Vitamin supplements - all change?

The British Dietetic Association recommends that if you are going to take a supplement, it should be a general multivitamin which contains at least 15 ingredients at or below 150% of the European Recommended Daily Amount.

'When the facts change, I change my mind - what do you do?' John Maynard Keynes

For years, I have been advising my patients that there is no evidence from any large scale studies of any benefit from taking a daily multivitamin. I was on strong ground as far as the research went. The Heart Protection Study, which followed over 20,000 40 to 80-year-olds who took a daily dose of vitamins A, C and E (600 mg vitamin E, 250 mg vitamin C, and 20 mg beta-carotene) were just as likely to have a heart attack or stroke, die or get cancer than the control group who took the 'placebo' (a pretend tablet which doesn't have any active ingredients). In the Iowa Women's Health Study, almost 40,000 women were followed up for almost 20 years. There were higher death rates among women taking some vitamins. As if that weren't confusing enough, women taking calcium supplements in this study had lower death rates than women who weren't, even though other recent studies have suggested that calcium supplements may increase the risk of heart attack.

Now a new large scale study has come along which directly contradicts previous research - or does it? The Heart Protection Study followed up subjects for only five years. In the Iowa Women's Health Study, women were left to their own devices in terms of the doses of vitamin and mineral supplements they took, and many supplements have way more than the recommended daily allowance. Much of the healthcare debate has centred on whether high-dose vitamins and minerals can do more harm than good, and a study looking at levels close to the amounts we should be eating was lacking.

Now a new major study has shown an 8% reduction in the risk of cancer among men over 50. The Physicians' Health Study II followed almost 15,000 doctors for over 11 years. In the USA, screening for prostate cancer is much more common than in the UK, and lots of men in the study were diagnosed with prostate cancer, mostly at an extremely early stage, because of screening. There's debate as to whether this saves lives and it certainly results in unnecessary treatment, but as a result over half the cancers found in the study were prostate cancer. Among the rest of the cancers, taking the multivitamin reduced the risk of cancer by a statistically significant 8%. Of the 1,300 men in the study who had a past history of cancer, the vitamin group was 27% less likely to be diagnosed with another cancer.

Is this study reliable? Almost certainly. The groups who took the real and the placebo were carefully matched, the study large and long so the results are highly unlikely to be coincidence. Does this mean we should all start taking supplements? No. This evidence only relates to men over 50. Does the type of vitamin matter? Almost certainly. The British Dietetic Association recommends that if you are going to take a supplement, it should be a general multivitamin which contains at least 15 ingredients at or below 150% of the European Recommended Daily Amount (see below). The closest equivalent to the multivitamin used in this study was Centrum Advance® 50+. Women who are pregnant or trying to get pregnant should take a folic acid supplement of 400 micrograms a day; and all pregnant and breast-feeding women, as well as over-65s and people who spend little time in the sun, should consider a vitamin D supplement of 10 micrograms (400 IU) a day. For the rest of us, a healthy balanced diet will usually do just nicely.

Vitamins RDA Minerals RDA

(ref NHS Choices: Supplements Who needs them? June 2011)

Vitamin A 800 μg

Calcium 800 mg

Vitamin D 5 μg

Magnesium 375 mg

Vitamin E 12 mg α-TE

Iron 14 mg

Vitamin K 75 μg

Copper 1 mg

Vitamin B1 1.1 mg

Iodine 150 μg

Vitamin B2 1.4 mg

Zinc 10 mg

Niacin 16 mg

Manganese 2 mg

Pantothenic acid 6 mg

Potassium 2000 mg

Vitamin B6 1.4 mg

Selenium 55 μg

Folic acid 200 μg

Chromium 40 μg

Vitamin B12 2.5 μg

Molybdenum 50 μg

Biotin 50 μg

Fluoride 3.5 mg

Vitamin C 80 mg

Chloride 800 mg

Phosphorus 700 mg

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.