[Part 1] The Silent Decline in Men's Testosterone and Sperm Counts

Men today are not the men their grandfathers were. At least not biologically.

Over the past five decades, something remarkable, and deeply concerning has been happening to male reproductive health. Sperm counts are falling. Testosterone levels are dropping. And the science is pointing increasingly clearly at the world we have built around us as the primary culprit.

This is not a niche concern for men trying to have children. Testosterone is the foundation of male vitality, energy, mood, cognition, bone density, cardiovascular health, and longevity. A decline in testosterone is a decline in overall male health. And the evidence suggests this is happening to men everywhere silently, and at scale.

The Scale of the Problem

The numbers are stark. A landmark 2022 meta-analysis published in Human Reproduction Update, updating a major 2017 analysis, found a worldwide decline in sperm concentration of more than 50% over the past 46 years, with the rate of decline actually accelerating since the year 2000.^[1] Importantly, this is now confirmed not just in men from North America, Europe and Australia, but also from South and Central America, Asia and Africa, making this a truly global phenomenon.^[1]

Meanwhile, testosterone levels in men have been falling in parallel. A 2025 review found that even among men who maintained constant weight over 20 years, mean testosterone declined by 117 ng/dL (approximately 19%), suggesting that rising obesity alone cannot explain the decline, and that wider environmental and lifestyle forces are at work.^[2]

The decline is not just a number. Lower sperm counts are associated with increased risk of testicular cancer, genital birth defects, and critically higher rates of premature mortality.^[1] In other words, sperm count is not just a measure of fertility. It is a barometer of overall male health.

What is Driving the Decline?

The causes are multifactorial. Genetics takes thousands of years to change, so the speed of this decline tells us immediately that environment and lifestyle are pulling the trigger. The evidence points to a combination of factors.

Endocrine-Disrupting Chemicals: The Invisible Hormonal Saboteurs

The most significant and well-evidenced culprit is chronic exposure to endocrine-disrupting chemicals (EDCs), synthetic compounds that interfere with the body's hormonal signalling systems. Two in particular have been extensively studied.

Bisphenol A (BPA)

Bisphenol A (BPA) is found in the lining of food cans, plastic water bottles, polycarbonate containers, thermal receipt paper, and medical devices. It is essentially unavoidable in modern life. BPA mimics oestrogen in the body, binding to oestrogen receptors and disrupting the delicate hormonal balance required for healthy sperm production and testosterone synthesis. A Kaiser Permanente study of 514 workers found that men with higher urinary BPA levels had 2–4 times the risk of poor semen quality, including low sperm concentration, motility, and vitality.^[3] Cross-sectional studies have further linked BPA to a 10–15% decrease in blood testosterone levels.^[4] BPA also suppresses the pituitary secretion of LH, which in turn directly reduces Leydig cell testosterone production in the testes.^[5]

Phthalates

Phthalates are plasticisers used to make plastics flexible. They are found in food packaging, flooring, cosmetics, fragrances, and pharmaceuticals. Like BPA, they are anti-androgenic and they suppress testosterone production and impair sperm quality.^[6]Both BPA and phthalates also interfere with thyroid hormone receptors, with downstream effects on energy metabolism and cognition.^[7]

Beyond plastics, heavy metals (cadmium, lead, arsenic, mercury) found in food, water, cosmetics and air pollution have been shown to directly reduce sperm count, vitality, motility, and morphology.[8] Air pollution, such as particulate matter, nitrogen oxide, sulphur dioxide, has been linked to abnormal sperm morphology and DNA fragmentation.^[8] Pesticides and herbicides round out the picture, acting as endocrine disruptors at very low concentrations.^[9]

Lifestyle Factors

Alongside chemical exposure, modern lifestyle choices are compounding the problem:

Obesity is one of the most powerful suppressors of testosterone in which fat tissue converts testosterone to oestrogen, creating a vicious hormonal cycle^[2]
Chronic stress elevates cortisol, which directly inhibits testosterone production^[10]
Poor sleep is deeply damaging the body produces the majority of its testosterone during deep sleep, and even moderate sleep disruption measurably reduces levels^[10]
Alcohol increases cortisol, promotes conversion of testosterone to oestrogen, impairs sleep quality, and has a direct toxic effect on Leydig cells^[11]
Sedentary behaviour and smoking are independently associated with poorer semen parameters^[8]
Poor diet low in zinc, selenium, Vitamin D, and antioxidants deprives the testes of the raw materials needed to produce healthy sperm and testosterone^[12]

The Microplastics Frontier

Emerging evidence adds another layer of concern. Microplastics, tiny particles shed from plastic products, have now been detected in human testicular tissue, blood, and organs. Animal studies have shown that even brief exposure to polystyrene microplastics at environmental levels causes testicular inflammation, disruption of the blood-testis barrier, and a significant decline in testosterone levels.^[13] While definitive human causal data are still accumulating, the findings are sufficiently alarming that reducing plastic exposure is a sensible precaution.

