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As you are reading this you have just enough time left to make Valentine’s Day plans and salvage the looming disaster brought on by your forgetfulness. The premium you will pay on flowers purchased at this late date should be a learning experience. You may try to be creative and bring some fresh oysters as a surprise. But lest you delude yourself into thinking they are an aphrodisiac, they are not.
The association of oysters as an aphrodisiac is a long-standing one. In Greek mythology, the goddess of love, Aphrodite, emerged from the sea on an oyster shell which is proof enough for many. Casanova reportedly ate 50 oysters a day and attributed his sexual prowess to their restorative powers. This, like much of Casanova’s account, is probably an exaggeration and even if taken at face value is nothing more than an anecdote.
When people try to apply some scientific justification to the power of oysters, they usually point to their high zinc content. You can find zinc in many foods and most of us get more than enough zinc from meat, cereal and yogurt. But oysters are exceptionally high in zinc with about 10 times as much as a comparably sized piece of beef. Zinc has many functions in the human body, and it is necessary for sperm production — and it was a short intuitive leap for people to assume that it would boost fertility and sexual performance.
But zinc’s — and consequently oysters’ — reputation as an aphrodisiac is unearned. First, fertility and sexual desire do not actually go hand in hand. We often conflate different concepts when it comes to sex. Viagra is often talked about as an aphrodisiac, but it doesn’t actually increase sexual desire. It treats erectile dysfunction, which is often a consequence of atherosclerosis, but it doesn’t make someone more willing to have sex. It merely makes them more able.
Fertility and sexual desire are also distinct concepts where a problem with the former does not imply a deficit in the latter. There’s nothing in the scientific literature to suggest that zinc can boost libido and even its ability to improve fertility is dubious. While a deficiency can impair sperm production, it doesn’t mean that taking more than necessary would improve fertility.
A 2020 randomized controlled trial published in the Journal of the American Medical Association tested whether a combination of zinc and folate would improve semen quality or live births in approximately 2,000 men who were planning fertility treatment. Neither outcome showed any improvement, which underscores an important point about hard clinical end points. The only end point that matters with fertility treatments is whether something can improve the live birthrate, and it was clear in this trial that zinc did not. Zinc and folate are commonly included in male fertility supplements but this study demonstrates that they are probably useless.
Zinc may seem like a harmless, if ineffectual, fertility treatment, and oysters like a fun indulgence on a special day. But high doses can lead to gastrointestinal upset, nausea and vomiting. The zinc in certain cold therapies can also cause permanent anosmia, loss of the sense of smell. And though often marketed as a cold remedy, systematic reviews of the evidence have shown that it has minimal benefit.
It is unlikely that you will overdose on zinc by eating a few oysters. The much greater threat is food poisoning. Two recent recalls in Canada and the United States due to norovirus contamination underscore the point. A good rule of thumb is that if an oyster’s shell is open, cracked or doesn’t close, or if it smells off, you should discard it immediately. Otherwise, you might be spending Valentine’s Day with copious diarrhea, which is very unromantic.
