There are astounding, but unverifiable, tales of couples who had many children: Take Valentina and Feodor Vassilyev. It is claimed that she gave birth to 69 children — 16 pairs of twins, seven sets of triplets and four sets of quadruplets between 1725 and 1765.

Today, with fertility rates falling and reliable tracking of births, such numbers seem highly unlikely. Sperm counts among men in North America, Europe, Australia and New Zealand declined more than 59% from 1973 to 2011, according to a 2017 meta-analysis published in Human Reproduction Update, most likely due to environmental pollution and ingested chemicals. But there may be a way to improve testicular function and production of semen and sperm: take fish oil supplements.

A Danish study compared markers of fertility in men who did not take fish oil supplements in the three months before they were surveyed with guys who had taken them — either fewer than 60 times or more than 60 times during those months. The researchers measured all the men’s reproductive hormone levels and semen samples to examine volume, total sperm count and sperm motility.

Both groups who took fish oil had greater semen production, sperm count, testicular size and enhanced testosterone production. And more was better: Those who took the most fish oil during those three months had twice the semen volume of those who took the supplement fewer than 60 days. Our recommendation: Take 900 mg omega-3 DHA supplement daily; ask your doctor first if you have any contraindications with medication or health conditions.

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