Regularly eating cheese may prove to be more dangerous than adding additional pounds in men after a new study found that it may decrease the chances of becoming fathers.
Even small amounts of full-fat dairy food have been shown to dramatically impair their fertility.
Harvard academics have discovered that men who eat just three portions a day had poorer quality sperm compared to others, the Daily Mail reported.
A portion included an ounce of cheese (28g), a teaspoon of cream, a scoop of ice cream or glass of full-fat milk.
The researchers believe that female hormones that occur naturally in milk may be interfering with men's ability to reproduce.
Until recently, experts have been far more concerned with how women's diets are affecting their chanced of having children.
But there is increasing evidence that men's lifestyles - and crucially what they eat - may be just as important.
Scientist from the Harvard School of Public Health in Boston, the US, compared the diets of 189 men aged 19 to 25.
None were overweight - they were all very fit and did at least one and a half hour's exercise a week.
They had each filled in a questionnaire answering how often they ate dairy products, fruit, meat and other types of food during a typical week.
The researchers also looked at their sperm, including how fast it travelled and its shape.
They found that the sperm of men who ate more than three portions of full-fat dairy food a day was 25 percent poorer quality than those who had less.
Myriam Afeiche, who led the study, explained that the female hormone oestrogen in milk that had come from the cow may be affecting men's fertility.
It may also be impaired by pesticides which find their way in to dairy products, she added.