As an antioxidant, it fights cell damage and may slow tumor growth. 100-200 micrograms daily. Take it with food to offset stomach upset. Food levels are often so low that a supplement is better. It's a more potent brew of protective chemicals than other teas, because its leaves are never fermented during processing.
Decaffeinated brands work just as well.
It could prevent tumors or stop growth before it reaches advanced stages. It's not recommended in supplement form, so add several servings of tomatoes or related products every week. Cooking makes more lycopene available for the body to absorb, so tomato-based sauces are ideal. Guavas, watermelon and grapefruit are other sources. It may be able to slow cancer growth when it binds to prostate cells.