Dietary and supplemental calcium intake and cardiovascular disease mortality: the National Institutes of Health-AARP diet and health study

Abstract

Importance: Calcium intake has been promoted because of its proposed benefit on bone health, particularly among the older population. However, concerns have been raised about the potential adverse effect of high calcium intake on cardiovascular health.

Objective: To investigate whether intake of dietary and supplemental calcium is associated with mortality from total cardiovascular disease (CVD), heart disease, and cerebrovascular diseases.

Design and setting: Prospective study from 1995 through 1996 in California, Florida, Louisiana, New Jersey, North Carolina, and Pennsylvania and the 2 metropolitan areas of Atlanta, Georgia, and Detroit, Michigan.

Participants: A total of 388 229 men and women aged 50 to 71 years from the National Institutes of Health-AARP Diet and Health Study.

Main outcome measures: Dietary and supplemental calcium intake was assessed at baseline (1995-1996). Supplemental calcium intake included calcium from multivitamins and individual calcium supplements. Cardiovascular disease deaths were ascertained using the National Death Index. Multivariate Cox proportional hazards regression models adjusted for demographic, lifestyle, and dietary variables were used to estimate relative risks (RRs) and 95% CIs.

Results: During a mean of 12 years of follow-up, 7904 and 3874 CVD deaths in men and women, respectively, were identified. Supplements containing calcium were used by 51% of men and 70% of women. In men, supplemental calcium intake was associated with an elevated risk of CVD death (RR>1000 vs 0 mg/d, 1.20; 95% CI, 1.05-1.36), more specifically with heart disease death (RR, 1.19; 95% CI, 1.03-1.37) but not significantly with cerebrovascular disease death (RR, 1.14; 95% CI, 0.81-1.61). In women, supplemental calcium intake was not associated with CVD death (RR, 1.06; 95% CI, 0.96-1.18), heart disease death (1.05; 0.93-1.18), or cerebrovascular disease death (1.08; 0.87-1.33). Dietary calcium intake was unrelated to CVD death in either men or women.

Conclusions and relevance: Our findings suggest that high intake of supplemental calcium is associated with an excess risk of CVD death in men but not in women. Additional studies are needed to investigate the effect of supplemental calcium use beyond bone health.

Figure 1

Multivariate relative risks (RRs) and 95% confidence intervals (CIs) for total cardiovascular disease (CVD), heart disease and cerebrovascular disease mortality for categories of supplemental calcium intake. The multivariate RRs were adjusted for age at baseline (continuous); race/ethnicity (non-Hispanic white; non-Hispanic, black; and others); education (less than high school, high school graduate, some college and college graduate/postgraduate); marital status (married, not married), health status (excellent, very good, good, fair, and poor); BMI (<18.5, 18.5–<25, 25–<30, 30–<35, ≥35 kg²/m) smoking status (never, former, and current), smoking dose (0, 1–10, 11–20, 21–30, 31–40, 41–50, 51–60, and >60 cigarettes per day); time since quitting (never quit, ≥10, 5–9, 1–4, <1 years), vigorous physical activity (never/rarely; ≤3 times/mo; 1–2, 3–4, and ≥5 times/wk), alcohol (0, <5, 5–<15, 15–<30, and ≥30 g/d), dietary calcium intake (quintiles), fruit and vegetable intake (continuous), red meat intake (continuous), whole grain intake (continuous), total fat intake (continuous) and total caloric intake (continuous). The use of menopausal hormone therapy (never, past and current) was adjusted in women. Dots indicate the RRs and horizontal lines indicate 95% CIs. The numbers of deaths in category 0 through ≥1000 mg/d were 3947, 2910, 794, and 253 for total CVD deaths, 3171, 2284, 627, and 200 for heart disease death, and 542, 440, 128 and 36 for cerebrovascular disease deaths in men; 1264, 1171, 893, and 576 for total CVD deaths, 931, 839, 607, and 400 for heart disease deaths, and 264, 255, 201, and 140 for cerebrovascular disease deaths in women. Person-years in each category were 1,237,051, 960,869, 234,209 and 725,40 for men, and 581,849, 604,732, 453,105, and 328,002 for women.

Figure 2

Nonparametric regression curve for the association between total calcium intake and total cardiovascular disease (CVD) mortality for men (A) and women (B). Both models were adjusted for age at baseline (continuous); race/ethnicity (non-Hispanic white; non-Hispanic, black; and others); education (less than high school, high school graduate, some college and college graduate/postgraduate); marital status (married, not married), health status (excellent, very good, good, fair, and poor); BMI (<18.5, 18.5–<25, 25–<30, 30–<35, ≥35 kg²/m) smoking status (never, former, and current), smoking dose (0, 1–10, 11–20, 21–30, 31–40, 41–50, 51–60, and >60 cigarettes per day); time since quitting (never quit, ≥10, 5–9, 1–4, <1 years), vigorous physical activity (never/rarely; ≤3 times/mo; 1–2, 3–4, and ≥5 times/wk), alcohol (0, <5, 5–<15, 15–<30, and ≥30 g/d), fruit and vegetable intake (continuous), red meat intake (continuous), whole grain intake (continuous), total fat intake (continuous) and total caloric intake (continuous). The use of menopausal hormone therapy (never, past and current) was adjusted in women.