Article on Folate and CRC on MedlinePlus

Buckwirth

Folate and CRC

Some key notes:

People who eat plenty of folate had a lower risk of colon and rectal cancers in a new study that examined the effects of folic acid fortification in the United States....

...In the late 1990s, the U.S. and Canadian governments began requiring that folic acid (a synthetic form of folate) be added to grain products in order to prevent some birth defects that had been linked to low folate levels in pregnant women.

...While previous studies have generally suggested that a diet rich in folate decreases the risk of colorectal cancer as well, most of those were done before fortification started...

...People who ate the highest amount of folate each day (at least 900 micrograms post-fortification) were 30 percent less likely to get colorectal cancer than those who got less than 200 micrograms each day, the researchers reported in the American Journal of Clinical Nutrition....

... the findings can't prove that increased folate drove the cancer benefits, because "people who report high levels of folate tend to be healthy in other ways," possibly including some the researchers didn't record....

... "But once cells are pre-cancerous, giving folate can increase the progression of these cancer cells."

In other words, it's possible that if someone already had cell changes that are precursors of colorectal cancer, too much folate could make the cancer grow faster....
...To be safe, Kim said that people who do have colon cancer should not take extra folate... 

Bottom line: If you do not have CRC (or pre-CRC polyps) extra folate is good. If you have CRC, extra folate is bad.

laurettas

Calcium also
I was reading about calcium a few months ago and the same thing was said about it. It is very necessary for preventing cancer but once you have cancer, it can start fighting for the other side. Makes one wonder what kind of diet is good when you have cancer, doesn't it?