Fred Hutch Keeps Testing Supplements. The Results Keep Coming Back Bad.

The bottles in the cupboard

Americans spent an estimated $60 billion or more on dietary and over-the-counter supplements last year. Fish oil, melatonin, turmeric, medicinal mushrooms: the shelf is wide and the claims on it are louder than the evidence under them. At Fred Hutch, the researchers who have spent decades testing these products keep finding the opposite of what the industry sells. Heather Greenlee is a naturopathic physician and epidemiologist, medical director of Fred Hutch's Integrative Medicine Program, and a past president of the Society for Integrative Oncology. In February 2026 she put it plainly: "Just because something is natural doesn't mean it's safe." In the same piece she added: "We know there's a lot of interest in the use of dietary supplements. But there are also many misleading health claims."

The trial built to prove the opposite

SELECT, the Selenium and Vitamin E Cancer Prevention Trial, was run by the SWOG cancer research cooperative group, and Fred Hutch went back through its data years later. It enrolled more than 35,000 men starting in 2001, on 400 IU of vitamin E and 200 micrograms of selenium a day, on a twelve-year plan researchers cut short in 2008. Fred Hutch's February 2026 review of the evidence states that vitamin E supplements increased prostate cancer risk by 17%. A separate Fred Hutch release from February 2014 dug into the same trial and surfaced worse numbers inside two subgroups of men. Men who started the trial with low selenium levels saw vitamin E raise their total prostate cancer risk 63% and their high-grade cancer risk 111%; men who already had high selenium saw selenium supplements raise high-grade risk 91%, the excess mineral turning toxic. The 2026 review adds the other half of the trial's result: selenium raised the risk of high-grade prostate cancer in some men. Alan Kristal, who led that 2014 analysis, did not soften it: "Many people think that dietary supplements are helpful or at the least innocuous. This is not true." His advice was general, and blunt: "Men using these supplements should stop, period. Neither selenium nor vitamin E supplementation confers any known benefits, only risks." Kristal died in Seattle in March 2019.

A second trial, a second reversal

SELECT was not the only study that turned against its own hypothesis. CARET, a Fred Hutch-led trial funded by the National Cancer Institute, tested beta-carotene and vitamin A supplements in heavy smokers and asbestos workers. The supplements increased their lung cancer incidence and death instead. Garnet Anderson, director of Fred Hutch's Public Health Sciences Division, named the pattern for what it is: "It would be nice if we had a pill that we could take that could protect us from disease. But it's not that easy."

Four bottles, four different mechanisms

Greenlee mapped the specific risks by supplement at the 2024 San Antonio Breast Cancer Symposium, and they do not line up neatly. Fish oil is the mildest case. Sold for anti-inflammatory support, it can cause bleeding, and that is the whole of its listed risk. Turmeric, pitched as an anti-cancer supplement, carries that same bleeding risk, plus estrogenic activity and CYP interactions, a mechanism that shows up again and again in drug-drug interactions. Melatonin bleeds too. Its CYP1A2 interactions link to cancer risk, and it carries estrogenic properties of its own. Medicinal mushrooms, turkey tail, lion's mane, reishi, taken for immune support, carry the same bleeding risk and the same CYP interactions, plus liver damage, which none of the other three carry, and the trail of risks does not stop there.

Who takes it, and who doesn't say so

A 2008 Fred Hutch study, led by Cornelia Ulrich, found that up to 81% of cancer survivors use dietary supplements, and up to 68% of those people never mention it to their oncologists. Ulrich said some vitamins, folic acid among them, "may be involved in cancer progression," while St. John's wort "can interfere with chemotherapy." That interference has a specific mechanism: St. John's wort reduces the effectiveness of cyclosporine, the immunosuppressant used in transplant patients, and of indinavir, an HIV protease inhibitor. A separate 2014 Fred Hutch study, this one on laxatives rather than vitamins, found the same split running through an entirely different aisle. Non-fiber laxatives raised colorectal cancer risk by about 50%. Fiber-based laxatives lowered it by 56%.

What she tells patients instead

Greenlee's own advice starts with food. She tells patients to emphasize plant foods. Her reasoning is unglamorous: they carry fiber and nutrients, including anti-inflammatory ones, and plant protein is cheaper than meat. Her benchmark is 30 grams of fiber a day; only about 10% of Americans hit it. For patients already inside Fred Hutch's care, the Integrative Medicine Program keeps clinical pharmacists on staff to help walk through interactions and contraindications during treatment. The program runs out of the Sloan Clinic in South Lake Union, split across 1354 Aloha St and 820 Yale Ave N, the largest outpatient center Fred Hutch has. It was the South Lake Union Clinic until it was renamed for the donors Stuart and Molly Sloan. The program itself takes established Fred Hutch patients only, not a walk-in audience. The pharmacists are the tell. The program's answer to a cupboard full of bottles is not a better bottle, it is somebody qualified to read the label against the chart.