Too many vitamins may be bad for you

The news that vitamins could damage your health was reported in eight newspapers (1-10) on Thursday 8th May 2003, with a mixed degree of accuracy. The articles were based on an FSA press release and detailed report from the Expert Group on Vitamins and Minerals (11,12) which issued warnings about vitamins and minerals.

• Eight newspapers (1-10) reported the news that vitamins could damage your health. The newspaper articles gave varying details of the vitamins and minerals that had had warnings issued about them by the Food Standards Agency (FSA).

• The newspaper articles were based on a large, detailed report by the Expert Group on Vitamins and Minerals (EVM) (11), and a press release (12) issued by the FSA. The EVM report contained a series of risk assessments to determine the safe upper dose limits for vitamins and minerals. It did not investigate possible benefits of the supplements. Following publication of the EVM report, the FSA issued advice on some vitamins and minerals that could have possible harmful effects if taken in too high a dose (13).

• Some of the newspaper articles inaccurately stated that the EVM report said that vitamins and minerals were a waste of money, and that many vitamin supplements did more harm than good. Only one newspaper article emphasised that the EVM report made no judgement on the health benefits claimed for various supplements.

Evaluation of the evidence base for safety of high doses of vitamins and minerals

Where does the evidence come from?

The review was carried out by the Expert Group on Vitamins and Minerals (EVM): an independent group established by the UK government in 1997. The group was comprised of eleven members from the medical and scientific community, one lay member and four observers representing consumer organisations, the health and food industries and alternative medicine interests. Possible competing interests of the members of the EVM were reported; none seemed to be relevant.

What were the authors' objectives?

To advise on safe upper limits (SULs) of intakes of vitamins and minerals in food supplements and fortified foods. The EVM were asked to consider only vitamins and minerals sold under food law. Review of nutritional or non-nutritional beneficial effects or non-nutritional use in medicine was outside the review objectives.

What was the nature of the evidence?

A non-systematic review. The EVM considered a detailed review of the relevant evidence for each substance and produced a 'Risk Assessment' and 'Establishment of Guidance Level' based on this evidence. The detailed reviews covered nutritional and toxicological information. The report stated that because of the diversity of the available data no formal systematic review methodology was used during the assessment process. However, the authors of the reviews of particular vitamins or minerals which were commissioned to inform the report, and the EVM, considered the strengths and weaknesses of study design and conduct in assessing the quality and reliability of particular studies. Both human and animal studies were included, as well as exposure data taken from UK Government Departments and from other scientific literature. Further details are given in the report.

What interventions were examined in the research?

Thirty-four substances were assessed in detail. These were: chromium; vitamin C; calcium; iron; beta-carotene; nicotinic acid (vitamin B3); zinc; manganese; phosphorus, vitamin B6; biotin; folic acid; pantothenic acid; riboflavin; niacin; thiamine; vitamin B12; vitamin D; vitamin E; vitamin K; boron; cobalt; copper; iodine; molybdenum; nickel; selenium; tin; magnesium; potassium; silicon; germanium; vanadium; and sodium chloride.

What were the findings?

For each of the 34 substances assessed, a 'Risk Assessment' and 'Establishment of Guidance Level' were reported.

What were the authors' conclusions?

Following publication of the EVM report, the FSA issued advice on some vitamins and minerals that could have possible harmful effects if taken in too high a dose (13).

How reliable are the conclusions?

The report is very large and is based on separate reviews of the evidence for each of the 34 substances included. Some details of the EVM's methodology are given in one of the Annexes to the report. No details of the methodology of the separate reviews were given, other than the statement that systematic review methodology was not used. It is therefore not possible to give a detailed appraisal of the methods used, or to decide how reliable the conclusions might be.

Systematic reviews

Information staff at CRD searched for systematic reviews relevant to this topic. Systematic reviews are valuable sources of evidence as they locate, appraise and synthesize all available evidence on a particular topic.

No related systematic reviews were identified on the Cochrane Database of Systematic Reviews or on the Database of Abstracts of Reviews of Effectiveness (DARE).

This report has been prepared for the National electronic Library for Health by the NHS Centre for Reviews and Dissemination, based at the University of York

References and resources

1. Too many vitamins may be bad for you. Daily Express. 8 May 2003, p14.

2. Vitamin sales boom sparks fears over excess doses. The Independent. 8 May 2003, p5.

3. Warning: Vitamin pills can damage your health. The Sun. 8 May 2003, p55.

4.Vitamin pills could damage health. The Guardian. 8 May 2003, p8.

5. Vitamins can damage your health, warns watchdog. The Times. 8 May 2003, p1.

6. Health in a bottle is not quite so simple as ABC. The Times. 8 May 2003, p4-5.

7. Vitamins can damage your health, says watchdog. Daily Telegraph. 8 May 2003, p1.

8. Vitamin pill alert will be hard to swallow. Daily Telegraph. 8 May 2003, p6.

9. Over-use of vitamins or minerals may lead to cancer. Financial Times. 8 May 2003, p3.

10. Government warning: vitamin pills are a waste of money and may damage health. Daily Mirror. 8 May 2003, p27.

11. Safe upper levels for vitamins and minerals. Expert Group on Vitamins and Minerals, May 2003.

12. New FSA advice on safety of high doses of vitamins and minerals. Ref 2003/0371. Food Standards Agency. 8 May 2003.

13. Vitamins and Minerals - New Advice. Food Standards Agency.

NB The Daily Mail reported on this subject the following day. A plague on all those pills. Daily Mail. 9 May 2003, p13.

Consumer information

British Nutrition Foundation

NHS Direct - Dietary Supplements