Does a man’s diet affect his sperm and fertility?

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One in six couples has difficulty becoming pregnant, and around half the time it’s because of a problem with the man’s sperm.

And yes, sometimes sperm problems are linked to what a man eats or drinks, says Sydney fertility specialist Dr Anne Clark.

While the number of sperm a man produces is not associated with diet, the health of those sperm can be.

Sperm count is actually predetermined by how many germ cells — which become sperm cells — migrate into a man’s testes before he is born.

What a man eats or drinks can influence how well a sperm performs, as well as the chance of any fertilised egg growing successfully in a woman’s womb.

Dr Clark says 53 per cent of men visiting her clinic have at least one form of nutritional deficiency that impacts on sperm function and fertility potential.

DNA damage in sperm

How well a sperm swims is known as motility.

In a fertile man, at least 32 per cent of sperm cells should be “rapidly progressive” — as in, moving fast enough and in the right direction to reach the egg.

Poor motility is a sign of sperm DNA damage, or fragmentation, caused by highly reactive substances called free radicals.

Some DNA fragmentation is fairly common, says Dr Clark, but at higher rates it begins to affect fertility.

“If more than 20 per cent of the sperm have got evidence of DNA damage, then that couple’s chances of getting pregnant is significantly reduced and the risk of miscarriage is three to four times higher,” she says.

Genetic problems can also be passed on to children.

Even if the man’s sperm count, motility, and shape are normal, if couples are having difficulty conceiving, in 40 per cent of cases there’s likely to be increased sperm DNA damage.

A woman’s eggs are able to repair some sperm DNA damage after fertilisation, but if that repair mechanism is compromised by the woman’s lifestyle factors, such as smoking or poor nutrition, the chance of a healthy pregnancy may be further reduced.

While diet is not the only factor influencing DNA fragmentation — a man’s age is another — it’s an important one.

Getting the right nutrients

Dr Clark says everyone trying to conceive should think about diet, not just those people who are having difficulty.

Foods such as fruit, vegetables, and wholegrains are important because they are rich in antioxidants, which inhibit the free radicals that can damage sperm DNA.

You should also limit soft drinks.

As well as the increased sugar load contributing to weight gain, studies have shown that if a man drinks one or two glasses of soft drink a day, that couple’s fertility will be reduced by up to 33 per cent.

The effect is similar if the woman consumes the soft drink, but it’s not so much about eating specific foods as having a healthy diet overall.

Lots of vitamins and minerals, such as vitamins C and E, zinc and selenium are needed for healthy sperm.

“Having the right nutrient mix is important,” Dr Clark says.

“If you have a normal balanced diet you’ll be getting all the important nutrients.”

Multivitamins and fertility

There are occasions when a healthy diet isn’t enough.

One in eight people have an enzyme variant called MTHFR which means they have difficulties absorbing folate from their diet.

So, even when they are eating the right food, their bodies may not obtain all the nutrients they need.

Deficiencies in folate, along with low levels of vitamin B6 and vitamin B12, are linked with DNA damage in sperm through raised levels of a chemical called homocysteine, which is a building block for proteins.

But if a man is unable to absorb folate from foods such as green leafy vegetables, a supplement will do the job.

Dr Clark says a good quality multivitamin supplement will provide adequate folate and two months is often enough time to reverse sperm DNA fragmentation.

To optimise fertility generally with a supplement, choose one that includes zinc, selenium, vitamin C, vitamin E, and co-enzyme Q, Dr Clark says.

However, beware of self-medicating with supplements because both too much and too little of some vitamins and minerals can be harmful to sperm.

For instance, selenium at higher doses significantly reduces the number of motile sperm a man has, possibly by changing normal thyroid metabolism.

Always check the recommended daily dosages for each vitamin and mineral to ensure you aren’t overdosing and ideally, discuss your concerns with your doctor first.

Think about weight, alcohol, smoking

A bad diet can also be linked with obesity, which on its own can contribute to infertility.

Approximately 50 to 70 per cent of Australian men in the reproductive age group are overweight or obese.

There are a variety of reasons this might make these men less fertile but a poor nutrient balance from eating higher amounts of manufactured food is probably one of them, Dr Clark says.

Of course, food isn’t the only thing we put in our bodies — alcohol and smoking are known to play a role in infertility, too.

“If a man is drinking more than about 10 glasses of alcohol a week, particularly if he’s binge drinking, then he’s potentially affecting his sperm quality,” Dr Clark says.

Alcohol may affect sperm quality by increasing oestrogen production in the liver, as well as poisoning cells in the testes.

And while we tend not to think of alcohol as a poison, it can be toxic at high doses.

Smoking is thought to cause around 13 per cent of infertility.

“Wherever blood goes, the toxic things in cigarettes goes, so as the sperm grow and develop, they do so in a toxic swamp,” Dr Clark says.

“In particular, this links back to DNA fragmentation, which also increases the risks of the resulting child developing diseases early in life, particularly a four-times-increased risk of cancer in childhood.”

Dietary and lifestyle changes

The bottom line is that a healthy balanced diet and keeping bad habits to a minimum is key to optimising fertility, Dr Clark says.

And when it comes to diet and sperm health, men are in luck.

“The good thing for a man is that because he makes sperm continuously, by making dietary and other lifestyle changes he can significantly improve his and the couple’s chance of an ongoing healthy pregnancy,” she says.

It’s also important to note that lifestyle and dietary changes can take two to three months before they show up in sperm, as it takes that long for sperm to mature.

So, pre-conception planning is just as important for men as it is for women.

This is general information only. For detailed personal advice, you should see a qualified medical practitioner who knows your medical history.

This story, which was originally written by Katherine Nightingale and published by ABC Health and Wellbeing, was updated in 2019.

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