After years of hearing about the supposed health properties of green tea, researchers in Japan have concluded that a component of the tea can stop HIV from binding to healthy immune cells, which is how the virus spreads.

Their laboratory tests suggest a chemical found in green tea called Epigallocatechin Gallate, or EGCG, protects cells.

Writing in the Journal of Allergy and Clinical Immunology, the scientists said the discovery could lead to new treatments to fight the disease.

Green tea is made up of a class of chemicals called catechins, the most abundant of which is EGCG.

It is believed that EGCG is responsible for green tea's health benefits. Previous studies have suggested it can protect against a range of diseases, including cancer and heart disease.

Dr. Kuzushige Kawai and colleagues at the University of Tokyo carried out tests to see if the chemical could help beat HIV.

They found that EGCG stopped the virus from binding to CD4 molecules and human T cells.

These are vital parts of the body's immune system. Usually HIV is able to sneak inside these cells and wipe them out.

The scientists said simply drinking green tea, however, would not offer people protection from the virus.

The concentration of EGCG used in the laboratory tests are many times over the blood concentration that could be achieved by just drinking green tea.

Another research team last week reported that green tea may fight lung cancer and could inspire the creation of new lung cancer drugs.

The researchers included Qing-Yi Lu, PhD, of the Center for Human Nutrition at the University of California at Los Angeles (UCLA).

Lu and colleagues exposed a sample of human lung cancer cells to a decaffeinated green tea extract. The lung cancer cells marinated in the green tea extract for up to three days.

The green tea extract remodeled a certain protein in the lung cancer cells. As a result, the lung cancer cells became more likely to stick together and less likely to move, the study shows.

Antioxidants in green tea may have tweaked the cancer cell protein, but it's not clear whether one antioxidant deserves all the credit or whether several antioxidants worked together, the researchers said.

The study also doesn’t prove that drinking green tea curbs lung cancer in people. However, it may be possible to make new lung cancer drugs based on green tea extract, Lu's team suggests.