A week before he was sworn in as secretary of the US Department of Health and Human Services in February, a video of anti-vaccination conspiracy theorist Robert F Kennedy Jr went viral.
In it, Kennedy, who has frequently promoted debunked health claims, is seen squirting inky blue liquid into a drinking glass. The substance was widely speculated to be a dye called methylene blue, though Kennedy has not publicly commented on it.
The fabric dye is also taken by the likes of Joe Rogan – who in a podcast weeks later said that “RFK Jr told me about it” – and Bryan Johnson, the sludge-eating American venture capitalist who has sunk millions into trying to prevent the (famously) inevitable process of death.
So what is methylene blue and is there any benchmark evidence that it’s good for your health?
What is methylene blue?
Methylene blue is a synthetic textile dye, noted for its ability to bind well to fabrics. (Kennedy, ironically, wants the US food industry to stop using artificial dyes.)
The substance has gained popularity in wellness circles, with a laundry list of claimed benefits, including that it boosts cognition, increases energy levels, has anti-ageing effects, relieves stress and has antioxidant effects. On TikTok, influencers poke out blue tongues and dropper the cobalt colourant straight into their mouths.
But ingestion of the dye for unapproved uses carries serious risks.
Methylene blue was first synthesised in the late 19th century. Dark green as a powder and deep blue when dissolved in water, the synthetic dye was soon discovered to kill the parasite that causes malaria.
It became one of the first fully synthetic drugs used in medicine, and was used widely in the second world war when quinine – the standard antimalarial treatment at the time – was in short supply.
“The troops weren’t impressed as it turned their urine blue,” says Dr Ian Musgrave, a molecular pharmacologist at the University of Adelaide. “This is one of the commonest reported adverse effects of methylene blue even today.”
Though it is now rarely used for malaria, methylene blue is considered by the World Health Organization as an essential medicine. It’s primarily used to treat methaemoglobinemia, a blood disorder in which there is an excess of methaemoglobin – a form of haemoglobin that cannot carry oxygen – in the blood.
Methylene blue has redox properties, meaning it can gain and give up electrons, and through a chemical reaction it restores haemoglobin to its functional form. It is also sometimes used to treat the effects of carbon monoxide and cyanide poisoning.
“I used methylene blue when I did my biochemistry major, because it’s one of the oldest dyes … for staining DNA and all sorts of biological molecules,” says Dr Slade Matthews, a senior lecturer in pharmacology at the University of Sydney. “It’s been used as a dye in surgery, but there’s been quite a lot of reported toxicity.”
Does methylene blue have health benefits?
Much of the wellness hype around methylene blue has origins in studies conducted in animals as well as in vitro – in cells tested in lab settings – and the Victorian Poisons Centre warns: “There is no current evidence that methylene blue improves health or brain function in healthy individuals.”
Methylene blue can cross into the brain through a protective membrane known as the blood-brain barrier. In rodents, studies suggest it can improve memory and prevent degeneration in conditions that mimic Alzheimer’s, but Musgrave notes it has “largely failed in human clinical trials for treatment of Alzheimer’s disease”.
As an antioxidant, he notes that “while there are some promising results in tissue culture, there is currently no evidence in humans that it has significant anti-ageing effects”.
Those selling methylene blue and other compounds marketed to boost brain function often make vague claims that are hard to prove or refute, Matthews says. “To prove that a drug is going to make you smarter – it’s just really difficult. That’s why they go for claims like that; they don’t say that it produces some effect that’s easily measurable.”
What are the health risks associated with methylene blue?
Across Australia, poisons information centres have noted an increase in calls as a result of methylene blue ingestion, with some patients developing significant symptoms.
The Western Australia Poisons Information Centre has recorded nine calls this year, compared with one call a year over the previous two years. Centres in Queensland and Victoria have already received more calls this year (eight in both states) as a result of methylene blue exposure than the previous four years combined.
“Most of these exposures appear to be linked to the ingestion of methylene blue for unapproved wellness purposes,” Carol Wylie, manager of the Queensland Poisons Information Centre, says. “Consuming unregistered or unapproved methylene blue can cause serious side-effects including nausea, vomiting, rapid heart rate, dizziness, confusion and skin discoloration.”
In September, the medicines regulator issued a safety advisory, noting an increase in importation and unregistered use of methylene blue, and warning that the dye can interact with drugs such as serotonin reuptake inhibitors (SSRIs), a common type of antidepressant.
Matthews has seen methylene blue sold online at dosages that, in people taking SSRIs, can cause serotonin syndrome – a potentially fatal condition that can cause muscle spasms, confusion and agitation.
And despite its use as a treatment for methaemoglobinemia, he points out that at high doses the dye can paradoxically cause the condition.
In healthy people, it also commonly results in pain in the extremities, nausea, excessive sweating, and changes in taste and skin colour.
Given the evidence, wellness influencers drink the dye at their own peril – the rest of us must resign ourselves to highlighting its risks until we’re blue in the face.
Donna Lu is an assistant editor, climate, environment and science at Guardian Australia
Antiviral is a fortnightly column that interrogates the evidence behind the health headlines and factchecks popular wellness claims
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