Peer-reviewed research on sperm concentration, motility, DNA fragmentation, and the factors that influence male fertility, including the temperature mechanism Oakman is built around.
This study set out to understand how lifestyle factors relate to semen abnormalities in men undergoing fertility evaluation in Ghana. It analyzed medical records of 221 men at a Ghanaian…
This study looked at whether ozone (a reactive gas in smog, formed when pollution meets sunlight) affects semen quality in lower-income men with unhealthy lifestyle habits (think smoking, heavy drinking,…
This study looked at how occupational heat exposure and fertility-related stress might affect semen quality. It compared 485 men, split into groups with normal and low semen quality based on…
This study looked at whether eating ultra-processed food around the time of conception affects fertility and early embryo development in couples. It followed 831 women and 651 men from before…
This systematic review set out to examine how phthalates, chemicals widely used to soften plastics and to carry fragrance in cosmetics, affect male fertility by altering semen quality. It pulled…
This study set out to explore whether the mix of bacteria in semen differs between men with normal and abnormal sperm counts. Researchers analyzed semen samples from 80 Greek men,…
This study set out to see if sperm quality changes with the seasons in Denmark and Florida, and whether outdoor temperatures play a role. It looked at semen samples from…
This study measured how outdoor temperature tracks with semen quality, using records from 5,114 men attending a reproductive medicine centre in Wenzhou, on China's east coast. The measure it used…
This review looked at whether the underwear a man wears, tight versus loose, actually affects his fertility. The testicles work best a little cooler than the rest of the body,…
This systematic review set out to assess how GLP-1 receptor agonists (a class of diabetes and weight-loss drugs) affect male reproductive hormones, semen quality, and metabolic health. It pooled data…
This study looked at whether the intensity of physical activity affects semen quality in men who already have impaired sperm health. It followed over 1,300 men undergoing fertility evaluations, each…
This study set out to review how different weight loss methods affect male fertility in men with obesity. It looked at 32 studies that compared lifestyle changes, medications, and bariatric…
This review looked at how psychological stress might affect male fertility through oxidative stress. It synthesized animal studies and human observational data to explore the link between stress, oxidative damage,…
This study aimed to assess how much adult men know about male fertility, focusing on medical and lifestyle factors that affect it. Researchers surveyed 156 men of reproductive age using…
This study set out to see if physical fitness is linked to semen quality in Spanish men. Researchers analyzed semen samples from 324 men without known fertility issues, comparing self-reported…
This study set out to examine how modifiable lifestyle factors like smoking, drinking, and weight affect semen quality in men. It analyzed data from over 3,300 men visiting a fertility…
This study set out to explore how coffee, exercise, and sleep relate to semen quality in men. It surveyed 3,302 men aged 18-60, collecting semen samples and lifestyle data through…
This study set out to examine whether astaxanthin (a potent antioxidant) could improve sperm quality after freezing and thawing. It pooled data from multiple studies to see how astaxanthin affected…
This study set out to examine how exposure to fine particulate air pollution (PM2.5) and its components affects semen quality, and whether living near green spaces might help protect against…
This umbrella review (a review of other reviews) set out to catalogue what damages male fertility. It gathered 43 systematic reviews and meta-analyses published between 2000 and 2025, covering 67…
This study set out to see if taking oral medications or zinc supplements affects zinc levels in the blood and whether that links to better sperm health or fertility outcomes…
This study set out to evaluate whether botulinum toxin injections near the scrotum or testicles affect male fertility. It reviewed animal studies and human case reports, focusing on outcomes like…
This study looked at how different measures of obesity relate to semen quality in men from infertile couples who had no other known fertility risks. It compared body mass index…
This review examined how oxidative stress, sperm DNA damage, and epigenetic changes interact to affect male fertility. It pulled together studies on men with infertility, looking at how these factors…
This study asked whether the pandemic changed how sensitive sperm production is to weather. It took 2,672 semen analyses from 1,287 Korean men collected between 2018 and 2024 and matched…
This review gathers recent evidence on what damages male fertility and how much of it can be undone. Smoking raises sperm DNA fragmentation (breaks in the genetic material inside sperm)…
This study looked at whether obesity speeds up the decline in sperm quality that has been seen over time. Researchers reviewed semen tests from 2,430 men with normal sperm counts…
