It was once thought that men remained equally fertile throughout their lives. But scientists now believe that the quality and quantity of sperm falls slowly as men get older, with male fertility declining steadily after the age of 50. Whether the father's age is linked to problems such as learning difficulties in the child is uncertain.
Bottom line: Don't leave it too late
Alcohol affects the body's ability to absorb zinc, a nutrient vital for healthy sperm. But research suggests that moderate drinking (two to four units a day, a unit is equivalent to about half a pint of standard-strength lager) has no harmful effects on sperm quantity or quality. "As many studies say there is a problem with alcohol as saying there is not," says Dr Allan Pacey, senior lecturer in andrology at Sheffield University. That said, heavy drinking can certainly reduce sperm counts.
Bottom line: Moderation is the key
Fertility problems in men may be caused by "oxidative stress" – the effects of highly reactive molecules in the body that can cause cell damage. Oxidative stress is linked to lifestyle factors such as obesity, alcohol, diet, pollutants and smoking. Studies have shown that men with fertility problems who take antioxidant supplements (vitamin E, vitamin C, folic acid) and zinc and fish oils, increase the chance of conceiving.
Bottom line: If you have been trying unsuccessfully to conceive for more than a year, consider dietary supplements
In 2009, the Vatican published a report claiming that male infertility had increased because of synthetic female hormones from the Pill. It argued that female hormones released into the sewage system find their way into the water supply. The report was viewed with scepticism by many scientists, who pointed out that the body's digestive system breaks down oestrogen, so it is unlikely to be released into the environment.
Bottom line: Case unproven
A healthy diet will help maintain healthy sperm, but there is little evidence that veganism, vegetarianism or protein-rich diets have any dramatic effect. There is certainly no truth in the claim that meat-eaters are more virile. "India has more than a billion people, 70 per cent of whom are vegetarian," says Dr Siladitya Bhattacharya, Professor of Reproductive Medicine at Aberdeen University. Chemicals called phytoestrogens, which are found in foods including soy, coffee and beer, have been linked to lower sperm counts, but the link is not proven. In south-east Asia, where soy is a staple, there is no evidence of declining fertility.
Bottom line: Eat sensibly and ignore the fads
Physically fit men tend to have healthier sperm. Still, excessive exercise (especially in combination with illicit bodybuilding steroids and other drugs) can decrease testosterone production and lower sperm counts. Exercise can help control weight and flood the body with stress-busting hormones.
Bottom line: Exercise regularly but don't overdo it, and stay off the steroids
More sex means the number of sperm in any given ejaculation declines. Intercourse every two or three days is thought to be the optimum for couples wishing to conceive. Having sex every day will probably decrease the chances of conception.
Bottom line: Go for quality over quantity
Chemicals present in plastic packaging, detergents and shampoos, paints, glues, coatings and construction materials are known to mimic the effects of female hormones such as oestrogen. Many environmentalists believe that when these substances find their way into the water supply, they may subsequently affect sperm. There is probably some truth in this, but the link is not clear. While some shellfish have changed sex due to "gender-benders" in seawater, adult human males are more robust. But oestrogen-mimics may affect the developing foetus, affecting fertility later in life.
Bottom line: A potential concern, but not a lot you can do about it
There is good evidence that keeping the testicles warm will reduce sperm counts. "Don't wear tight underpants," says Dr Pacey. Resting a laptop on the lap really can impair a man's ability to conceive – not due to the transmission of Wi-Fi signals, but because of the heat generated by portable computers. The negative effects of cycling on male fertility that are found in some studies are probably related to the warmth generated in the crotch area. A decent saddle and padded cycle shorts will help.
Bottom line: Keep it cool
Untreated sexually transmitted infections are one of the main causes of male infertility. Men exposed to the infection chlamydia, which is symptomless in males, can have problems in the testicular vesicles, where sperm is stored. Gonorrhoea, too, can affect male fertility. Mumps can sometimes lead to permanent damage to the testicles or even lead to male sterility.
Bottom line: Use a condom and consider getting tested for chlamydia. Ensure you have been vaccinated against mumps, and that your children have their MMR vaccinations
Mobile phones, washing machines, wifi signals
Numerous electronic devices, including TVs, washing machines and Wi-Fi devices, emit low-energy, non-ionising radiation. Hundreds of studies have looked at possible links between them and male fertility problems. To date, the evidence for any effect is lacking. "If you take sperm and irradiate them in a dish [as was done in the recent Argentinian study of Wi-Fi], you see changes, but that is so far from what happens in the real world, and I see no evidence that it affects male fertility," says Dr Pacey. Mobile phones have been linked to lower sperm counts in some studies, but many scientists remain sceptical.
Bottom line: Probably no cause for concern
Pesticides and other pollutants
A host of chemicals, from solvents to pesticides, have been linked to male fertility problems, but hard evidence is limited. Some studies have shown that regular exposure to pesticides can affect sperm quality and quantity, with agricultural workers having more fertility problems. Dr Pacey says men who work in construction may be at risk from glycol ether, a solvent found in some paints, adhesives and coatings, which has been found to double the risk of fertility problems. There is no evidence that routine DIY is a risk.
Bottom line: Men working with chemicals need to be aware of the risks involved and wear appropriate protective clothing
Low-level ionising radiation is found in the natural environment and is harmless. But higher levels produced by materials such as uranium and plutonium, cosmic rays from space, X-rays, and medical techniques such as radiotherapy may damage the genetic material in cells and theoretically pose a risk to male fertility. There is little evidence that frequent air travel or proximity to a nuclear power station affects sperm.
Bottom line: Probably not a worry. If your job means you are at risk from radiation, training and protection should be provided
Some studies suggest that the regular consumption of drugs such as cannabis and cocaine can impair male fertility. Cannabis seems to dramatically affect sperm, making them swim too fast and "burn out" before they reach the egg. Prescribed drugs can also adversely affect fertility, so anyone taking medication and wishing to conceive should talk to their doctor.
Bottom line: Stay clean
Men who smoke heavily – between one or two packs per day – are more likely to have abnormal sperm, but the effect on fertility is unclear. "The effects of smoking are controversial, but there are irrefutable effects on sperm quality," says Dr Pacey. There is some evidence, he adds, that children whose fathers were heavy smokers may be more susceptible to leukaemia.
Bottom line: Don't smoke. Get help, book your self an appointment to stop smoking through hypnosis!
Stress can cause hormone changes that may affect male fertility, but it is far from proven. "I don't know of any studies showing that stress is directly linked to sperm production," says Dr Bhattacharya. Stress may affect how regularly you have sex.
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Being overweight or obese has been linked in some studies to poor sperm quality – but so has to be underweight. Scientists think this happens because oestrogen, usually present at low levels in men, maybe released from fat cells and affect male fertility. Low body weight may result from chronic disease or poor diet, which could both affect fertility.
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