A magic pill is a sexy concept. It can instantly remedy any wrongs in our diet or lifestyle.

The astounding array of pills and supplements on offer means there is something for everyone. Sheep's placenta or essence of kangaroo anyone? There are pills for your skin and nails, for stress and for every ailment under the sun.

But appealing as a magic pill may be, there is a problem.

They may not be able to target the health issue with precision.

The vitamins and minerals we find in pills and supplements are extracted and chemically refined and not in the form our bodies recognise, says Dr Jaroslav Boublik, associate member of the Australian College for Nutritional and Environmental Medicine.

"While there is no difference at a molecular level between a synthetic vitamin molecule and a naturally occurring one, what is important is the synthetic molecule is the vitamin in isolation, whereas the naturally occurring one is usually encountered in a matrix, typically food, that may also contain other molecules that allow it to carry out its role more efficiently or more effectively," Boublik says. "So rather than make the distinction between synthetic and natural I prefer to distinguish isolated vitamins from those that are present in a food form matrix.

"There is [a] certain arrogance in nutritional science that we know what all of the required nutrients are for good health, and how much of each, everybody needs to consume," says Boublik, who is chief science officer for Activated Nutrients.

"The reality is that even in the past 10 years a number of new micro-nutrients have been described. Many people use vitamin C and it's an easy compound to synthesise but it's much better absorbed when it's taken with bioflavonoids, which naturally occur in citrus skin. It's a perfect example of how nature includes key additional factors to optimise the effectiveness of nutrients in food but which we can easily miss if we just use isolated or synthetic vitamins."

Despite this, and despite questions about whether they contain the ingredients they claim, nearly half of the Australian population (42 per cent) take vitamins.

"We love the notion of a magic pill. It's something that makes it all better. It's just too seductive," paediatrician Paul Offit, from the Children's Hospital of Philadelphia, said in a New York Times and PBS Frontline investigation, aired in an episode of Four Corners on May 16. The investigation raised questions about the quality and safety of vitamins and dietary supplements.

"You need vitamins to live. The question is, do you get enough in food? And I think the answer to that question is yes," Dr Offit said.

"Then you look on the back [of product bottles] and you find that a number of these vitamins are contained in amounts that are much greater than the recommended daily allowance.

"Now there are studies done showing if you take a mega vitamin, you actually can hurt yourself.

"You actually can increase your risk of cancer, increase your risk of heart disease. I think few people know the risks they're taking."

Vitamins are particularly seductive for those who aren't getting enough vitamins and minerals from their diet. Just 6.8 per cent of the Australian population meet the recommended usual intake of vegetables, according to ABS data.

Are vitamins and supplements ever beneficial?

Accredited practising dietitian, Melanie McGrice, believes so, but suggests being careful with how you take them and where you receive your advice.

"I often find that when I prescribe a supplement to treat a clinical issue, the patient often returns having received differing advice from a pharmacy assistant who hasn't seen their blood tests and has little idea of their medical history," McGrice says. "Unfortunately I often find that both patients and retailers tend to have a 'more is better' attitude when it comes to nutritional supplements, but when we look at the research, that's just not the case.

"I don't have a problem with nutritional supplements being sold over-the-counter at pharmacies and supermarkets, but I do believe that the up-selling needs to stop and people should only be buying nutritional supplements based on the advice of their treating practitioner."

McGrice's tips for choosing quality supplements:

1. Choose supplements in opaque bottles - some supplements such as vitamin C degrade in light.

2. Ask your healthcare professional for advice about quantities - just because the supplement contains an ingredient doesn't mean that you're getting that ingredient at a therapeutic dose. For example some gummies only have miniscule amounts of nutrients and are more of a lolly than a nutritional supplement.

3. Understand how much you are taking - the supplement may have a long list of ingredients, but if the nutrients are only there in minute amounts it may not do much good. There's a big difference between milligrams (mg) and micrograms (mcg) as it takes 1000mcg to make 1mg!

4. Be careful of nutrient interactions - some nutrients compete against one another for example calcium and iron, so these should be taken at different times of day. Ask your health care professional when you should take each supplement.