Scientific Support for Glycemic Value Flour and Flakes
By Durk Pearson & Sandy Shaw®
Our glycemic control strategy is the first part of our new approach to managing your weight. Simply by adding 2 tablespoons of our special beta-glucan-rich barley to your meals, you can reduce carbohydrate digestion and lower your glycemic response to those carbohydrates. Beta-glucan is a natural fiber found in large amounts in some grains, especially in barley and oats.
Our barley was developed by conventional selective breeding to contain about three times as much beta-glucan as in oats, and twice as much as in ordinary barley. In 100 g of our barley, there are 30 g of total dietary fiber, including 15 g of beta-glucan, as well as 18 g of high-quality, high-lysine protein the fat content is 6.5 g.
The calorie content is, by FDA standards, 3.9 calories/g. However, this is true only if you measure calories by burning foodstuffs in a calorimeter, which is not how it works in your body. The actual calorie content of our glycemic-control barley flour (also available as quick flakes and nuggets) is about 2.7 calories/g. The FDA’s definition of calories is grossly false and misleading, since it attributes the same number of calories/g to all carbohydrates, including indigestible fiber. If you can’t use it to generate energy for your body’s use, it shouldn’t be considered to have caloric content.
The carbohydrate content in 100 g of our barley flour or quick flakes is 64.3 g (but 30 g of that is dietary fiber, so there is actually only 34.3 g of potentially digestible carbohydrates per 100 g of this barley).
Our barley has one of the lowest glycemic indexes for commonly consumed foods: just 25 for a serving as a hot cereal—almost as low as lentils (22) and remarkably low for a grain-based food. Whole wheat bread, for example, has a glycemic index of about 60, while oats as a hot cereal is about 58. Numerous studies report beneficial effects of a diet high in beta-glucan from barley.Feeling Full and Satisfied After a Meal
The longer elevation of the satiety hormone cholecystokinin after consumption of barley-containing meals means feeling full and satisfied longer. Cholecystokinin, released by the small intestine following a meal, is one of the major signals telling you that you are full. In one study, 11 healthy men were fed either barley pasta high in beta-glucan or a low-beta-glucan wheat pasta. Although their cholecystokinin levels returned to baseline concentrations 3 hours after the low-fiber pasta meal, cholecystokinin levels remained above baseline concentrations for 6 hours following consumption of barley pasta high in beta-glucan.1
Another study2 reported that, in a sample of 39 overweight or obese young adults 18–40 years old who were on an energy-restricted diet that was either low-glycemic or low-fat, the resting energy expenditure (which typically decreases when energy is restricted) decreased less with the low-glycemic-load diet than with the low-fat diet. Participants receiving the low-glycemic-load diet reported less hunger than those receiving the low-fat diet. CRP and blood pressure were also reported to improve more with the low-glycemic-load diet. (CRP is C-reactive protein, a marker of inflammation high CRP levels correlate with high risk for cardiovascular disease.)
A review of a number of studies on high-glycemic-index foods, hunger, and obesity3 revealed, not surprisingly, that not all studies produced the same results. The contents of human diets are very complex (hence studies of their effects on glycemic index are usually just estimates), with subject populations varying greatly. The review noted that the majority of short-term studies showed either a significant or a nonsignificant reduction in subsequent hunger and/or increased satiety following consumption of low-GI foods, compared with consumption of high-GI foods. However, the author notes that there were differences between the test diets in variables such as energy density or palatability that may have contributed to the results.
The author also says, “Hunger, as assessed by subsequent energy intake, however, was consistently higher in five of five studies (significantly so in three studies), suggesting that when direct measurements are made of the parameter of interest (i.e., energy intake), consumption of high-GI foods does tend to promote subsequent overeating relative to consumption of low-GI foods.” [Emphasis added] Also, as summarized in his Table 5, “… most but not all studies attempting to separate the effects of glucose and insulin as satiety signals have suggested that glucose level, rather than associated insulin level, is a primary signal of satiety.” Thus, the effect of our special barley’s dietary fiber in producing a “slow release” of glucose from carbohydrate may play a role in its effects on extended feelings of fullness and satisfaction.
