Men’s Fertility Facts


Understanding the effects of age on male fertility is important as couples are delaying parenthood much more frequently. In developed countries couples are more likely to postpone having children for financial and career planning reasons.

Men’s fertility deteriorates with age but at a much slower rate than women. Men start producing mature sperm in the testicles during puberty and there have been several studies looking at the subsequent age related decline in sperm quality.

We have fairly good evidence that sperm volume decrease by around 30% after the age of 50 years old. Around the age of 40 years old there seems to be a tipping point where sperm parameters such as sperm motility and morphology may begin to change. The exact mechanisms that are responsible for this decline are still not fully understood.

One theory is that as men age they are more likely to produce more sperm with damaged DNA and gene mutations. If the DNA in the sperm is damaged it can increase the risks of miscarriage and increased risk of genetic abnormalities in offspring. If you want to find out more about what you can do to reduce sperm damage see our article on optimising sperm.

Body Mass Index

‘Overweight’ and ‘Obese’ are common terms used to describe excesses of body fat. Obesity is a national health problem affecting both men and women and in 2017 it was recorded that 67% of men are either overweight or obese. Obesity has been shown to be an important factor that influences male fertility.

The most commonly used scale to measure obesity is Body Mass Index (BMI) and it is calculated from a person’s height and weight (BMI = weight [kg] / height2 [metres]).

Obesity is defined as > 30 and recent studies have shown abnormal sperm parameters in this group of men. Obese men are far more likely to have a reduced sperm count and reduced sperm motility. A normal BMI is defined as being under 25. Check out your BMI using our BMI calculator and work out your target weight.


Tobacco smoking is considered as one of the major factors leading to male infertility. It is clear from studies that smoking has a detrimental impact on both the quantity and quality of sperm.

It is thought that the toxins contained in cigarettes might be harmful to  male germ cells and their development. Smoking does not seem to affect male hormones so the mechanism of injury to sperm is damage due to nicotine and the toxins in tobacco.

Several studies have shown that tobacco smoking is associated with a reduced sperm count and a higher number of abnormal sperm in the ejaculate. If you are wanting to quit smoking and looking for support you can become Smoke Free.


Alcohol consumption has been shown in several studies to have a detrimental impact on the male reproductive system. Alcohol seems to alter semen parameters and affect the testes. In most cases low levels of alcohol probably have minimal impact. However, some individuals may be more susceptible to sperm damage than others.

Alcohol consumed in high quantities can cause testicular and liver damage and in some cases lead to impotence and more severe problems. The vast majority of people who consume low levels of alcohol will not see an impact. Though if you are noted to have poor quality sperm it may be an important factor to consider.


The evidence for maintaining a healthy diet has been confirmed in several studies to improve sperm quality. In general studies have shown that diets rich in nutrients like omega-3, antioxidants and vitamins D but low in saturated fats are better for sperm.

Eating foods like fish, shellfish, seafood, poultry, cereals, fruits and vegetables, low fat dairy have all been associated with improved sperm parameters. Foods to avoid are diets rich in processed meats, full-fat dairy, cheese, coffee, alcohol and sugar-sweetened beverages.

Taking a multi-vitamin pre-conceptually that contains vitamin E, Vitamin C, b-carotene, selenium, zinc and coenzyme Q-10 may help improve sperm quality. A high intake of alcohol, caffeine, red meat and processed meats will have a negative impact on male fertility.


The health benefits of exercise are well known, but the natural question is can exercise be damaging to male fertility? This is not an easy question to answer as there are so many variables to consider here with different sport types, intensities and durations.

The testes operate optimally at around 2°C lower than body temperature. Research focussed around excess heat in the scrotal area and found that it can affect sperm production. Typically men participating regularly in motorsports, cycling and horse-riding may see a deterioration in sperm quality.


It is possible for some infections to affect sperm production and overall sperm health and these account for around 10% of male fertility problems. Infections can cause inflammation, scarring and blockages of the important tissues that transport sperm from the testes during ejaculation. The two structures of importance that can become affected are the epididymis (epididymitis) and the testicles (orchitis).

Mumps used to be a common childhood infection before the MMR vaccine was fully introduced. Associated with this childhood viral infection is orchitis (inflammation of the testicles) and around 10% of men who experience this will see testicular atrophy and a reduced sperm count.

Epididymitis (inflammation of the epididymis) may be caused by chlamydia and gonorrhoea. These are sexually transmitted infections that require treatment and are often silent without symptoms. It is important if you have had unprotected sexual intercourse with more than one partner to be certain that you don’t have a sexually transmitted infection that could affect your own fertility and that of a future relationship.