Dr Tim Trodd

Family Medicine, Functional Medicine, General Practice

MBBS (London)
DCH (London)
DRCOG (UK)
MRCGP (UK)
FHKAM (Family Medicine)

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References

Levine, H., Jørgensen, N., Martino-Andrade, A., Mendiola, J., Weksler-Derri, D., Jolber, M., Swan, S.H. et al. (2023). 'Temporal trends in sperm count: a systematic review and meta-regression analysis of samples collected globally in the 20th and 21st centuries.' Human Reproduction Update, 29(2), pp. 157 to 176. Available at: https://doi.org/10.1093/humupd/dmac035.
Fraile-Martínez, O., García-Montero, C. and Ortega, M.A. (2026). 'Understanding the secular decline in testosterone: mechanisms, consequences, and clinical perspectives.' International Journal of Molecular Sciences, 27(2), p. 692. Available at: https://doi.org/10.3390/ijms27020692.
Kaiser Permanente Division of Research. (2010). 'Exposure to BPA associated with reduced semen quality.' Kaiser Permanente Division of Research. Available at: https://divisionofresearch.kaiserpermanente.org/exposure-to-bpa-associated-with-reduced-semen-quality [Accessed: 16 June 2026].
Stavros, S., Kathopoulis, N., Moustakli, E., Potiris, A., Anagnostaki, I., Topis, S., Arkouli, N., Louis, K., Theofanakis, C., Grigoriadis, T., Thomakos, N. and Zikopoulos, A. (2025). 'Endocrine-disrupting chemicals and male infertility: mechanisms, risks, and regulatory challenges.' Journal of Xenobiotics, 15(5), p. 165. Available at: https://doi.org/10.3390/jox15050165.
ARC Fertility. (2026). 'Microplastics are destroying male fertility fast.' Available at: https://arcivf.com/microplastics-are-destroying-male-fertility-fast [Accessed: 16 June 2026].
Hu, C.J., Garcia, M.A., Nihart, A.J., Liu, R., Yin, L., Adolphi, N.L., Gallego, D.F., Kang, H., Campen, M.J. and Yu, X. (2024). 'Microplastic presence in dog and human testis and its potential association with sperm count and weights of testis and epididymis.' Toxicological Sciences, 200(2), pp. 235 to 245. Available at: https://doi.org/10.1093/toxsci/kfae060.
Olson M. (2024). 'Microplastics: their impact on our health and how to reduce our exposure.' Valley Healthspan. Available at: https://valleyhealthspan.com/microplastics-their-impact-on-our-health-and-how-to-reduce-our-exposure [Accessed: 16 June 2026].
Tesarik, J. (2025). 'Lifestyle and environmental factors affecting male fertility, individual predisposition, prevention, and intervention.' International Journal of Molecular Sciences, 26(6), p. 2797. Available at: https://doi.org/10.3390/ijms26062797.
Smith, R.P. (2021). 'Male fertility is declining; studies show that environmental toxins could be a reason.' UVA News. Available at: https://news.virginia.edu/content/male-fertility-declining-studies-show-environmental-toxins-could-be-reason [Accessed: 16 June 2026].
Kyle C, (2025). 'A functional medicine approach to low testosterone in men.' STAT Wellness. Available at: https://www.statwellness.com/a-functional-medicine-approach-to-low-testosterone-in-men [Accessed: 16 June 2026].
Kyle C, (2025). 'What does alcohol do to your testosterone levels?' Valida Health. Available at: https://validahealth.dk/en/blogs/news-room/hvad-gor-alkohol-ved-dit-testosteronniveau [Accessed: 16 June 2026].
Torres-Arce, E., Vizmanos, B., Babio, N., Márquez-Sandoval, F. and Salas-Huetos, A. (2021). 'Dietary antioxidants in the treatment of male infertility: counteracting oxidative stress.' Biology, 10(3), p. 241. Available at: https://doi.org/10.3390/biology10030241.
Sciorio, R., Greco, P.F., Greco, E., Tramontano, L., Elshaer, F.M. and Fleming, S. (2025). 'Potential effects of environmental toxicants on sperm quality and potential risk for fertility in humans.' Frontiers in Endocrinology, 16, p. 1545593. Available at: https://doi.org/10.3389/fendo.2025.1545593.