Vitamin D supplementation and prevention of cardiovascular disease and cancer in the Finnish Vitamin D Trial: a randomized controlled trial

Abstract

Background: Vitamin D insufficiency is associated with risks of cardiovascular diseases (CVD) and cancer in observational studies, but evidence for benefits with vitamin D supplementation is limited.

Objectives: To investigate the effects of vitamin D3 supplementation on CVD and cancer incidences.

Methods: The study was a 5-year, randomized, placebo-controlled trial among 2495 male participants ≥60 years and post-menopausal female participants ≥65 years from a general Finnish population who were free of prior CVD or cancer. The study had 3 arms: placebo, 1600 IU/day, or 3200 IU/day vitamin D3. Follow-up was by annual study questionnaires and national registry data. A representative subcohort of 551 participants had more detailed in-person investigations. The primary endpoints were incident major CVD and invasive cancer. Secondary endpoints included the individual components of the primary CVD endpoint (myocardial infarction, stroke, and CVD mortality), site-specific cancers, and cancer death.

Results: During the follow-up, there were 41 (4.9%), 42 (5.0%), and 36 (4.3%) major CVD events in the placebo, 1600 IU/d (compared with placebo: HR: 0.97; 95% CI: 0.63-1.49; P = 0.89), and 3200 IU/d (HR: 0.84; 95% CI: 0.54-1.31; P = 0.44) arms, respectively. Invasive cancer was diagnosed in 41 (4.9%), 48 (5.8%), and 40 (4.8%) participants in the placebo, 1600 IU/d (HR: 1.14; 95% CI: 0.75-1.72; P = 0.55), and 3200 IU/d (HR: 0.95; 95% CI: 0.61-1.47; P = 0.81) arms, respectively. There were no significant differences in the secondary endpoints or total mortality. In the subcohort, the mean baseline serum 25-hydroxyvitamin D concentration was 75 nmol/L (SD, 18 nmol/L). After 12 months, the concentrations were 73 nmol/L (SD, 18 nmol/L), 100 nmol/L (SD, 21 nmol/L), and 120 nmol/L (SD, 22 nmol/L) in the placebo, 1600 IU/d, and 3200 IU/d arms, respectively.

Conclusions: Vitamin D3 supplementation did not lower the incidences of major CVD events or invasive cancer among older adults, possibly due to sufficient vitamin D status in most participants at baseline.

Keywords: cancer; cardiovascular disease; elderly; randomized controlled trial; supplementation study; vitamin D.

Graphical Abstract

FIGURE 1

Recruitment and randomization of the study participants.

FIGURE 2

Serum 25-hydroxyvitamin D concentration at baseline and after 6 and 12 months in the placebo, 1600 IU/day and 3200 IU/day vitamin D₃ arms among the 503 participants with data from all 3 study visits. The values are shown in nmol/L. To convert to ng/mL, divide by 2.5.

FIGURE 3

Cumulative incidence rates of major cardiovascular events and invasive cancer of any type, according to year of follow-up, in the placebo arm, 1600 IU/day vitamin D₃ arm, and 3200 IU/day vitamin D₃ arm. HR values are from Cox proportional hazards regression models adjusted for age and sex.