Reduced or Slower Absorption of Carbohydrate
Carbohydrate was more slowly absorbed from the two high-fiber barley meals.1 Both barley meals also resulted in a significantly lower cholesterol increase at 30 minutes after the meal than did the low-fiber meal. Although the plasma glucose response was not blunted by the high-fiber meals in this study, the plasma insulin response did differ, indicating that the meal with beta-glucan-enriched pasta was associated with increased insulin sensitivity.
In another study, carbohydrate digestion in humans from a beta-glucan-enriched barley was reported to be reduced.4 The particular type of naturally beta-glucan-rich barley we use, Prowashonupana (which contains about 15% beta-glucan soluble fiber plus about the same percentage of insoluble fiber) was particularly effective in reducing carbohydrate digestion. As the authors report, “When cereals such as Prowashonupana are consumed with a meal, once the bolus reaches the small intestine the viscosity of the meal is increased. This high viscosity delays absorption. A 50% reduction in the glycemic peak has been achieved with a concentration of 10% beta-glucan in a cereal.” [Emphasis added]Reduced Glucose and Insulin Peaks Following Meals
Another paper(5) reported that barley beta-glucan-enriched durum wheat pasta resulted in a lower glycemic response and a lower insulin response in five fasted adult subjects who were fed test meals of a barley and durum wheat blend pasta containing 100 g of available carbohydrate, with 30 g of total dietary fiber, including 12 g of beta-glucan. The authors of this paper suggest that “Barley beta-glucan may be an economical and palatable ingredient for processed food products formulated to modify glycemic and insulin response.”
Another study compared the effects of a barley (Prowashonupana) cereal vs. oatmeal on the blood glucose and insulin response in normal and diabetic subjects.(6) The paper reports that in normal (nondiabetic) subjects, the maximal rise in glucose from baseline was 41.3 ± 3.9 mg/dL after oatmeal and 6.4 ± 2.7 mg/dL after barley (Prowashonupana), while the maximal increase in glucose was 26.3 ± 3.9 mg/dL after the commercial liquid meal replacer (LMR) used as a reference standard. The maximal increase in glucose in the diabetic subjects was 80.8 ± 8.8 mg/dL after oatmeal, 28.4 ± 3.5 mg/dL after barley (Prowashonupana), and 69.9 ± 4.5 mg/dL after LMR. The maximal increase in insulin after oatmeal was 29.9 ± 4.2 mIU/ml in the nondiabetic subjects and 21.4 ± 2.5 mIU/ml in the diabetic patients, while the maximal insulin increase after barley (Prowashonupana) was 8.6 ± 1.5 mIU/ml in the nondiabetic controls and 6.8 ± 1.2 mIU/ml in the diabetic patients.
In another study,(7) ten overweight women (age 50 years) consumed 1 g of glucose per kg of body weight and four test meals containing 1 g of carbohydrate per kg of body weight, with two-thirds of the carbohydrate from oat flour, oatmeal, barley flour, or barley flakes and the other one-third from pudding. The barley used was Prowashonupana. Results showed that peak glucose and insulin levels after barley were significantly lower than those after glucose or oats. Areas under the curve (AUC, a measure of the total amount of a given substance in the bloodstream over time) after test meals showed that glucose AUCs were reduced by both oats (29–36% lower) and barley (59–65%). The insulin AUCs after test meals compared with glucose AUCs were significantly reduced only by barley (44–56%).Reduced Total Cholesterol and LDL-Cholesterol
In a study of 11 healthy men,(1) the two barley-containing meals significantly reduced cholesterol after 30 minutes as compared with a low-fiber meal. Consumption of the barley-containing meals appeared to stimulate reverse cholesterol transport, the process by which cholesterol is eliminated from cells, and that may have contributed to the cholesterol-lowering effect of the barley.
