Glycaemic response to barley porridge varying in dietary fibre content. Br J Nutr. 2012;107:719-724. [PMID: 21787456 DOI: 10.1017/s0007114511003461]

Health-promoting properties of barley: A review of nutrient and nutraceutical composition, functionality, bioprocessing, and health benefits

Barley is one of the world's oldest cereal crops forming an important component of many traditional diets. Barley is rich in a variety of bioactive phytochemicals with potentially health-promoting effects. However, its beneficial nutritional attributes are not being fully realized because of the limited number of foods it is currently utilized in. It is therefore crucial for the food industry to produce novel barley-based foods that are healthy and cater to customers' tastes. This article reviews the nutritional and functional characteristics of barley, with an emphasis on its ability to improve glucose/lipid metabolism. Then, recent trends in barley product development are discussed. Finally, current limitations and future research directions in glucolipid modulation mechanisms and barley bioprocessing are discussed.

Potential contributions of the methodology to the variability of glycaemic index of foods

Glycaemic index (GI) testing provides a useful point of comparison between carbohydrate sources. For this comparison to be meaningful, the methods used to determine GI values need to be rigorous and consistent between testing events. This requirement has led to increasing standardization of the GI methodology, with an international standard developed in joint consultation with FAO/WHO (ISO 26642:2010) currently the most up to date document. The purpose of this review is to compare the international standard to methods of published studies claiming to have performed a GI test. This analysis revealed that the international standard permits a wide range of choices for researchers when designing a GI testing plan, rather than a single standardized protocol. It has also been revealed that the literature contains significant variation, both between studies and from the international standard for critical aspects of GI testing methodology. The primary areas of variation include; what glucose specification is used, which reference food is used, how much reference food is given, what drink is given during testing, the blood sampling site chosen and what assay and equipment is used to measure blood glucose concentration. For each of these aspects we have explored some of the methodological and physiological implications of these variations. These insights suggest that whilst the international standard has assisted with framing the general parameters of GI testing, further stan-dardization to testing procedures is still required to ensure the continued relevance of the GI to clinical nutrition.

Effect of macronutrients and fiber on postprandial glycemic responses and meal glycemic index and glycemic load value determinations

Background: The potential confounding effect of different amounts and proportions of macronutrients across eating patterns on meal or dietary glycemic index (GI) and glycemic load (GL) value determinations has remained partially unaddressed.Objective: The study aimed to determine the effects of different amounts of macronutrients and fiber on measured meal GI and GL values.Design: Four studies were conducted during which participants [n = 20-22; women: 50%; age: 50-80 y; body mass index (in kg/m²): 25-30)] received food challenges containing different amounts of the variable nutrient in a random order. Added to the standard 50 g available carbohydrate from white bread was 12.5, 25, or 50 g carbohydrate; 12.5, 25, or 50 g protein; and 5.6, 11.1, or 22.2 g fat from rice cereal, tuna, and unsalted butter, respectively, and 4.8 or 9.6 g fiber from oat cereal. Arterialized venous blood was sampled for 2 h, and measured meal GI and GL and insulin index (II) values were calculated by using the incremental area under the curve (AUC_i) method.Results: Adding carbohydrate to the standard white-bread challenge increased glucose AUC_i (P < 0.0001), measured meal GI (P = 0.0066), and mean GL (P < 0.0001). Adding protein (50 g only) decreased glucose AUC_i (P = 0.0026), measured meal GI (P = 0.0139), and meal GL (P = 0.0140). Adding fat or fiber had no significant effect on these variables. Adding carbohydrate (50 g), protein (50 g), and fat (11.1 g) increased the insulin AUC_i or II; fiber had no effect.Conclusions: These data indicate that uncertainty in the determination of meal GI and GL values is introduced when carbohydrate-containing foods are consumed concurrently with protein (equal amount of carbohydrate challenge) but not with carbohydrate-, fat-, or fiber-containing foods. Future studies are needed to evaluate whether this uncertainty also influences the prediction of average dietary GI and GL values for eating patterns. This trial was registered at clinicaltrials.gov as NCT01023646.

Qualified health claim for whole-grain intake and risk of type 2 diabetes: an evidence-based review by the US Food and Drug Administration

The objective of this review is to explain how the US Food and Drug Administration (FDA) used its evidence-based review system to evaluate the scientific evidence for a qualified health claim on the role of whole-grain consumption in reducing the risk of type 2 diabetes. The labeling of health claims, including qualified health claims, on conventional foods and dietary supplements requires premarket approval by the FDA. Health claims characterize the relationship between a substance (food or food component) and a disease (eg, diabetes or cardiovascular disease) or a health-related condition (eg, hypertension). This review describes the FDA's evaluation of intervention and observational studies that characterize a relationship between whole grains and type 2 diabetes. This evidence-based review provides very limited evidence to support a health claim of a relationship between intake of whole grains and a reduced risk of type 2 diabetes.

