© 2004 by Oxford University Press
© 2004 Oxford University Press
CORRESPONDENCE |
Research and Public Health Implications of the Intricate Relationship Between Calcium and Vitamin D in the Prevention of Colorectal Neoplasia
Correspondence to: Robert P. Heaney, MD, University Professor, Creighton University, 601 N. 30th St., Ste. 4841, Omaha, NE 68131-2137 (e-mail: rheaney{at}creighton.edu)
The recent study by Grau et al. (1) demonstrated that calcium’s protection against colorectal adenoma recurrence is confined to patients with adequate vitamin D status and that vitamin D’s effect is confined to those receiving calcium. These results are consistent with those of a recent study (2) indicating that calcium supplementation and low-fat dairy foods are independently associated with a statistically significant reduction in the growth of abnormal cells that lead to colorectal polyps. Both studies add to the growing body of evidence that calcium and vitamin D reduce the risk of colon cancer. Given the widespread insufficiency of both nutrients, it is perhaps not surprising that it takes relative adequacy of both to produce the benefits of either.
However, the accompanying editorial by Jacobs et al. (3) cautioned against using dairy foods as the source of the needed calcium and vitamin D. This statement is misleading and incorrect. There are many good reasons for public health efforts to be directed, instead, at increasing dairy consumption, not only for its potential role in reducing colon cancer risk but also for its protective role in at least eight other disorders (4).
The cautions expressed by Jacobs et al. are based on early data from the Health Professionals Follow-up Study (5), which reported an association between high intakes of dietary calcium and prostate cancer risk. The study was observational in character and hence could not establish causality. Therefore, it should not be used for nutritional policy recommendations, particularly when other observational studies report no association. Moreover, as new cases have accumulated in the Health Professionals Study itself, the association of calcium and prostate cancer incidence has disappeared (6), and in the only randomized controlled trial data available on the relationship between calcium and prostate cancer, calcium, rather than increasing prostate cancer risk, actually cut it in half (7). I would urge caution before excluding a major food group with many demonstrated benefits. I also call attention to the fact that the intake of milk has been declining at the same time as prostate cancer incidence has been rising.
Jacobs et al. cite the problem of lactose intolerance as further justification for discouraging increased consumption of dairy products. This conclusion appears to be based on an overestimate of the prevalence and severity of lactose intolerance (as contrasted with lactase nonpersistence). Unfortunately, misunderstanding of lactose intolerance is common and often leads to unnecessary reduction of dairy consumption, eliminating a major source of calcium and other essential nutrients. In reality, most lactase-nonpersistent individuals can consume one cup or more of milk with each meal without experiencing symptoms. Also, regular lactose intake improves tolerance.
Dairy foods, in addition to containing calcium and vitamin D, are excellent sources of many nutrients and contain compounds such as conjugated linoleic acid, butyric acid, and sphingolipids, all of which exhibit anticancer properties. These are yet more reasons not to exclude them out of hand.
NOTES
Robert P. Heaney consults for the dairy industry. Any consultant income is not retained by him but is paid to Creighton University.
REFERENCES
1 Grau MV, Baron JA, Sandler RS, Haile RW, Beach MA, Church TR, et al. Vitamin D, calcium supplementation, and colorectal adenomas: results of a randomized trial. J Natl Cancer Inst 2003;95:1765–71.
2 Holt PR, Wolper C, Moss SF, Yang K, Lipkin M. Comparison of calcium supplementation or low-fat dairy foods upon epithelial cell proliferation and differentiation. Nutr Cancer 2001;41:150–5.[CrossRef][Web of Science][Medline]
3 Jacobs ET, Martinez ME, Alberts DS. Research and public health implications of the intricate relationship between calcium and vitamin D in the prevention of colorectal neoplasia. J Natl Cancer Inst 2003;95:1736–7.
4 McCarron DA, Heaney RP. Estimated healthcare savings associated with adequate dairy food intake. Am J Hypertens 2004;17:88–97.[CrossRef][Web of Science][Medline]
5 Chan JM, Giovannucci EL. Dairy products, calcium, and vitamin D and risk of prostate cancer. Epidemiol Rev 2001;23:87–91.
6 Michaud DS, Augustsson K, Rimm EB, Stampfer MJ, Willett WC, Giovannucci E. A prospective study on intake of animal products and risk of prostate cancer. Cancer Causes Control 2001;12:557–67.[CrossRef][Web of Science][Medline]
7 Wallace K, Pearson LH, Beach ML, Mott LA, Baron JA. Calcium supplementation and prostate cancer risk: a randomized analysis [abstract 2479]. Proceedings of the American Association for Cancer Research; 2001 Mar 24–28; New Orleans (LA): American Association for Cancer Research; 2001. p. 260.
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J Natl Cancer Inst 2004 96: 806-807.
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