We have emphasized human studies here, but there have been far more animal studies on the effects of beta-glucan. One study reported that beta-glucan fractions from barley and oats are similarly antiatherogenic in hypercholesterolemic hamsters.(8) Aortic cholesterol ester concentrations were reported to be significantly reduced in hamsters consuming 8 g/100 g of beta-glucan from barley or oats. The study showed that the cholesterol-lowering potency of beta-glucan “is approximately identical whether its origin was oats or barley.” However, our special barley flour, quick flakes, and nuggets contain three times as much beta-glucan per unit volume compared with oat fiber.
Some, but not all, studies of oat beta-glucan have shown positive effects (i.e., a reduction) on LDL-cholesterol. As we explained above (in the section on “Feeling Full and Satisfied After a Meal”), discrepancies are to be expected because of the complexity of human diets and the tremendous diversity among individuals in how they deal with carbohydrates and other dietary constituents. McIntosh et al.(9) reported that plasma LDL-cholesterol concentrations were lowered by 7% in mildly hypercholesterolemic men who consumed about 170 g of barley containing 8 g/day of beta-glucan for 4 weeks. (Note that 170 g of our barley flour or quick flakes contains 25.5 g of beta-glucan, not 8 g.) The barley was incorporated into pasta.
In another study(1) (see more on this study above, under “Feeling Full and Satisfied”), Bourdon et al. reported that postprandial plasma cholesterol concentrations were lowered at 30 minutes and at 4 hours after beta-glucan-containing meals in a study of men who were fed either of two high-beta-glucan (from barley) pastas that provided 5 g of beta-glucan per meal.
Another study(10) reported that, in mildly hypercholesterolemic women (9) and men (7), the addition of 3 g (medium) or 6 g (high) beta-glucan/day from barley to an American Heart Association Step I (reduced-fat) diet reduced cholesterol significantly compared with the Step I diet or the diet with low beta-glucan.
Improvement in Gut Bacterial Populations Increased Formation of Short-Chain Fatty Acids
One study in which dietary fiber-rich barley products were fed to rats(11) showed that the numbers of potentially pathogenic coliform and Bacteroides bacteria in the small intestine, cecum, and colon were reduced, whereas the numbers of beneficial Lactobacillus bacteria were higher, as compared with placebo-fed rats. Similarly, short-chain fatty acids were higher in the colon and feces of the groups receiving the high-fiber barley supplements, and the concentrations of excreted bile acids increased by up to 30% during the feeding period. The increased excretion of bile acids as a result of the increased viscosity of the beta- glucan helps to decrease cholesterol, since more cholesterol must be used to replace the cholesterol excreted in the bile acids. The short-chain fatty acids occur as a result of bacterial fermentation of the indigestible beta-glucan (as well as the resistant starch included with the barley in this study).
The increased production of short-chain fatty acids has protective effects against the development of colon cancer and has also been reported to inhibit cholesterol synthesis by the liver.(12)Reduction of C-Reactive Protein
C-reactive protein (CRP) is a nonspecific marker of inflammation that has been shown in a number of studies to be a strong predictor of risk for cardiovascular disease. A large epidemiological study(13) of 3920 men and women aged 20 years or more (data from the National Health and Nutrition Examination Survey 1999–2000) reported that dietary fiber intake was inversely associated with serum C-reactive protein concentration. (The higher the dietary fiber intake, the lower the CRP.) The odds ratio for increased CRP concentration (> 3.0 mg/L) was 0.49 for the highest quintile of fiber intake compared with the lowest. After adjusting for age, gender, race, education, smoking, physical activity, body mass index (BMI), total energy intake, and fat intake, the odds ratio was 0.59. This means that there was a 41% decrease in likelihood of having an increased CRP concentration in those consuming fiber intake in the highest quintile compared with the lowest. The researchers did not have information on the type of dietary fiber, such as soluble (which is harder to get in the diet) vs. insoluble. The fiber intake was estimated from dietary interviews for foods and beverages consumed during the previous 24-hour period.
