We really only understand the tip of the iceberg
In Cape Town, a young biotech company called Biomine has begun transforming one of the body's most overlooked outputs into a map of human health, offering South Africans a window into the microbial ecosystems that govern digestion, immunity, and mood. For R5,000, the company returns a detailed portrait of what lives in the gut — not as a diagnosis, but as a data point in a larger continental ambition to understand how the microbiome shapes disease and drug response. The science is genuine, the promise is real, and the caution from the medical establishment is equally so: humanity is still learning to read a language it has only just begun to decipher.
- A Cape Town startup is commercializing gut microbiome testing at R5,000 per stool sample, betting that Africans will pay to peer inside their own biology before medicine fully knows what to do with the view.
- The company's deeper ambition — predicting which cancer patients will respond to immunotherapies costing over R1 million a year — raises the stakes far beyond consumer wellness into life-and-death clinical territory.
- Medical professionals, including the South African Gastroenterology Society, are pushing back, warning that no standardized framework exists to interpret commercial microbiome results and that many reports offer recommendations unsupported by evidence.
- Biomine's co-founders are threading a careful line, positioning their test explicitly as non-diagnostic while quietly building the data infrastructure they hope will one day make it indispensable to doctors and pharmaceutical companies alike.
- The company is still in its research and development phase, with future value tied to the size and quality of the database it can assemble — meaning today's paying customers are, in a sense, also its earliest research participants.
In Cape Town, a three-year-old biotech company called Biomine has found a way to turn something most people discard into a detailed map of human health. By analyzing a teaspoon of stool sent by courier, the company returns a portrait of the trillions of bacteria, viruses, and fungi living in a customer's gut — the microbiome, the largely invisible ecosystem that governs digestion, immunity, and even mood. The test costs R5,000 and delivers results within three weeks.
Co-founder and CTO Diego Castillo, a geneticist by training, launched the consumer product in July 2025 alongside CEO Vaughn Barendsen, with backing from Cape Town's OneBio Venture Studio. The company's stated ambition is to build Africa's largest microbiome database — collecting consented samples from across the continent to understand how microbial composition influences disease and drug response. The science behind this is credible: decades of genetic sequencing research have confirmed that the microbiome shapes human biology in profound ways, and that greater microbial diversity tends to correlate with better health.
Castillo is deliberate about what the test does not do. It is not diagnostic — it shows what is present, not what it means clinically. But the company's longer horizon is more consequential: using microbiome data to predict which patients will respond to cancer immunotherapies that cost over R1 million annually and work in only about 40 percent of cases. If the microbiome could identify likely responders in advance, it could spare patients from ineffective treatment and direct resources toward those who will benefit.
The medical establishment is not yet persuaded. Cape Town gastroenterologist Dr. Leah Murray says she can usually read a patient's gut health from symptoms alone, and finds the test useful only in specific diagnostic dead ends. The South African Gastroenterology Society has gone further, stating that routine commercial microbiome testing lacks the standardized interpretation and evidence base needed for general clinical use. A Lancet editorial cited by society council member Dr. Yonela Qubekile echoes these concerns, noting that dysbiosis scores and probiotic recommendations common in such reports often outrun the science.
Biomine acknowledges it is still in the research and development phase. Castillo speaks of possible future partnerships with diagnostics or pharmaceutical companies, but for now the company is doing the slower work: collecting samples, growing its database, and waiting for the moment when a stool sample might tell a doctor something genuinely actionable. That moment has not yet arrived — but the infrastructure being built today is a bet that it will.
In Cape Town, a three-year-old biotech company called Biomine has found a way to turn something most people flush away into a window onto human health. The company collects stool samples—about a teaspoon's worth, sent by courier—and for roughly R5,000, returns a detailed map of what lives in your gut: the trillions of bacteria, viruses, and fungi that form the microbiome, that largely invisible ecosystem that controls digestion, sends signals to the brain, shapes mood, and anchors the immune system.
