The secrets sperm carry
Men are curious about their health but reluctant to engage in primary care – could their sperm be the key?
Dr. Paul Turek embodies the California Dream. He surfs and drives a vintage Maserati. He admires Jack Nicholson and the Brat Pack. In Beverly Hills, and in San Francisco, when men step into one of his clinics for male fertility and sexual health, Dr. Turek’s personality is on full display. In fact, it’s part of the care model.
Men are more likely to be open if they feel like they know you. Dr. Turek’s waiting room is fashioned like a den, with darkly colored walls and sports on the TV. In the exam room he listens intently, like a trusted friend, and only then does he investigate what might be wrong.
Dr. Turek is also a Yale-educated, highly skilled microsurgeon and a former NIH-funded professor of urology. We met one year ago at a medical conference in Napa, overlooking a sweeping vista of sun-kissed fields and lush vineyards. Dr. Turek was holding court, surrounded by a gaggle of fertility futurists—investors, biotechnology entrepreneurs and fellow doctors (including me).
He relayed a highly provocative theory, supported by his decades researching infertility and treating men: much like blood pressure and cholesterol, a semen analysis could be a critical biomarker for a man’s overall health. Beyond fertility it could convey important information about a man’s metabolism, his toxic exposures, his cancer risk, and even his longevity.
Swimming cells
Just about as long as men have been looking through microscopes, we’ve been using them to look at sperm. Antony van Leeuwenhoek, the 17th century inventor of the 300x zoom lens, credited one of his students with getting the first glance at the male gamete. It quickly become the centerpiece of his research but neither Leeuwenhoek nor his student were sure what exactly these tiny swimming cells seemed to be doing.
They dutifully chronicled them, noting how long they could stay alive, how they moved (motility), and what they looked like (morphology). They exhaustively studied the sperm of dogs, pigs, rabbits, fishes, mollusks, amphibians, and birds. Ultimately, they decided sperm might be some kind of parasite.
It wouldn’t be until the 1930s that anyone correlated sperm with fertility, and even longer before someone noticed that the number of sperm swimming around in a given sample seemed to matter. In the decades since, and now with the introduction of assisted reproductive technology, semen analysis has become widely accepted as a cornerstone of male fertility care. Today it is one of the first recommended steps to understand why a couple might be struggling to conceive.
But nearly a century after it was first established, the mechanics of the test haven't really changed. And the male fascination with looking at our sperm hasn’t changed either. The limiting factor has always been the embarrassment of needing to collect it at a fertility clinic, in some fluorescently-lit room with nurses and doctors just outside the door.
In 2012, the first FDA-approved home collection kit was introduced—a potential game-changer. Today, home kits can be purchased on Amazon, and there are multiple start-ups that bundle at-home semen analysis with additional fertility services. One of them, Legacy, has raised $45M and counts DJ Khaled, Justin Bieber, and Orlando Bloom as strategic investors.
Experts caution that at-home tests may be unreliable. Sperm is fickle, requiring careful temperature regulation, rapid analysis, and multiple spaced readings for an accurate result. But the skyrocketing popularity of these tests is telling.
What’s normal anyway?
Dr. Turek has spent a lot of time looking at sperm. So last week I gave him a call.
A semen analysis, he says, is like holding playing cards. There are four parameters of interest: volume (how much fluid), concentration (how many sperm), motility (how much movement) and morphology (how well-shaped). Much like pulling from a deck, two different readings from the same man can vary widely. And while each draw tells you something, they’re only really helpful when read as a hand.
“Much like pulling from a deck, two different readings from the same man can vary widely. And while each draw tells you something, they’re only really helpful when read as a hand.”
Low volume can point to low testosterone, or obstruction, or simply performance anxiety (what Dr. Turek calls “first sample syndrome”). Low concentration can be indicative of a chronic condition, like diabetes, or a short-term condition, like fever, or even a habit, like too much time in hot tubs. Reduced motility is particularly sensitive, and often a sign of toxic exposure—including excessive drinking or marijuana use. Morphology, meanwhile, is all over the place.
Since 1980, the World Health Organization has published benchmarks for normal sperm shape. At first, they considered a “normal” morphology reading to be when more than 80% of sperm had a standard shape. But then, in the second edition, they revised that number to 14%. By the fifth and sixth editions, they’d lowered it to 4%.
It turned out that Leeuwenhoek was right to be confused—while in most mammals sperm are relatively uniform, in humans their shape can be completely irregular without necessarily impacting a man’s chances to conceive. Unless of course every sperm is identically misshapen—in that case it may be a real cause for concern.
Notably, even when all visual parameters are normal, infertility persists about 15% of the time and is labeled “unexplained.” The assumption is that the cause is beyond the microscope, reflecting a host of potential genetic abnormalities that may cause sperm to look normal from the outside while malfunctioning from the inside. Unlike our ability to genetically test embryos and even eggs, diagnostic tools for unexplained male infertility are highly limited.
Dr. Turek tells me that the semen analysis is but one tool for assessing fertility, and a blunt one at that. If he was forced to pick only one tool to assess fertility he’d probably drop it entirely, sticking instead with the patient conversation, what doctors refer to as “taking a history.” In the majority of cases, listening and thoughtful questioning will get him to the diagnosis.
