Human breast milk sold online to adult buyers poses disease risks including HIV, hepatitis B and C and syphilis, a British expert has warned.

Often bought by mothers who are unable to breastfeed, breast milk sold online can be cheaper than that from regulated milk banks and has emerged as a recent craze for cancer sufferers, fetishists and bodybuilders.

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But an academic at Queen Mary University of London warns that the purported benefits of breast milk, hailed as a “super-food” by those who use it, did not meet clinical standards.

Writing in the Journal of the Royal Society of Medicine, Dr Sarah Steele said online forums boasted about the immune, recovery, nutritional and muscle building benefits of human milk.

“Such purported benefits do not stand up clinically, however,” she said.

“Nutritionally, there is less protein in breast milk than other milks like cow’s milk.

“Chemical and environmental contaminants are known to make their way into breast milk, just like the food chain more broadly.”

Bacteria was detected in 93 per cent of samples, according to research cited by Dr Steele.

This was due to a lack of sanitisation, pasteurisation and testing, and meant the milk could contain contaminants such as alcohol, chemicals and other milk products used to bolster the volume for profit, she said.

Other threats include hepatitis B and C, HIV and syphilis.

“In sum, breast milk purchased online is not optimal for adult nutrition or in the treatment of disease, as milk bought online poses more risks than proven benefits,” Dr Steele wrote.

Experts at the Queen Mary University have previously warned that buying human breast milk on the internet posed serious health risks to babies, and have called for tighter regulation of the market.