Global infertility could be human-induced

Infertility affects about one in six people. According to the WHO, access to fertility treatment should expand, and the topic garner more focus in health research and policy.

Infertility: becoming widespread in aging societies

There is limited variation in the prevalence of infertility between different regions of the world. This means that infertility can affect us all over the globe, as infertility rates in low-, middle- and high-income countries are comparable. Infertility is therefore a global problem. Infertility is also an increasing problem for couples who wish to have children.

Infertility is an increasingly important topic that can no longer be minimised or overlooked. The Director-General of the WHO commented on this issue as follows:

"The sheer proportion of people affected demonstrates the need to expand access to fertility treatments and to stop this issue being sidelined in health research and policy so that safe, effective, and affordable routes to parenthood are available to all who want them."1

Infertility affects both sexes

Infertility is the failure to become pregnant after 12 months of unprotected and routine sexual intercourse. Infertility affects 35% of females, 30% of males and in 20% of the cases both women and men in couples engaging in reproductive paths are affected. Female infertility can be caused by impaired ovulation, reduced ovarian reserves, disorders of the reproductive system, or even chronic diseases. If a woman has never given birth to a child, it is called primary female infertility.

Secondary female infertility is when a woman has already given birth to a child or has suffered a miscarriage and another clinical pregnancy cannot be achieved. Female fertility is influenced by other factors such as environment and lifestyle, in addition to the pathophysiology of the reproductive organs. The most common reproductive pathologies include endometriosis, impaired ovarian function, and tubal infections.2

What factors can lead to infertility?

Various aspects can influence fertility and, in case of doubt, lead to infertility.

The human microbiome: Impact on fertility 

In 2021, Skoracka's research group looked at the influence of nutrition on female fertility (doi: 10.1093/advances/nmab068). The microbiome seems to play an important role here. There is evidence that a diet high in trans fats, refined carbohydrates and added sugars can negatively affect fertility. A Mediterranean dietary pattern, on the other hand, has a positive effect on fertility. It is important here that the diet is rich in fibre, omega-3 fatty acids, vegetable protein, and vitamins and minerals. Phytoestrogens also seem to have a positive influence on female fertility. Caffeine consumption in the recommended amounts does not seem to affect fertility.2

The role of the glycaemic index in female fertility

It has been shown that a diet high in glycaemic index and rich in animal protein can negatively affect fertility. Insulin sensitivity and glucose metabolism can have a significant impact on ovulation and female fertility. For example, eating foods with a high glycaemic index can increase insulin resistance, dyslipidaemia and thus oxidative stress. This in turn can have a negative effect on ovarian function. Insulin regulates reproductive functions in addition to metabolism. It can modulate ovarian steroidogenesis and hyperinsulinemia. Both are associated with hyperandrogenism and ovulatory dysfunction.2

Vitamin D could be important for fertility

It is suspected that vitamin D is involved in the modulation of female reproductive functions. This is supported by the vitamin D receptors in the area of the reproductive organs such as the ovaries, the endometrium, the placenta and also the pituitary and hypothalamus. Vitamin D plays a role in the regulation of glucose metabolism and could therefore be an essential component in the development of the PCO syndrome.2

Do microplastics harm male fertility?

Over the last century, male sperm analysis parameters have decreased significantly for unknown reasons. It is suspected that this is due to pollutants in the diet and water. A link between microplastics and male infertility has already been investigated in scientific studies. A research team from China concluded that the minimum human equivalent dose of microplastics that leads to abnormal male semen quality is a value of 0.016 mg/kg/d.

Exposure to microplastics is already close to this value in Japan and South Korea.3 In Germany, 0.0007 particles of microplastics per litre of tap water were detectable in 2019, according to WHO data. This means that tap water performed significantly better than mineral water. Here, 300 and 6000 particles per litre were already detectable.4

Pollution is costing us our future

The rising infertility rate in recent years has now drawn the attention of various scientists to environmental pollution with microplastics, plasticisers and endocrine disrupting chemicals (EDCs). A study from Italy was also critical of microplastic pollution. In their publication Microplastics: A Threat for Male Fertility (doi: 10.3390/ijerph18052392), they addressed the impact of microplastics on male reproduction and sperm quality.

Environmental pollutants can mimic the activity of endogenous steroid hormones as endocrine-disrupting chemicals (EDCs). This can affect various mechanisms. Currently, the etiology of about 40% of male infertility cases associated with impaired spermatogenesis remains unclear. Spermatozoa have an epigenetic signature that can respond to environmental factors such as EDCs and to paternal lifestyle. It has been observed that individuals with a history of exposure to environmental pollutants may have reduced sperm quality.5

The list of possible causes of infertility is long and is largely related to the way we as humanity treat the planet and our environment. Since everything is interconnected, it was only a matter of time before we could finally detect the pollutants we release into the environment in our own bodies. Microplastics are already finding their way into unborn humans via the placenta.6

  2. Skoracka K. et al. (2021). Female Fertility and the Nutritional Approach: The Most Essential Aspects. Adv Nutr. 2021 Dec 1;12(6):2372-2386.
  3. Zhang C. et al. (2022). Microplastics May Be a Significant Cause of Male Infertility. Am J Mens Health. 2022 May-Jun;16(3):15579883221096549.
  4. In German only:,0.0007%20Partikel%20pro%20Liter%20gefunden.
  5. D'Angelo S. et al. (2021). Microplastics: A Threat for Male Fertility. Int J Environ Res Public Health. 2021 Mar 1;18(5):2392.
  6. Ragusa A. et al. (2021). Plasticenta: First evidence of microplastics in human placenta. Environ Int. 2021 Jan;146:106274.