Oat Foods: A Smart Choice
On January 23, 1997, the U.S. Food and Drug Administration announced a final ruling on the federal register regarding the use of food labeling health claims based on the association between soluble fiber from whole oats and a reduced risk of coronary heart disease.
Ten years later, science still points to oats for heart health benefits. Additional data has continued to be collected and analyzed. Analyses of the new data consistently agree with the 1997 FDA review. The more recent analyses also suggest oatmeal and oat-based products may contain additional health benefits, including reducing the risk of high blood pressure, type 2 diabetes and weight gain.Nutritional Properties of Oats and Oat Products
Oats, like other cereal
grains, are valued primarily as a source of
carbohydrates to provide calories for energy needs.
Oats contribute both starch and dietary fiber to the
diet. Because of a higher concentration of
well-balanced protein than other cereals, oats have
greater potential value to provide protein,
especially for vegetarians. Oats also contain
essential vitamins, minerals, and fatty acids and, in
recent years, have been recognized as an important
source of soluble fiber. Finally, oats contain
phytochemicals (plant chemicals) that have been
associated with protection from chronic disease.
Carbohydrates
Starch is the most abundant constitutent of the oat grain. Starch is located in the starch endosperm and constitutes about 70% of the weight of oat product. Although it is generally assumed that starch is completely digested, recent research suggests that approximately 10% of starch escapes digestion and has been called resistant starch. The amount of resistant starch in a product is determined by the fiber content of the food, food processing, the presence of antinutrients and enzyme inhibitors, and interactions between starch and protein components in starch granules. Resistant starch is probably metabolized in a manner similar to dietary fiber in the body.
Oatmeal and oat bran are significant sources of dietary fiber. The dietary fiber in oatmeal and oat bran contains a mixture of soluble and insoluble dietary fiber fractions. Oats are particularly high in beta-glucans, a soluble fiber which has proven effective in lowering serum cholesterol. Insoluble fibers are known as effective laxation aids and may play a role in prevention of gastrointestinal disorders. Insoluble fibers are thought to be effective in diluting carcinogens in the gastrointestinal tract that relates to their protective role in colon cancer.
As early as 1963 it was reported that rolled oats lowered serum cholesterol in healthy young men. Research in 1970's and 1980's confirmed these findings and a summary of oat bran studies published in 1992 concluded that oat bran does significantly lower serum cholesterol, particularly when ingested by persons with initially elevated blood cholesterol values. Wide media coverage of a 1990 article in The New England Journal of Medicine convinced the public that oat bran was not particularly effective in lowering cholesterol and that perception remains widespread, despite overwhelming scientific support that soluble fibers including oat bran effectively lower serum cholesterol. The cholesterol lowering effect of soluble fiber (beta glucan) from oats is one of the fourteen recognized health claims allowed by the FDA in food labeling providing the product meets the required guidelines.
Soluble fibers have also been shown to slow the increase in blood glucose that normally follows a meal. This can be important in the management of Type II diabetes. Both oatmeal and other oat products decreased the glycemic index (blood glucose response relative to that induced by white bread) in healthy subjects and diabetics in a recent study.
Lipids
Whole grain oats contain more lipids than other grains. The lipid composition of oats is favorable since it is high in unsaturated fatty acids, especially linoleic acid, an essential fatty acid. Linoleic acid is used in the synthesis of prostaglandins that are found in all tissues and regulate smooth muscles. Lipids are distributed throughout the oat grain rather than being concentrated in the germ, as is the case in other grains. This lipid fraction of oats also contains food components, including vitamin E, carotenoids, and tocotrienols with fascinating biological properties which are discussed later.
Micronutrients
Grain products are significant contributors to our micronutrient intake, provided the grains have not been extensively milled. Oats are a good source of manganese, magnesium, selenium, and iron, as well as calcium, zinc, and copper. Oats contain small but significant quantities of several of the essential vitamins, particularly thiamin, folic acid, biotin, and pantothenic acid. Oats contain little or no vitamins A, C, or D. The micronutrient composition of oats and other grains varies across cultivars and growing environments.
Phytochemicals in Oats
Like other grains and vegetable products, oats contain hundreds of phytochemicals or plant chemicals that are currently being studied for their protective properties against chronic diseases such as heart disease and cancer. Whole grains including oats are concentrated sources of antioxidants, substances that delay the onset or slow down the rate of oxidation in the body. Antioxidants in whole grains include vitamins (vitamins E, beta-carotene), trace minerals which are components of enzymes performing antioxidant functions (selenium, copper, zinc, and manganese), and nonnutrients such as phenolic compounds (phytoestrogens, phenolic acids) and antinutrients (phytic acid).
