Almost a million Brits have been alerted to the potential risks of combining certain dietary supplements with their prescribed medication, with experts warning that such combinations could be "harmful".
A dietitian has spotlighted three commonly consumed supplements that could pose a threat when taken alongside warfarin, a blood-thinning drug frequently prescribed by doctors. It's estimated that approximately 1.5 per cent of the UK population, or roughly 700,000 individuals, are currently on warfarin.
Victoria Taylor, a dietitian for the British Heart Foundation (BHF), emphasised that maintaining a healthy, balanced diet is always more beneficial than relying on supplements. In an article for Heart Matters, she stated: "Many different supplements are available in the shops and on the internet, some of which make claims about improving general health and specific conditions like heart disease. But these claims are not always true."
Furthermore, she warned: "Taking a supplement cannot undo the negative effects of an unhealthy diet. Research also shows that supplements do not help to stop or improve heart and circulatory diseases. In some cases, supplements can even be harmful."
She also questioned the common assumption that supplements are better because of their higher vitamin and mineral content. She said: "You may think supplements are healthier than food because they contain high levels of vitamins and minerals. But more is not always better. Having too much of some vitamins and minerals can be bad for your health."
Victoria stressed the serious risks of taking particular supplements alongside warfarin, drawing attention to vitamin K, omega-3, and St John's wort. "Some supplements can also affect the medicines you are taking, causing side effects," she warned.
"For example, vitamin K, omega-3 and St John's wort all interact with the blood-thinning drug warfarin." The NHS has likewise advised caution when using certain herbal remedies with warfarin.
Its official guidance states: "Do not take St John's wort, the herbal remedy for depression, while you're taking warfarin. It can increase your risk of side effects."
Furthermore, the health service recommends consulting a GP before using vitamin K if you're already on warfarin. The NHS advised: "Tell your doctor if you're taking vitamin K supplements before you start taking warfarin. Do not start taking vitamin K supplements while you are taking warfarin without checking with your doctor first."
NICE has expressed its concern over increased bleeding risk when warfarin is taken alongside omega-3-acid ethyl esters. The organisation noted: "Warfarin causes bleeding, as can omega-3-acid ethyl esters; concurrent use might increase the risk of developing this effect."
The manufacturer's guidance similarly advises caution or complete avoidance of such combinations. Victoria suggests that anyone considering adding supplements to their health routine should consult their GP first, stressing the vital importance of professional advice.
She advised: "Talk to your doctor before spending money on supplements. If you need them they will prescribe or recommend them." She pointed out that vitamin D is the only routine supplement that is universally recommended.
Victoria explained: "The exception to this is that it is recommended we all take 10 micrograms a day of vitamin D supplement in the autumn and winter, because vitamin D is mainly made in our bodies with the help of sunlight.
"Just a little comes from food. Apart from this, a healthy, varied, balanced diet provides all the energy, vitamins and minerals you need."