Research has found health benefits of eating whole foods, including grains, fruits, and vegetables, but is less definitive about the benefits of consuming individual nutrients or phytochemicals. Among a large group of women, age 55 to 69 years, eating at least 1 serving a day of whole-grain foods significantly reduced the risk of death from all causes compared with women who ate almost no whole-grain products.
In this particular study, dark breads and whole-grain breakfast cereals made up the largest portion of whole-grain foods consumed.
Some of the health benefits associated with a high-fiber diet may come from other components, not just from fiber itself. For example, whole-grain foods contain hundreds of identified phytochemicals, such as phytoestrogens, antioxidants, and phenols, which together with vitamins and minerals such as vitamin E and selenium may play important roles in disease prevention. These and other unidentified phytochemicals in whole grains may be protective or may act synergistically to exert protective effects.
Intact whole grains are also rich sources of fermentable carbohydrates, including dietary fiber, resistant starch, and oligosaccharides. Indigestible carbohydrates reach the colon and are fermented by intestinal microflora to short-chain fatty acids such as acetate, butyrate, and propionate, which have been associated with lowered serum cholesterol and decreased risk of cancer.
In any case, whole foods such as whole grains and fruits and vegetables deliver packages of nutrients and phytochemicals that may work together to protect health.
