Sperm and egg cells explain lifespan differences between men, women
Japanese scientists have discovered that the smallest and largest cells in the body, sperm and egg cells, may explain why women generally outlive men. The researchers found that removing these cells resulted in animals with equal life expectancies. This groundbreaking study was conducted on small, turquoise killifish, a species whose aging process is similar to humans according to Prof Tohru Ishitani of Osaka University.
Lifespan disparity influenced by sperm and egg cells
Globally, women live approximately 5% longer than men on average, a disparity influenced by factors including lifestyle choices and risk-taking behavior. This trend is also observed in female apes and old-world monkeys. The size of the life expectancy gap varies significantly between countries. Ishitani's team found that eliminating germ cell production (cells that develop into sperm or eggs) resulted in males living longer and females dying younger, effectively closing the lifespan gap.
Hormonal changes and vitamin D impact lifespan
The researchers found that blocking sperm and egg production significantly affected the killifish. In females, hormonal changes led to growth at the cost of maintaining healthy tissues, while reduced estrogen increased the risk of cardiovascular disease. Conversely, males produced more vitamin D in their livers, potentially improving bone, muscle, and skin health. Ishitani's team also discovered that vitamin D supplementation extended lifespan in killifish by 21% in males and 7% in females. However, it's crucial to use the "appropriate amount."
Sperm suppression and lifespan: A possible connection
While it remains unclear whether sperm suppresses men's life expectancy, there is some evidence to support this. A 2012 study found that Korean eunuchs lived 14 to 19 years longer than non-castrated men from similar socioeconomic backgrounds. However, these records are centuries old and other influencing factors are difficult to exclude. Dr. David Clancy from the University of Lancaster observed that blocking reproduction often extends lifespan, particularly in females, indicating a trade-off between growth and reproduction versus maintenance and lifespan.
Sex differences in lifespan modulation by germ cells
Clancy explained that when sperm or egg precursor cells were removed, the lifespan of females was shortened, while that of males was extended, pointing to the potential influence of these cells on sex differences in lifespan. This indicates that the signaling these cells do to modulate lifespan differs between sexes in killifish and possibly other animals as well.
