Positive Health Online

Research studies show that the consumption of whole grain foods is beneficial to human health. Despite proven data, most people living in the UK and the US eat less than one whole grain serving per day.[1] This is far below current recommendations. Through teaching practices at work and in their community, health professionals must stress the importance of choosing foods which will ensure improved and optimum health.

This article describes evidence-based health benefits of consuming whole grain foods. It offers practical tips for incorporating more whole grains into existing diets. The relationship between dietary fibre and whole grains is explained. Comparisons between and among whole and refined grains are addressed. The topic of carbohydrate digestion, food package labelling and consumer education, related to whole grains, is discussed.

Background

A single grain serving comprises: one slice of bread; one small muffin; one ounce ready-to-eat cereal; one-half cup cooked cereal, rice or pasta.[2] By definition, a whole grain product contains at least 51% whole grain ingredients, by weight. Grains supply the body with sugar and starch (complex carbohydrates) for energy, in the form of glucose. Glucose is vital for a healthy functioning brain and central nervous system. Major sources of whole grain foods include breakfast cereal, yeast bread, cooked oatmeal, popcorn and crackers. These are mostly made from wheat, oats and brown rice.[3] Whole grain corn, rye, buckwheat and barley are eaten less often.[2]

A whole grain food contains three significant parts of the grain kernel: the germ; the bran; the endosperm. The germ contains vitamins, minerals, unsaturated fatty acids and phyto-chemicals (e.g. chemicals which occur naturally in plants). The bran or shell contains plenty of fibre, B vitamins, minerals and phyto-chemicals. The endosperm contains mostly starch and protein, along with small amounts of vitamins.[3] To be more palatable, the whole grain kernel must be cracked, crushed or flaked. This mechanical alteration results in very little change to the original seed.[2]

A refined grain product contains only the endosperm portion of the seed. During the refining process, there is a loss of fibre, minerals, vitamins and other health promoting constituents. Law requires that all refined grain products be fortified with only a few vitamins and iron. The overall nutrient value of refined grains is far less than that of whole grains.[2]

Recommendations

The Dietary guidelines for Americans (2005) recommend eating three to ten servings of grains daily, with at least 50% of these coming from a whole grain source. Nutritionists recommend that 45% to 65% of the total daily calorie intake should come from carbohydrates. Approximately one-half of these calories are supplied through grains.[2]

Carbohydrate Digestion

Whole grains contain starch. The digestion of starch begins in the mouth, with the action of maltose. The process continues in the small intestine via a pancreatic enzyme. Intestinal lining enzymes break sugar and starch into simple sugars, which can then be absorbed. The starch in white bread quickly breaks down into glucose. This swift action may negatively affect how the body handles glucose. Whole grain foods contain resistant starch, which is “the fraction of starch in a food that is slowly digested, or not digested, by human enzymes.”[4]

Dietary Fibre

Whole grain foods are valuable sources of dietary fibre, which is a plant-food carbohydrate not easily digested in the body.[2] Health benefits are more prominent when starch is accompanied by soluble and insoluble fibre. In order for dietary fibre to be utmost effective, unless contraindicated, consuming at least eight glasses of water daily is important. The amount of dietary fibre in a grain product greatly varies. For example, one cup of white flour contains three grams of fibre, while the same quantity of whole wheat and dark rye flour, contains 15 grams and 18 grams, respectively. Oats, barley and rye are sources of soluble fibre which promotes a feeling of fullness.[4] Soluble fibre dissolves in water. It binds to fatty acids, some of which eventually exit from the colon. Insoluble fibre or roughage can neither be digested nor dissolved in water. While absorbing water, it swells and adds bulk and softness to waste products. Insoluble fibre speeds the transit time of stool throughout the gastrointestinal tract. Wheat bran, oat bran and corn bran are food sources of insoluble fibre. Lignin, not to be confused with lignan, is one component of insoluble fibre. It is a woody, coarse part of plant stems.[5]

Health Benefits

Heart disease is a leading cause of premature death. Although certain risk factors for heart disease (e.g. genetics) cannot be changed, others can be reduced by the intake of whole grain foods. A number of theories explain this outcome. The oil in brown rice bran lowers low-density lipoprotein or bad cholesterol.[6] One scientific analysis used statistics from a ten-year Nurses’ Health Study to evaluate how grain intake affects the risk for cardiovascular disease. Thousands of healthy nurses participated in this study. Findings show that cereal fibre reduces the risk of coronary heart disease to a much greater extent than vegetable fibre and fruit fibre. The germ and bran portion of a whole grain food contains heart-healthy bioactive compounds which include dietary fibre, resistant starch, antioxidants (e.g. Vitamin E and selenium) and lignans. Results of a food survey show that people who eat refined diets and not whole grains, have elevated serum cholesterol levels.[7]

Type 2 diabetes mellitus (DM) is associated with high blood insulin levels. It accounts for 90% of all DM diagnosis.[6] DM results from abnormalities in glucose and insulin metabolism. Biomarkers are used to evaluate how whole grain foods affect metabolism. Glycaemic Index is one such marker which is used for “measuring the blood glucose response to a standard amount of a specific food.”[7] The lower the glycaemic index, the greater the health benefits! Whole grains, especially oats and barley, cause a decreased glycaemic reaction and a small rise in blood insulin and glucose levels. Glycaemic index values are lower in whole grains, compared to refined grains. This might result from whole grain starch having a slow digestion rate. Other factors affecting the blood glucose response to food include: whether food is in solid or liquid form; whether small or large amounts of soluble fibre and fat are present; how the food has been processed and cooked.[7]

Cancer is the second highest cause of deaths in the US.6 Clinical studies report that high blood insulin levels lead to an increased risk of developing breast and colon cancer. Whole grains decrease blood insulin levels. Whole grain cancer protective mechanisms include: stabilized blood sugar levels; weight control; insoluble fibre benefits (e.g. less time for cancer-causing molecules to interact with the intestinal lining). Antioxidants may protect against cell membrane oxidative damage and subsequent cancer formation.[7] Phyto-nutrients, which are non-nutrients that may contain anti-cancer components, are plentiful in whole grains. Lignan is one example which may act on the body’s hormone system.[5]

Obesity is an increasing health problem. It is a risk factor for developing cancer and Type 2 DM. Preliminary studies show an association between increased whole grain intake and a reduced rate of obesity. One possible explanation is that whole grains’ high fibre content causes improved satiety (e.g. feeling full) for extended periods. Whole grain foods have a low caloric density. This term refers to foods which are high in fibre, low in fat and have few calories.[6]

Whole grain foods contain B vitamins, iron, magnesium and selenium. B vitamins are vital in maintaining a healthy nervous system and aid the body in releasing energy for carbohydrate, protein and fat metabolism. Iron carries oxygen in the blood to tissues and organs. Magnesium is a bone-builder and aids in releasing energy from muscles. Selenium ensures a well functioning immune system.[8]

Food Labelling

A food package ingredients label lists items in descending order, according to quantity, by weight. A whole grain food ingredients label usually lists one of the following terms first: whole wheat flour; whole oat flour; whole grain rye flour; whole grain barley flour; brown rice. Some misleading terms are: wheat flour; 100% wheat; multi-grain; seven-grain; pumpernickel; stone-ground. A food label listing ingredients such as wheat bran or wheat germ alone, without a whole grain, is not considered whole grain. These ingredients simply add dietary fibre to a food.8 As evident in food stores, an increasing number of food companies exhibit the wording whole grain in large print on food packages. A nutrition facts label on a food package lists a value for calories, fat, protein, carbohydrates and often, dietary fibre, per single or 100 gram serving.

Practical Tips

Time does not hinder a consumer from eating whole grains. Simply substitute! Whole grain products are readily available in retail stores. More recently, product labeling allows easier identification of these healthy foods. The daily quota for whole grain servings can be met without significant added cost. One hundred percent whole wheat flour and white flour are similarly priced in retail stores.[9]

Select a whole grain cereal (e.g. whole wheat flakes) with at least five grams of fibre per serving.[5] As apparent at retail grocers, many cereals made from whole grains contain as little as one gram of fibre per serving. Large-flake oats is an alternate whole grain breakfast food which can easily be cooked in a microwave oven or on the stove top.

Whole grain bread can be cubed, dried and added to soup or a salad. Include whole grain bread, rolls, bagels or pitas with each meal. Substitute whole grain flour for approximately one-half white flour, called for, in home baked recipes. Use oats for making cookies and desserts. Prepare pancakes and waffles with whole wheat flour or buckwheat. Make healthy cornbread or corn muffins with whole grain cornmeal which is commonly found in health food stores. Avoid pumpernickel bread. It usually contains insufficient amounts of whole rye and whole wheat flour.[3] Never assume that dark coloured grains are whole grain, because molasses or food colouring may have been added. In meat-loaf recipes or as a coating for raw meats, use whole grain crackers or breadcrumbs. Prepare pilaf using brown rice, barley or wild rice. Use whole wheat pasta in a main dish or as a side dish.[8]

Whole grain rice-cakes, containing brown rice, buckwheat, millet or quinoa, are good snacking foods. Popcorn, a whole grain food best prepared using a hot air popper, may have less fat and salt added, compared to that present in prepackaged varieties. Cereal bars, granola bars, cookies, muffins, dark rye crisp-breads, flatbreads, tortilla corn chips and dry cereal are all healthy snacks, if the first ingredient lists a whole grain.

Eat breakfast! One study shows that 80% of dieters, who lost weight and kept it off, started off their day with breakfast. Rice, a staple food in many countries, is a good source of carbohydrates. The insoluble fibre content of brown rice is four times that of refined white rice. For a gluten-free diet, use brown rice flour for home baking instead of white flour. For vegetarians, and for those who are lactose intolerant, drink rice milk. Follow exact directions for cooking long grain and parboiled brown rice, to help maintain vital nutrients. Whole grain basmati rice and wild rice hold a luscious flavour and are healthy food choices. Use brown rice in a stir-fry, a casserole or as a side-dish.[6]

Consumer Education

In 2002, health and nutrition experts in the UK created an official claim, stating that “people with a healthy heart tend to eat more whole grain foods as part of a healthy lifestyle”. This proclamation was based on scientific research. A 1999 US health claim delivers a similar message; that whole grain products are heart healthy and may contain anti-cancer components. Food manufacturers in the US may use this information when marketing whole grain products.[10] In the past, similar food claims have shown positive results. One of these, associating whole grain oats and a low fat diet with a reduction in blood cholesterol, has led to an increased consumption of whole oat products.[9] In the UK, many ready-to-eat cereal packages bearing a whole grain logo clearly differentiates them from high-fibre cereals. Nutrition campaigns such as Go Grains in Australia and Whole Grain for Health in the UK educate consumers regarding whole grain health benefits.[1] MyPyramid.gov (2006) is an educational resource which offers science-based nutrition information and counsel to health professionals and consumers. This model distinguishes between whole and refined grain products. It explains why whole grains are important and offers tips to help identify them.

The Internet is a useful resource for seeking facts regarding whole grains. It is especially useful for information (e.g. glycaemic index values) which is not available on food package labels. Evaluate the authenticity of a website and the credibility of those providing facts. Obtain up-to-date nutrition information from colleges, universities and certain community libraries.

Since families often eat away from home, investigate how restaurants and fast-food chains incorporate whole grains into meal plans. Many restaurants offer handouts describing nutrition facts for menu items. Others list this information on respective websites. Involve young family members when shopping for whole grains, reading food package labels and preparing whole grain meals. Habits may be carried forward to adult life. Disregard programme logos on food packaging! Many food manufacturers, grocers and certain health organizations have created their own nutrition information programmes. Researching details for such programmes can be overwhelming. Many food companies are largely concerned about financial gains.

The consumption of whole grain foods promotes wellness. Health professionals must use effective communication strategies to deliver the health message related to whole grains. This holistic approach will ensure that consumers achieve protection against developing certain diseases. There may also be protection from the advancement of some existing disease.

References

1.    Lang R and Jebb SA. Who Consumes Whole Grains, and How Much? Proceedings of the Nutrition Society. 62(1): 123-127. 2003.
2.    US Department of Health and Human Services and US Department of Agriculture. Dietary Guidelines for Americans. 6th ed. US Government Printing Office. Washington (DC). 2005. Available from:
www.health.gov/dietaryguidelines/dga2005/document/pdf/dga2005.pdf
3.    Higgins MM. Healthful Whole Grains! Kansas State University. 2002. Available from: http://www.oznet.k-state.edu/humannutrition/mf2560.pdf
4.    Sizer FS and Whitney EN. Nutrition: Concepts and Controversy. 8th ed. Wadsworth/Thomson Learning, Belmont (CA). 2000.
5.    Duyff RL. American Dietetic Association Complete Food and Nutrition Guide. 2nd ed. John Wiley & Sons Inc. Hoboken. NJ. 2002.
6.    Hark L and Deen D. The Whole Grain Diet Miracle! DK Publishing, New York. 2006.
7.    Slavin JL. Whole Grains and Human Health. Nutrition Research Reviews. 17: 99-110. 2004.
8.    US Department of Agriculture. MyPyramid.gov. Modified June 28, 2006. Replaced by MyPlate. Available from: https://www.choosemyplate.gov/ 
9.    Adams JF and Engstrom A. Helping Consumers Achieve Recommended Intakes of Whole Grain Foods. Journal of the American College of Nutrition. 19(3): 339S-344S. 2000.
10.    Richardson DP. Wholegrain Health Claims in Europe. Proceedings of the Nutrition Society. 62(1): 161-169. 2003.