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What impacts male fertility? Everything you need to know about the male reproductive system

What impacts male fertility? Everything you need to know about the male reproductive system

10 min read

This article was produced in collaboration with Dr. Rashmi Kudesia, a board-certified reproductive endocrinologist at CCRM Fertility.

Couples experiencing infertility may often assume that the person with ovaries is the only partner in need of treatment and tests — but a male factor is solely responsible in about 20% of infertility cases in opposite-sex couples, and “informative” (meaning partially responsible) in another 30-40% of infertility cases, according to the American Society for Reproductive Medicine.

In other words, when opposite-sex couples visit a fertility specialist, 5-6 out of 10 cases will receive a diagnosis that either directly or indirectly relates to sperm quality or another aspect of the male reproductive system.

Here, we’ll give you the lowdown on what impacts male fertility and how the male reproductive system functions. We’ll cover the factors that play a role in healthy sperm development (including lifestyle and environmental factors), conditions that cause fertility issues in men, and ways to boost male fertility.

Male reproductive system 101

First things first: a basic anatomy lesson. The male reproductive system includes the penis, testicles, scrotum, and prostate — medical terminology that likely sounds familiar. But it also includes parts of the body that may sound less familiar, like vas deferens, epididymis, and seminal vesicles. When they’re functioning normally, all of these things work together to produce sperm and help it reach an egg for possible fertilization.

  • The penis and scrotum are two external parts of the male reproductive system, meaning they’re outside of the body. The scrotum is the sac of skin hanging beneath the penis, and it contains the testicles, which are especially important when we talk about sperm. The two testicles (sometimes called testes) are the site of initial sperm production (spermatogenesis)  and also contain cells that produce sex hormones (like testosterone).
  • Connected to each testicle is the epididymis, which is a tube that contains sperm that needs to undergo additional maturation before it is ejaculated. The epididymis also connects each testicle to two more long, skinny tubes, each called a vas deferens. Those two tubes transport sperm from the epididymis during ejaculation, picking up secretions from the seminal vesicles and prostate gland along the way.
  • So what are seminal vesicles exactly? These two tiny organs near the bladder play vital roles in helping sperm swim, because they produce the fluid that carries sperm (aka semen). The prostate is another gland that also produces an alkaline fluid to help the sperm survive the acidic vaginal environment.

The sperm

You might picture sperm as cartoonish tadpoles thanks to images from sex ed textbooks, but there is a lot more to them than that. Each individual sperm consists of three parts (if the sperm formed normally — we’ll talk more about that in the next section).

  • The head of the sperm, which contains the DNA, penetrates the egg.
  • The midpiece or body produces energy to help the sperm move (or swim).
  • The tail propels the sperm to move forward on its journey toward the egg through the vaginal tract.

The hormones

We’ve already mentioned testosterone, which helps stimulate sperm production (which is also called spermatogenesis). And just like their key roles in the female reproductive system, LH (luteinizing hormone) and FSH (follicle stimulating hormone) have important jobs helping your testicles function so they can produce testosterone.

What factors play a role in healthy sperm development?

Healthy or normal sperm can be measured by four parameters in a semen analysis or sperm test. These parameters determine “sperm quality,” or whether or not sperm can effectively do its job — which is to reach and penetrate an egg.

  • Concentration refers to the count, or amount, of sperm in 1 milliliter of ejaculate.
  • Volume is the amount of semen that gets ejaculated.
  • Motility describes sperm’s ability to move, or swim.
  • Morphology is about the form, size, and shape of the sperm. If the sperm developed abnormally, then its head may be too big or may have multiple tails. The medical community remains undecided about the importance of morphology in assessing infertility.

Male infertility can often be explained by one of these three causes:

  • Issues in sperm production (how sperm is made)
  • Issues in sperm delivery (how sperm moves through and exits the reproductive organs)
  • Issues with sexual function (whether erectile issues prevent ejaculation.)

Dr. Rashmi Kudesia, a fertility specialist at CCRM Fertility, says that male factor infertility is most commonly related to sperm production, such as lower sperm count or motility. Other causes of infertility, such as blockages in the reproductive organs, are more rare.

What lifestyle and environmental factors can impact male fertility?

