If you’re having trouble getting pregnant, forget about oysters – the best fertility foods are fruit and vegetables, wholegrains, healthy fats and plant protein. Not some half-baked theory but the result of years of scientific studies on diet and fertility. There is solid evidence behind the claim.
Around one in seven couples have difficulty conceiving and there are many possible causes that can affect both men and women. The most common cause of female infertility is ovulatory problems – lack of periods. In men, it is poor quality semen.
There are many lifestyle factors that can have an influence on fertility, such as the age at which you try to start a family, your diet, weight, exercise and the amount of stress you’re under. You can’t change your age or your genes but you can do something about the risk factors under your control, such as diet, smoking, alcohol consumption and weight. The effect of diet on fertility mostly seems to be overlooked despite the scientific evidence.
The typical Western diet is pretty bad but it’s been getting progressively worse for decades, with substantial increases in sugar, saturated fat and refined carbohydrates such as white flour in bread and pasta. This is at the expense of healthy fruit and vegetables and plant protein. Perhaps no surprise, it has coincided with a downward trend in fertility.
A number of studies suggest that meat and dairy foods may be linked to fertility problems. One study looked at 189 young, healthy US men aged between 18 and 22 and found that those who ate the most meat and full-fat dairy products had fewer and slower sperm. Those who ate the most fruit and vegetables had higher quality sperm that swam faster. Lead researcher Professor Jaime Mendiola said “…among the couples with fertility problems coming to the clinics, men with good semen quality ate more vegetables and fruit, which means more vitamins, folic acid and fibre and fewer proteins and fats, than those with poor sperm quality”.
Around one in seven couples have difficulty conceiving and there are many possible causes that can affect both men and women. The most common cause of female infertility is ovulatory problems – lack of periods. In men, it is poor-quality semen.
Harmful substances called ‘reactive oxidative species’ can affect fertility by damaging the sperm membrane, which may have an impact on fertilisation or affect the sperm’s DNA.
Called oxidative stress, it is believed to cause between 30-80 per cent of male subfertility cases. Antioxidants such as vitamins A, C and E are found in fruit and vegetables and can help combat this by protecting cell membranes from oxidation damage by mopping up the harmful compounds. Think of a big fresh salad with green leafy vegetables, tomatoes, sprouted seeds and avocado as sending in the cavalry!
It follows that people who eat lots of fruit and vegetables get lots of antioxidants and have less cancer, heart disease and neurological (nerve) diseases. Antioxidants also protect against macular degeneration, an eye disease that affects older people. Oh yes, and they are anti-aging too!
In a large review of studies, antioxidants were linked to a higher pregnancy and live birth rate in men with impaired fertility. The authors suggest that in couples who are undergoing help with reproduction and where the man has fertility problems, his taking antioxidant supplements may improve the outcome.
However, antioxidants are widely available in fruit and vegetables, particularly the brightly coloured varieties – sweet potato, red pepper, mango, red cabbage and so on.
Mediterranean-style diets rich in fresh fruit and vegetables, wholegrains and healthy fats are not only linked to a lower risk of all our biggest killers – obesity, heart disease and cancer – they can also help improve fertility. A Spanish study looking at 209 male university students found that those eating a Mediterranean diet, with high intakes of fruit and vegetables, had a better sperm count than those eating a Western diet with its high intakes of processed meats, French fries, pizza and snacks. The conclusion was that Mediterranean diets may help reproduction because of its high level of antioxidants.
But it’s not just men who are helped as the Mediterranean diet has been linked to a lower risk of infertility among Spanish women. There is also evidence that it may improve the likelihood of becoming pregnant after fertility treatment. Researchers in the Netherlands found that among 161 couples undergoing fertility treatment, those eating a traditional Mediterranean-style diet were 40 per cent more likely to become pregnant than those eating a diet described as ‘health conscious, low processed’.
Presumably the results would have been even better if the other diet had been a meaty, Western one. The authors suggested that B vitamins and healthy fats might be involved.
