Ariel Poler is a veteran angel investor who spends his days traveling around the Bay Area to meet with entrepreneurs. Now in his early fifties, he also thinks a lot more about his own health, so he makes an effort to keep his stress levels low by eating well and taking regular kite-surfing trips.
But he also takes a tiny, white pill called metformin, which is prescribed to millions of people with diabetes to help control high blood sugar. Poler does not have diabetes, but he takes it for a different reason. He hopes that it will help keep him healthier for longer.
Unlike some in Silicon Valley, who are increasingly investing in wonder drugs and starting companies to crack the code on aging, Poler isn't planning to live forever. But he does believe that his metformin use, coupled with his commitment to nutritious food and exercise, will help delay the onset of serious health issues. "Maybe I won't get cancer until later, like 85 instead of 83," he says with a shrug.
He's not alone. Metformin is undergoing a bit of a renaissance in Silicon Valley tech circles -- among people who do not have diabetes.
CNBC interviewed a dozen executives and investors working in the tech industry who take the drug as a hedge against aging. Some were willing to speak publicly about it, while others preferred to remain anonymous as they did not want their employers to find out. Bolstering their case, there are also some high-profile supporters in the medical field, including the renowned aging researcher Nir Barzilai.
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Metformin is not a new innovation. The drug, which is available in generic form for about 5 cents a pill, has been around for decades.
But in recent years, researchers have studied the long-term effects and found that diabetics who took it for years wound up experiencing unintended health benefits, including a reduced cancer risk compared to the general population. Further studies of the drug in mice showed evidence of an improved life span.
The drug is thought to mimic some of the positive effects of calorie restriction by lessening the amount of sugar the body produces and absorbs. Calorie restriction is a huge challenge for people to maintain, as it involves eating a lot less over a long period of time, but some studies have shown that it can help to extend the human life span.
Poler, alongside his doctor, has reviewed the research on metformin and talked to other friends in the medical fields about the potential downsides of his $2-a-month habit.
"Some people told me it was a slam dunk for its anti-aging effects," he adds, over coffee in San Francisco. "And some were skeptical, but most gave it a thumbs up that it's fairly safe."
The side effects associated with prolonged metformin use include diarrhea, slow blood sugar, and abdominal pain. The most serious risk is that excessive acid accumulates in the body, causing a condition known as lactic acidosis.
Poler hasn't experienced any of these side effects, so he intends to continue taking it for the long-term.
Others who take metformin maintain that it's already benefiting them.
"I followed the mounting evidence, then when a biotech investor friend Bob Nelsen (Nelsen, of Arch Venture Partners, regularly takes 500mg of the diabetes drug metformin for its anti-aging effect) told me he was taking it, I had a discussion with my physician and reviewed the studies," explained Zen Chu, a prominent angel investor. "Even though I'm not pre-diabetic, it was low-risk so I tried it and I could rapidly feel that improved my metabolism as well. "
All of them agree that metformin's effects have been under-studied, in part because there isn't much of a financial incentive for the pharmaceutical industry to research the impact of an extremely cheap, generic drug. That could explain why doctors don't routinely recommend it to people without diabetes, and why metformin hasn't made it into the mainstream.
Medical experts said they have mixed feelings about whether people without diabetes should take the drug, in light of this lack of research.
"Theoretically someone can take it without diabetes, as there are some known side effects but they're usually tolerated if the patient gradually increases dosage over time," said Greg Burrell, a practicing physician and the co-founder of Carbon Health, a start-up with a chain of medical clinics across the Bay Area.
Burrell said he wouldn't "block" a patient from taking it, but he would also educate them about the lack of human data. Animal trials can be useful, but humans and mice often react differently to medications so it's not enough to prove safety and efficacy.
"I would suggest to my patients to wait for more human results," he said.