Impact of lifestyle and environmental factors on fertility.
Plain-language summary
This review gathers recent evidence on what damages male fertility and how much of it can be undone. Smoking raises sperm DNA fragmentation (breaks in the genetic material inside sperm) by about 10%, and alters hormone levels, with e-cigarettes possibly carrying similar risks. Heavy drinking raises DNA fragmentation by a similar amount, disrupts the hormonal signalling between brain and testicles, and can shrink the testicles. Obesity impairs sperm production through hormonal imbalance and inflammation, and even modest weight loss improves sperm measures. Steroids, cannabis and opioids all suppress fertility. On the environmental side, heat waves, fine particulate air pollution and endocrine-disrupting chemicals all reduce semen quality. The review also credits certain diets and antioxidant supplementation with modest improvements, without naming which antioxidants, at what dose, or how large 'modest' is.
Key findings
- Smoking raises sperm DNA fragmentation by about 10% and alters hormone profiles.
- Chronic alcohol use raises DNA fragmentation by a similar amount and disrupts the hormonal signalling between brain and testicles.
- Obesity impairs sperm production, and even modest weight loss improves sperm measures.
- Steroids, cannabis and opioids suppress fertility.
- Heat waves, fine particulate air pollution and endocrine-disrupting chemicals reduce semen quality.
- Certain diets and antioxidant supplementation modestly improve sperm quality, though the review does not specify which antioxidants, at what dose, or how large the improvement was.
How to analyze the study yourself
- Study type
- A narrative review summarizes recent findings but does not systematically pool data or weigh study quality like a meta-analysis would.
- Population
- The review synthesized evidence from various studies on male fertility, but specific population details were not reported.
- Funding
- Not reported
- Watch for
- This study found that the biggest modifiable harms to fertility are smoking, heavy drinking, carrying excess weight, and exposure to heat and air pollution, and that most of the damage is reversible. If you are trying to conceive, stopping smoking and losing even a modest amount of weight have the clearest evidence behind them of anything on the list.