What you need to know about male fertility

Male fertility has been somewhat ignored in fertility conversations. Sometimes it can feel like men are forgotten when it comes to fertility, but the role of a man (or at least the sperm) is crucial to achieving a pregnancy.

Among heterosexual couples who have trouble getting pregnant, it has been shown that in 50% of cases, it's due to a male factor. So men cannot be left out when it comes to fertility testing, or when you start thinking about and preparing for a pregnancy.

Male fertility is almost exclusively about the sperm - they must be large enough, high enough quantity, fast enough, and good enough quality. There could be many reasons why a man has problems with his sperm, which we'll explore below.

It is also important to remember that fertility is complex, and depends on many factors in both the woman and the man. If everything from a sperm test "looks good," that's of course a good sign, but there is no guarantee that you will easily get pregnant.

To get pregnant, only one sperm has to succeed in fertilizing an egg

Fertilizing an egg is hardly the goal every time a man ejaculates, but biologically this is the sole purpose of the sperm.

To increase the odds of success, a single batch contains millions of sperm. It may seem a bit excessive, but the sperm have a very long way to go, and a lot can go wrong along the way.

On the journey to the fallopian tubes (where fertilization of the egg takes place), several million sperm have already died. Only a few thousand make it this far.

In the end, only ONE sperm will be the winner, and when this sperm has drilled into the egg, the "tail" falls off. From that moment, it becomes impossible for any other sperm to penetrate the egg and fertilize it.

Given the hardships the sperm have to deal with and how many of them never make it all the way, it's clear that the number of sperm and the quality of the sperm play a very big role in getting pregnant.

Every day, 100 million new sperm are formed (!)

In order for a child to be born, one cell from a woman and one from a man are needed - an egg cell and a sperm cell.

However, eggs and sperm are produced in completely different ways. Women are born with all their eggs and do not produce more during their lifetime, while men can continue to produce new sperm throughout life.

A healthy man is estimated to produce as many as 100 million viable sperm every day!

As with the woman's reproductive system, sperm production is a complex and sensitive process that depends on all steps functioning optimally. The sperm are produced and mature in the man's testicles, but are also dependent on the hormones FSH, LH and testosterone whose secretion is controlled by hormone glands in the brain called the hypothalamus and pituitary gland.

The sperm is produced in the testicles by a type of cell called spermatogonia, a type of stem cell, which later differentiates into male reproductive cells (spermatozoa).

They are then transported further down into the epididymis (a tube connecting the testicles to the vas deferens), where they mature into viable sperm. How long it takes for a sperm to be fully developed varies slightly from person to person, but it is estimated that it usually takes around 72 days.

If you are going to change your lifestyle to improve sperm quality (more on this below), then you need to think ahead.

When a man is sexually stimulated, the fully developed sperm begin to mix with semen coming from the seminal vesicles and prostate gland.

This mixture of sperm and semen is called semen or seed. Once the man ejaculates, the sperm swim into the vagina, through the cervix and the rest of the uterus, out to the fallopian tubes where - if you have sex during the fertile window in connection with ovulation - they can fertilize an egg.

The sperm can live up to five days in the woman's fallopian tubes and wait for an egg - that's why a woman is fertile for a few days before (and slightly after) ovulation.

What can cause male infertility?

There are several factors that can cause male infertility and disrupt the production, maturation and delivery of sperm. The problems can manifest themselves in three different ways:

  1. Insufficient sperm production (too few sperm)
  2. Reduced sperm quality and motility (too few normal or motile sperm)
  3. Blockages in the seminal vesicles that interfere with the transport of sperm

There can be many underlying factors, including genetic factors, damage to the scrotum, infections, chronic health problems, medication or lifestyle. Most men have no idea that they have impaired fertility; it's usually only discovered in connection with a fertility examination. But, just like for women, there are opportunities for men to proactively test their fertility. This can be especially important if a man has experienced any of the following:

  • Surgery in the scrotum, e.g. due to a scrotal hernia
  • Surgery for a non-migrated testicle
  • Infection of the scrotum or prostate
  • Major trauma to the scrotum that required a doctor's visit or surgery (e.g. a large blood clot)
  • Testicular torsion
  • Mumps as a child
  • Medication that is known to affect fertility
  • Cytotoxic drugs or radiation
  • Erection or ejaculation difficulties

Does a man's age affect sperm quality?

Most people are aware that age is an important factor for women when it comes to fertility problems, but for men it also plays a role. In women, fertility stops abruptly when they reach menopause, while in men, fertility gradually decreases with age.

Although age has a milder effect in men than in women, a link has been found between the men's age and the time it takes for the woman to become pregnant.

As men age, their testicles tend to shrink in size and soften, which can result in lower sperm production and poorer sperm quality. As men get older, the levels of testosterone in their blood also fall. Testosterone plays a crucial role in sperm production and in men's health in general.

Older age has also been found to be linked to a higher proportion of defective sperm, such as poorer morphology (shape) and motility (mobility). Both of these defects affect the chance of a sperm succeeding in fertilizing an egg.

DNA fragmentation in a sperm, which involves damage to DNA or to the critical hereditary material in the sperm, is also something that increases with age.

Because the man, via the sperm, delivers half of the chromosomes to the fetus, the DNA fragmentation affects both the chances of becoming pregnant and the possibility of a healthy pregnancy that does not lead to miscarriage or birth defects.

What can be done to improve sperm quality?

Lifestyle has an effect on the sperm, so if you're wanting to have a child using your sperm, it's a good idea to make conscious choices that can optimize sperm quality.

As always when talking about lifestyle and health effects, things are not black and white. There are people who have an unhealthy lifestyle but don't experience problems getting pregnant, as well as many who live healthy lives but nevertheless have fertility issues.