Another study(14) reported that, in a study of 244 apparently healthy middle-aged women, there was a strong and statistically significant positive association between dietary glycemic load and plasma high-sensitivity CRP. CRP levels were measured, whereas average dietary glycemic load was determined with a validated semiquantitative food-frequency questionnaire. Adjustments were made for age, treatment status, smoking status, BMI, physical activity, parental history of heart attack, history of hypertension, diabetes, or high cholesterol, postmenopausal hormone use, alcohol intake, and other dietary variables.Increased HDL-Cholesterol
In a cross-sectional study of 1420 middle-aged adults15 (from the 1986/87 Survey of British Adults), the glycemic index of the diet was the only dietary variable significantly related to serum HDL-cholesterol concentration. The authors concluded, “… our findings are compatible with the hypothesis that a diet with low glycaemic index increases HDL-cholesterol concentration by improving insulin sensitivity …” The results showed an even stronger effect on HDL for women than for men.Immune System Stimulation
Beta-glucans from a variety of sources, including barley, fungi, yeast, and seaweed, have been shown to stimulate the immune system by their effects on granulocytes (neutrophils and eosinophils), monocytes, macrophages, and natural killer cells.(16) One paper(16) reports that orally administered beta-glucans from barley and yeast were “taken up by macrophages that transported them to spleen, lymph nodes, and bone marrow. Within the bone marrow, the macrophages degraded the large beta-1,3-glucan into smaller, soluble beta-1,3-glucan fragments that were taken up by the CR3 [a receptor for complement, part of the innate immune system] of marginated granulocytes.” Granulocytes with CR3-bound beta-1,3-glucan fragments were shown to kill tumor cells coated with iC3b [an inactivated complement receptor] in a mouse tumor model where mice were treated with antitumor monoclonal bodies and beta-glucan. In this model, tumor regression required the presence of iC3b on tumors and CR3 on granulocytes.(11 )
A particularly interesting study(17) reported that 5-day-old piglets pretreated with beta-glucan from yeast orally (50 mg/day per pig) and then exposed to the infamous swine flu (capable of infecting humans) did much better than piglets exposed to the flu without pretreatment with beta-glucan. The untreated piglets had significantly more severe microscopic lung lesions induced by the swine flu than did the beta-glucan-treated piglets. There were significantly higher concentrations of interferon-gamma and nitric oxide in bronchoalveolar lavage fluid from piglets pretreated with beta-glucan and infected with swine flu, indicating a stronger antiviral immune response in the beta-glucan-pretreated piglets.
Other studies have shown protective effects of beta-glucan against a variety of infections in mice, including Staphylococcus aureus septicemia, Venezuelan equine encephalomyelitis virus, and Rift Valley fever virus.18-20 Beta-glucan was administered in these studies intravenously, intranasally, or intraperitoneally, presumably because it is easier to control the administered dose by these routes than by oral treatment. Effects depended upon the route of administration. For example, in Reference 18, treatment of mice before challenge with virulent Francisella tularensis provided increased resistance when beta-glucan was given intravenously, but not when it was given intranasally. On the other hand, intranasal beta-glucan pretreatment increased the survival of mice when challenged by aerosol with Pseudomonas pseudomallei, whereas intravenous beta-glucan pretreatment did not increase survival.
Clearly, more research needs to be done on the potential immune-stimulating effects of beta-glucan, but this natural product cannot be patented, so no pharmaceutical industry research funds can be expected to be invested in this effort. Nor can it be expected that the NIH will be interested (they have a lot on their plate, and there is no political constituency pushing the agency for beta-glucan research). The work will be done by the dietary supplement and food industries, but only if the truthful and nonmisleading information resulting from this research can be communicated to the public. A lot depends upon the FDA, and the communication of truthful information is not one of their priorities.References
1. Bourdon I, Yokoyama W, Davis P, Hudson C, Backus R, Richter D, Knuckles B, Schneeman BO. Postprandial lipid, glucose, insulin, and cholecystokinin responses in men fed barley pasta enriched with beta-glucan. Am J Clin Nutr 1999 69(1):55-63.
2. Pereira MA et al. Low-glycemic load diet and resting energy expenditure. JAMA 2004 282:2482-90.
3. Roberts SB. High-glycemic index foods, hunger, and obesity: is there a connection? Nutr Rev 2000 58(6):163-9.
4. Lifschitz CH, Grusak MA, Butte NF. Carbohydrate digestion in humans from a beta-glucan-enriched barley is reduced. J Nutr 2002 132(9):2593-6.
