Taking high doses of vitamins could actually damage your health

The Food Safety Authority of Ireland (FSAI) has warned that people who exceed the recommended daily amounts (RDAs) of vitamins by taking high doses of supplements risk damaging their health.

It comes after a study by the University of Colorado linked some vitamin supplements to heart disease and cancer.

Vitamin pills and supplements are big business in Ireland - we spend €13m on them in supermarkets and convenience stores alone, with millions more spent in healthfood stores and pharmacies.

FSAI chief specialist in public health nutrition Dr Mary Flynn said that vitamin and mineral supplements at recommended levels could be beneficial, but in high doses they can be harmful, due to complex interactions with other minerals in the body or with medications.

"It is not the case that because a small amount of something is good, that a large amount will be better, as there are so many complex interactions in the body," she said.

For example, too much vitamin D could cause calcium to leach into the soft tissues of the body, while high calcium supplementation could disrupt the body's magnesium levels.

Consumers must be particularly careful about taking excessive amounts of vitamins A, D or E as they are stored up in the body.

Many vitamin C tablets on sale are very high strength, at 1000mg compared with an RDA of 80mg. Consumers should be aware that doses of 2g can cause gastric upset and smaller people or those with sensitive stomachs could be affected by less, said Dr Flynn.

She said that the only vitamin supplements the FSAI specifically recommended consumers take were folic acid for all women who could get pregnant, and vitamin D for infants.

Given 50pc of all pregnancies are unplanned, all women of childbearing age who are sexually active should take 400 micrograms of folic acid daily to prevent neural tube defects such as spina bifida.

All babies should be given five micrograms of Vitamin D for bone development, and pregnant women and toddlers also benefit from this.

Dr Flynn said she would like to see maximum levels of vitamins set to protect consumers, but it had so far proved difficult to get agreement on this in the European Union.

However, while consumers should always follow their doctor's advice if a specific deficiency was identified, most people did not need to take supplements as they would get everything they needed from a balanced diet, apart from the two exceptions of folic acid and Vitamin D.

"In general, you would be much better off eating a healthy diet, with plenty of fruit and vegetables, lean meat, oily fish, wholemeal bread and cereals and low-fat dairy products," she said.

The Irish Association of Health Stores, which represents 100 stores, said that the FSAI took a very conservative approach to vitamin use, as RDAs were usually set at a minimum level. However, in their view higher levels could often be more beneficial.

Studies had shown that food was dramatically lower in nutrients and minerals such as iron, copper and calcium than it used to be, meaning higher-dose supplements were often simply replacing those losses said spokeswoman Jill Bell.

"In 17 years in business I have never seen someone suffer an adverse reaction to a vitamin supplement, and I have only seen two minor reactions to a valerian herbal supplement," she said.

"We talk to our customers to find what their needs are, and if someone is on a medication where there's a risk of interaction, we'd rather lose a sale than sell them something unsuitable," she said.

Many customers take vitamin C as a remedy for the common cold, but research has shown it does not reduce the risk of getting one. It might slightly reduce the duration or symptoms, but not if you start taking a supplement after you catch one.

Kelkin brand owner Valeo Foods said its 1000mg Vitamin C tablets complied with EU legislation and it would accept any maximum levels that were imposed.

Kelko head of nutrition Adrienne O'Reilly said EFSA had accepted health claims about vitamin C that it contributed to normal functioning of the immune system and blood vessels and to reducing tiredness, though supplements should never be used as a substitute for a healthy diet.

Holland & Barrett said that EFSA set safety limits for vitamins that were well above RDAs.

While it was true high doses of vitamin C could cause gastrointestinal upset in sensitive individuals, the regulations recognised this was not enough to ban high doses, which could be helpful in reducing the longevity of colds and coughs.