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preventative health · 2026 · 8 min read

Supplements: facts versus fiction

key points

  • Australians really do spend big on this: about half of us use a vitamin, mineral or herbal product in a given year, and the industry now turns over roughly $6 billion annually. That part isn't a myth.
  • What is a myth, mostly, is that spending equals benefit. No supplement has been shown to extend a healthy person's life or replace food, movement, sleep and not smoking.
  • A short list genuinely helps, but usually only if you actually need it: vitamin D if you're deficient, B12 if you're at risk, magnesium if you're low or your blood pressure runs high, creatine for muscle and strength.
  • "Natural" doesn't mean risk-free. Some supplements interact with prescription medicines.
  • In Australia, most supplements are "listed" (AUST L), not individually tested by the TGA before they reach the shelf. The ingredients are checked as low-risk. The company's efficacy claims mostly aren't.
  • Always tell me and your pharmacist what you're taking, even the "harmless" stuff. About half of people take something alongside a prescription medicine on the same day, and a fair few never mention it.

Barely a week goes by without someone bringing a bottle to the consult and asking whether it's worth it. Fair question. The supplement aisle at the chemist is often bigger than the actual pharmacy counter these days, and about half of us are buying something from it. What isn't backed by anything like that scale of evidence is the assumption that all of it is doing something. After enormous amounts of trial data in generally healthy adults, no supplement on the market has been shown to extend life or prevent disease the way that eating reasonably, moving regularly, sleeping enough and not smoking clearly do. Supplements can be useful. They are not a substitute for the boring stuff.

What actually has decent evidence, if you need it

A handful of supplements do have solid evidence behind them, almost always for correcting an actual, measured shortfall. Not for topping up someone who is already fine.

Vitamin D genuinely helps if you are deficient, which a blood test can confirm. In people who already have normal levels, a large randomised trial of nearly 26,000 adults found no reduction in cancer, heart disease or death from taking it anyway. Vitamin B12 is similar: worth correcting in vegetarians, vegans, people on long-term metformin or acid-suppressing medication, and many people over 60, but not something a well-nourished 40-year-old needs to add for insurance. Magnesium can lower blood pressure meaningfully in people who are deficient or already being treated for hypertension, with a much smaller effect in everyone else. Creatine monohydrate has one of the best safety records of any supplement, with real benefit for muscle strength, and some emerging benefit for older adults doing resistance training. Omega-3 is the one I'd call genuinely mixed. Some large trials show a cardiovascular benefit, others show none at the same dose, and eating fish twice a week does much the same job without the capsule.

What doesn't hold up

Bigger doses are not automatically better. For some vitamins they're worse. High-dose vitamin E and beta-carotene supplements have been linked to a small but real increase in death and, in smokers, a higher rate of lung cancer: the opposite of what people are usually buying them for. A large review of antioxidant supplement trials, involving some 300,000 people, found no reduction in mortality overall, and a slightly higher rate in the more rigorous trials. Calcium supplements taken in large single doses have been linked to more heart attacks and kidney stones, without the fracture protection people expect, unless you're older and genuinely deficient. And the trendy "longevity stack" ingredients, things like NMN, resveratrol and rapamycin, mostly rest on mouse data or short, industry-funded trials. None of it has been shown to do in people what it's marketed as doing.

"Natural" doesn't mean risk-free

This is the myth I'd most like to bust. Supplements aren't inert just because they didn't come from a pharmaceutical lab. St John's wort can seriously reduce the effect of some antidepressants and the oral contraceptive pill. Vitamin K can undo the effect of warfarin. Independent testing regularly finds products that are contaminated, mislabelled, or simply don't contain what the label says. Melatonin has been one of the worst offenders internationally, with actual content in some products ranging from well under to several times the labelled dose.

In Australia, most vitamins and supplements are what the Therapeutic Goods Administration calls "listed" medicines, marked with an AUST L number. The ingredients themselves have been assessed as low-risk. But the TGA does not routinely check, before the product goes on sale, whether the specific claims on the label are actually backed by evidence. The company self-declares that they are, and the TGA reviews products afterwards, on an ongoing basis, rather than approving each one in advance the way it does with prescription medicines. That's a real and useful check. Just a lighter one than most people assume.

A word on where the "pro-supplement" argument comes from

You'll also find pieces defending supplements more broadly, arguing that real nutrient gaps exist even in people who eat reasonably well, and that the safety record is strong given how many servings are consumed daily. Some of that is fair. But a lot of this material traces back to industry lobbying groups and people who work for supplement companies, the Council for Responsible Nutrition among them. That doesn't make it wrong. It does mean it's advocacy, not independent analysis, and it's worth reading with that in mind, the same way I'd want you to read anything a drug company writes about its own drug.

before you buy one

Ask whether you've actually been tested for the deficiency you're trying to fix, look for the AUST L number on an Australian product, and tell your GP or pharmacist what you're taking, especially if you're on any regular medication. More is not automatically better.

None of this means never take a supplement. It means treat the decision the way you'd treat any other health decision: based on whether you actually need it, not on how convincing the packaging is. If you're not sure, bring the bottle in and we'll work it out together.

Where this comes from

All free to read in full, accessed 28 August 2026.

Dr Ahmed Al-Obaidi

Dr Ahmed Al-Obaidi · FRACGP

General information only, not personal medical advice. Talk to your own GP about what suits you.

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