Oats are good sources of compounds with vitamin E activity, including tocotrienols. Grains contain more tocotrienols than other food products. Tocotrienols have vitamin E activity but are also inhibitors of cholesterol synthesis and have been found to lower serum cholesterol. Whole grains are also good suppliers of selenium, copper, zinc, and manganese, which function as antioxidants. Grains also contain phenolic acids and phytate, which are known antioxidants. Antioxidants in grains may contribute to a health benefit since antioxidants are thought to decrease the risk of cancer and cataracts, as well as aging. Free radicals produced during the oxidation process are involved in disease processes and antioxidants can prevent or delay their formation.
Whole grains also contain phytoestrogens, which have been linked to decreased risk of hormone-related diseases such as breast cancer. Epidemiological data support that breast cancer is positively related to early menarche, late menopause, nulliparity and delayed first pregnancy. Populations at low risk for developing breast cancer have been found to have high intake of phytoestrogens, compounds in plants that have estrogenic activity in humans. Although it is generally accepted that fat intake is a major contributor to the high incidence of breast cancer in the United States, fat intake in Finland is just as high as in the U.S., yet incidence of breast cancer is low. One theory is that the Finnish diet is high in whole grains that supply phytoestrogens that protect against breast cancer. Both oat bran and oats have been shown to be significant sources of the phytoestrogens called lignans. While much of the work on lignans and phytoestrogens has concentrated on their effect on breast cancer, the same effects on other hormone-related cancers, such as cancer of the prostrate, endometrium, and ovary would be expected.
Oats also contain phytic acid, which has historically been considered a negative since phytic acid is known to bind minerals and, therefore, decrease their absorption. Practical problems with phytic acid impairing nutritional status have been only described in populations with marginal nutritional intakes that ingest unleavened breads. Phytic acid also functions as an antioxidant and may be important when intake of iron or copper is excessive, causing increased lipid peroxidation.
Summary of Nutritional Attributes of Oats
Oats fit well into existing dietary guidelines. They are whole grain products, low in grain net carbohydrates and high in dietary fiber, low in fat, and concentrated in micronutrients including vitamins and minerals and the exciting new area of phytochemicals. Consumer interest in oats peaked in 1990 when oat bran popularity was at its height and has decreased with media coverage of research that suggested that oat bran did not lower serum cholesterol. Oat bran is not a magic bullet for decreasing cholesterol, but can be a useful product to lower serum cholesterol when used in conjunction with other appropriate public health measures, including a low fat diet, exercise, smoking cessation, and appropriate drug therapy.
Oats and oat products do fit well into dietary guidelines and consumers need more ways to incorporate oats into their diets. Ready-to-eat cereals, hot cereals, and granola bars are widely accepted and consumed in the United States. Oats are also used in baked products, especially cookies. Improved processing techniques to include oats in more convenience foods and snacks could increase consumption of this highly nutritious food.
Nutritional Value
of oats:
Nutritional information per 100 gram sample dry
basis.
Proximate Nutrients per 100 grams
Calories (kcal) 421
Sodium (mg) 4.4
Protein (g) 14.0
Calcium (mg) 57
Total Fat (g) 6.9
Potassium (mg) 384
Saturated Lipid (g) 1.3
Iron (mg) 4.6
Monounsat. Lipid (g) 2.2
Phosphorous (mg) 520
Polyunsat. Lipid (g) 2.5
Total Vitamin A (IU) 0.0
Cholesterol (mg) 0.0
Vitamin C (mg) 0.0
Total Carbohy. (g) 74
Sugars (g) 0.0
Total Dietary Fiber (g) 11.6
Ash (g) 2.1
Dry basis data
calculated from information contained in:
USDA Nutrient Database for Standard Reference Release
13 USDA-ARS Nutrient Data Laboratory
For further information see the USDA website for nutritional data at: http://www.nal.usda.gov/fnic/foodcomp/.
- Oat Products
- Oat Milling Methods: Learn
how oats are milled to make oat products in
this section.
- Oat Recipes:
Tips for preparing hot breakfast cereals and
recipes for muffins, cakes and cookies.
- Oats & the Environment
References
Oats: Chemistry and Technology, Webster, F.H., ed., American Association of Cereal Chemists, Inc., St. Paul, MN, 1986.
Oat Science and Technology, Marshall, H.G., Sorrells, M.E., eds., American Society of Agronomy, Agronomy, A Series of Monographs, #33, Madison, WI, 1992.
Whole Grains: Health and Nutritional Issues, Critical Reviews in Food Science and Nutrition, Clydesdale, F.M., ed., Vol 34(5&6), 1994.
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