A study in Europe’s leading reproductive medicine journal Human Reproduction, shows that men’s diets could be linked to their sperm quality, particularly the amount and type of different fats they consume.

A study in 99 American men demonstrated that a high total fat intake is linked to lower total sperm count and concentration. It also showed that men, who consumed more omega-3 polyunsaturated fats, i.e. fats found in fish and plant oils, had better formed sperm compared with those who ate less of these fats. The researchers warn however, that the findings need to be supported by further research to validate the impact of fats on men’s fertility given that this study was only performed in a small number participants.

Professor Jill Attaman, Clinical and Research Fellow in Reproductive Endocrinology and Infertility at Massachusetts General Hospital and an Instructor in Obstetrics, Gynecology and Reproductive Biology at Harvard Medical School declared:

“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. 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.”

Even though numerous earlier studies of the association between body mass index (BMI) and sperm quality have produced mixed outcomes, little knowledge exists regarding the potential impact of dietary fats on sperm quality.

Prof Attaman and her team decided to evaluate whether dietary fats affect sperm quality in 99 men attending a fertility clinic, between December 2006 and August 2010. The team first surveyed the participants about their diet after which they analyzed the men’s sperm samples, including measuring the levels of fatty acids within the sperm. They also measured seminal plasma in 23 of the 99 participants.

The participants were then split into three groups based on their consumed fat intake. The researchers found that the sperm count was 43% lower, with a 38% lower sperm concentration in the highest fat-intake group than the group with the lowest fat intake. The team defined the ‘total sperm count’ as the overall number of ejaculated sperm and the ‘sperm concentration’ as the concentration of sperm in number per unit volume.

According to the World Health Organization, a “normal” total sperm count should contain at least 39 million sperm in the ejaculate, whilst the concentration of spermatozoa should contain a minimum of 15 million per ml. The study showed that the link between dietary fats and sperm quality was largely affected by the consumption of saturated fats, i.e. participants who consumed the most saturated fats had a 35% lower total sperm count and a 38% lower concentration of sperm compared to men who ate the least fat.

Prof Attaman declared:

“The magnitude of the association is quite dramatic and provides further support for the health efforts to limit consumption of saturated fat given their relation with other health outcomes such as cardiovascular disease.”

The study also showed that men who consumed the most omega-3 fats had a marginally higher number of correctly formed sperm (1.9%) compared with those who ate the least amount of omega-3 fats. The team also highlights the fact that 71% of all study participants were either overweight or obese, a factor that could also impact the quality of the sperm, however, they added that they already accounted for this.

Prof. Attaman said: “We were able to isolate the independent effects of fat intake from those of obesity using statistical models. Notably, the frequency of overweight and obesity among men in this study does not differ much from that among men in the general population in the USA (74%).”

The study has several limitations that could impact the results, such as collecting only one sperm sample per man and that using a food frequency questionnaire might not accurately reflect the men’s actual diets. The researchers also highlight that their study does not show that dietary fats actually cause poor semen quality; they only state that there is a link.

In a concluding statement they write:

“To our knowledge, this is the largest study to date examining the influence of specific dietary fats on male fertility. Given the limitations 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.”

Prof Attaman, and her team are conducting ongoing investigations into how dietary and lifestyle factors impact men’s and women’s fertility as well as outcomes of couple’s fertility treatment.

Written By Petra Rattue