Golomb et al1 suggest that calcium may have counteracted the effect of vitamin D in the Women's Health Initiative (WHI) study, as the reason for the calcium–vitamin D supplement showing no benefit against myocardial infarction, whereas Giovannucci et al2 found that higher plasma 25-hydroxyvitamin D concentrations lowered the risk of myocardial infarction in men.
Glaser JH. Vitamin D Supplements vs Plasma Level. Arch Intern Med. 2009;169(16):1536. doi:10.1001/archinternmed.2009.280