Toward a more standardised and accurate evaluation of glycemic response to foods: recommendations for portion size calculation

This study aimed at evaluating the adequacy of calculation methods for portions to be provided to subjects in clinical trials evaluating glycemic response to foods. Portion sizes were calculated for 140 food samples, based on Nutrition Facts labels (current practice) and actual available carbohydrate content (current recommendation), and compared against the amount of monosaccharides yielded by the digestive breakdown of their actual available carbohydrate content (basis for glycemic response to food). The current practice can result in significant under- or over-feeding of carbohydrates in 10% of tested cases, as compared to the targeted reference dosage. The method currently recommended can result in significantly inadequate yields of monosaccharides in 24% of tested cases. The current and recommended calculation methods do not seem adequate for a standardised evaluation of glycemic response to foods. It is thus recommended to account for the amount of absorbable monosaccharides of foods for portion size calculation.

The health benefits of whole grains and fibre

Purpose

– The purpose of this paper is to evaluate the latest mounting evidence reporting associations between the important role of whole grains and fibre in lowering the risk of chronic diseases and health.

Design/methodology/approach

– A general systematic review was conducted to locate and summarise up-to-date published studies within the field. A Medline search identified human-controlled trials and observational studies published in the past five years.

Findings

– A total of 49 studies were identified. In observational studies, higher intakes of whole grain and dietary fibre were associated with a significantly lower risk of cardiovascular disease, diabetes, abdominal adiposity and certain cancers. This was further supported by human intervention trials, which reported benefits for appetite control, blood lipid levels, glycaemic control, digestive health and secondary cancer prevention. Mechanisms may relate to the micronutrients and phytonutrients present in high fibre foods.

Practical implications

– Practical advice is needed to help people identify foods rich in whole grains, e.g. breakfast cereals. UK fibre recommendations should be aligned with European guidelines and food labelling regulations, and a whole grain dietary recommendation, e.g. similar to the US guideline of three portions a day, could be introduced. Government and industry should play a role in communicating dietary fibre guidelines and the health benefits associated with whole grain and fibre, particularly insoluble fibre.

Originality/value

– This paper develops knowledge about whole grains, health and the importance of establishing whole-grain dietary recommendations.

Glycaemic responses of staple South Asian foods alone and combined with curried chicken as a mixed meal

BACKGROUND

The glycaemic responses of staples differ when eaten as mixed meals. We determined the glycaemic responses and glycaemic index (GI) values for common South Asian carbohydrate rich foods and the effect of adding curried chicken to them as mixed meals.

METHODS

The GI and glycaemic response to staples (basmati rice, pilau rice and chapatti) and mixed meals (pilau rice with chicken curry and chapatti with chicken curry) were measured in healthy volunteers. Paired comparisons in each subject were carried out for staples and their equivalent mixed meals (n = 9).

RESULTS

GI values for the mixed meals were significantly lower than the staples alone (41 and 60 for pilau rice with chicken curry and pilau rice alone, P = 0.001; 45 and 68 for chapatti with chicken curry and chapatti alone, P = 0.004). Both, pilau rice and chapatti with chicken curry had a significantly lower glycaemic response than their equivalent staples alone: incremental area under the blood glucose response curves (IAUC) 111.9 mmol min(-1 ) L(-1) for pilau rice with curry versus 162.4 mmol min(-1 ) L(-1) for pilau rice alone (P = 0.001) and IAUC 110.1 mmol min(-1 ) L(-1) for chapatti with chicken curry versus 183.6 mmol min(-1 ) L(-1) for chapatti alone (P = 0.002).

CONCLUSIONS

Adding fat and protein-containing curries as part of a mixed meal to carbohydrate rich staple foods reduced glycaemic responses, and also changed the GI category.

Review of human studies investigating the post-prandial blood-glucose lowering ability of oat and barley food products

Oat and barley foods have been shown to reduce human glycaemic response, compared to similar wheat foods or a glucose control. The strength of the evidence supporting the hypothesis that the soluble fibre, mixed linkage β-glucan, reduces glycaemic response was evaluated. A search of the literature was conducted to find clinical trials with acute glycaemic response as an end point using oat or barley products. Of the 76 human studies identified, 34 met the inclusion and exclusion criteria. Dose response and ratio of β-glucan to available carbohydrate as predictors of glycaemic response were assessed. Meals provided 0.3-12.1 g oat or barley β-glucan, and reduced glycaemic response by an average of 48 ± 33 mmol · min/l compared to a suitable control. Regression analysis on 119 treatments indicated that change in glycaemic response (expressed as incremental area under the post-prandial blood-glucose curve) was greater for intact grains than for processed foods. For processed foods, glycaemic response was more strongly related to the β-glucan dose alone (r(2)=0.48, P<0.0001) than to the ratio of β-glucan to the available carbohydrate (r(2)=0.25, P<0.0001). For processed foods containing 4 g of β-glucan, the linear model predicted a decrease in glycaemic response of 27 ± 3 mmol · min/l, and 76% of treatments significantly reduced glycaemic response. Thus, intact grains as well as a variety of processed oat and barley foods containing at least 4 g of β-glucan and 30-80 g available carbohydrate can significantly reduce post-prandial blood glucose.