Abstinence myth: How men ruin their sperm without realising it

Anna Sandner

15/4/2026

Translation: machine translated

If you save sperm for the perfect moment, you ruin their quality without realising it. A large-scale meta-analysis by the University of Oxford shows that sperm cells become rusty if they remain in the body for too long. This now calls into question the common practice in fertility clinics.

«A lot helps a lot» is apparently a biological fallacy when it comes to the topic of fertility. Nevertheless, men who want to have their fertility tested in a clinic or donate sperm are almost always given the same medical advice. They should abstain sexually for two to seven days before providing the sample. The idea behind this is simple. So that there are more sperm in the ejaculate, abstinence first builds up a supply. However, a new study by the University of Oxford now reveals a serious disadvantage of this advice: waiting significantly damages sperm quality.

The biology of abstinence

Sperm are biological minimalists. They consist almost exclusively of the tail as the motor and the valuable DNA as the cargo. What they lack is the classic cellular toolbox for their own repair and energy supply, the so-called cytoplasm. This is precisely where the problem lies.

Study author Dr Rebecca Dean sums up the crux of this design: «Because sperm cells are highly motile and have minimal cytoplasm, they quickly exhaust their stored energy reserves and have only limited repair capacities. Compared to other cell types, this makes them particularly susceptible to damage caused by storage. Our study shows how regular ejaculation can provide a small but significant boost to male fertility.»

This means that mature sperm cells steadily degrade while waiting in the body. Without energy reserves, they become more and more sluggish and increasingly break down due to a lack of their own repair options. The driving force behind this deterioration is oxidative stress. Aggressive oxygen molecules attack the sperm cells like biological rust, damaging the DNA.

A universal law of nature

For their study, the research team summarised 115 existing studies with data from almost 55,000 men from 31 countries. To test whether this «biological expiry date» is a fundamental law of nature, they also analysed 56 studies on 30 different animal species. The spectrum ranged from fruit flies to bats. The latter sometimes carry sperm unused over months of hibernation.

The consequences of storage were even more drastic in animals than in humans. The long storage period not only reduces the quality of the sperm. It also leads to a poorer fertilisation rate and reduces the quality of the resulting embryos.

Consequences for fertility treatment

The findings from the study call for a rethink in reproductive medicine: to date, many clinics have followed the recommendation of the World Health Organisation, which stipulates abstinence for several days for artificial insemination in a test tube. Although a long wait increases the pure quantity of sperm in the sample, this is of little help if the cells deteriorate as a result. If you want to minimise damage to the DNA, it is therefore better to use fresher sperm.

Anna Sandner

Senior Editor

Anna.Sandner@galaxus.de

Science editor and biologist. I love animals and am fascinated by plants, their abilities and everything you can do with them. That's why my favourite place is always the outdoors - somewhere in nature, preferably in my wild garden.

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