This study looked at whether vitamin D3 supplementation improves hormone levels and semen quality in infertile men. It pooled data from six randomized controlled trials involving 945 men, measuring changes…
This scoping review set out to map the evidence on how psychosocial work factors affect male fertility and sperm quality. It analyzed 18 peer-reviewed studies from 1990 to 2024, focusing…
This review set out to examine whether mobile phones and laptops, as sources of electromagnetic radiation and heat, might harm male fertility by affecting semen quality. It analyzed existing studies,…
This study set out to identify which factors might influence pregnancy success in couples undergoing assisted reproductive technology (ART, fertility treatments that handle eggs and sperm outside the body). It…
This narrative review set out to explore how lifestyle choices affect male fertility, examining diet, exercise, stress, sleep, weight, and environmental exposures. It synthesized existing research on how these factors…
This study looked at whether exposure to air pollution, especially fine particles (PM2.5 and PM10), affects semen quality in men. It included 1,180 men aged 18, 45 from Foshan, China,…
This study set out to see if sticking to a Mediterranean diet (MedDiet) is linked to better sperm quality and fertility outcomes in men. It pooled data from 11 studies,…
This scoping review aimed to assess how diet before conception affects male fertility and reproductive outcomes. It analyzed 37 studies, including one randomized controlled trial and 36 observational studies, published…
This study set out to see whether microplastics turn up in semen in ordinary men with no plastics job, and whether they track with sperm quality. Researchers took semen from…
This study set out to see whether microplastics in the body track with sperm quality. Researchers checked semen and urine from 113 men across three regions of China for eight…
This narrative review argues that a man's fertility is a readable signal of his health generally, not just of his ability to father a child. The reasoning runs like this:…
This study looked at whether sleep duration affects markers of male fertility in young men. It analyzed 1,055 Danish men who reported their sleep habits and gave semen and blood…
This systematic review set out to assess whether following a Mediterranean diet affects sperm quality in men of reproductive age. It analyzed 10 studies involving over 2,000 men aged 18-55,…
This study set out to clarify how bisphenol A (BPA, a chemical used in food packaging and container linings) affects men's reproductive health. It pooled 18 studies that measured BPA…
This study looked at whether following a Mediterranean diet is linked to better semen quality in men visiting fertility clinics. It compared semen parameters across 274 men grouped by how…
This is a narrative review, which means the authors gathered and discussed existing work rather than running a study of their own. It asks whether the damage COVID-19 does to…
This systematic review and meta-analysis set out to find which lifestyle, environmental and health factors go with higher sperm DNA fragmentation, meaning breaks in the genetic material inside sperm, where…
This meta-analysis set out to examine how alcohol intake affects male reproductive health by looking at semen quality, antioxidant levels in semen, sperm DNA damage, and sex hormones. It pooled…
This study looked at whether following a Mediterranean diet (MD) is linked to healthier sperm in men. Researchers surveyed 300 men (average age 35) visiting a reproductive medicine center, using…
This meta-analysis set out to work out how high ambient temperature affects sperm quality. It pooled nine studies covering 356 men in Iran, Italy, Thailand, China and Egypt, comparing men…
This study asked whether a man's heat exposures affect how quickly his partner conceives, which is a harder and more useful question than whether they affect a semen sample. It…
This study set out to find out whether men actually use scrotal cooling devices as directed, and what happened to their semen results when they did. Forty men attending a…
This study tested whether a specially designed cooling garment could lower scrotal skin temperature during ordinary daily life. Three volunteer urologists wore it, with a cold pack inside that was…
This study set out to find which stage of sperm production is most sensitive to mild heat. Five healthy volunteers wore a specially designed underwear that held the testicles up…
This study set out to see whether N-acetyl-cysteine (NAC, an antioxidant supplement, taken here at 600 mg a day) improves sperm quality in infertile men. Fifty infertile men with poor…
This study asked what a mild, sustained rise in testicular temperature does to the chromosomes inside sperm. Five fertile volunteers wore specially designed underwear that held the testicles up against…
This meta-analysis set out to see whether omega-3 fats improve sperm in infertile men. It pooled three randomized trials, 147 men on omega-3 and 143 on control treatments, and measured…
This review pulled together what is known about how everyday life affects a man's fertility, covering age, psychological stress, nutrition, physical activity, caffeine, scrotal temperature, hot water and mobile phone…
