Kevin begins his day by swimming laps at his neighbourhood pool, just around the corner from his house in St. Louis, Missouri. Along with his towel and trunks, the 25-year-old takes with him a collection of supplements and medications he has assembled over nearly a decade. His haul consists of an antidepressant, protein shake, Amazon-bought supplements including zinc, sunflower lecithin, and various amino acids, plus an occasional sprinkling of fenugreek seeds. But the latest supplement he is trying is something a little different: a bacterium called Lactobacillus reuteri. The reason? Kevin is trying to supersize his balls.
L reuteri is a probiotic typically taken to help the digestive system. It’s in formula milk, but has recently gained an evangelistic following who are convinced that it holds the key to heftier testicles. Despite the lack of solid evidence, and the fact that gut health experts decry the trend as misleading and irresponsible, companies are jumping on the craze. Facebook, Instagram and YouTube are littered with adverts promising men that bacteria can boost the size of their balls, and they’re finding an audience who are eager to put that claim to the test.
Since it was first isolated in 1962, scientific studies have found that in a probiotic form, L reuteri – which is also found naturally in the digestive system – can help inflammatory diseases in the gut as well as conditions such as colic. Today, millions of L reuteri supplements are sold each year in health food shops and online retailers, with the market-leading producer, Swedish healthcare company BioGaia, selling more than £60 million of probiotics in 2020 alone. But the scientific evidence that L reuteri does anything to expand testicles is almost nonexistent, with a spokesperson for BioGaia distancing the company from self-experimentation and rival’s claims, saying it would be “unethical” to make such “unsupported claims”. In fact, all claims about L reuteri’s potency as a ball-enhancer rest on a single study from 2014, which found that one strain of the bacterium could help reduce testicular shrinkage in mice.
But that hasn’t stopped at least one company claiming otherwise. Colorado-based supplement supplier UMZU, the first brand to publicly market L reuteri as a probiotic that can enlarge testicles, acknowledges the limited evidence, calling the claims “controversial” in many of its adverts. But in promotions for its probiotic Floracil50 that appear across Instagram, Facebook, and YouTube and UMZU’s website this doubt is downplayed. On its website UMZU calls L reuteri “the only living bacteria that can solve the problem of small balls”. One YouTube video featuring UMZU founder Christopher Walker is called “How To Grow Bigger Testicles (Not Kidding)”. It had 1.3 million views at the time of publication. Facebook did not respond to an initial request for comment. After this article was published it removed one of the adverts we reported to it from both Facebook and Instagram. A spokesperson said that the advert violated Facebook’s misleading claims policy.
Walker, the man at the centre of it all, is an Instagram influencer with 423,000 Instagram followers. UMZU also bills him as a microbiome expert, based on his claims to be the first person to complete the Duke University neuroscience course in three years, and to have cured a brain tumour with nutrition, supplements and exercise. A now-deleted page on Walker’s personal website claims that his passion for health began when he performed an illegal bladder stone surgery on a man in Mexico at the age of 16.
UMZU is riding a wave of microbiome science that has discovered new links between our guts and our overall health. But where there are gaps in our knowledge, rumours of probiotic miracle cures are enthusiastically filling that space and “spreading like wildfire”, explains Faysal Yafi, medical director of the department of urology’s Men’s Health programme at UC Irvine in California. “This is beyond just laypeople. This is, unfortunately, something that is affecting even doctors. Now, if you look at how medicine is conducted, often it’s sensationalism,” says Yafi.
This sensationalism finds an eager audience online. On forums and subreddits people who tested L reuteri on themselves share their experiences with other men eager to get in on the trend. Many buy probiotic pills like those sold by UMZU or BioGaia and use them to culture a yoghurt which, according to one Redditor, tastes disgusting.
Among those who took L reuteri for at least a few weeks, some noticed little effect, but others reported “fuller testicles”, “hard morning wood”, and “increased libido”. “At one point you wake up and you’re just like ‘Wait, my balls just are bigger!’” says Kevin, who takes a single daily pill of a cheaper, generic alternative to UMZU. “Noticeable enough to me without having to measure them.”
Other L reuteri users describe all kinds of strange effects. Some say their anxieties melted away, others claim feeling “wildly optimistic”, “unstoppable” and performing well in the gym. But others describe histamine reactions, headaches and feeling “knocked out cold” by sudden tiredness. Many complain of gut-churning digestive issues and serious gas.