The sperm development cycle is about three months, according to Dr. Kudesia, which means altering your lifestyle can have very real impacts on the sperm you produce, both beneficial and harmful:

  • Smoking and drinking: Smoking cigarettes, using tobacco, using cannabis, and “heavy” alcohol drinking (14+ drinks per week) has a negative impact on sperm production, count, and motility. The exact effects of cannabis are still being studied, and Dr. Kudesia shares that “We don’t know the impacts of these substances on a cellular level for sperm,” but there is a potential risk.
  • Nutrition: Some studies show that diets high in certain foods can be linked to lower sperm counts, specifically soy, processed meat, trans fats, and high dairy fat. Because of the high levels of estrogen in soy products, Dr. Kudesia explains that consuming soy can result in an imbalance of androgens and estrogen (you may have previously heard these hormones described as “male hormones” and “female hormones,” but everyone has both). Just like how people with ovaries may not ovulate due to hormonal imbalances, people with testes may not be able to produce sperm normally if their hormone levels are off.

Increased estrogen levels don’t only come from eating foods containing soy, but from fat tissues within the body. For that reason, consuming foods high in trans fat (such as processed foods) can lead to excess estrogen in the body.

In the case of red meat and dairy, Dr. Kudesia says the direct correlation between those foods and lower sperm count isn’t as clear to researchers. However, there is data showing that some people have inflammatory responses to them, which can potentially affect sperm production. There are also concerns about standards in the United States dairy industry, and whether dairy contains endocrine-disrupting chemicals that can affect fertility.

  • Stress: Some studies point to a link between stress, mental health, and sperm quality. Stress can periodically make it difficult for someone with a penis to maintain an erection, but a direct impact on sperm quality has not been conclusively proven, “In theory, stress can conceptually be bad on a cellular level,” Dr. Kudesia says, but more research is needed to make a definitive connection between mental health and sperm quality.
  • Exposure to heat: Lower temperatures are ideal for sperm production, which makes sense considering that testes develop outside of the body where it’s cooler. Frequently using hot tubs or saunas and/or wearing tight underwear can increase blood flow to the scrotum, raising its temperature and potentially affecting how sperm get produced. But in terms of how exposure to heat from cell phones and laptops may impact sperm quality, the data is inconclusive.
  • Exposure to toxins: BPA (an industrial chemical found in some plastics), pesticides, radiation, and heavy metals (such as mercury and lead) can affect various aspects of a person’s sperm quality if they’re exposed to high amounts of these toxins.

How does age impact male fertility?

Just as it can be difficult for a person with ovaries to get pregnant when they get older, sperm quality and male fertility also decreases as a person ages — albeit at a slower rate and likely with less clinical significance.

Semen quality, including sperm motility and morphology, has been shown to be lower when comparing results from 30-year-old men to 50-year-old men, however sperm parameters cannot accurately predict male fertility (only the ability to achieve a pregnancy can!). Because there is no significant decline in male fertility until the mid 40s-50s, it is unlikely that older male age drastically contributes to male factor infertility, unlike advanced female age.

Male factor infertility can be related to many disorders that we don’t typically think about in the context of sperm and pregnancy.

Can health conditions directly connected to sperm and the male reproductive system affect male fertility?

There are a few main production disorders that cause male infertility:

Cancers, injuries, infections, hormone imbalances, and more can result in male factor infertility.

  • Surgical scarring, cancers or tumors in the reproductive organs, injury, or previous infections can result in obstruction of the vas deferens, which can make it difficult or impossible to ejaculate.
  • Untreated STIs, such as gonorrhea or HIV, can cause infertility.
  • Varicocele, which is the swelling of the veins that drain the testicles, may cause male infertility and decreased sperm quality due to poor temperature regulation in the testicles.
  • Hormone imbalances, specifically low levels of testosterone and androgens and/or high levels of estrogen, can affect sperm production.
  • Undescended testes, or a testicle that did not descend from the abdomen to the scrotum during fetal development, can cause a person to have infertility.
  • Childhood illnesses like mumps orchitis can affect sperm motility and decrease sperm count and/or lead to azoospermia, resulting in potential infertility later in life.

Can you "boost" male fertility?

From medication, surgery, and assisted reproductive technology to basic lifestyle changes, there are numerous steps a person can take to improve their fertility (with a doctor’s guidance!).

