VOA标准英语2011--Study: Vitamin D is Powerful Weapon Agai

（单词翻译）

Study: Vitamin D is Powerful Weapon Against TB

Vitamin D plays a critical role in fighting infection and now scientists say that it may be a powerful weapon against tuberculosis¹.
In a study reported in the journal Science Translational Medicine, researchers studied how T-cells - a kind of white blood cell that fights infection - are especially effective against the bacteria that cause tuberculosis.
People with low vitamin D levels are more susceptible² to infection. It’s also known that people with reduced immunity³ - like those with HIV, the virus that causes AIDS - are more susceptible to tuberculosis.
Robert Modlin, chief of dermatology at the University of California Los Angeles School of Medicine and study co-author says the researchers examined that connection.
“And through that, we discovered that one particular type of T-cell, the one that secreted⁴ a protein called interferon-gamma, was able to activate⁵ white blood cells that were infected with the tuberculosis bacteria to then kill the bacteria.”
But Modlin says it required vitamin D. “People that had low levels of vitamin D in their blood were unable to mount this mechanism⁶ and kill the bacteria.”
In lab experiments, scientists supplemented blood samples that were deficient⁷ in vitamin D. That activated⁸ the T-cells to destroy the TB bacteria.
Modlin says the findings could lead to new therapies using supplements to prevent TB or help in its treatment. “I think it could change how we think about vitamin D supplementation.”
The paper also notes that while the skin absorbs vitamin D naturally from the sun, it takes more exposure for African Americans to reach the same level of vitamin D as white individuals.
But too much sun can lead to skin cancer. So Modlin recommends supplements over sun exposure, while cautioning that high doses can be toxic⁹.
“I recommend that people consult with their internal medicine doctor and perhaps have their vitamin D levels measured if they think that’s appropriate and institute the right supplementation for them.”
Modlin says the next step is to initiate¹⁰ clinical trials to learn whether vitamin D supplements can augment¹¹ resistance to tuberculosis or other infections.