Herbal supplements are classified into different groups. Many herbal supplements, including daily vitamins, are classified as a food supplement, which means that they are not regulated by the Medicines Control Agency.

Without regulation herbal supplements carry many risks. This is largely because herbal supplements do not undergo the same stringent testing that conventional medicines would, both in terms of how they are formulated and quality control.

The danger for people taking herbal supplements is that there is no follow-up in terms of adverse effects. It is possible for a person taking a herbal supplement to have side effects that are not listed on the packaging.

What are the risks of taking unregulated herbal supplements?

The first danger for people taking herbal supplements is in how the drug is made. As it is not regulated the contents of each tablet can vary. For example, in the case of St John’s Wort, the label simply says ‘St John’s Wort’ but the strength of each batch may vary.

The second danger for people taking herbal supplements is the lack of monitoring by a healthcare professional. With prescription medication there is a very stringent way of following patients up and documenting side-effects so that any concerns with that medication can be highlighted. No such regulation exists for herbal supplements.

If a person is taking a herbal supplement they should regard it in the same way as a conventional medicine and be aware of any risks to how it might interfere with other medications.

For example, there are some case reports that herbal supplements, when taken in conjunction with other medicines, can actually increase the risk of bleeding. So if a person is already taking a medicine that increases the risk of bleeding then they should be very cautious before starting a herbal supplement.

It is also vital that a person tell their doctor which herbal supplements they are taking if admitted to hospital, particularly for a person undergoing an operation because herbal supplements may interact with drugs given at the time of anaesthesia or may increase the risk of bleeding during the operation.

There is no reason to take herbal supplements, like vitamins, for people with a well balanced diet. As long as a person does not have a problem with absorbing nutrients then taking vitamins is unnecessary.

For elderly individuals with intercurrent illnesses that mean they are not absorbing food properly in their stomach, then a specialist may recommend vitamin supplements.

Is it possible to overdose on vitamin supplements?

There is a recommended daily allowance for each vitamin. It is important for people to check the bottle to make sure they are not exceeding their allowance, particularly when taking vitamin formulations that contain many different vitamins in one tablet.

Many people may not be aware that they are overdosing. It is important to be aware of foods that contain fortified vitamins. The main example is cereals fortified with vitamins. If a person is taking a vitamin supplement and eating cereals that contain fortified vitamins they may be overdosing on their recommended daily allowance.

Does vitamin C help you recover from a cold?

There is no scientific evidence that vitamin C improves the recovery after a common cold.

For conditions such as a common cold where there is actually no cure, people do still feel the need to try and do something to speed up their recovery and as there are no dangers associated with taking vitamin C a clinician is unlikely to dissuading people if it makes them feel better.

Dr Daman Mulhi, Anaesthetic Consultant, NHS Specialist in anaesthesia, diabetes, obesity, metabolic syndrome, and public health awareness

10017 December 2011