Semen quality


Semen quality is a measure of male fertility, a measure of the ability of sperm in semen to accomplish fertilization. Semen quality involves both sperm quantity and quality. Semen quality is a major factor in fertility.
Cryptorchidism, hypospadias, testicular cancer and poor semen quality make up the syndrome known as testicular dysgenesis syndrome.

Factors

Many factors influence sperm quality. Exposure to any of the temporary factors can cause up to a three-month delay before sperm quality returns to normal, due to spermiogenesis.

General decline

A 2017 review and meta-analysis found sperm counts among Western men declined 50–60% between 1973 and 2011, with an average decline of 1.4% per year. The meta-analysis found no indication the decline is leveling off. The decline among North American and Australian/European men is similar. The decline in sperm count among men in South America, Asia, and Africa is less than men in Western countries, though the amount of decline in these regions is uncertain. The reasons for the decline are not known with certainty, but it may be associated with chemical exposure, maternal smoking during prenatal development, pesticide exposure, or lifestyle changes during adulthood.

Age

Although it is possible for men to father children into old age, the genetic quality of sperm, as well as its volume and motility, all typically decrease with age. Advancing paternal age has been implicated in several possible health effects. One particularly well-studied connection is the link between advancing age and autism. For example, one study of 943,664 children less than 10 years old found that, with confounding variables controlled, the risk of autism increased with increasing paternal age.
In men with a normal level of sperm production, the percentage of sperm DNA fragmentation is positively correlated with age, and inversely correlated with progressive sperm motility.
No age-related effects on sperm were noted in separate control groups recruited in different geographical locations, indicating that dietary habits, lifestyle, or ethnicity could play a part in the quality of sperm.
While advanced age can be a possible factor in sperm motility and health, the sperm of men below 20 years of age has likewise been linked to an increase in birth defects such as neural tube defects, hypospadias, cystic kidney, and Down syndrome.

Heat

Sperm are heat-sensitive, and cannot endure high temperatures. Increases of 2–3 °C are associated with increased DNA fragmentation.
The body has compensatory mechanisms, like the cremaster muscle relaxing and letting the testicle hang further away from the warm body, sweating, and a countercurrent exchange of blood cooling inflowing blood. However, despite these compensations, some activities should not be performed too often, to prevent infertility due to heat:
Fever raises the body temperature, which can affect sperm quality.
Contrary to widely held beliefs, no evidence supports that wearing tight underpants decreases fertility. Even with an elevation in temperature of 0.8–1° caused by wearing constrictive underwear, no changes in sperm parameters, no decrease in spermatogenesis, and no changes in sperm function are observed.

Physical trauma

A blow from the outside does not affect the sperm quality of already produced sperm cells. Furthermore, the testes are well protected in the scrotum, for example by the tunica vaginalis, making the testes slide away from external pressure rather than being malformed from it; however, a hard enough hit can close or crush the capillaries that supply the sperm-producing tissue, resulting in permanent or temporary and partial or total inability to produce sperm in the affected testicle.

Chemicals

There is suspicion that many toxic substances, including several types of medication and hormones, and also constituents of the diet, influence sperm quality. While a few chemicals with known effects on fertility have been excluded from human consumption, we cannot know if others remain undiscovered. Many products that come into direct contact with spermatozoa lack adequate testing for any adverse effect on semen quality.

Endocrine disruptors

s are chemicals that interfere with the endocrine system.
A 2008 report demonstrated evidence of the effects of feminizing chemicals on male development in each class of vertebrate species as a worldwide phenomenon; these chemicals are suspected of reducing the sex ratio and sperm counts in humans. Ninety-nine percent of over 100,000 recently introduced chemicals are poorly regulated.
At least three types of synthetic toxins have been found in the semen of student volunteers: polychlorinated biphenyls, DDT, and hexachlorobenzene. DDT and hexachlorobenzene are associated with decreased semen quality, while PCBs are associated with decreased fertility overall. Leaks of dibromochloropropane have caused sterility in men. Soldiers that were exposed to dioxins and dioxin-like compounds during the Vietnam war have given rise to children with an increased rate of birth defects.
Phthalates, a ubiquitous pollutant, may cause decreased sperm production when having been exposed to it during prenatal development.
Other potential xenoestrogens that have been associated with decreased sperm quality in some studies are bisphenol A, nonylphenol and octylphenol.

