Jill Attaman, who was at Massachusetts General Hospital and an instructor at Harvard Medical School at the time of the research, said the study of 99 men found men who ate more omega-3 polyunsaturated fats -- found in fish and plant oils -- had better formed sperm than men who ate less.
The researchers questioned the men about their diet and analyzed samples of their semen from December 2006 to August 2010, measuring fatty acids in sperm and seminal plasma in one-quarter of the men.
The study participants were divided into three groups according to the amount of fats they consumed. The study, published in the journal Human Reproduction, found the one-third with the highest fat intake had a 43 percent lower total sperm count and 38 percent lower sperm concentration than men in the third with the lowest fat intake.
However, researchers warned this was a small study and the findings need to be replicated by further research.
"In the meantime, 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," Attaman said in a statement. "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."