Eating junk food may reduce a man’s sperm count, research has shown. A study of men attending a US fertility clinic found those with the fattiest diets produced significantly less sperm. Their sperm density was also lower. The research also showed that diets high in omega-3 fatty acids, found in fish and plant oils, were associated with improved sperm quality. Men were divided into three groups according to how much fat they consumed. Compared with those eating the least fat, men with the highest fat intake had a 43% lower sperm count and 38% lower sperm concentration. Sperm concentration, or density, is defined as the number of sperm per unit volume of semen.