Infertility affects about 15 percent of the world's population, which is what makes this question worth asking. This systematic review and meta-analysis pooled randomized trials testing whether nutrients, dietary supplements…
This is a history of forty years of French research into male contraception (hormonal, chemical and thermal) summarising clinical trials involving thousands of men and couples. Those trials established that…
This study set out to see whether zinc in semen is linked to male infertility and whether zinc supplements improve sperm. It pooled 20 studies, comparing zinc levels and sperm…
This experiment followed what whole-body heat does to sperm as they are made, in laboratory mice. Adult males were held at 37 to 38 degrees Celsius (98.6 to 100.4 degrees…
This study set out to see what repeated heat does to sperm. Twenty men with normal semen results were randomly split into two groups, and both had their testicles warmed…
This study looked at how sleep duration relates to semen quality and reproductive hormones in young men. It recruited 796 male college students in Chongqing, China and followed up 656…
This study set out to see what sustained scrotal heating does to semen and to the sperm's genetic material in fertile men. Nineteen healthy volunteers wore a warming belt at…
This study looked at what sustained scrotal heating does to semen and to the sperm's genetic material in already fertile men. Twenty-five healthy volunteers wore a warming belt at 40…
This review gathers what is known about why heat harms sperm production, and how. It sets out the things that raise testicular temperature, from the surroundings a man is in…
This study set out to see how regular sauna use affects sperm health in men whose sperm counts were normal to begin with. Ten men used a Finnish sauna twice…
This study set out to work out which sperm DNA fragmentation test best predicts male infertility. Sperm DNA fragmentation means breaks in the genetic material inside sperm, where more breaks…
This review set out to gather what is known about whether cooling the scrotum helps sperm production. The authors searched two large medical databases, EMBASE from 1980 to 2010 and…
This study looked at whether poor sleep affects semen quality in young men. It surveyed 953 healthy Danish men aged around military-service age, asking about their sleep patterns and measuring…
This study tested ways to prevent scrotal overheating in men using laptop computers. Twenty-nine healthy men had their scrotal temperature measured during three one-hour sessions: sitting with legs close together,…
This experiment asked whether heat reaches sperm that have already been made, rather than only the ones still forming. Fourteen C57BL/6 mice (a laboratory strain bred so that individuals within…
It has been suggested that cycling warms the testicles as a ride goes on, and that this in turn harms semen quality. This study tested the first half of that…
This study looked at whether stopping hot tubs, hot baths and whirlpools improves semen quality in infertile men. Eleven men with a regular wet heat habit were assessed before and…
This experiment asked whether heat makes sperm worse at their actual job, or simply leaves fewer of them. Male mice were held at 36 degrees Celsius (96.8 degrees Fahrenheit) for…
This study looked at whether cooling the scrotum overnight improves semen quality in men with a history of undescended testicles and a low sperm count, a group with few options…
This study set out to see how different types of underwear and physical activity affect scrotal temperature, which in turn affects testicular temperature. Fifty healthy men with normal fertility had…
This study looked at what a fever does to semen quality in healthy men. Twenty-seven men with a median age of 24.4 years gave a semen sample every month and…
This study asked why men differ so much in how warm their testicles run. Scrotal skin temperature was logged every five minutes for 24 hours in 48 men, made up…
This study set out to find which parts of an ordinary day actually move scrotal temperature. A thermistor (a small temperature sensor) was clipped to the underwear of 101 men…
This study looked at whether reducing genital heat could improve semen quality in men with a poor sperm count, poor movement and abnormal shape. It compared those men against men…
This study asked whether the ordinary, everyday variation in scrotal temperature is enough to matter for sperm. Sixty men from a group of couples planning their first pregnancy wore a…
This lecture is the field's own summary of why the testicles sit outside the body and what happens when they get warm. It sets out the evidence that the testes…
This study looked at whether cooling the testicles every day helps men whose couples had been unable to conceive. It followed 64 men who had subfertile semen and a raised…
This study set out to test whether cooling the scrotum could improve semen in men with a low sperm count or poor sperm movement. Fifty such men wore jockey shorts…
This study looked at whether cooling the scrotum could improve semen quality in men whose infertility came with a raised testicular temperature. Six men with poor semen results and a…
This study set out to measure how long sperm take to develop in men. The researchers injected tritiated thymidine, a radioactive marker, into the testicle, then took biopsies at intervals…