Implementation of the Women's Health Initiative study design.

The Women’s Health Initiative (WHI) Clinical Trial (CT) includes three overlapping components, each a randomized controlled comparison among women who were postmenopausal and 50 to 79 years of age at randomization. The dietary modification (DM) component randomly assigned 48,836 (target 48,000) eligible women to either a sustained low-fat eating pattern (40%) or self-selected dietary behavior (60%), with breast cancer and colorectal cancer as designated primary outcomes and coronary heart disease as a secondary outcome. The nutrition goals for women assigned to the DM intervention group have been to reduce total dietary fat to 20%, and saturated fat to less than 7% of daily calories and, secondarily, to increase daily servings of vegetables and fruits to at least five and of grain products to at least six and to maintain these changes throughout trial follow-up. The randomization of 40%, rather than 50%, of participating women to the DM intervention group was intended to reduce trial costs, while testing trial hypotheses with specified power. The postmenopausal hormone therapy (PHT) component comprises two randomized, double-blind trials among 27,347 (target 27,500) women, with coronary heart disease