To understand the importance of consumption of whole grains versus refined grain products, we must understand the structure of the grains. A grain kernel is composed of three layers.
The first is the outer shell, composed mainly of fiber. In addition to fiber, it also contains various nutrients and phytochemicals. The second is the germ, which contains large amounts of vitamins and minerals.
The third layer is the endosperm, consisting chiefly of starch and protein. When a whole grain is refined, (as in making white flour or white rice) both the outer layer and the germ are removed from the endosperm.
As a result, compared to whole grain flour, white flour is composed primarily of starch and protein with a small amount of micronutrients (vitamins and minerals), fiber and phytochemicals. For example, making white flour reduces the fiber content by nearly 80 percent compared to whole wheat flour. Similarly, white flour contains just 7 percent of vitamin E, and only about 26 percent of potassium in comparison to whole grain flour.
Some countries mandate that some vitamins and minerals lost in the refining process be added back into the white flour or white rice. In the United States, it is mandatory that food manufacturers add five nutrients to refined grain products. They include vitamins B1, B2, niacin, folic acid and the mineral iron. When these nutrients are added back to the refined flour it is then called enriched flour. Yet, in comparison to flour made of whole grains, it is still a nutrient-deprived product.
In addition to fiber and micronutrients, grains are a source of other important compounds such as stanols and sterols. Studies have shown that these compounds are effective in lowering blood cholesterol.
Also, grains are a good source of magnesium and iron. Higher intake of magnesium is associated with lower blood pressure, and consequently a lower risk of stroke.
In the United States, grains provide 30 to 50 percent of iron consumed, which means that they provide more iron than any other food group. It is precisely because of the relatively large amounts of fiber content, micronutrients, and other compounds including sterols and stanols that grains play an extremely important role in human nutrition and in the prevention of diseases.
Studies have consistently shown that whole grains have a beneficial effect on the prevention of virtually all chronic health conditions including cardiovascular disease (e.g. heart attack, hypertension), cancer and diabetes. Whole grains may also play a significant role in the treatment of some of these health problems. An example of such a study is the Health Professionals Follow-Up Study conducted by researchers from Harvard University. It involved more than 51,000 men aged 40 to 75 years. This study has shown that individuals with an average consumption of whole grains in the amount of 46 grams per day had a 19 percent lower risk of being diagnosed with high blood pressure compared with those individuals who on average consumed only 3.3 grams.
(Submitted by Betty Dean. Written by Roman Pawlak, Ph.D., RD. Used by permission from www.LifeandHealth.org. Courtesy of LifeSpring – Resources for Hope and Healing Stuart, VA)
