Supplements being marketed by influencers and celebrities are made in the same laboratories "as the stuff you're buying in Boots", an expert has said.
Author and disinformation expert David Robert Grimes said there is a "massive" rise in the sale of such supplements like vitamin C, particularly in the US.
He told The Pat Kenny Show there is a lack of scientific evidence.
"The supplement market is genuinely massive - in the US alone, Americans spend about $50bn a year on food supplements, typically vitamins," he said.
"Despite the enthusiasm which the public adopts them... the scientific evidence really isn't, for the most part, there.
"For the most part, the recommendation is that unless you're medically directed to take supplements you probably don't need them."
'Regulated as foodstuffs'
Mr Grimes said some supplements - such as vitamin A and E - can be associated with "higher cancer risks."
"A lot of supplements do not contain what they claim to," he said. "They're regulated as foodstuffs not as medicines.
"The labs that make them are not held to any particularly high standards and you don't always know what you're getting."
Mr Grimes said there's been a flurry of new players in the supplement market.
"In the last few years there's been a massive rise of celebrities and influencers selling their own branded, blended bespoke supplements for massive prices," he said.
"To put this in context, both the Kardashians and people like Alex Jones and Joe Rogan are selling their own blends.
"Alex Jones made $65m a year selling supplements. So it's a big market".
Mr Grimes said people are essentially paying higher prices for the name.
"They're made in the exact same laboratories and manufacturing places as the stuff you're buying in Boots for a fraction of the price," he said.
"You're paying for the branding."
Mr Grimes recently conducted an experiment of his own.
"A few weeks ago I contacted one of the European manufacturers of these influencer packets," he said.
"They're legitimate manufacturers... you send them in your label."
He said the supplements can make whatever claim they like.
"They don't care what's on the label - I could have written 'this brings your ancestors back from the dead' - they will print it and put it on a packet," he said.
"There are several celebrities and influencers doing it already.
"They sent me a massive spreadsheet and you picked out what you wanted in it and they put it in."
Dietary supplements, 29-5-20. Image: Robert Michael/dpa-Zentralbild/dpaMr Grimes said there is a massive mark-up on most of these products.
"The unit price is very cheap but I've seen these retailing online for about €60 a packet," he said.
He said vitamin D cost about 88c a unit resulting in "a mark-up of 4,500%".
"So even if you needed these vitamins or supplements, you shouldn't be buying them."
He added that "no one is doing the microbiological testing to check they actually contain what they do."
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