How vital are vitamins? Niki Bezzant explains pill popping for better health.

Vitamins and other supplements are big business. Around a third of Kiwi women and a quarter of men regularly take some sort of supplement; it's estimated we spend more than a billion dollars a year on supplements like vitamin C, omega-3, garlic and echinacea.

We often take supplements because we think they're going to improve our health in some way. They're promoted as ways to boost our immunity, balance our hormones, improve our mood, relieve stress and give us energy. Some promise to keep us young and lubricate our joints.

Some are really expensive; there are prominent natural health advocates and self-titled nutritionists who will happily sell you supplements online that will set you back close to $300 a month.

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But do these things really work? Do we need them to get or be well? Or can we get what we need from food? Are supplements super, or are they a waste of money?

The answer to that is not straightforward, it seems. When you talk to registered dietitians or nutritionists they don't like to give a blanket answer; that's because individual needs are very different. Some people with specific health conditions may benefit from expert advice and expert-recommended supplements. By expert I mean a degree-qualified dietitian or nutritionist, not someone in a pharmacy, health food store or on social media.

Do these things really work? Do we need them to get or be well? Or can we get what we need from food? Are supplements super, or are they a waste of money? Photo / Getty Images
Do these things really work? Do we need them to get or be well? Or can we get what we need from food? Are supplements super, or are they a waste of money? Photo / Getty Images

So if you see someone promoting any supplements as ideal "for everyone" it would pay to be cautious.

True experts often say that healthy people don't need supplements. If we eat well and live a generally healthy life we should, in theory, get everything we need from food. In general, very few people in New Zealand have true deficiencies.

Vitamin C is an example of something often promoted as a miracle cure for everything from cancer on down. But it's not something we can use in mega doses. I recently heard Otago University's Magreet Vissers interviewed: she is an expert in vitamin C and spends her time researching vitamin C and cancer. Yet she's the first to say healthy people don't need vitamin C supplements; she herself eats a kiwifruit a day to get her daily dose. If we simply eat five serves of vegetables and fruit a day, we'll get the 200mg of vitamin C we need to reduce our risk of chronic disease.

When we have a cold, there's limited evidence vitamin C supplements might reduce the duration of the cold by a day. The evidence on cancer is interesting, and researchers are excited about it, but it's far from proven yet. What's more, if we have too much vitamin C in the form of supplements, we risk unpleasant side effects like diarrhoea, nausea and stomach cramps.

That's worst case; best case is we simply generate expensive urine.

Some other supplements might be useful in specific situations, under medical advice. For example, folate and iodine are recommended during pregnancy. Vegans need to take vitamin B12, or eat foods fortified with B12, since they can't get it from a plant-only diet. People who spend very little time outside and have dark skin may need vitamin D supplements during the winter. People with osteoporosis or low bone density can be prescribed calcium supplements or infusions.

Omega-3 supplements are popular with Kiwis, but controversial: a large review published last year found no benefit to heart health or reduction in stroke risk from omega-3 supplements.

We're better off, experts say, getting our omega-3 from oily fish.

Multivitamins are popular, too. We tend to take these as a kind of insurance policy; if we don't manage to eat as well as we should, we reason, we'll make up for it with a multi. That sounds good, but it's probably not a great long-term solution to health. That's because the vitamins and minerals in food are all wrapped up in what they call the "food matrix". That means whole foods are more than the sum of their nutrients; they're complex and their benefits come from that whole.

A reason we sometimes hear for why we need supplements is that our food now is not as nutritious as it used to be. We can't get everything from food, they say, because our soils are depleted and our food is, too. But there's no evidence this is true in New Zealand – and only limited evidence it's true anywhere else in the world.

So what's the best advice when you're standing in front of all the rows of supplements in the store? I'd say, firstly, remember there is very little regulation of these products, what's in them, or what marketers can claim about what they do. Then, think about how much fresh whole food you could buy for that money. In the end that is highly likely to give your health more of a long-term boost.

• Niki Bezzant is editor-at-large for Healthy Food Guide. Follow her on Facebook or Instagram @nikibezzant