Men who want to become fathers should eat their greens.
A study has shown that couples who are struggling to conceive eat less fruit and vegetables than people who have just become parents.
And men are particularly lazy at following a healthy diet.
British experts said that most pre-pregnancy advice is aimed at women and as a result men "have really missed out on the public health message".
Around one in seven couples in the UK has trouble conceiving, and although infertility is traditionally thought of as a female issue, the problem is as likely to lie with the man as the woman.
Italian doctors asked 1,134 patients to fill in an extensive questionnaire about their diet and lifestyle.
One third of the men and women were classed as infertile because they had been trying, unsuccessfully, for a baby for a year.
The others had recently had a baby.
The patients were in their mid-30s, on average, and of normal weight.
The results showed clear differences between the diets of the two groups, the European Society of Human Reproduction and Embryology's annual conference in Lisbon heard.
Some 44 per cent of fertile men ate fruit and veg almost every day, compared to 34 per cent of those whose partners were struggling to conceive.
And 55 per cent of fertile men ate five portions of fruit a week, compared to 46 per cent of those who were infertile.
The fertile men also ate more eggs, while the fertile women ate more beans, pulses and fruit than those who were still trying to conceive.
There was no difference in the consumption of cereals, read meat, poultry and fish between the fertile and infertile patients.
However, the infertile men and women drank more and were more likely to smoke.
Researcher Professor Andrea Salonia, of the IRCCS Ospedale San Raffaele in Milan, described the differences as "striking" and said the infertile patients "clearly" had worse diets and lifestyles.
She said that fruit and vegetables may be particularly good for male fertility because they contain compounds that could protect sperm from damage.
The minerals zinc, found in beans and pulses, and selenium, found in eggs, help keep testosterone levels high.
For women, beans, nuts and pulses 'provide a rich source' of iron and folate, or vitamin B12, which are important for egg development and ovulation.
Co-researcher Eugino Ventimiglia said that people eating lots of fruit and vegetables tend to eat less fatty food.
He said the results showed women to be better at adhering to a healthy diet.
"Men don't pay such great attention to it," he said.
"We have to prompt and try to convince infertile men that, yes, diet and lifestyle is an issue."
He added that when fertility is proving a concern, it is "always the wife" who seeks medical help.
Asked why this is, he said: "Perhaps women are smarter and men are lazier and are keen to rely on their female partner.
"I would advise my patients to have a proper healthy lifestyle to avoid smoking and drinking. The healthier the patients the higher their chance of getting pregnant."
Stuart Lavery, director of IVF at Hammersmith Hospital in west London, said while it isn't possible to "eat yourself pregnant", a balanced diet is good for overall health, including reproductive health.
Allan Pacey, a male fertility expert from Sheffield University, said that the focus on women's health has led to men missing out on advice about how to boost their chances of fatherhood.
Professor Pacey added: "I agree that men are generally less interested than women in how their diet links to health, and in particular issues of fertility and infertility.
"When push comes to shove, I think all men inherently know what foods and lifestyle habits are good and which of them are bad.
"But sometimes they need to hear it from someone who isn't their partner.
"My advice for any man is not to go on any kind of fad diet, but simply try and be healthy and make sure they get five portions of fresh fruit and vegetables each day.
"The only absolute requirement is to stop smoking as we know the compounds in cigarette smoke can damage sperm DNA and since it takes about three months to produce a sperm from start to finish, men need to make a sustained and long term change if their sperm health is to improve."
Professor Geeta Nargund, head of reproductive medicine at St George's Hospital in London, said that men having fertility treatment tend to show little interest in improving their diet unless they are shown to have a severe problem with their sperm.
Then, the fear that their masculinity is under treat spurs them into action.
- Daily Mail