Women with higher intakes of calcium from both food and supplements appear to have a lower risk of cancer overall, and both men and women with high calcium intakes have lower risks of colorectal cancer and other cancers of the digestive system.
A large prospective study followed 293,907 men and 198,903 women aged 50 to 71. Participants were given a food frequency questionnaire when they enrolled in the study, asking how much and how often they consumed dairy, as well as other conventional foods, and whether they took supplements. After seven years of follow-up, the study found that women with a calcium intake of up to 1,300 mg/day from a combination of conventional foods and supplements had a decreased risk of total cancer.
The study also found that women who were in the top fifth for calcium consumption (1881 mg/day from a combination of conventional food and supplements) had a 23% lower risk of digestive types of cancer, particularly colorectal cancer, than those in the bottom fifth (494 mg/day). Men who consumed the most calcium from conventional foods and supplements (about 1530 mg/day) also had a 16% lower risk of digestive types of cancer than those who consumed the least calcium.
Previous observational studies have shown an inconsistent relationship between calcium intake and cancer. The researchers commented that calcium may provide benefits that go beyond bone health, but more research is still needed to help explain the observed differences in gender and to better assess the effects on other non-digestive cancers. (1)