Health & beauty

Dietary supplements

Updated 10 May 2008
Dietary-supplements-hero

Introduction

Dietary supplements are big business; more than half of New Zealanders take them.

People hope to increase their daily dose of vitamins and minerals, boost their immune systems, or revitalise their mental faculties.

But little of this really happens. Some supplements have genuine health benefits, but many others do not.

Useful supplements

The Ministry of Health says most people in New Zealand can get all the nutrients they need from their food. Professor Jim Mann of the Department of Human Nutrition at Otago University says millions of dollars are wasted on dietary supplements each year. We agree with both points.

These are the supplements with well-established health benefits, and the circumstances in which they should be taken. It's a small list.

Folate

(also called folic acid) is a B vitamin, important for women planning or in the early stages of a pregnancy. There is evidence it reduces the incidence of neural tube (birth) defects.

The Ministry of Health recommends women take a 0.8mg supplement of folate four weeks before they conceive and for the first 12 weeks of the pregnancy.

They should also increase the folate in their diet by eating fruit and vegetables and wholegrain breads and cereals. Some breakfast cereals and some fruit juices are fortified with folate - this will be stated on the label.

New Zealand and Australian food ministries have decided it will be compulsory to add folate to some bread. Mandatory fortification on its own won't increase intake to the levels required. Those planning a pregnancy will still need to take a supplement.

Vitamin B12

is only found in animal products. The richest sources are liver and kidney. It's also found in other meats and in lesser amounts in milk and milk products.

Vegetarians, and especially vegans, are at risk of vitamin B12 deficiency.

Vitamin D

aids in the absorption of calcium and is important for bone health. Most of us get enough vitamin D from exposure to sunlight. The only people who may need a top-up are those who rarely get outside.

Margarine, eggs, butter and oily fish like salmon are good sources of vitamin D.

Iron

deficiency may result in anaemia. This is a medical condition and should be properly diagnosed by a doctor.

Supplements are necessary when there is evidence of iron-deficiency anaemia, or when women have high menstrual losses, or are pregnant and have low iron stores.

Vegetarians may also have low iron stores. The iron in meat, poultry and seafood (called "haem" iron) is more easily absorbed than the non-haem iron in vegetables.

Calcium

is needed for strong bones and is especially important for growing children and women after menopause. Doctors sometimes recommend supplements to people at risk, especially frail, older women.

Milk and milk products are good sources of calcium. You can also keep up your calcium levels from non-dairy sources like green vegetables, wholegrain cereals and breads, canned fish with bones, beans, nuts and calcium-fortified soy drinks.

Less useful supplements

Multivitamins

are often taken as a kind of nutritional "insurance" to top up an inadequate diet. They're unlikely to do any harm - except to your wallet - but it's far from clear if they will do you any good.

Other supplements

Other nutrients, such as mineral supplements, vitamin C and B type vitamins, are widely consumed. However, there is disagreement about how beneficial they are and little evidence they alter health outcomes - despite what their manufacturers say.

Body overload

More is not necessarily better when it comes to vitamin and mineral supplements. Very big doses can be unsafe.

The Food Standards Agency in Britain released its largest safety review of vitamins and minerals in 2004. It suggests people who take excessive doses of some supplements are at risk of cancer, liver damage, loss of feeling in the arms and legs, and weakened bones.

Vitamin and mineral deficiencies aren't common in New Zealand. It is unlikely that a problem you have is caused by a deficiency. Check with a doctor.

Our advice

  • Supplements are no substitute for food. Nor will they "cancel out" the effects of a poor lifestyle, which may include smoking or drinking too much alcohol. Nor will they reverse the ageing process.
  • Eat a healthy diet based on wholegrain breads and cereals, fruits and vegetables, low-fat dairy products, lean meat, poultry and seafood. Evidence suggests that health benefits are gained from the way a combination of substances in food works together, not from a single nutrient.
  • Do not diagnose and treat yourself. If you are in an at-risk group or have an ongoing health concern, discuss your diet with a doctor or dietitian.
  • If the claims for a supplement sound too good to be true, they probably are.

More help

There are a number of websites where you can find reliable advice and information about supplements.