Eat your greens for healthy sperm genes

By Sally Robertson, B.Sc.Sep 3 2012

Men who consume a high amount of certain nutrients may produce healthier sperm than men who do not, an effect that appears to be more pronounced in older men, report US researchers.

In an analysis of participants from the California Age and Genetic Effects on Sperm (AGES) Study, men with a higher intake of vitamin C, vitamin E, folate, and zinc produced sperm that had significantly less DNA damage than men who consumed lower amounts.

Andrew Wyrobeck (Lawrence Berkeley National Laboratory, Berkeley, California) and colleagues determined dietary micronutrient intake among the 80 individuals (aged 22-80 -years) using a food-frequency questionnaire and assessed sperm using Comet analyses that included both neutral and alkaline assays.

As reported in Fertility and Sterility, the team found no significant associations between any of the micronutrient measures and sperm DNA damage, as measured by the neutral assay.

However, the alkaline assay showed that men in the highest quartile for daily intake of vitamin C (459-3370 mg/day) had 16% less sperm DNA breaks than men in the lowest quartile (26-99 mg/day).

Those in the highest quartile for the antioxidant composite measure (vitamin C, vitamin E, β-carotene) also had significantly decreased sperm DNA damage compared with the lowest quartile, at 39.1% versus 45.9%, although this was not significant for β-carotene. Increased folate and zinc intake showed similar protective effects.

Further analysis showed that older men with an intake below that of the population's median levels for vitamin C, vitamin E, and zinc (but not β-carotene or folate) had significantly more sperm DNA damage compared with all other groups, including older men with above median intakes.

Furthermore, older men who were in the top versus bottom quartile for consumption of these nutrients had sperm DMA damage comparable with that found among the younger men.

The researchers say the findings may be explained by changes in oxidative stress in the male reproductive tract, over time.

Oxidative stress, which increases with age, primarily causes single-strand breaks (SSBs) and alkali-labile sites (ALS), but only very few double-strand breaks (DSBs), they explain.

"The alkaline comet assay detects DSB, SSB, and ALS, whereas the neutral version predominantly detects DSB and to a much lesser extent SSB," they add.

"This suggests that antioxidant and micronutrient intake protects specifically against SSB and ALS in sperm, which are increased in aging males… but show no detectable protection for DSBs in sperm, which are not increased in aging males."

Future studies are needed to determine whether increased antioxidant intake in older fathers will improve fertility, reduce risks for genetically defective pregnancies, and result in healthier children, concludes the team.

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