Other studies agree that healthy diets are linked to better semen quality but not necessarily sperm counts. One investigated the influence of diet on sperm quality and intracytoplasmic sperm injection (ICSI). This is a treatment for infertile men that’s used in nearly half of all IVF treatments that require just one sperm injected directly into the egg. They found that among the 250 men undergoing ICSI cycles, fruit and cereal consumption was a positive influence.
Negative factors included BMI, alcohol consumption, smoking and the consumption of red meat, all of which had an impact on the implantation rate. The authors suggested that in couples seeking assisted reproduction, both should be advised of the dramatic effect lifestyle can have on the treatment’s success.
Replacing animal protein such as chicken, red and processed meat with plants that are as high in protein – peas, beans, lentils, tofu and nuts – may help improve a woman’s fertility. One study looked at the diets of over 18,000 women eight years as they attempted to become pregnant or succeeded in doing so. It found that the risk of infertility was 39 per cent higher in those eating the most animal protein. Simply by consuming just five per cent of their total energy intake as vegetable protein rather than animal protein lowered their risk of infertility by 50 per cent.
Soya foods contain plant hormones called phytoestrogens, which are similar to oestrogen but considerably weaker. There have been numerous scare stories about soya, claiming that it can feminise boys and make men grow ‘man boobs’, to more serious reports that it can alter sexual development and fertility. They are based on in vitro (test tube) and animal experiments which bear no relevance to humans. The research is clear and shows that soya foods do not affect reproductive hormone levels in men and adds to the large body of evidence that shows soya as being completely healthy.
Vegans who eat soya are not exposed to levels higher than those seen in many Asian countries and there is no evidence that people who regularly eat high quantities of soya, such as the Chinese and Japanese, have altered sexual development or impaired fertility. It should be remembered that China is the world’s most populous nation, with over 1.3 billion citizens who have been consuming soya for over 3,000 years!
Perhaps it’s not surprising that recent studies have also found a link between men’s weight and their risk for infertility.
A weighty issue
Being either overweight or underweight can negatively impact fertility and pregnancy outcomes. Around two-thirds of adults in the UK are overweight and of these, one in four is obese. The body has a natural tendency to store fat so if you eat lots of fatty foods such as meat, dairy, cake and biscuits, you gain weight. Even lean cuts of meat contain relatively high levels of fat compared to plant foods.
Again, chicken is not the answer as modern supermarket birds contain more fat than protein! People who eat meat and dairy foods tend to consume more calories than vegans but even when they eat the same number of calories, meat-eaters gain more weight. Researchers also found that those who eat lots of protein at the expense of fat or carbohydrate – which contains fibre – also gain more weight too. Research from 170 different countries shows that meat intake is directly linked to weight gain while a different study came to the conclusion that meat is as bad as sugar for putting on weight. It found that if we eat more food than we require, fats and carbohydrates are digested first for the energy we need.
Unlike plant protein, that contains fibre, meat protein contains none and its energy ends up being stored as fat. They say that public health strategies should be put in place to reduce meat consumption but despite this all the concentration focuses on sugar.
Perhaps it’s not surprising that recent studies have also found a link between men’s weight and their risk for infertility. In a study of 520 men, those with the highest BMI had the lowest sperm count while other studies show that obese men are more likely to have semen with a decreased sperm count and significant abnormalities in sperm morphology and motility (its structure and ability to move). There are many factors thought to be responsible for the link between obesity and infertility, one of which is thought to be the hormonal changes that take place in the obese men – raised oestrogen and lower testosterone levels. Weight is clearly one of the keys to infertility and there is a wealth of research showing how a low-fat vegan diet can help achieve and maintain healthy weight – so not a bad starting point.
There is no doubt that diet has a huge impact on health and fertility is no exception. Men who eat the most vegetables and fruits – and all the vitamins, folic acid and fibre they contain – tend to have healthier sperm than those who eat lots of protein and fat found in meat and full-fat dairy foods, French fries and snacks. Infertility in women is also linked to diet, with higher rates being found in women who eat the most animal protein.
Given there are only positive effects in steering people towards a healthy diet and lifestyle, it is inexplicable that couples seeking help with reproduction aren’t told of the dramatic effect diet can have on its success.