AP Photo/Mary Esch, File

Millions of people could be risking their health by taking herbal remedies and prescription drugs at the same time, scientists warn.

Statins, warfarin and other common drugs can interact with health supplements, producing dangerous side effects or reducing the drugs’ life- saving powers, they said last night.

Herbal treatments such as St John’s wort, ginseng and chamomile are taken by an estimated one in four UK adults, who buy them without a prescription at health food shops or online.

But doctors say that while they are seen as harmless health boosters, if taken alongside powerful medication the combination can be extremely dangerous. They warn of ‘life-threatening adverse drug events, prolonged hospitalisation and loss of life’.

Cancer patients have seen their drugs stop working after drinking ginseng energy drinks, transplant patients’ new kidneys have been rejected after taking chamomile, and people with HIV have seen the virus levels in their blood soar after taking ginkgo supplements.

People who take blood-thinning warfarin drugs for heart problems have been treated

for major internal bleeding after using St John’s wort and other herbal medicines such as sage, goji juice or chamomile. And the millions of people who take cholesterol-busting statins risk severe muscle pain if they drink green tea.

The study’s authors, from the University of Stellenbosch in South Africa, said the dangers were grossly under-reported because people often did not realise the herbal remedies were to blame.

And they said the rise in obesity, diabetes and cancer meant the problem was going to get worse – because more people were taking medication, and seeking additional relief from supplements.

The authors, who based their findings on 49 case reports and two small studies of 15 cases each, said the middle-aged and elderly were the most at risk.

In most cases the interactions come about because the active ingredient in the herbal remedy works on the same part of the body as the drug, meaning it either cancels it out or boosts its power.

The study, published in the British Journal of Clinical Pharmacology, comes after the Medicines and Healthcare products Regulatory Agency (MHRA) warned that St John’s wort could stop the morning-after pill from working properly.

Sotiris Antoniou, of the Royal Pharmaceutical Society, said: ‘If you are taking herbal medicines, you should let your doctor or pharmacist know, so they can ensure that it is safe for you to take them with statins or warfarin and there are no interactions which could increase the risk of experiencing side effects.’

An MHRA spokesman said last night: ‘Prescription-only medicines are prescription-only for a reason – they are potent and their use should be supervised by a healthcare professional so your treatment can be monitored and any adverse reactions dealt with.

‘If you are taking medicines, and also taking herbal medicines, please read the patient information provided and if you have any further questions, speak to your healthcare professional.’

The herbal medicine market in the UK is worth £500 million. Since 2011, products have to be registered with the MHRA and granted a Traditional Herbal Registration before going on sale. But they do not require the same evidence as pharmaceutical drugs as to whether they actually work.

Their labels require information about drug interactions – but experts are worried that people do not read the safety labels in the same way they do for prescription drugs, because the herbal products are not considered to be as powerful.

The NHS says: ‘Herbal medicines are those with active ingredients made from plant parts, such as leaves, roots or flowers. But being “natural” doesn’t necessarily mean they’re safe for you to take.

‘Herbal medicines... will have an effect on the body and can be potentially harmful if not used correctly.’

Daily Mail