Thursday 23 October 2014

Ask the doctor: Do vitamin supplements really work?

vitamins, pills and tablets
vitamins, pills and tablets

I am generally quite healthy and would like to remain that way. I went to the health food shop recently and they recommended taking all kinds of different vitamins to help reduce my risk of chronic disease. Are these really necessary and are they going to help keep me well?

Vitamin supplements have become very popular. It is estimated that one in four people in Ireland takes some kind of supplement, and this is big business for the pharmaceutical companies that make them.

Over the years it has been suggested that certain vitamins and minerals may help cure illness, improve wellbeing and prevent or reduce the risk of a whole host of chronic diseases and cancers. However, the evidence to support these claims is increasingly lacking, and newer evidence actually suggests that high doses of some supplements may even be harmful.

Vitamins and minerals are essential to the normal functioning of the body, but the best place to get these is through a varied and healthy diet. A diet high in wholegrains, fruit, vegetables, lean protein, healthy fats and sufficient dairy is considered complete, and extra supplements are not normally necessary.

There are certain cases where supplementation is advised. All women of childbearing years who are sexually active should take a supplement of 400 micrograms of folic acid. This has been shown to significantly reduce the chance of birth defects such as spina bifida. As one in two pregnancies is unplanned, taking folic acid provides the greatest protection. Vegans should also supplement their diet, as they may miss out on calcium and certain B and fat-soluble vitamins.

So what about the popular supplements – are they worth it? Vitamin C has long been thought to help keep coughs and colds at bay. This isn't the case. A review of studies going back many years looking at vitamin C intake in over 11,000 people showed that it does not prevent colds and flus. It may shorten the duration of a cough or cold in some people by maybe a day or so: hardly worth forking out for large doses of this. Many studies have looked at the role of vitamin E in heart health, and no benefit was shown. Some studies actually suggested that high doses of vitamin E can in fact increase the risk of lung cancer.

Another supplement, B carotene, has also been shown to increase the risk of lung cancer in smokers. High doses of folic acid may be associated with a higher risk of colonic polyps. The Iowa women's study followed a group of women for 22 years. Those taking supplements of vitamin B6, folic acid, magnesium, iron and zinc actually had a higher risk of premature death.

There are some supplements that have shown themselves necessary or beneficial. Vitamin D is one I have written about previously. Sunlight is our main source of this vitamin – and as we are so far north, we do not get enough from the months of October through March. It is hard to get vitamin D in food, although it is present in small amounts in oily fish. Some cereals, milk and yoghurts are now fortified with vitamin D. All babies under a year should receive a daily vitamin D supplement. It is also advised in children up to age five, those over 65 and anyone with dark skin living in northern latitudes.

Adequate calcium intake has been linked with better health, so if dairy is lacking in your diet it is worth taking this as a supple-ment also. Calcium and vitamin D work together and are important for bone health and are often combined in supplements.

Fish oils are beneficial to heart health. The best source of these is eating oily fish twice weekly, but if you can't tolerate this, then a supplement is a good idea in those with other cardiovascular risk factors. A certain combination of vitamins has been shown to help those who have or are at risk of the eye condition macular degeneration.

The message is simple and clear. The best way to prevent disease and improve health is to eat a varied, healthy diet and to lead a healthy lifestyle, avoiding cigarettes and excess alcohol and including exercise as part of your daily routine. For times when the pace of life means diet and lifestyle suffer, a short course of a general multivitamin may help fill the gap. However, there is no case for multiple high-dose vitamin supplements – and they should never be a license for unhealthy habits.

drnina@independent.ie

Health & Living

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