A daily calcium intake of at least 700 milligrams may significantly reduce the risk of developing cancer in the lower part of the colon. Daily calcium intake beyond this level does not appear to add any further protection against colon cancer.
Researchers examined the association between calcium intake and colon cancer risk among nearly 88,000 women in the Nurses' Health Study and more than 47,000 men in the Health Professionals Follow-up Study.
All of the study participants answered questions about diet, weight, smoking habits and alcohol consumption and had examinations of the colon.
During follow-up, which lasted 16 years for the women and 10 years for the men, 626 women and 399 men developed colon cancer. The investigators found that men and women with a calcium intake of 700 to 800 milligrams per day from diet or supplements had a 40% to 50% lower risk of cancer of the lower, or distal, colon than those who consumed 500 milligrams of calcium per day or less.
The bulk of calcium in the diets of study participants came from dairy products.
Journal of the National Cancer Institute March 20, 2002;94:437-446
Most of the calcium in this large study was from dairy products. Interestingly, in the US, dairy products are also the largest source of vitamin D for most people.
Milk has synthetic vitamin D2 (ergocalciferol) added. Although this form of vitamin D is vastly inferior to vitamin D3 from animal products or sunshine, it clearly is better than nothing.
Other studies document an unquestionable association of sun exposure and colon cancer.
The UV-B in sunshine causes the body to make vitamin D.
One of the main actions of vitamin D though is to increase calcium absorption. So, calcium may still reduce colon cancer, and maybe the mechanism of how it reduces colon cancer in those who receive adequate sunshine.
It would seem the safer way to approach this issue would be to make certain you have enough vitamin D. If you live in the US, this means it is likely that for most of the year you will need to rely on vitamin D supplement.
Please read my comprehensive information on vitamin D for further details.
If you optimize your vitamin D levels you will get more than enough calcium from your diet if you are following the eating plan.
The vegetables offer major sources of bioavailable calcium that is far safer than calcium supplements as it is completely balanced with other minerals. Vegetables also alkalinize the body and that helps improve bone density far more than a simple calcium supplement.
Milk is not the best source of calcium, as most should consider avoiding milk for other reasons.
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