Views / Science Says

Who stole the sperm? We rounded up some usual–and unusual–suspects

A new study has found men in rich countries are making about half the sperm they did in the 1970s. We asked two experts why.

A few of the possible culprits in the case of the missing sperm include lifestyle, STIs, and drugs.

Andres Plana

A few of the possible culprits in the case of the missing sperm include lifestyle, STIs, and drugs.

Do animals experience menopause the way humans do? Metro's Citizen Scientist, Genna Buck, has the answers. Tune in to Facebook Live Friday at 12 p.m. EST.

Who stole the sperm?

A new study has found men in rich countries are making about half the sperm they did in the 1970s. One in six otherwise healthy young men have perilously-low sperm counts. It may take their partners longer to get pregnant, if they can conceive at all. It’s an overall sign something is wrong with men’s health. What the heck is going on? We asked two experts whodunit.

DIET & EXERCISE: Both Richard Sharpe, University of Edinburgh reproductive health scientist, and Dr. Keith Jarvi, head of urology at Toronto’s Mount Sinai hospital, pointed to poor diet, obesity, inactivity and related chronic diseases as prime suspects. They’re clearly linked to low sperm count, and they’ve grown a great deal in the last 40 years.

INFECTIONS: Sexually transmitted infections are on the rise in many regions. At the individual level, these kinds of issues, from chlamydia and gonorrhea to syphilis, can have a devastating effect on men’s fertility, Dr. Jarvi said. However, more studies are needed to determine whether STIs are a major driver of the fall in sperm counts.

HOT LAPTOPS AND TIGHT SHORTS: Expose sperm to even a little extra heat, over a long period, and their quality and quantity declines dramatically, Dr. Jarvi said. Trap the scrotum in tight shorts or smoosh it on a bicycle, and trouble could ensue. Laptops might be a culprit. Their heat has been shown to affect sperm, and people use them for long stretches. Plus, they’ve obviously increased since the 1970s. Luckily, if you remove these factors, most men’s fertility will rebound in a few months, Dr. Jarvi said.

DRINKING & SMOKING & DRUGS: Studies have shown heavy consumption of marijuana, tobacco or alcohol are all definite sperm depressors. Drugs that affect the central nervous system, like cocaine and ecstasy, impact the functioning of the whole body and possibly sperm production, Sharpe said. His research finds prenatal exposure to acetaminophen (Tylenol) is a possible (but NOT proven) cause of male reproductive issues.

CHEMICALS: Many are concerned about studies showing some common chemicals in plastics and textiles have estrogen-like effects, possibly interfering with sperm production. These findings (most in animals), show an association but don’t prove anything, Sharpe said. If they’re to blame, the damage likely happened when the man was in utero.

Toadally mysterious

Sandra Goutte

Pumpkin toadlets are screaming, but no one hears their cries. These orange critters, each less than 2 cm long, live in Brazil's rainforests. They make high-pitched calls — thought to be a communication signal — but a new study shows they lack the proper anatomy in their ears to actually hear them. Normally when something like this happens, through evolution, the creatures would have lost the ability to produce the calls. Scientists speculate that maybe the frogs can still interpret the calls by observing the movements of each other's throats — a sort of froggy lip reading.

Sound smart

Definition: Haploid living things or cells have only one set of chromosomes. Humans normally have two sets (one from each parent), making us diploid. Sperm and egg cells are haploid because they combine to make one cell that eventually becomes you.

Use it in a sentence: Did you know worker bees are haploid? They only have 16 chromosomes, while the diploid queen bee has 32.

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