There are many different forms of cancer, but they do have several commonalities, some of which appear to be affected by curcumin supplementation (33).
Researchers have been studying curcumin as a beneficial herb in cancer treatment. It can affect cancer growth, development and spread at the molecular level (34).
Studies have shown that it can reduce angiogenesis (growth of new blood vessels in tumors), metastasis (spread of cancer), as well as contributing to the death of cancerous cells (35).
Whether high-dose curcumin (preferably with an absorption enhancer like pepper) can help treat cancer in humans has yet to be tested properly.
However, there is some evidence that it may help prevent cancer from occurring in the first place, especially cancers of the digestive system (like colorectal cancer).
In one study in 44 men with lesions in the colon that sometimes turn cancerous, 4 grams of curcumin per day for 30 days reduced the number of lesions by 40% (38).