• Vitamins are organic compounds used by the body in small amounts for various metabolic processes.
  • Vitamin supplements cannot replace a healthy diet.
  • Those who may need vitamin supplements include women who are pregnant or breastfeeding, people who consume alcohol in amounts over those recommended as safe, drug users, and the elderly.
Vitamins are organic compounds that our bodies use, in very small amounts, for a variety of metabolic processes. It is best to get vitamins and minerals from eating a variety of healthy unprocessed foods.

While taking a general ‘broad-spectrum’ vitamin and mineral supplement ‘just in case’ poses little health risk, and may benefit a person whose diet is restricted and lacks variety, taking vitamin and mineral supplements instead of eating a nutritious diet is not recommended.

Vitamin and mineral deficiencies

Your body only needs a small amount of vitamins and minerals every day. A varied diet generally provides enough of each vitamin and mineral. However, some people may need supplements to correct deficiencies of particular vitamins or minerals.

People who may benefit from vitamin and mineral supplements include:
  • pregnant women
  • women who are breastfeeding
  • people who drink alcohol above the amount that is recommended for reducing risk of disease (one standard drink a day for non-pregnant women and two for men)
  • cigarette smokers
  • illegal drug users
  • crash dieters or people on chronic low-calorie diets
  • the elderly (especially those who are disabled or chronically ill)
  • some vegetarians or vegans
  • women with excessive bleeding during menstruation
  • people with allergies to particular foods
  • people with malabsorption problems such as diarrhoea, coeliac disease or pancreatitis.
Women planning a pregnancy should consider taking folic acid (folate) supplements to reduce the risk of neural tube defects in the baby. Folic acid can also be found in some fortified foods such as some breads. Foods fortified with folic acid have the nutrient added to them during production to boost their nutritional value.

Vitamins and minerals from food

Research indicates that most of the vitamins you get from the food you eat are better than those contained in pills. Even though vitamins in supplements are synthesised to the exact chemical composition of naturally-occurring vitamins, they still don’t seem to work as well.

The main exception to this is folate. The synthetic form (in a supplement or fortified food) is actually better absorbed by the body than folate from food sources.

Food is a complex source of vitamins, minerals and phytochemicals (plant chemicals), which all work together. Supplements tend to work in isolation. Research has shown that a food component that has a particular effect on the body may not have the same effect when it is isolated and taken as a supplement. This could be because the vitamins and minerals in foods are also influenced by other components of the food, not just the ‘active ingredient’.

Phytochemicals are an important component of food and are thought to reduce the incidence of heart disease and some cancers. Supplements do not provide the benefits of phytochemicals and other components found in food. Taking vitamin and mineral supplements is no substitute for a healthy diet.

Using vitamin and mineral pills like medicine

It is commonly believed that taking mega-doses of certain vitamins will act like medicine to cure or prevent certain ailments. For instance, vitamin C is suggested as a cure for the common cold, and vitamin E is widely promoted as a beneficial antioxidant to help prevent heart disease.

After extensive research, however, neither of these claims has been shown to be true. Large-scale studies have consistently shown little benefit in taking mega-doses of supplements. In fact, there is some evidence that taking high-dose supplements to prevent or cure major chronic diseases, such as heart disease and cancer, may be harmful to your health.

Vitamin and mineral supplements can be toxic in high doses

Taking higher than recommended doses of some vitamins may cause problems. For example, the vitamins A, D, E and K are fat soluble, which means they are stored in the body. High doses of these vitamins can be toxic.

High doses of some water soluble vitamins, like vitamin B6, can also become toxic. Large folate intakes can hide vitamin B12 deficiencies. In extreme cases, for example, where people take 100 times the recommended dietary intake (RDI), this can stop the work of anticonvulsant drugs, such as those used in epilepsy.

Excessive doses of some minerals may also cause problems. At just five times the RDI, zinc, iron, chromium and selenium can be raised to toxic levels in the body. For example:
  • Large intakes of fluoride (especially in childhood) may stain, and even weaken, the teeth.
  • Very large doses of fish oil can lead to decreased blood clotting.
  • Iron toxicity is also common. Even a small amount over the RDI can cause gastrointestinal upset, nausea and black bowel actions (poo). Severe toxicity can lead to coma and even death.
  • High levels of vitamin B6 have been linked to some types of nerve damage.
  • Doses of vitamin C above one gram can cause diarrhoea.
  • High doses of vitamin A may cause birth defects, as well as central nervous system, liver, bone and skin disorders.
For a healthy adult, if supplements are used, they should generally be taken at levels close to the RDI. High-dose supplements should not be taken unless recommended under medical advice.

Stress, tiredness and vitamin pills

Vitamin supplements are commonly considered to be an antidote to stress. Feeling under pressure doesn’t automatically lead to a vitamin deficiency, so taking a vitamin supplement won’t necessarily make the stressful feelings go away.

Popping a pill will not likely cure persistent tiredness either. If you are feeling run down, it is more likely to be due to stress, depression, insufficient sleep or other factors, rather than a deficiency of a particular vitamin.

Vitamins and minerals as a short-term measure

Taking vitamin and mineral supplements should be viewed as a short-term measure. The long-term use of some high-dose supplements can lead to symptoms of toxicity. If you feel that you could be lacking in certain vitamins and minerals, it may be better to look at changing your diet and lifestyle rather than reaching for supplements.

Where to get help

  • Your doctor
  • Dietitians Association of Australia Tel. 1800 812 942
  • Nutrition Australia.

Things to remember

  • Vitamins are organic compounds used by the body in small amounts for various metabolic processes.
  • Vitamin supplements cannot replace a healthy diet.
  • Those who may need vitamin supplements include women who are pregnant or breastfeeding, people who consume alcohol in amounts over those recommended as safe, drug users, and the elderly.
  • All about food – vitamins and minerals , Parenting and Child Health, Child and Youth Health Unit, Government of South Australia. More information here.
  • Kris-Etherton P, Lichtenstein A, Howard B et al. 2004, 'Antioxidant vitamin supplements and cardiovascular disease', Circulation , vol. 110, pp. 637-641. More information here.
  • Nutrient Reference Values (NRVs) for Australia and New Zealand (including recommended dietary intakes), Australian National Health and Medical Research Council. More information here.
  • 'Supplement use: is there any nutritional benefit?', Journal of the American Dietetic Association , vol. 102, no. 6, pp. 818–25. More information here.
  • Combs GF Jr, The vitamins: fundamental aspects in nutrition and health (3rd Edition) 2007, Elsevier Academic Press. More information here.
  • 'What vitamins should I be taking, doctor?', New England Journal of MedicineMore information here.

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This page has been produced in consultation with and approved by: Deakin University - School of Exercise and Nutrition Sciences

Last updated: October 2012

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Content on this website is provided for education and information purposes only. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your doctor or other registered health professional. Content has been prepared for Victorian residents and wider Australian audiences, and was accurate at the time of publication. Readers should note that, over time, currency and completeness of the information may change. All users are urged to always seek advice from a registered health care professional for diagnosis and answers to their medical questions.