5. Yokoyama WJ, Hudson CA, Knuckles BE, Chiu MM, Sayre RN, Turnlund JR, Schneeman BO. Effect of barley-glucan in durum wheat pasta on human glycemic response. Cereal Chem 1997 74:293-6.
6. Rendell M, Vanderhoof J, Venn M, Shehan MA, Arndt E, Rao CS, Gill G, Newman RK, Newman CW. Effect of a barley breakfast cereal on blood glucose and insulin response in normal and diabetic patients. Plant Foods Hum Nutr 2005 60(2):63-7.
7. Behall KM, Scholfield DJ, Hallfrisch J. Comparison of hormone and glucose responses of overweight women to barley and oats. J Am Coll Nutr 2005 24(3):182-8.
8. Delaney B, Nicolosi RJ, Wilson TA, Carlson T, Frazer S, Zheng GH, Hess R, Ostergren K, Haworth J, Knutson N. Beta-glucan fractions from barley and oats are similarly antiatherogenic in hypercholesterolemic Syrian golden hamsters. J Nutr 2003 133(2):468-75.
9. McIntosh GH, Whyte J, McArthur R, Nestel PJ. Barley and wheat foods: influence on plasma cholesterol concentrations in hypercholesterolemic men. Am J Clin Nutr 1991 53(5):1205-9.
10. Behall KM, Scholfield DJ, Hallfrisch J. Diets containing barley significantly reduce lipids in mildly hypercholesterolemic men and women. Am J Clin Nutr 2004 80(5):1185-93.
11. Dongowski G, Huth M, Gebhardt E, Flamme W. Dietary fiber-rich barley products beneficially affect the intestinal tract of rats. J Nutr 2002 132(12): 3704-14.
12. Kerckhoffs DA, Brouns F, Hornstra G, Mensink RP. Effects on the human serum lipoprotein profile of beta-glucan, soy protein and isoflavones, plant sterols and stanols, garlic and tocotrienols. J Nutr 2002 132(9): 2494-505.
13. Ajani UA, Ford ES, Mokdad AH. Dietary fiber and C-reactive protein: findings from National Health and Nutrition Examination Survey data. J Nutr 2004 134(5):1181-5.
14. Liu S, Manson JE, Buring JE, Stampfer MJ, Willett WC, Ridker PM. Relation between a diet with a high glycemic load and plasma concentrations of high-sensitivity C-reactive protein in middle-aged women. Am J Clin Nutr 2002 75(3):492-8.
15. Frost G, Leeds AA, Dore CJ, Madeiros S, Brading S, Dornhorst A. Glycaemic index as a determinant of serum HDL-cholesterol concentration. Lancet 1999 353(9158):1045-8.
16. Hong F, Yan J, Baran JT, Allendorf DJ, Hansen RD, Ostroff GR, Xing PX, Cheung NK, Ross GD. Mechanism by which orally administered beta-1,3-glucan enhance the tumoricidal activity of antitumor monoclonal antibodies in murine tumor models. J Immunol 2004 173(2):797-806.
17. Jung K, Ha Y, Ha SK, Han DU, Kim DW, Moon WK, Chae C. Antiviral effect of Saccharomyces cerevisiae beta-glucan to swine influenza virus by increased production of interferon-gamma and nitric oxide. J Vet Med B Infect Dis Vet Public Health 2004 51(2):72-6.
18. Kokoshis PL, Williams DL, Cook JA, Di Luzio NR. Increased resistance to Staphylococcus aureus infection and enhancement in serum lysozyme activity by glucan. Science 1978 199:1340-2.
19. Reynolds JA, Kastello MD, Harrington DG, Crabbs CL, Peters CJ, Jemski JV, Scott GH, Di Luzio NR. Glucan-induced enhancement of host resistance to selected infectious diseases. Infect Immunol 1980 30(1):51-7.
20. Di Luzio NR, Williams DL. Protective effect of glucan against systemic Staphylococcus aureus septicemia in normal and leukemic mice. Infect Immunol 1978 20(3):804-10.