Social media misinformation about the use of dietary supplements such as turmeric, St John’s wort and magnesium is now so common that dispelling online claims has become a routine part of NHS clinicians work.

Two out of five frontline health workers say they encounter patients who raise inaccurate or misleading information about supplements at least once a week.

Polling by YouGov for the World Cancer Research Fund found that the figure is even higher (53%) among nurses and midwives, with false information about nutrition and supplements now taking up what doctors describe as “precious time” in NHS consultations.

The WCRF says it fears that patients’ belief in unproven dietary regimes, vitamins and minerals is putting their health in danger and increasing their risk of getting cancer.

Dr Philippa Kaye said she saw the consequences of health misinformation every week in her GP surgery.

“My patients arrive clutching newspaper stories, social media screenshots, printouts from wellness websites or saved videos from TikTok.

“What particularly worries me is the widely held belief that if something is sold over the counter, marked as ‘natural’ or endorsed online, then it must automatically be safe and harmless, while prescribed medicines are somehow toxic,” she added. “As doctors, we know this simply is not true.”

Some popular supplements can involve hidden risks, according to Kaye. “People assume that supplements are safe because you can buy them over the counter without a prescription. But if something works, then there is an active ingredient in it that may also cause problems.

“For example, liver injury related to turmeric supplements, St John’s wort interacting with other medications, people thinking they are taking magnesium for sleep but there are different types of magnesium, and some can cause diarrhoea and various supplements, and various supplements leading to itchy skin reactions.”

The WCRF commissioned the survey of 795 NHS staff before Cancer Prevention Action Week, which starts on Monday.

Cancer specialists behind the initiative are so concerned about public misunderstanding about health that for the next three years its activities will highlight the risks posed by misinformation.

Steven Greenberg, the WCRF’s UK director, spoke of people who believe dubious claims about diet and supplements, including “advice that’s distorted, taken out of context or presented in a way that hides the risks”.

“From horse wormers to apricot kernels, which can cause serious cyanide toxicity, to everyday items like sugar and vitamin C, social media is flooded with false promises and dangerous claims about cancer prevention and cures.

“We are hearing from patients, nurses, GPs and oncology dietitians that this is pulling people away from the evidence-based changes to diet and lifestyle that can genuinely make a difference, while eating up precious time in NHS consultations,” he said.

Sharon Moffat became a campaigner against ill-founded claims about alleged therapies to treat cancer after being diagnosed with breast cancer in 2024.

“After sharing my cancer diagnosis publicly I wasn’t prepared for the influx of opinions, suggestions and advice that followed,” she said. “Almost overnight people were recommending everything from special waters and supplements to products claiming to boost recovery or even cure cancer.

“Many of these recommendations came from a place of genuine care. Friends and family wanted to help and others had seen claims online that sounded convincing. When you’re living with cancer, you’re searching for hope and looking for anything that might improve your chances of getting better. I understood that instinct because I felt it too.

“But when I started asking what evidence supported some of these claims I often found there wasn’t a clear answer. Some were being promoted by influencers with huge followings. Yet when questioned, I was met with vague responses, hostility or simply no answer at all.”

Moffat’s experience has taught her that, for cancer patients, “when fear is driving your decisions, the promise of a miracle cure can be incredibly tempting”, she said.

Rachel White, an oncology dietitian, said misinformation was a “challenging” part of her job advising cancer patients.

“Patients are making changes to try to improve their health and survival, but what they often do not realise is the danger or harm they can be doing instead,” she said.

It is now common for people with cancer to use supplements because they believe they will help them regain control over their health, she added. When discussing supplements with patients she tells them what the research evidence shows about them and talks about the risks and benefits.

People worried about their health should always seek advice from a qualified doctor or other specialist, a government spokesperson said, responding to the WCRF’s findings.

“Your health is too important to leave to social media and the internet,” the spokesperson said. “Always speak to a qualified health professional before making decisions about your diet, supplements or treatment.

“We expect social media platforms to act swiftly and take action against misleading health content on their platforms. If you’re concerned about something you’ve seen online, you should report it following the platform’s guidelines.”

The WCRF’s survey also found that many NHS staff feel ill-equipped to counteract mistaken beliefs in unorthodox therapies that patients think work, for example that eating certain “superfoods” most days or undertaking a dietary detox can reduce their cancer risk. It is urging ministers to use the forthcoming NHS long-term workforce plan for England to ensure that staff get the training and access to trustworthy resources to help them tackle the “emerging crisis of misinformation”.