However, if you want to maximize your chances, or if you have a confirmed reduced sperm quality, then it's worth considering some lifestyle changes.

Since men are constantly producing new sperm, the positive lifestyle changes can show results relatively quickly. But remember that the sperm that can be ejaculated today started to be produced about 10 weeks ago.

So, you'll see any results from your lifestyle changes in 10 weeks at the earliest.

An interesting piece of evidence that a man's lifestyle and general well-being are related to sperm quality is that men with impaired sperm quality tend to also have other health problems, like cardiovascular disease and diabetes, later in life. So sperm quality is, just like a functioning menstrual cycle for women, a good indicator of a man's general health.

Oxidative stress adversely affects sperm cells

The main reason why lifestyle can play a role in male fertility is that an unhealthy life can create oxidative stress, which negatively affects the cells - including the sperm cells.

So what is oxidative stress? You could say that there is a struggle going on every day in the body: the cells are attacked by free radicals and the antioxidants fight back.

Free radicals are formed when nutrients and oxygen are converted to carbon dioxide and water in a process that gives us energy. Free radicals are an important part of the body's signaling system, but an excess of them can damage the body's cells.

Oxidative stress is an increased production of free radicals, which can render the body's antioxidant defenses insufficient. In technical terms, this is called biological oxidation; the body "rusts" from within. Some other examples of oxidation are when an apple turns brown when it is peeled, when nails rust, or when we get wrinkles with age.

In very simplistic terms, it can therefore be said that diets or supplements with a lot of antioxidants protect your sperm, and lifestyle choices that increase free radicals have a negative impact on your sperm.

Male infertility: Smoking and nicotine affect sperm production

It is clearly proven that smoking and nicotine affect sperm production and sperm quality negatively. It's the nicotine that's harmful, because it affects blood circulation and hormone levels.

Nicotine can also increase oxidative stress (explored above), which in turn can damage sperm.

Alcohol in large quantities can affect sperm quality

Researchers do not completely agree on how much alcohol a man can drink without affecting his sperm quality and fertility, so the recommendations vary from country to country.

However, most of the studies show that a moderate consumption of a maximum of 2 drinks per day does not seem to have an effect on sperm quality.

Being overweight lowers testosterone levels

Research has previously shown that there is a link between obesity in women and difficulties in getting pregnant, but now there have also been clear links between obesity in men and a reduced chance of pregnancy.

The main reason is that abdominal obesity, high blood sugar and high blood fats lower the levels of the hormone testosterone, which is absolutely necessary for male fertility.

Diet can both improve and impair male fertility

Studies have shown that diet can affect men's fertility positively and negatively.

It's always good to try to eat as balanced and healthily as possible, and to make sure you get all the nutrients you need. In addition, to increase fertility, you can ensure that you get a lot of antioxidants through your diet and supplements, like zinc, folate, and vitamin C.

Good fats, vegetables, fruits, poultry, seafood, whole grains, and nuts are good for male fertility. You can limit intake of foods that contribute to oxidative stress (like saturated fats that are most often found in meat and dairy products, sweetened beverages and other products with added sugar), as well as soy products which upset your hormonal balance.

Proper exercise is best for sperm quality

Physical activity has many benefits, both physical and mental, and can also improve sperm quality. But it is important to exercise in moderation to avoid excessive stress for the body.

Studies have shown that both inactivity and overtraining have a negative effect on sperm quality.

It was concluded that 45 minutes of exercise (aerobic or strength training), three times a week, has the most positive effect on both sperm quality and the hormones involved in male reproduction. Exercise also reduces oxidative stress and improves your mood.

The testicles like spacious underwear and a cool temperature

Sperm is very sensitive to heat, which is why the testicles are on the outside of the body. Therefore, exposing the testicles to excessive heat should be avoided as it may adversely affect sperm production. Some things to avoid are:

  • Wearing pants or underwear that are too tight - boxer shorts are best
  • Sitting still for several hours in a row - make sure that the testicles can hang freely from time to time
  • Sitting with a laptop or other hot objects in your lap for a long time
  • Keeping your mobile phone in the pockets on the front of your trousers
  • Doing long spinning classes or cycling for several hours a day
  • Taking long hot baths or being in a sauna too often.

How often should you have sex or ejaculate to improve sperm quality?

There is a myth that says that you should "save up your sperm" before trying to conceive to avoid impairing the possibility of conception. But studies have shown that it's just the opposite.

Men who have not ejaculated in 7-10 days have been shown to have poorer sperm quality, while men who ejaculated every day or every other day had sperm with better motility and a smaller proportion of DNA-damaged sperm.

Having ejaculation regularly on your own or through sex is therefore best for sperm quality. Then, of course, it is also important to time intercourse correctly in relation to the woman's menstrual cycle in order to achieve a pregnancy.


1 - https://www.hsph.harvard.edu/news/hsph-in-the-news/excess-weight-sperm-fertility/#:~:text=They%20found%20that%20overweight%20men,likely%20to%20produce%20no%20sperm.

2 - https://www.nhs.uk/common-health-questions/mens-health/how-can-i-improve-my-chances-of-becoming-a-dad/

3 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3253726/

4 - https://www.mayoclinic.org/diseases-conditions/male-infertility/symptoms-causes/syc-20374773


Evangelia Elenis, MD, PhD.

This text is fact checked by Evangelia Elenis, MD, PhD. Dr. Elenis is a chief physician in Obstetrics and Gynecology, and a subspecialist in Reproductive Medicine. She is a PhD and affiliated researcher at Uppsala University with postdoctoral studies at Harvard Medical School.

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