A recent study sought to determine whether dietary supplementation with vitamin D3 and calcium reduces the risk of cancer among older women. The clinical trial, conducted in 31 rural counties, randomized about 2,300 healthy postmenopausal women aged 55 years or older to receive 2000 IU/d of vitamin D3 and 1500 mg/d of calcium or identical placebos. The primary outcome was the incidence of all-type cancer, excluding nonmelanoma skin cancers. The participants' mean baseline serum 25-hydroxyvitamin D level was 32.8 ng/mL. After 1 year, serum 25-hydroxyvitamin D levels were 43.9 ng/mL in the treatment group and 31.6 ng/mL in the placebo group. A total of 109 women had a new diagnosis of cancer: 45 (3.89%) in the treatment group and 64 (5.58%) in the placebo group. The researchers conclude that in this group of healthy postmenopausal older women, supplementation with vitamin D3 and calcium compared with placebo did not result in a substantially lower risk of all-type cancer at 4 years. Additional research should examine the possible role of vitamin D in preventing cancer, the authors suggest.