Vitamin C can kill multidrug-resistant TB in the lab, scientists have found.
The surprise discovery may point to a new way of tackling this increasingly hard-to-treat infection, the US study authors from Yeshiva University say in Nature Communications.
An estimated 650,000 people worldwide have multidrug-resistant TB.
Studies are now needed to see if a treatment that works using the same action as vitamin C would be useful as a TB drug in humans.
In the laboratory studies, vitamin C appeared to be acting as a "reducing agent" - something that triggers the production of of reactive oxygen species called free radicals. These free radicals killed off the TB, even drug resistant forms that are untreatable with conventional antibiotics such as isoniazid.
Lead investigator Dr William Jacobs, professor of microbiology and immunology at Albert Einstein College of Medicine at Yeshiva University, said: "We have only been able to demonstrate this in a test tube, and we don't know if it will work in humans and in animals.
"This would be a great study to consider because we have strains of tuberculosis that we don't have drugs for, and I know that in the laboratory we can kill those strains with vitamin C.
"It also helps that we know vitamin C is inexpensive, widely available and very safe to use. At the very least, this work shows us a new mechanism that we can exploit to attack TB."
It might be that vitamin C could be used alongside TB drugs. Alternatively, scientists could create new TB drugs that work by generating a big burst of free radicals.
Vitamin C, or ascorbic acid, has many important functions in the body, including protecting cells and keeping them healthy.
Good natural sources of the vitamin include oranges, blackcurrants and broccoli and most people get all they need from their diet.
Dr Ibrahim Abubakar, head of TB at Public Health England, said: "We welcome any new research which will widen our understanding of how to treat TB. While the findings of this study appear promising, further research to confirm the observations would be essential before Vitamin C can be used to supplement TB treatment."