The truth behind dietary supplements: What you need to know

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25 March 2023

Reading Time: 4 minutes

It may be a bitter pill to swallow, but many popular natural health products don’t actually do what they claim to.

Take a look at my kitchen drawers and you’ll find one that’s full of small jars of dietary supplements. Most are half full, and – full disclosure – most have been sent to me by PR companies. I’m pretty bad at taking them; what I tend to do is try them out of curiosity, and then if I feel no significant effect after a month or so, I lose interest.

I suspect I’m not alone there.

If you’re a regular supplement taker, though, you’re far from alone. Around 40% of us say we regularly pop supplements. It’s big business; New Zealand’s natural products industry is worth $2.3 billion a year. Visit a pharmacy or health food store and you’ll be confronted by thousands of products vying for your attention, aimed at improving every aspect of your health.

Only a small percentage of us, it seems, take supplements for a specific health issue. More of us subscribe to the “insurance policy” philosophy: if my diet is less than perfect, a supplement – especially a multivitamin – might plug the gaps.

Unfortunately, there’s very little evidence this approach works. A 2018 report published in the Journal of the American Medical Association reported that for a generally healthy person, there is no additional benefit from supplementation. It recommended it’s best to get vitamins and minerals from foods, where we absorb them better.

The other thing you might find surprising about supplements – I know I do – is that there’s not much in the way of regulation around them. No-one is really checking that what supplement marketers say is in their products, or say their products do, is actually true or backed by evidence. Right now, supplements in Aotearoa are scooting through the gaps in regulation, essentially unmonitored. So I could decide to start making “Niki’s Nutritional Wonder Tonic”, and as long as I comply with food safety regulations, don’t put any actual drugs in there, and don’t call it a medicine, I can start selling it.

There’s a voluntary code governing so-called therapeutic claims, but as you’ve probably seen if you’ve perused those shelves, there are lots of ways around that. It’s why you’ll see phrases like “supports immunity” or “assists gastro-intestinal health”.

As a consumer, it pays to know that you might not be getting what you think you’re paying for. That aside, there are some people, conditions and life stages that might benefit from specific supplements.

Supplements that might be useful

Pregnancy and pre-pregnancy supplements
This is a time when we do need a bit of help. If you’re thinking of trying for a baby or are newly pregnant, talk to your doctor about iodine and folic acid supplements; there are specific recommendations around these – including dosage – and you should be able to get them on prescription.

Vitamin D
People who don’t get outside much, or who have darker skin, might benefit from vitamin D supplements, especially in winter. Talk to your doctor.

Low iron is surprisingly common, especially in women and teens, and it can have serious consequences. If you’ve been diagnosed with low iron levels, your doctor may prescribe a supplement. It’s important to take these under supervision though, as they can have side effects.

There’s some evidence fish oil and other omega-3 supplements may benefit those with heart disease or high cholesterol. It’s worth remembering that you can also get this healthy fat from regular servings of fish.

There’s emerging evidence collagen supplements may benefit skin and relieve joint pain, though not gut health, as is sometimes claimed. Look for supplements that offer specific evidence of effect.

Supplements you probably don’t need

Far be it from me to tell you to stop taking anything you believe is giving you benefit. Even if it’s just from the placebo effect, it’s still an effect. If you love your supplements and you’re happy spending the money, good for you. But you might want to read on, just so you know what the evidence says about some popular products.

Homeopathic products
Homeopathy is top of the woo tree, for me. There’s no science here; what you’re buying is essentially water and alcohol (which might actually do something, but probably not what you hope). Homeopathy is based on a “pre-scientific” theory, invented back when people thought illnesses were caused by bad humors or “corrupted juices”.

A 2019 report of the European Molecular Biology Organization put it plainly: “The almost unanimous view of the scientific community is that the basic assumptions on which homeopathy rests are either refuted or implausible.”

A recent review found calcium supplements offer little benefit for bone health, and there might be some risks. Don’t self-prescribe, talk to your doctor about your bones and try to get your calcium from food instead.

Joint supplements
Evidence on things like glucosamine, turmeric and chondroitin for joint pain – especially from osteoarthritis – is pretty patchy. Try them, but if you don’t feel a benefit within a couple of months, it’s probably not going to work.

Immunity supplements
Even though we hear every winter to pop vitamin C, zinc, echinacea and olive leaf extract, the best science can say is that they might shorten a cold by a day or so. They don’t seem to stop us getting a virus in the first place.

Black cohosh and other menopause supplements
These, again, show patchy evidence – and some are pretty pricey. There’s little harm in trying, but if you’re not feeling relief fairly promptly, save your money and move on.

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