Oat Foods: A Smart Choice

Nutritional Properties of Oats and Oat Products

Oat consumption by humans dates back to 400 BC where it was described as a bulk former, a healing agent, and a desiccant when applied to the skin. The grain found widespread acceptance in Ireland and Scotland where the Highlanders used it in a variety of porridges and baked goods. Oats probably reached the American continent in 1602 but were used mostly for relief of stomach discomforts and other ailments. Oats were effectively promoted to the public as a healthy foodstuff at the turn of the century when several mills joined together as The Quaker Oats Company. Production of oats has declined since the 1950's, although interest in the cholesterol lowering properties of oat bran in the late 1980's increased oat consumption in the United States.

Oats are consumed mainly as a breakfast food, snack product, or bran form in this country. Before oats are milled, the hulls are removed, leaving the oat groat. Groats are milled into steel-cut oat, rolled flakes, quick and instant flakes, oat flour, and oat bran. Industry sources estimate that 85% of human oat products are consumed as either standard or instant oatmeal or oat bran. The remaining 15% are used as oat flour or in snack products like granola bars.

Breakfast cereals, including both hot and ready-to-eat, are typical breakfast mainstays in the United States. Currently hot cereals comprise about 10% of the cereal market with the rest as ready-to-eat. Oatmeal-based products are the largest portion of the hot cereal industry, contributing two-thirds of all hot cereal production by weight. Instant oatmeal make up over one-half of the hot cereal market and continues to increase. Oat bran is added to both hot cereals and ready-to-eat cereals and oat flour is used in many cold cereals, including Captain Crunch, Fruit Loops, Lucky Charms and Cheerios.

Oats are also used in breads, muffins, and cookie mixes. Oat products offer moisture retention properties, which keep baked goods fresh longer. Oats contain little gluten so they need to be combined with high gluten grains, such as wheat, to make a yeast bread. Oat flour is used in baby cereals and rolled oats are a major ingredient in granola cereals and bars. With increased interest in health and nutrition, oats will continue to find new used in food products.

Oats and Dietary Guidance

Complex carbohydrates should supply the majority of our calories according to all current dietary guidance. The Dietary Guidelines for Americans (1990) state "Choose a diet with plenty of vegetables, fruits and grain products." The Food Guide Pyramid (1992) recommends 6-11 servings per day from the bread, cereal, rice and pasta group. Oats and oat products can contribute to this necessary grain intake.

Nutritional Properties of Oats

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 flour. Although it is generally assumed that starch is completely digested, recent research suggests that from 3 to 20% 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.

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.

Protein

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 area currently being studies 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, high in starch and 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 buffet 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.

Please click a link below to be taken to your desired oats section:

• 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:

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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.