Calcium intake is not related to breast cancer risk among Singapore Chinese women

Abstract

There is experimental evidence that calcium protects against breast cancer development. Prospective epidemiologic studies supporting a protective effect of calcium on breast cancer risk have mainly been limited to Western populations. We examined the association between calcium intake and breast cancer risk in the Singapore Chinese Health Study, a large population-based prospective cohort. Calcium intake and supplement use was assessed by in-person interviewer using a validated food frequency questionnaire. After a mean follow-up of 14.2±3.5 years, 823 cohort participants developed invasive breast cancer. Multivariate proportional hazards regression models were fitted to examine the associations between calcium intake and breast cancer risk. Vegetables were the primary food source of calcium in this study population, followed by dairy products, grains and soy foods. Calcium intake was not associated with breast cancer risk, comparing highest quartile (>345.6 mg/1000 kcal/day) to lowest quartile (<204.5mg/1000 kcal/day) of intake. There was no evidence of effect modification by menopausal status, body mass index, dietary vitamin D or stage of disease at diagnosis. Our findings do not support a hypothesis for calcium in breast cancer chemoprevention, contrary to findings from previous studies among Western populations with higher calcium intake primarily from dairy products and supplements.

Calcium intake and breast cancer risk: meta-analysis of prospective cohort studies

“…With additional five large prospective studies (15)(16)(17)(18)(19) included and comprehensive analyses conducted, our findings are generally consistent with those from the previous meta-analysis (14) , and thereby further support a potentially beneficial role of Ca in the development of breast cancer. Indeed, a possible U-shaped association between Ca intake and health outcomes has been widely considered (45,46) Numerous studies also suggested that a high intake of Ca, particularly from supplements, may be associated with increased risks of CVD (19)(20)(21)(22)(23) and kidney stones (24,25) .…”

“…1. We included eleven studies (11)(12)(13)(15)(16)(17)(18)(19)(35)(36)(37) that fully met our inclusion criteria for this meta-analysis. The characteristics of the included studies are summarised in Table 1.…”

“…Their results became statistically non-significant after correcting for publication bias. The meta-analysis was followed by several subsequent prospective studies (15)(16)(17)(18)(19) that also focused on the same topic, but their findings continued to be inconsistent. To clarify the association between Ca intake and risk of breast cancer, we performed an updated meta-analysis of prospective studies.…”

Dietary and Supplemental Calcium Intake and Mortality

“…3 Results of both studies reveal that increasing calcium intake increases mortality, in particular CVD mortality, but the relationship is possibly dependent on habitual calcium intake. 4,5 In a Chinese population with comparatively low habitual calcium intake, high calcium intake has a protective effect.…”

“…4 Although the study by Xiao et al 1 indicates that supplemental calcium may adversely affect cardiovascular health in men only, other studies indicate that supplemental calcium intake puts women at cardiovascular risk as well. 5 To further underpin the crucial importance of vitamin K in the prevention of arterial calcification, we recommend that vitamin K intake or MGP carboxylation is included as potential confounder when analyzing the association between calcium intake and cardiovascular disease.…”