“When you take a probiotic that doesn’t mean it’s a good thing,” says Yafi, explaining that the gut microbiome exists in a complex balance of trillions of bacteria, fungi, eukaryotic organisms and viruses, which can be harmed both by antibiotics and the introduction of more “good” bacteria. “So what happens is you end up with what we call ‘dysbiosis’: microbiome dysbiosis is when that very fragile balance that you have within your gut microbiome is affected, and your ratios are not what they’re supposed to be anymore,” he says.
One group that seems particularly enamoured with ball-growing supplements are bodybuilders worried that steroid use is causing their testicles to shrink. Up to a million people in the UK are now taking anabolic steroids and other performance-enhancing drugs, but it’s not clear how many L reuteri users are taking the supplements because of steroid-linked shrinkage, hypogonadism (the medical name for smaller testes caused by low levels of sex hormones), or other body image insecurities or desires.
Those posting on Reddit and other forums are a mixed bag: young, ageing, hyper-focused on nutrition or weightlifting, or not. Kevin says a similarly diverse group of people have reached out to him in private messages, although his own route into probiotics was a little different to most. “When I was a kid, Chatroulette popped off, so I was on Chatroulette jacking off. And then from there, you’re like, ‘Whoa it’s way more fun to, like, shoot big loads, with big dicks’” he says. “But if there’s something you’ve struggled with – like, ‘I’ve always thought my testicles were too small’ or you’ve struggled with erectile dysfunction, low libido, or anything like that – and you find something that gives you even a small increase in testicle size, I can see how that would have a really profound effect on your anxiety.”
Theofilos Poutahidis, a veterinary scientist at Aristotle University of Thessaloniki, Greece, who performed the original study on L reuteri, explains that his study showed that mice consuming one particular strain of L reuteri perform better at resisting testicular atrophy as they grow older. “This is completely different from saying that one would consume the probiotic and find out that his balls got bigger the next day,” he says. Yafi also criticised the lack of evidence behind UMZU’s claims. Both say much more study is needed. To that end, BioGaia recently launched a clinical trial to better understand whether L reuteri affects testosterone levels in older men.
Omara Naseem, a London-based psychologist specialising in nutrition and body issues, says it is “really worrying” that scientifically unproven claims like those in the UMZU adverts are being offered up on Instagram and YouTube, where many of us have spent more time during lockdown, being sold a head-spinning selection of exercise products, supplements, and clean-eating diets. While adverts targeting women often emphasise weight control, Naseem says the men she sees are often sold on ideas of masculinity and “this idea of feeling more powerful and the body used as a vehicle for expression, strength and feeling in control”.
A lot of online conversations around L reuteri centre on testosterone. Testicles – the testosterone-producing organs – are the centre of the manosphere’s present infatuation with masculinity. On sites such as 4chan, where some men first found L Reuteri, advice about body enhancement is mixed with misogynistic, alt-right, and self-loathing commentary. Here, testosterone levels (and big balls) are interpreted as the secret ingredient to beating physical weakness, the effects of ageing, low energy or sex drive, and a lack of social confidence (despite limited evidence).
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Men often seek out products or approaches that claim to have a backbone of published scientific papers, says Naseem. “It’s really dangerous. I see so many [men] on social media where people are getting information from coaches, motivational speakers or celebrities,” she says. “They’re espousing nonsense, dressing [it] up with words like ‘biohack’ and a few scientific studies, and they’re telling [men] it’s wonderful for [them]. It’s not true. It’s not true. It’s really damaging. I wish it didn’t happen.”
UMZU and Walker did not respond to interview requests. But, since being contacted by WIRED, the company has removed a number of the claims we highlighted from its website and promotional materials. UMZU’s website claims hundreds of peer-reviewed articles support its supplement line, but until recently its own page of “Peer-Reviewed Studies & Health References for UMZU Supplements” linked to Wikipedia pages, Amazon products (including a stainless steel lunchbox), and a YouTube clip from a David Attenborough documentary about a monkey.
Yafi, for his part, is not at all convinced that his research supports the claim that L reuteri probiotics can enlarge your testicles. “I mean, on the level of weak evidence for something, this is as weak as it can possibly get,” he says. “To call it a stretch is the least you could say, basically. It’s really not rooted in any kind of evidence whatsoever.”