How male infertility gets diagnosed

Before you can receive medical treatment for male factor infertility or figure out whether you might benefit from changing aspects of your lifestyle, you’ll need to undergo semen analysis (also called getting your sperm tested). This type of testing can be done at a doctor’s office by an andrology lab or through at-home testing kits.

In either scenario, when you provide a semen sample, various features (motility, morphology, concentration, and volume) are examined to find any abnormalities in the sperm or reasons why the sperm may not be able to complete the journey to an egg.

Semen analysis combined with additional testing (like bloodwork to test hormones) may help confirm that you’re experiencing fertility issues. Here are the following categories of infertility you may fall into:

  1. Primary testicular defects in the production or development of sperm: This refers to infertility, and happens in 65-80% of male infertility cases.
  2. Idiopathic male infertility: This condition means that your sperm analysis results are “normal,” but for an unidentified reason, the sperm is not fertile. This will be the case in ~30% of male infertility cases.
  3. Sperm transport disorders: ~5% of male infertility cases relate to the sperm’s ability (or inability) to move, aka its motility. Sperm transport disorders are typically caused by an abnormality that prevents the sperm from successfully swimming.
  4. Endocrine and systemic disorders: In these cases, hormone imbalances caused by specific disorders affect how your brain signals to the testes to produce sperm, explaining 2-5% of male infertility cases. These disorders usually impact your levels of gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH) luteinizing hormone (LH), thyroid-stimulating hormone (TSH), and/or testosterone (T).

Once the potential cause of male factor infertility has been narrowed down, you may be directed towards a specific medical treatment or get suggestions on how to make your lifestyle healthier for your sperm.

Medical treatments for male fertility

Under the care of a reproductive urologist or reproductive endocrinologist, a person experiencing male infertility can take hormone medications to improve their sperm production. Commonly prescribed treatments to improve testosterone levels and/or motile sperm count may include gonadotropin therapy (hCG), clomiphene citrate, and anastrozole.

  • For people who are experiencing infertility due to a vas deferens obstruction or varicocele, surgical treatment may be recommended.
  • Assisted reproductive technologies (ART) such as in-vitro fertilization (IVF), intrauterine insemination (IUI) and intracytoplasmic sperm injection (ICSI) can all help sperm more easily reach a partner’s egg if low sperm motility and/or low sperm count is making it difficult. In a situation where male infertility persists, then a sperm donor can be used to impregnate a partner with ovaries through ART or IUI.
  • While dietary supplements, folic acid, and zinc supplements can be suggested to improve male fertility, there are differing perspectives about whether these supplements have a positive or neutral impact — meaning they may not cause any harm to sperm quality, but they may not necessarily help either.

Lifestyle changes for male fertility

  • Studies show a link between improved sperm parameters and eating walnuts, fruits, vegetables, whole grain products, and healthy proteins like fish, lentils, and legumes. Dr. Kudesia recommends a Mediterranean-style diet — meaning an antioxidant heavy diet, which can be achieved through fresh fruits and vegetables. Limit your intake of red meat, dairy, and processed foods.
  • Avoid smoking and drinking alcohol.
  • Exercise in order to maintain a healthy weight for your body. For people who produce sperm, higher levels of body fat can decrease their testosterone levels, increase their estrogen levels, and decrease their sperm count. According to University of Utah Health, doing just 30 minutes of any aerobic exercise per day can help prevent weight-related negative impacts on sperm quality.
  • Dr. Kudesia notes that, in general, the male reproductive system is not as affected by physical activity as the female reproductive system, but exercise is important because it can also help relieve stress. “There could be more of a connection between stress and subsequent erectile issues,” Dr. Kudesia says, so exercise may help treat infertility caused by erectile dysfunction. (As we discussed in an earlier section, the link between stress and actual sperm quality is still being studied.)

Reproductive health is important for everybody. Whether you’re a person with sperm, a person whose partner has sperm, or a person with ovaries seeking donor sperm, knowing how to improve male fertility and understanding the tests and treatments available to you can help make the journey to conceive more manageable. Here at Modern Fertility, we’ll empower you with knowledge each step of the way.

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Rachel Sanoff

Rachel Sanoff is a writer and editor in Los Angeles. She was previously an essays editor at O.school, a digital sex education platform, and the features editor at HelloGiggles.

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