The Safety of Vitamin and Mineral Supplements
– Dr Alan Stewart

In the light of the concern about the restrictions which are to be imposed on over the counter sales of high dose vitamins and minerals Dr Alan Stewart looks at the Expert Group on Vitamins and Minerals’ report on ‘Safe Upper Levels For Vitamins and Minerals’.

In May this year the Expert Group on Vitamins and Minerals, an independent expert advisory committee set up by the Food Standards Agency, reviewed the safe levels of intakes for vitamins and minerals in food  supplements and fortified foods. Their report Upper Safety Levels For Vitamins and Minerals, is over 350 pages long, is very detailed and well referenced and contains a lot of information on the toxicity of nutrients in animals and humans. The committee has set limits for many vitamins and minerals in nutritional supplements that mean a change in formulation of many products, or their removal from sale.
            The Committee has adopted a very cautious approach without any consideration as to the possible or actual benefits of nutritional supplements. The eight nutrients for which levels have been set are:

•            Beta-carotene                        7,000ug / day            
•            Vitamins B6                        10 mg / day
•            Zinc                                      25 mg / day
•            Boron                                  6mg / day
•            Vitamin E                           540(800)IU/day
•            Copper                                   1mg / day
•            Selenium                                 350 ug / day
•            Silicon                                  700 mg / day

Set Upper levels (SULs) have been set for eight vitamins and Guidance Levels(GLs) for twenty-two others. Whilst there is little issue for most of the vitamins and minerals there is a strong and justifiable view that the levels set for Vitamin B6 and Vitamin C are unduly cautious. These levels, it should be stressed, apply to supplements that are being bought over the counter and not on the recommendation of a doctor who, in theory, is in a position to assess the specific needs of the individual.
            The levels apply to the general population and assume that intake from diet and in the case of some minerals, drinking water, are high. It is also assumed that intake from supplements is sustained at a relatively high level for a long period of time.
            Additionally there are other recommendations including the Guidance Levels on 22 other nutrients. These nutrients include; Calcium1500mg/day, Magnesium 400mg /day, Iron 17 mg/day and Vitamin C 1000mg/day. Higher amounts may well be safe if they are supervised.

Consequences for those Taking Supplements

For most people taking simple supplement regimes including most one-a-day preparations, calcium and modest amounts of other minerals and vitamins no action is necessary. For those taking strong multivitamins or high dose Vitamin B or C, or for any of the groups below, occasional review by your doctor or an experienced nutritional therapist is advisable.

The Elderly

Those aged 65 years and over should be kept under regular review because of changing needs, the possibility of new medical problems occurring which might influence the risk of  toxic effects, and drug-nutrient interactions.

Ill Patients

Those with chronic liver, kidney or blood disorders and anyone with an uncertain medical diagnosis needs regular review.  Children with growth problems or any chronic illness also need regular review.

Pregnant/Breastfeeding Women

As a rule women in this situation should not take anything other than folic acid or an appropriate multivitamin/mineral supplement for pregnancy without professional advice, although many additional supplements are likely to be safe in low doses and may be needed. Women seeking to become pregnant and taking supplements should also seek professional advice and switch to an appropriate pre-pregnancy supplement. High intakes of supplements in breastfeeding women could well result in an excessive intake for the infant.

Drug Nutrient Interactions

There are many possible drug/supplement interactions and whilst they were not considered in detail by the Expert Group it is relevant to mention some.
Warfarin's anticoagulant action can be reduced by Vitamin K and enhanced by Vitamin E and neither should be taken without medical supervision.
Aspirin may increase breakdown and lower the blood levels of Vitamin C.
Many diuretics that can cause potassium loss can also increase the urinary losses of magnesium.
Prolonged use of broad-spectrum antibiotics can result in Vitamin K deficiency.
Oral steroids can lead to osteoporosis and increase the need for calcium.
Drugs that slow gut transit such as codeine may increase the absorption of riboflavin, Vitamin B2, and possibly some minerals.
Prolonged use of anti-epileptic drugs, especially multiple therapy, can result in folate or Vitamin D deficiency but usually only if there are other risk factors as well such as poor diet or poor sunlight exposure in the case of Vitamin D inadequacy.
Those taking High Dose Supplements
There are possible interactions between nutrients as well as additive effects in those who regularly take several  different types of supplements. As a rough guide if you are taking  more than four different types then a review every one to two years is appropriate.

Medical Problems

Those with pre-existing medical problems (see table below) also need careful regular review and should not take supplements containing relevant nutrients without professional advice.  Most of these situations are relatively rare but virtually all doctors will have come across them at some time.


The vast majority of supplements are indeed safe but there are concerns about some high dose preparations, about the prolonged use of some supplements in both the healthy population and those with certain illnesses or taking certain drugs, and about the use of supplements in people in particular situations such as pregnancy.
            Perhaps the most difficult situation is where someone develops a new illness that will alter their tolerance of a supplement which was previously of some benefit but might now aggravate their new emerging problem.Their needs have changed and their use of supplements should be reviewed.
            Doctors, complementary practitioners, dietitians and nutritionists should be aware of some of these possible problems and should regularly enquire about their patients use of supplements and be prepared to assess and advise them accordingly.
            It would be helpful if this report had the effect of alerting doctors as to the need to be thorough in the appraisal of their patients’ nutritional requirements and to realise that they may change. It will not be helpful if all it manages to do is to frighten them off recommending anything in the first place. 

The Expert Group on Vitamins and Minerals; Safe Upper Levels. The Stationery Office, London 2003

First published in 2003

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