On Monday I wrote about a potential link between low calcium intakes and overweight, especially in women. Today I would like to write about a new piece of research (1) linking low intakes of calcium to an increased risk of cancer.
The study was the work of researchers from the National Cancer Institute in Bethesda, Maryland and the AARP (American Association of Retired Persons) in Washington, DC. The researchers (1) found that higher calcium intakes were linked to a lower risk of total cancers in women; and for both men and women, it was linked to lower risk of cancers of the digestive system, and colorectal cancer in particular.
The research involved the analysis of data from 293,907 men and 198,903 women. Intakes of dairy food and calcium from foods and supplements were assessed with a specially constructed food frequency questionnaire. The participants were followed for an average of 7 years. In this time 36,965 cases of cancer were identified in men and 16,605 in women (1).
In men there was no link between total calcium intake and overall cancer risk. However in women calcium intake was linked to total cancer risk. The risk went down as daily calcium intakes went up until reaching about 1,300mg calcium per day. Above this level no further risk reduction was seen. In both men and women a high calcium and dairy food intake were linked to a reduced risk of cancers of the digestive system, especially colorectal cancer.
Comparing the 20% of participants who ate the most calcium (1,530mg per day for men and 1,881 mg per day for women) with the 20% who ate the least (526mg per day in men and 494 mg per day in women) there was a significantly reduced risk of cancer of the digestive system of 16% lower for men and 23% lower for women. Calcium intake from supplements was also linked to a lower colorectal cancer risk.
Calcium may be having a cancer preventing effect through a variety of mechanisms in the body. In cell and laboratory studies calcium has been shown to reduce abnormal cell growth. In the body calcium is thought to reduce damage to the mucous membrane of the large intestine. This study certainly shows an association between higher calcium intake and a lower risk of total cancer and cancers of the digestive system, especially colorectal cancer. However, further clinical trials are necessary before any firm conclusions can be drawn or specific recommendations made.
As mentioned on Monday the recommended nutrient intake for calcium in the UK for men and women aged 19-64 is 700mg per day but in the USA and other parts of the world it is higher, at around 1000mg/day. It may be that in the UK our recommendations are revised over time in order to promote optimal health and wellbeing. Individuals who are concerned that they are not eating enough calcium rich foods may want to consider a calcium supplement to provide 500-1000mg calcium per day. Calcium can be found in dairy foods, broccoli, cabbage, tofu, nuts and seeds (especially almonds and sesame seeds) and tinned fish where the bones are eaten such as sardines and pilchards.
(1) Yikyung Park et al. 2009. Dairy Food, Calcium, and Risk of Cancer in the NIH-AARP Diet and Health Study. Arch Intern Med. 169(4):391-401.
Written by Ani Kowal
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