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In the late 19th century, Michigan physician John Harvey Kellogg lectured patients at his health spa on the life-prolonging benefits of whole-grain cereals such as corn flakes and granola. This holistic health fad has since evolved into a staple of the modern American breakfast and a more than $10 billion industry.
Today, a growing body of research suggests Dr. Kellogg was on to something with his high-fiber philosophy. Cereals, such as barley, oats and wheat, have a number of health benefits. Cereals have been shown to aid digestion, promote clear skin, reduce cholesterol, and protect against diabetes and stroke.
Scientists have linked cereal's disease-fighting potential to beta glucans-molecules that make up the structural components of grain cell walls. Beta-glucans molecules play a powerful role in preventing cardiovascular disease, regulating insulin response and stimulating the immune system.
Types and Sources of Beta-glucans
A glucan is a complex polysaccharide molecule made up of hundreds of thousands of D-glucose molecules bound together by glycosides. A variety of different beta-glucan structures exist within nature. Cellulose is a primary single linkage of (1,4)-beta-D-glucans, providing the cell wall structure for many plants. Chrysolaminarin provides cell wall structure for various algae and phytoplankton, composed primarily of (1,3) linkages.
Yeasts also contain (1,3) linked beta-D-glucans among their cell walls within a structure called zymosan. Opportunistic fungi such as Candida albicans contain (1,3)-beta-D-glucans cell wall components as well. This is why (1,3)-beta-D-glucans testing is now considered a diagnostic tool for Candida infections.1
Other living organisms contain mixed linkage beta-D-glucans. These tremendously complex helical molecules can have marked health benefits. Medicinal mushrooms, for example, typically have mixed linkage (1,3)(1,6)-beta-D-glucans. This structure may render immunostimulatory benefits that include T-cell increase and tumor inhibition.2
Certain yeasts like Saccharomyces cerevisiae also contain mixed linkage cell wall structures with (1,3)(1,4)-beta-D-glucans composition. Researchers observed increases in p24 antibodies and T cells in 70 percent of study participants given a yeast-derived beta-glucans isolate intramuscularly.3
The cell walls of cereal grasses, such as rye, oats, wheat and barley, contain another form of mixed-linkage (1,3)(1,4)-beta-D-glucans. While wheat contains less than 1 percent beta-glucans content, barley appears to contain the highest levels. Typical barley varieties contain 5 percent to 7 percent beta-D-glucans. Meanwhile, typical oat varieties contain 4 percent to 5 percent; rye provides 2 percent beta-D-glucans content by weight.
Research over the past two decades has confirmed that insoluble and soluble dietary fibers in grains and other foods provide a variety of health benefits. These include lowered risks of heart disease, diabetes, obesity, stroke, ulcer, acid reflex, diverticulitis and hemorrhoids.
While the balance of water insoluble and soluble fibers appears to be necessary for these effects, soluble fibers have demonstrated effects that lower blood pressure, reduce glycemic and insulin response, lower colon cancer risk, and lower LDL cholesterol.4
Cardiovascular Health
Four types of water-soluble fiber appear to decrease cholesterol levels and improve cardiovascular health: psyllium fiber from the seed husks and other parts of the Plantago ovata and Plantago psyllium plants; pectin from citrus and other fruits; galactomannan or guar gum from the Cyamopsis tetragonolobus tree; and (1,3)(1,4)beta-D-glucans from cereal grains' cell walls.
Every gram of additional soluble fiber added to the diet reduces serum total cholesterol by an average of 1.08 mg/dL and LDL cholesterol by an average of 1.12 mg/dL, research shows.5
(1,3)(1,4)-beta-D-glucans reside in cell walls throughout the bran and endosperm. After an in-depth review, the U.S. Food and Drug Administration announced in 2002 that beta-D-glucans soluble fiber had been shown to have significant cardiovascular benefits.6
In 2007, a Cochrane review comparing 10 studies showed oats lowered total cholesterol and low density lipoproteins an average of 7.7 mg/dL and 7 mg/dL respectively.7 The key mechanism cited was the ability of beta-D-glucans in oats to inhibit bile acid absorption.
Barley beta-D-glucans have illustrated similar results. In a 2007 study at University of Minnesota's Medical School, 155 volunteers were divided into four treatment groups for six weeks of beta-D-glucans consumption or controls. The beta-D-glucans groups were given either high or low molecular weight barley beta-D-glucans in either 5-gram or 3-gram daily doses.
The 5-gram high molecular weight beta-D-glucan group experienced a 15 percent reduction of LDL, while the low molecular weight 5-gram beta-D-glucan group had a 13 percent reduction of LDL. The 3-gram groups both experienced 9 percent LDL reduction, illustrating a dose-relationship between beta-D-glucans consumption and LDL levels.8
Beta-D-glucans also increase high-density lipoprotein levels. In a study at Venezuela's University of Zulia in 2007, 38 volunteers with mild hypercholesterolemia were given either the American Heart Association Step II diet alone or the AHA Step II diet plus 6 grams of beta-D-glucans per day for eight weeks. HDL levels among the beta-D-glucans group increased by an average of 28 percent-from 39.4 to 49.5. The beta-D-glucans group also experienced significant decreases in LDL and total cholesterol, and small decreases in VLDL and triglycerides.9
Balancing insoluble and soluble fiber accompanying beta-D-glucans content appears to have additional anti-atherosclerosis effects.10
Diabetes Prevention
A number of studies demonstrate beta-D-glucans consumption can significantly decrease the risk of type II diabetes. Mechanisms appear to combine a slower release of glucose into the bloodstream with beta-D-glucans' effect upon insulin response and sensitivity.11,12
A systematic review illustrated that hyper- and hypoglycemic symptoms are reduced with consumption of high beta-D-glucans cereals. The review showed a 50 percent reduction in glycemic peak with the consumption of either a cereal with 10 percent beta-glucans content or 3 grams. Researchers proposed diabetics incorporate these cereals into their meals.13
Immune Function
Cereals also boost immune function. Oat-derived beta-D-glucans increase activity and count of neutrophils in conjunction with exercise.14 These molecules also decrease antiviral resistance among macrophages.15
Other benefits of oats include their ability to stimulate immune responses to Staphylococcus aureus and Eimeria vermiformis infections.16 Researchers found infections decreased 39.6 percent and 28.5, respectively, when people incorporated oat-derived beta-D-glucans into their diets. CD4, CD8 and Thy1/2 activity also increased among beta-D-glucans groups compared to untreated groups.
Cereal beta-glucans, such as those from barley, are anti-mutagenic and DNA-protective.17 The DNA protective and anti-mutagenic effects are similar to those derived from the beta-D-glucans present in the cell walls of certain yeasts, fungi and bacteria.18
A key mechanism for cereal beta-D-glucan's immunostimulatory effects relates to unique alkaloid polyphenols referred to as avenanthramides (in oats) and alkylresorcinols (in barley). Oats contain at least three avenanthramide molecules, and avenanthramide levels are more than double in oat flakes (26-27 mg/kg) than in oat bran (13 mg/kg).19 Recent research indicates that avenanthramides may reduce incidence and complications of atherosclerosis-the scarring and inflammation of the artery walls.
Avenanthramides have anti-inflammatory and antioxidant effects.20,21 In vitro studies confirmed they create efficiencies among immune cell signaling.22 Furthermore, avenanthramides reduce the growth of vascular smooth muscle cells while increasing nitric oxide production among artery walls.23 Smooth muscle cell growth and reduced levels of nitric oxide has been shown in various studies to increase atherosclerosis.
Avenanthramides increase the stability of the genetic protein p53.24 The p53 protein regulates tumor necrosis factor, a self-destruct switch for mutated cells. Avenanthramides also are considered the key constituent giving oats their ability to combat skin inflammation.25
Barley's beta-glucan immunostimulating effects relate to phenolic acids called alkylresorcinols, which produce anti-fungal and antioxidant effects.26 As they do in plants, alkylresorcinols in barley and the avenanthramides in oats provide potent immune defense mechanisms.27-29
Adding Beta-glucans to the Diet
We can most simply obtain the benefits of cereal beta-D-glucans by adding them to our diet. Barley and oats have the highest beta-D-glucans content, and both are readily available on grocery store shelves in the form of oatmeal and barley-oat hot porridges, muesli, cereal grain bars, muffins and a variety of breakfast cereals.
One cup of oatmeal or barley cereal will provide 4 grams to 6 grams of soluble fiber and 2 grams to 4 grams of beta-D-glucans-rendering enough for a significant dose.
Supplements containing isolated (1,3)(1,4)-beta-D-glucans also are available. Most of these are extracted from oats or barley, and either sold in powder form or encapsulated. One of the more prominent beta-glucans products is an oat bran concentrate with label claims of 54 percent beta-D-glucans content. Note, however, that there are also concentrated oat and barley bran extracts that may not have higher beta-glucans content.
Plant breeders have isolated new varieties of high beta-D-glucans oat and barley. These can provide from 40 percent to 60 percent higher beta-glucans levels. A higher beta-D-glucans oat variety was developed through research at the North Dakota State University in conjunction with the USDA's Agricultural Research Service. Higher beta-D-glucans barley varieties have come out of breeding research at Montana State University.
As consumers' knowledge grows about the benefits of adding cereals to their diets, beta-glucans statements on products likely will become more prominent.
Casey Adams holds a Ph.D. in natural health sciences, a doctorate of sciences in integrative health and a degree in traditional naturopathy. He is board certified as an alternative medical practitioner, practices at the Wellness and Rehabilitation Medical Center in Santa Cruz County, California, and serves the nutritional industry as a consultant.
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