In a vitamin D study, researchers evaluated the diets, lifestyles and blood levels of vitamin D in 520,000 men and women and followed up for several years. During this time, 1,248 participants developed colorectal cancer. Doctors matched these people to 1,248 healthy participants from the study who had similar diet and lifestyle characteristics. Overall, men and women who began the study with the highest blood levels of vitamin D were 40 percent less likely to develop colorectal cancer compared to those who started with the lowest vitamin D levels. Scientists also found that those who consumed more calcium were less likely to develop colorectal cancer. Researchers said that the results did not vary by sex or in what season people gave blood.
In a related lab study, researchers gave 92 people with a confirmed colorectal adenoma 2,000 mg of calcium with or without 800 IU of vitamin D per day or a placebo. After six months, while there was no change for placebo or calcium alone, colon tissue from the calcium plus vitamin D group showed 22 percent fewer signs of the DNA damage that can lead to colorectal cancer.
In a colon cancer study, researchers measured magnesium in the diets of over 87,000 men and women, average age 57, and followed up for eight years. While there was no link between low levels of magnesium and cancer in women, men who consumed at least 327 mg of magnesium per day were 52 percent less likely to have colon cancer compared to men who got the least magnesium.