Male infertility is a women’s health issue
In a Tik Tok series coined “Sperm Monday,” Dr. Allison Rodgers, an infertility specialist, shows viewers what an average semen sample looks like under a microscope. “Clearly not normal,” she jokes, pointing to one sperm swimming in circles. We know, of course, that one misshapen or misdirected sperm doesn’t mean much. But Dr. Rodgers seems to land on exactly what so many men might fear out of a doctor’s appointment: the realization that something may be fundamentally wrong with their manhood.
Sixty percent of men grappling with infertility scored in the clinical range for anxiety, and 32% scored in the range for depression. A landmark 1993 paper led by psychologist Dr. Alice D. Domar found that infertility patients report mental distress similar to those of cancer patients. She originally studied women so I emailed her asking about men. Dr. Domar told me the mental health role in men is likely underreported because “it is very challenging to engage men at all.”
“While several missed periods might signal to a woman that she should book a primary care appointment, men simply have no equivalent check engine light.”
Men talk about sex, but we rarely talk about fertility. For women, menstruation is a monthly metronome for fertility. They are often ushered to gynecologists for birth control as teenagers, and to their first pap smear as young adults. While several missed periods might signal to a woman that she should book a primary care appointment, men simply have no equivalent check engine light.
Where medicine evolved to bundle primary care and reproductive care for women, many men might go much of their life before a physician prods them to contemplate their fertility…and that’s if they have a physician, which they usually don’t.
These gendered relationships to medicine, naturally, come to a head when making a baby, and particularly if making a baby doesn’t come easily. Suddenly, men are in the conversation right as the stakes feel impossibly high. Any new information or findings become a bombshell.
As author and investor Leslie Shrock of puts it, women, armed with a better sense of their health and a clearer doctor to call, become treatment surrogates for their male partners. While men account for roughly 50% of infertility cases, 18-27% are never tested during an infertility evaluation. And regardless of the diagnosis, most assisted reproductive technology doesn’t actively target sperm—meaning women ultimately end up shouldering the burden of physical intervention.
Come for the semen analysis, stay for the health care
Counterintuitively, semen tests tell a lot less about fertility than we might assume. But they may tell us a lot more about overall health than we might assume as well—both in the long term, and in the short term.
Consider: a longitudinal cohort study conducted with some of the most robust longitudinal population registers in the world. Its findings suggest that Danish men with normal semen quality lived 29% longer than those with abnormal readings.
Consider also that men who eat a Mediterranean diet are nearly 3x more likely to have normal sperm. Likewise, men who eat less processed red meat and more fish see higher sperm counts. In contrast, men exposed to pollution see more sperm abnormalities, as do men with heart disease. Excessive drinking, smoking, and marijuana use all negatively impact sperm. Semen analysis has even been used to diagnose prostate cancer.
Most remarkable–and reassuring–is that even markedly abnormal semen analysis results are often reversible. Unlike eggs which are fully and permanently formed in a female fetus, the sperm of an adult male regenerates on a roughly monthly basis throughout their reproductive lives.
Incidentally, this is about the same rate that real lifestyle changes might be implemented. Improvements can happen relatively quickly and visibly—moreso perhaps, than other biomarkers like cholesterol, which may only shift every three to six months. As one man vividly reported, after healthier habits, his sperm went from “a graveyard to a rave.” What could be more motivating than that?
“As one man vividly reported, after healthier habits, his sperm went from ‘a graveyard to a rave.’ What could be more motivating than that?”
Enabling consistent behavior change for better health is one of medicine’s slipperiest predicaments. But, we know men often engage with opportunities to improve their virility, even if changing their diet isn’t at the top of their priority list. Perhaps more regular semen tests, with measurable and actionable results, could bridge that gap.
Dr. Turek agrees, explaining that fertility and health maintenance are inextricably linked. Recalling a smoker in his practice, he emphasizes that good care requires not just correcting for sperm, but correcting for lifestyle.
“The goal of my practice is not only to help you have a baby,” Dr. Turek told his patient, “but to help you live 5-10 years longer in the process.”
What my team is reading, thinking, and building against:
Scott Burkholder is a man living with infertility. In a short film for the New Yorker, he records what that looks like—mournful doctor’s visits. Church basement support groups. A tight hug from his mother, and a terse conversation with his wife. It’s worth a watch to see Scott’s extraordinary vulnerability in unflinching detail…something we usually aren’t great at encouraging in men.
Dr. Turek reminded me that the CDC’s newest mortality data is out now. Men continue to live on average five fewer years than women. In recent years, COVID-19 contributed to the gap, but largely by exacerbating the chronic conditions they already disproportionately carried. As secular trends, men also experience a heavier burden of drug overdoses and of loneliness.
Recently, Dr. Alice Domar created an emotional support app for both women and men experiencing infertility, albeit with very different branding. The women’s app is called FertiCalm, while the one for men is called FertiStrong. She found a statistically significant difference in the reported mental health of men who consulted the app. Her findings hammer home what we already know: more research is needed to understand how to engage men with virtual health tools.
In a scientific finding I can’t stop thinking about, new evidence published in Nature suggests that sperm can transmit information from a father’s gut to his children. You read that right. Using a microbiome model in mice, researchers altered gut flora using antibiotics, diet and laxatives. They observed a significant impact on sperm RNA, and also, on the birthweight and lifespan of offspring. Thank you to for highlighting the findings in his latest newsletter.
Gendered approaches to care are also built into the bones of U.S. health care billing. For example, federal law requires that insurance cover breast reconstruction in female mastectomy patients, but not testicular prostheses for men with orchiectomies. Which begs a very big question: how can a medical system built by men (and largely for men), also serve them so poorly? More on that one soon. :)