Here’s an interesting — and alarming — article from The Independent. One third of healthy young men between 18 and 25 have abnormal sperm counts. And the sperm they do produce is often of poor quality. Studies show that “only between 5 and 15 per cent of their sperm is, on average, good enough to be classed as ‘normal’ under strict World Health Organisation rules – and these are young, healthy men.”
Twenty years ago, a Danish scientist warned the world that male fertility rates in the west were plummeting:
Professor Niels Skakkebaek of the University of Copenhagen presented data indicating sperm counts had fallen by about a half over the past 50 years. Sperm counts in the 1940s were typically well above 100m sperm cells per millilitre, but Professor Skakkebaek found they have dropped to an average of about 60m per ml. Other studies found that between 15 and 20 per cent of young men now find themselves with sperm counts of less than 20m per ml, which is technically defined as abnormal. In contrast, a dairy bull has a viable sperm count in the billions.
Reproductive biologists were shocked by Skakkebaek’s research. The outlook was bleak, although new studies show that sperm counts may be “bottoming out.”
Skakkebaek had no explanation for the terrible rates. Since then, experts seem to agree that lifestyle changes, environmental toxins, diet, and tight clothing play a role. But new research points to another major factor… what’s happening when males are in their mothers’ wombs:
The process of sperm production, called spermatogenesis, starts in adolescence, but the groundwork is laid down in the few months before and immediately after birth. An increasing number of studies point to a crucial “window” of testicular development that begins in the growing foetus and ends in the first six months of life. Interfere with this critical developmental period, and a baby boy will suffer the lifetime consequences of being a suboptimally fertile man.
Numerous studies show a relationship between fetal development and adult male reproductive problems:
For example, men whose pregnant mothers were exposed to high levels of toxic dioxins as a result of the 1976 industrial accident in Seveso, Italy have been found to have lower-than-average sperm counts. But men exposed to dioxins in adulthood showed no such effect. Another study found women who ate large amounts of beef during pregnancy, a diet rich in potentially damaging chemicals called polycyclic aromatic hydrocarbons (PAHs), had sons with relatively low sperm counts. But eating beef as an adult man shows no similar impact.
Meanwhile, studies of migrants between Sweden and Finland, showed that a man’s lifetime risk of testicular cancer tends to follow the country he was born in rather than the country where he was brought up. It was his mother’s environment when she was pregnant with him, rather than his own as a boy or as an adolescent, that seems to have largely determined a man’s risk of testicular cancer.
One of the strongest pieces of evidence in support of this idea comes from studies of people who smoke. A man who smokes typically reduces his sperm count by a modest 15 per cent or so, which is probably reversible if he quits. However, a man whose mother smoked during pregnancy has a fairly dramatic decrease in sperm counts of up to 40 per cent – which also tends to be irreversible.
According to a scientist quoted in the article, anything that interferes with the development of Sertoli cells in the male fetus — cells which determine the number of sperm produced in an adult male — can be detrimental to future fertility.
The tricky part now is identifying the specific factors affecting pregnant women that are relevant to male fertility. And there hasn’t been enough research into other possible — though more subtle — causes like obesity, air pollution, and soy.