Medication

  • Depo-Provera, Adjudin, and gossypol are examples of substances used as male contraceptives or in chemical castration. Recent studies have found that THC present in cannabis can confuse the movements of intact sperm, reducing their ability to achieve fertilization.
  • Many antibiotics, e.g., penicillin and tetracycline, suppress sperm production.
In addition, in vitro studies have observed altered sperm function by the following medications:
  • Many psychoactive drugs, including many antidepressants, many antiepileptics, and propranolol
  • Opioid analgesics
  • Calcium channel blockers
  • Phosphodiesterase inhibitors
  • Statins
  • Calcium chelators
Also, numerous products intended for exposure to spermatozoa have only a general assumption of safety based on the absence of evidence of actual harm.

Hormones

  • Anabolic steroids use and use of other hormones can reduce sperm quality. Changes in hormone homeostasis affect the spermatogenesis.
The body also has natural variations in hormone concentrations, giving sperm quality natural fluctuations as well.

Diet

  • Drinking over 1 litre of cola a day might decrease sperm quality by up to 30%
  • Soy products decrease sperm quality due to the high content of a type of phytoestrogen called isoflavones. Theoretically, this exposure to high levels of phytoestrogen in men may alter the hypothalamic-pituitary-gonadal axis. A few studies on animals have shown that such a hormonal effect may be significant and decrease fertility. On the other hand, most studies have shown that isoflavone supplements have little to no effect on sperm concentration, count, or mobility, and cause no changes in testicular or ejaculate volume.
  • A review in 2010 concluded that there is little evidence for a relationship between semen parameters and increased BMI.
  • Folate may protect sperm cells from aneuploidy.
  • Gossypol has been associated with reduced sperm production. It is present in crude cottonseed oil, and potentially the organ meats from animals poisoned with it
  • A review of epidemiological/observational studies provided the most comprehensive analysis of the associations between diet or nutrient intake and the risk of infertility. It suggests that diet modifications may be useful in modulating male fertility and fecundability. Healthy diets rich in such nutrients as omega-3 fatty acids, some antioxidants and vitamins, and low in saturated fatty acids and trans-fatty acids are associated with high semen quality parameters. In terms of food groups, fruit, seafood, poultry, eggs, cereals, leafy vegetables, dark chocolate, and low-fat dairy products have been positively related to sperm quality. However, diets rich in processed meat, fried foods, potatoes, full-fat dairy products, caffeine, alcohol, and sugar-sweetened beverages have been inversely associated with the quality of semen in some studies. The few studies relating male nutrient or food intake and fecundability also suggest that diets rich in red meat, processed meat, tea, and caffeine are associated with a lower rate of fecundability. This association is only controversial in the case of coffee, because a little bit of coffee, two to three cups a day, has been shown to help improve sperm motility, but more than three cups a day have been shown to have impaired fertility. The potential biological mechanisms linking diet with sperm function and fertility are largely unknown and require further study.
  • One study found that following a diet rich in fruits, vegetables, potatoes, meat, full-fat dairy products, seafood, and pastries increased sperm count by 50%. Men who consume such a diet have sperm counts nearly twice as high as men who do not.

    Other chemicals

Environmental mutagens that are associated with decreased semen quality include the following:
  • Plutonium, widely spread from nuclear weapon tests, accumulates in the testes, where it disrupts zinc metabolism, in turn causing genetic damage.
  • Ethylene oxide, a chemical sterilizer, is associated with decreased semen quality.
Other environmental agents associated with decreased semen quality include: