* Tuberculosis killed 1.4 million people in 2010
* Research finds high-dose vitamin D speeds recovery
* Also explains why old-style treatment was of use
By Kate Kelland
LONDON, Sept 3 (Reuters) - Scientists have shown how and why the "sunshine" vitamin D can speed recovery in tuberculosis (TB) patients, helping explain why the so-called heliotherapy of a bygone, pre-antibiotic era may have done some good.
From the late 1800s - well before the development of antibiotics in 1930s - TB patients were often sent to retreats where they were encouraged to soak up the sun's rays in what was known as heliotherapy or phototherapy.
A study led by British researchers has found that high doses of vitamin D - which is made in the body when exposed to sunlight - given alongside antibiotic treatment, appears to help patients recover more quickly from the infectious lung disease.
The findings suggest high doses of the vitamin dampen down the body's inflammatory response to infection, reducing damage to the lungs, said Adrian Martineau, a senior lecturer in respiratory infection and immunity at Queen Mary University of London, who led the study.
"Sometimes these inflammatory responses can cause tissue damage leading to ... cavities in the lung," he said.
"If we can help these cavities to heal more quickly, then patients should be infectious for a shorter period of time, and they may also suffer less lung damage."
The researchers also said they think vitamin D's ability to dampen inflammatory responses without interfering with the action of antibiotics suggests supplements might be useful for patients taking antibiotics for diseases like pneumonia, sepsis and other lung infections.
TB, which people in wealthier parts of the world often mistakenly believe to be a thing of the past, is proving a tough disease to beat. In 2010, it infected 8.8 million people worldwide and killed 1.4 million.
The infection destroys lung tissue, causing patients to cough up the bacteria which then spreads through the air and can be inhaled by others.
In recent years, rates of drug-resistant TB have been spreading fast across the world, causing alarm among public health officials and prompting calls for more research into new and more effective treatments.
The researchers, whose study was published by the Proceedings of the National Academy of Sciences on Monday, split 95 TB patients who were on standard antibiotic treatment into two groups. For the first eight weeks of their treatment, 44 of them were also given high dose vitamin D, while the remaining 51 got placebos.
Anna Coussens from Britain's National Institute for Medical Research measured signs of inflammation in blood samples to see what effect the vitamin D had on immune responses.
"We found that a large number of these inflammatory markers fell further and faster in patients receiving vitamin D," she said.
The researchers also found that Mycobacterium tuberculosis, the bacteria that cause TB, cleared from the phlegm coughed up from deep in the lungs faster in patients on vitamin D, taking an average of 23 days to become undetectable under the microscope compared to 36 days in those on placebo.
Martineau said it was too early to recommend all TB patients take high-dose vitamin D alongside antibiotics, as more research with a larger group of patients was needed first. (Reporting by Kate Kelland; Editing by Robin Pomeroy)