Oxford University researchers have discovered that releasing sperm frequently could provide fertility benefits.
Current World Health Organisation guidance advises people to avoid sexual activity for between two and seven days before providing sperm samples for testing or fertility treatments.
However, a study published today by Oxford researchers suggests that consistent sperm release—whether with a partner or alone—produces healthier sperm with less genetic damage.
The findings come from a comprehensive review across numerous animal species, from insects to mammals.
Sperm kept in storage (in either males or females) deteriorates rapidly, resulting in reduced fertilisation ability and inferior embryo development. The study also explains the biological reasons behind this decline.
The team gathered information from 115 investigations involving 54,889 people alongside 56 studies covering 30 non-human species.
The review showed that stored, mature sperm always declines in quality regardless of the male’s age—a condition researchers call post-meiotic sperm ageing.
For humans, prolonged periods without sperm release linked to increased sperm DNA damage and oxidative stress, as well as reduced sperm motility and survival rates.
Main researcher Dr Rebecca Dean from Oxford’s Biology department stated that because sperm move rapidly and contain minimal cytoplasm, they quickly exhaust their energy stores and struggle to repair themselves.
This means storage proves especially harmful compared to other cell types.
The research shows that regular sperm release can make a small but meaningful contribution to male reproductive health.
Both male and female creatures can store sperm as a reproduction strategy (in humans, sperm survives for several days inside females, though the effects of this storage remain uncertain).
In males, storage ensures adequate sperm availability for reproduction, while in females it allows fertilisation even when males are scarce.
Yet the study revealed a significant difference in deterioration rates between sexes. Across the species studied, females generally maintained better sperm quality over extended periods than males.
Dr Irem Sepil, senior author from Oxford’s Biology department, noted that this likely results from female-specific adaptations developing over time, such as specialised storage organs containing antioxidants that extend sperm viability.
These structures often release reproductive fluids to nourish sperm and could inspire biomimetic technologies to improve artificial sperm preservation methods.
Dr Krish Sanghvi, also from Oxford’s Biology department and lead author, observed that ejaculates should be considered collections of individual sperm cells that undergo birth, ageing, death, and selective removal.
The rates of these demographic processes differ between males and females, shaping the demographic composition of sperm populations and causing sex-specific differences in storage effects.
Sperm ageing in both sexes, unrelated to the organism’s actual age, has received little attention in reproductive medicine.
These findings therefore hold immediate relevance for clinical practice.
For instance, the results suggest the WHO’s maximum suggested interval of seven days may be too long.
This supports recent findings indicating that releasing sperm within 48 hours of sample collection can significantly improve IVF success rates.
By connecting biomedical and zoological research, this study provides a new viewpoint on reproduction.
Beyond potentially affecting fertility clinic procedures and assisted reproduction techniques, the findings could also help captive breeding programmes for endangered species while deepening understanding of how species evolved mechanisms to minimise sperm damage during storage.
The study Sperm storage causes sperm senescence in human and non-human animals was published in Proceedings of the Royal Society B.