The quality of a man's diet and quantity of fat intake can be linked to lower fertility, a study claims.
Researchers in the United States found a link between a high fat intake and a 43 percent lower sperm count.
It was also found that men who ate more unsaturated, omega-3 fats - as found in fish and plant oils - had "better formed" sperm.
The study, published in the journal Human Reproduction, was carried out at Harvard Medical School and included 99 men as subjects. They were questioned about their diet when they attended a fertility clinic.
Professor Jill Attaman, instructor in obstetrics, gynecology and reproductive biology at Harvard, said that while this was a small study and further tests needed to be carried out, the results had interesting implications.
"If men make changes to their diets so as to reduce the amount of saturated fat they eat and increase their omega-3 intake, then this may not only improve their general health, but could improve their reproductive health too," she said.
"At a global level, adopting these lifestyle modifications may improve general health, as high-saturated fat diets are known to be a risk factor for a range of cardiovascular diseases; but in addition, our research suggests that it could be beneficial for reproductive health worldwide.
For the study, the men were divided into three groups according to the amount of fats that they consumed. Those with the highest intake were found to have a 43 percent lower total sperm count.
Saturated fats appeared to have the greatest effect, with those who consumed the most having a 35 percent lower sperm count.
"The magnitude of the association is quite dramatic and provides further support for the health efforts to limit consumption of saturated fats given their relation with other health outcomes, such as cardiovascular disease," Attaman added.
The authors stressed that the study only shows a connection between diet and fertility, rather than a causal relationship.
"To our knowledge, this is the largest study to date examining the influence of specific dietary fats on male fertility," the authors said.
"Given the limitations of of the current study, in particular the fact that it is a cross-sectional analysis and that it is the first report of a relation between dietary fat and semen quality, it is essential that these findings be reproduced in future work."