Specialists are now encouraging a diet high in fruit and grains to increase the chances of successful IVF treatment.
In the past female fertility problems have been linked to obesity as well as smoking and drinking, but it hasn't been clear before now if the same applies to men.
But the latest study of men with partners who were undergoing a type of fertility treatment, has revealed that those who regularly drank alcohol and ate poorly were slowed down on the fertility front.
Lead researcher Edson Borges, from the Fertility-Assisted Fertilization Center in Sao Paolo said: 'The sperm concentration was negatively influenced by body mass index (BMI) and alcohol consumption, and was positively influenced by cereal consumption and the number of meals per day.'
The Brazilian study involved 250 men with partners who were undergoing a type of fertility treatment called intracytoplasmic sperm injection (ICSI).
Each participant was asked how often they ate a range of foods, including fruits and vegetables, beans, grains, meat and fish, as well as how much they drank and smoked.
Semen samples were then analysed to assess sperm health and concentration and each couple were monitored during the IVF process.
Eggs were successfully fertilised in about three-quarters of the treatments, and just under forty per cent of women got pregnant during the study.
From the speed of their sperm to their partner's chance of pregnancy, men who drank and had a poor diet were less fertile.
Lynn Westphal, a women's health and fertility specialist at Stanford University hopes that the results, published in the Fertility and Sterility journal, will encourage men to make healthier lifestyle choices.
'We talk about having a healthy lifestyle and trying to eliminate any of these things that are bad for health, but I think most of the emphasis tends to be on making sure the woman is as healthy as possible.
'I think this is really interesting data that lifestyle factors for men, even when you're doing ICSI, are significant.
'This is probably more of a difference than most people would have thought.'