Men who are vegans and vegetarians may have significantly reduced sperm counts than meat eaters, according to a new study.
Researchers at Loma Linda University Medical School in the US found that while a diet that is rich in fruit and vegetables can protect against many illnesses and can prolong life, it appears that it may also harm fertility.
Researchers studied how diets affect sperm in study participants in southern California.
The region has a high population of Seventh-Day Adventist Christians who are strict vegetarians.
Seventh-day Adventists live an average of 10 years longer than the American life expectancy of about 79 years and the researchers wanted to find out if their longevity might be linked to sperm quality, 'The Telegraph' reported.
They found that vegetarians and vegans had significantly lower sperm counts compared with meat eaters, 50 million sperm per ml compared with 70 million per ml.
They also had lower average sperm motility - the number of sperm which are active. Only one third of sperm were active for vegetarians and vegans compared with nearly 60 per cent for meat eaters.
The team believes that vitamin deficiencies may be to blame or replacing meat with soy could be responsible.
"We found that diet does significantly affect sperm quality. Vegetarian and vegan diets were associated with much lower sperm counts than omnivorous diets," said Dr Eliza Orzylowska, an obstetrician at Loma Linda University Medical Centre in California.
"Although these people are not infertile, it is likely to play a factor in conception, particularly for couples who are trying to conceive naturally," Orzylowska said.
The study will be presented at the American Society of Reproductive Medicine's annual meeting in Hawaii.