Dairy food, calcium, and risk of cancer in the NIH-AARP Diet and Health Study

Abstract

Background: Dairy food and calcium intakes have been hypothesized to play roles that differ among individual cancer sites, but the evidence has been limited and inconsistent. Moreover, their effect on cancer in total is unclear.

Methods: Dairy food and calcium intakes in relation to total cancer as well as cancer at individual sites were examined in the National Institutes of Health (NIH)-AARP (formerly known as the American Association of Retired Persons) Diet and Health Study. Intakes of dairy food and calcium from foods and supplements were assessed with a food frequency questionnaire. Incident cancer cases were identified through linkage with state cancer registries. A Cox proportional hazard model was used to estimate relative risks and 2-sided 95% confidence intervals (CIs).

Results: During an average of 7 years of follow-up, we identified 36 965 and 16 605 cancer cases in men and women, respectively. Calcium intake was not related to total cancer in men but was nonlinearly associated with total cancer in women: the risk decreased up to approximately 1300 mg/d, above which no further risk reduction was observed. In both men and women, dairy food and calcium intakes were inversely associated with cancers of the digestive system (multivariate relative risk for the highest quintile of total calcium vs the lowest, 0.84; 95% CI, 0.77-0.92 in men, and 0.77; 95% CI, 0.69-0.91 in women). Decreased risk was particularly pronounced with colorectal cancer. Supplemental calcium intake was also inversely associated with colorectal cancer risk.

Conclusion: Our study suggests that calcium intake is associated with a lower risk of total cancer and cancers of the digestive system, especially colorectal cancer.

Figure 1. Non-parametric regression curve^* for the association between total calcium intake and risk of all cancers

* A Men: the model adjusted for race/ethnicity, education, marital status, body mass index, family history of cancer, vigorous physical activity, smoking status, time since quitting smoking, smoking dose, antacid use, personal history of diabetes and hypertension, PSA test, alcohol, and intakes of fat, red meat, fruit and vegetables, whole grains, protein, beverages, folate, tomatoes, alpha-linolenic acid, selenium and total energy. B. Women: the model adjusted for race/ethnicity, education, marital status, body mass index, family history of cancer, vigorous physical activity, smoking status, time since quitting smoking, smoking dose, antacid use, age at menopause, parity, oral contraceptive use, HRT use, duration of hormone replacement therapy use, personal history of diabetes, hypertension, oophorectomy and hysterectomy, alcohol, and intakes of fat, red meat, fruit and vegetables, whole grains, total beverages, protein, folate and total energy.

Figure 1. Non-parametric regression curve^* for the association between total calcium intake and risk of all cancers

* A Men: the model adjusted for race/ethnicity, education, marital status, body mass index, family history of cancer, vigorous physical activity, smoking status, time since quitting smoking, smoking dose, antacid use, personal history of diabetes and hypertension, PSA test, alcohol, and intakes of fat, red meat, fruit and vegetables, whole grains, protein, beverages, folate, tomatoes, alpha-linolenic acid, selenium and total energy. B. Women: the model adjusted for race/ethnicity, education, marital status, body mass index, family history of cancer, vigorous physical activity, smoking status, time since quitting smoking, smoking dose, antacid use, age at menopause, parity, oral contraceptive use, HRT use, duration of hormone replacement therapy use, personal history of diabetes, hypertension, oophorectomy and hysterectomy, alcohol, and intakes of fat, red meat, fruit and vegetables, whole grains, total beverages, protein, folate and total energy.

Figure 2. Multivariate relative risk* and 95% confidence intervals of cancers by anatomical system** comparing the highest quintile of total calcium intake vs. the lowest

* Adjusted for race/ethnicity, education, marital status, BMI, family history of cancer, vigorous physical activity, alcohol and intakes of red meat and total energy + additional variables listed in each footnote. The squares and horizontal lines correspond with the multivariate RR and 95% CI. † Adjusted for variables listed in the asterisked footnote + smoking status, time since quitting smoking, smoking dose, intake of fruit and vegetables, and menopausal hormone therapy (MHT) use in women. ‡ Adjusted for variables listed in the asterisked footnote + smoking status, time since quitting smoking, smoking dose, MHT use in women, antacid use, intakes of fruit and vegetables, whole grains, and folate § Adjusted for variables listed in the asterisked footnote + smoking status, time since quitting smoking, smoking dose, and MHT use in women. || Adjusted for variables listed in the asterisked footnote + smoking, personal history of diabetes, PSA test, and intakes of tomatoes, alpha-linolenic acid, and selenium in men. For women, the model was adjusted for variables listed in the asterisked footnote + smoking, MHT use, parity, oral contraceptive use, personal history of oophorectomy and hysterectomy, and intake of fat. ¶ Adjusted for variables listed in the asterisked footnote + smoking status, time since quitting smoking, smoking dose, personal history of diabetes and hypertension, parity, MHT and oral contraceptive use in women, and intakes of fruit and vegetables, total beverages, and protein. ** Cancers in each anatomical system are: digestive system (C150-C189, C199, C209-C212, C218, C220-C221, C239-C260, C268-C269, C480-C482, C488), respiratory system excluding larynx (C300-C301, C310-C319, C339-C349, C381-C384, C388, C390, C398, C399), reproductive system (men: C600-C609, C619-C639; women: C510-C519, C529-C549, C559, C569-C589), urinary system (C649, C659, C669-C689), brain/other nervous system (C700-C729), and endocrine system (C739-C759, C379).