Biomine launched its consumer test in July 2025 and is now building what it says will be Africa's largest database of microbiome data. The vision, according to co-founder and chief technology officer Diego Castillo, is ambitious: to collect samples from as many people as possible across the continent, with consent, and use that data to understand how the microbiome influences disease and drug response. Castillo, who holds a PhD in genetics, started the company with CEO Vaughn Barendsen. The venture was backed by OneBio Venture Studio, a Cape Town-based funder of biotech entrepreneurs that also provides laboratory space through its nonprofit arm, OneBio Innovation Centre.
The science underlying Biomine's work is real. For the past quarter-century, advances in genetic sequencing and computing have allowed researchers to move beyond knowing that the microbiome matters to actually understanding how deeply it shapes human biology. The results a customer receives include a list of the specific microbes living in their intestines and an assessment of microbial diversity—the principle being that, as with any ecosystem, greater variety tends to correlate with better health.
But Castillo is careful about what he claims. The test, he emphasizes, is not diagnostic. It is a tool that shows you what is there, not a medical judgment about what it means. This distinction matters because the company's ambitions extend beyond consumer curiosity. Castillo describes a more consequential application: using microbiome data to predict whether expensive cancer immunotherapies will work for individual patients. These drugs cost more than R1 million annually and are effective in only about 40 percent of people who take them. If the microbiome could identify who will respond, it could spare patients from costly, ineffective treatment and accelerate those who will benefit.
Yet skepticism is already present in the medical establishment. Dr. Leah Murray, a Cape Town physician specializing in digestive health, says she is unconvinced that a microbiome test is worth the cost. In her practice, she can usually infer what is happening in a patient's gut from their symptoms alone. A test becomes useful only when she is stuck—when she needs to know whether a patient has sufficient quantities of keystone bacteria, the foundational good microbes that appear abundant in healthy people. "We really only understand the tip of the iceberg when it comes to the human microbiome," Murray told the publication.
The South African Gastroenterology Society has issued a cautionary statement: routine commercial microbiome testing is not supported for general clinical use outside research settings. The concerns are concrete. Results vary between companies. There is no standardized way to interpret them. Many reports offer dysbiosis scores, dietary advice, and probiotic recommendations that lack strong scientific backing. Dr. Yonela Qubekile, a council member of the society, cited an editorial in The Lancet making these points.
Castillo acknowledges that Biomine is still in the research and product-development phase. He hints at future possibilities—mergers or acquisitions with diagnostics or pharmaceutical companies—but those remain speculative. For now, the company is collecting samples, building its database, and working toward the day when a stool sample might tell a doctor something genuinely useful about how to treat a patient. Whether that day comes, and how soon, remains an open question.
Notable Quotes
We want to have the biggest, most diverse African microbiome database, that's the vision … the big moonshot— Diego Castillo, Biomine CTO
We really only understand the tip of the iceberg when it comes to the human microbiome— Dr. Leah Murray, Cape Town physician
The Hearth Conversation Another angle on the story
Why does a stool sample matter more than, say, a blood test?
Because your gut microbiome is almost entirely separate from your bloodstream. You can't see it in blood. You have to look at what's actually there—the bacteria, viruses, fungi living in your intestines. That's where the signal is.
But the doctor we spoke to said she can usually figure out what's wrong just by asking questions. Doesn't that make the test redundant?
For straightforward cases, maybe. But there are patients where the symptoms don't point clearly to a cause. That's when knowing whether you have the right foundational bacteria becomes useful. The test is a tool for when intuition isn't enough.
The gastroenterology society says the interpretation isn't standardized. What does that actually mean?
It means Company A might look at the same sample and tell you one thing, Company B tells you another. There's no agreed-upon rulebook for what a "healthy" microbiome looks like, or what to do about an unhealthy one. The science is still being written.
So why is Biomine confident enough to charge R5,000 for this?
Because they're not claiming to diagnose anything. They're saying: here's what's in your gut. What you do with that information is between you and your doctor. The real value, for them, is the data. Every sample builds the database.
And that database could eventually predict whether cancer drugs will work?
That's the theory. If the microbiome influences immune response, and immune drugs only work for 40 percent of people, then maybe the microbiome can predict who's in that 40 percent. If it works, it saves patients from expensive, pointless treatment.
But that's still years away.
Yes. Right now they're collecting samples and building the foundation. The clinical applications are the moonshot.