuming walnuts, however, had significantly increased levels of omega-6 and omega-3 fatty acids and experienced improvement in sperm vitality, motility, and morphology. Those eating walnuts also had fewer chromosomal abnormalities in their sperm following the walnut dietary intervention. The control group, on the other hand, experienced no changes.

Healthy oils, healthy sperm

Although this research (which was supported by the California Walnut Commission), indicates that eating 75g of walnuts per day can positively affect a young man’s sperm quality, the authors say it is still unknown whether the benefits would apply to young men with fertility problems and whether they would actually translate into increased fertility.

But previous studies suggest we already have some understanding about the role fatty acids could play in promoting healthy sperm.

For example 2010 a similar study found that infertile men have lower levels of omega-3 fatty acids in their sperm than fertile men. In addition, infertile men had significantly higher blood ratios of omega-6 to omega-3 fatty acids.

Another study this year in the Journal of Human Reproduction examined levels fatty acids in sperm samples. It showed that higher intakes of saturated fats decreased total sperm count by 43% and sperm concentration by 38%. But men with the highest omega-3 fatty acid levels showed an almost 2% improvement in sperm morphology, compared to men with the lowest omega-3 fatty acid levels.

Yet another study this year concluded that a considerable number of infertile men with idiopathic infertility might be benefit from omega-3 fatty acid supplementation.

See our feature on Plant Sources of Omega-3 Fatty Acids for more on this topic.