Musa-Veloso, K., Noori, D., Venditti, C., Poon, T., . . . Chu, Y. (2021). A systematic review and meta-analysis of randomized controlled trials on the effects of oats and oat processing on postprandial blood glucose and insulin responses. The Journal of Nutrition, 151(2), 341-351. doi:10.1093/jn/nxaa349

Abstract:

Background

Oats are a whole grain cereal with potentially favorable effects on the postprandial glycemic response; however, the effects of oat processing on these glycemic benefits are not well understood.

Objectives

The study objective was to determine the effects of differently processed oats on the postprandial blood glucose and insulin responses relative to refined grains.

Methods

Eleven electronic databases were systematically searched to identify studies published up to and including May 2019. Randomized controlled trials comparing the postprandial blood glucose and insulin responses to oats compared with any refined grain were included, so long as the available carbohydrate content of the test meals was similar. Pooled effect sizes were computed using the difference in incremental area under the curves for blood glucose and insulin following the consumption of oats compared with the refined grain control.

Results

Ten publications were included, with intact oat kernels studied in 3 comparisons, thick oat flakes (>0.6 mm) in 7 comparisons, and thin/quick/instant oat flakes (≤0.6 mm) in 6 comparisons. Compared with the consumption of the refined grain control, the consumption of intact oat kernels was associated with significant reductions in postprandial blood glucose (−45.5 mmol x min/L; 95% CI: −80.1, −10.9 mmol x min/L; P = 0.010) and insulin (−4.5 nmol x min/L; 95% CI: −7.1, −1.8 nmol x min/L; P = 0.001) responses; the consumption of thick oat flakes was associated with significant reductions in postprandial blood glucose (−30.6 mmol x min/L; 95% CI: −40.4, −20.9 mmol x min/L; P < 0.001) and insulin (−3.9 nmol x min/L; 95% CI: −5.3, −2.5 nmol x min/L; P < 0.001) responses; but, the consumption of thin/quick/instant oat flakes was not associated with any effects on the postprandial blood glucose and insulin responses.

Conclusions

A disruption in the structural integrity of the oat kernel is likely associated with a loss in the glycemic benefits of oats.

Rebello, C. J., Johnson, W. D., Pan, Y., Larrivee, S., . . . Greenway, F. L. (2020). A snack formulated with ingredients to slow carbohydrate digestion and absorption reduces the glycemic response in humans: A randomized controlled trial. Journal of Medicinal Food, 23(1), 21-28. doi:10.1089/jmf.2019.0097

Abstract:

This study compared the effect of a snack with ingredients to slow carbohydrate digestion (Test-snack) on postprandial blood glucose and insulin concentrations and subjective appetite ratings. We hypothesized that Test-snack would lower glucose and insulin responses and reduce appetite compared with a Control-snack. Overweight or obese subjects (n = 17) completed a randomized crossover study. Glucose, insulin, and appetite ratings were measured before consuming each snack or white bread (Bread) and over a period of 4 h. Subjects received Test-snack, Control-snack, or Bread in random order at least a week apart. The a priori primary outcome was the glucose response, and the secondary outcomes were appetite ratings and insulin responses. Mixed effects statistical models were used to perform analysis of variance in terms of the area under curve (AUC) and at specific time points. The 2-h AUC for glucose was significantly lower with Test-snack compared to Control-snack and Bread (AUC and 95% confidence intervals: Test = 2186.43 [1783.36–2589.51]; Control = 3293.75 [2893.97–3693.54]; Bread = 2800.28 [2405.79–3194.77] mg/dL · min). Four-hour AUC for glucose, and insulin, followed a similar pattern except that Test-snack did not differ from Bread. The glucose concentrations peaked at 45 min under all three conditions, but Test-snack elicited a lower response than Control-snack and Bread (P < .01). Test increased fullness and satisfaction and reduced hunger and prospective intake compared to Bread (P < .02), but was not significantly different from Control-snack. Ingredients that slow carbohydrate digestion in a snack reduce the postprandial glucose and insulin responses compared to a product without these ingredients.

Wolever, T. M. S., Tosh, S. M., Spruill, S. E., Jenkins, A. L., . . . Steinert, R. E. (2020). Increasing oat β-glucan viscosity in a breakfast meal slows gastric emptying and reduces glycemic and insulinemic responses but has no effect on appetite, food intake, or plasma ghrelin and PYY responses in healthy humans: A randomized, placebo-controlled, crossover trial. American Journal of Clinical Nutrition, 111(2), 319-328. doi:10.1093/ajcn/nqz285

Abstract:

Background: The viscosity of oat β-glucan (OBG) determines its effect on serum cholesterol and glycemic responses, but whether OBG viscosity affects gastric emptying, appetite, and ad libitum food intake is unknown. Objectives: We aimed to determine the effect of altering the amount or molecular weight (MW) and, hence, viscosity of OBG in a breakfast meal on the primary endpoint of food intake at a subsequent meal. Methods: Overnight-fasted males (n = 16) and nonpregnant females (n = 12) without diabetes, aged 18–60 y, with BMI 20.0–30.0 kg/m² who were unrestrained eaters participated in a double-blind, randomized, crossover study at a contract research organization. Participants consumed, in random order, breakfast meals equivalent in weight, energy, and macronutrients consisting of white-bread, butter, jam, and 2% milk plus hot cereal [Cream of Rice (CR), or instant-oatmeal plus either 3 g oat-bran (2gOBG), 10 g oat-bran (4gOBG), or 10 g oat-bran plus β-glucanase (4gloMW) to reduce OBG MW and viscosity compared with 4gOBG]. Gastric emptying, subjective appetite, and glucose, insulin, ghrelin, and peptide tyrosine tyrosine (PYY) responses were assessed for 3 h and then subjects were offered an ad libitum lunch (water and pizza). Results: Pizza intakes (n = 28) after CR, 2gOBG, 4gOBG, and 4gloMW (mean ± SEM: 887 ± 64, 831 ± 61, 834 ± 78, and 847 ± 68 kcal, respectively) were similar (nonsignificant). Compared with CR, 4gOBG significantly reduced glucose (78 ± 10 compared with 135 ± 15 mmol × min/L) and insulin (14.0 ± 1.6 compared with 26.8 ± 3.5 nmol × min/L) incremental area-under-the-curve and delayed gastric-emptying half-time (geometric mean: 285; 95% CI: 184, 442, compared with geometric mean: 105; 95% CI: 95, 117 min), effects not seen after 4gloMW. Subjective appetite, PYY, and ghrelin responses after 2gOBG, 4gOBG, and 4gloMW were similar to those after CR. Conclusions: The results demonstrate that OBG viscosity determines its effect on postprandial glucose, insulin, and gastric emptying. However, we were unable to demonstrate a significant effect of OBG on appetite or food intake, regardless of its viscosity.

Wang, X., Storsley J., Thandapilly S. J., Chu, Y. F., & Ames, N. (2016). Effect of processing, cultivar, and environment on the physicochemical properties of oat β-glucan. Cereal Chemistry, 93(4), 402-408. doi:10.1094/CCHEM-12-15-0245-R

Abstract:

Several food regulatory agencies around the world have approved health claims for oat-derived β-glucan for cholesterol lowering and glycemic control. The biological efficacy of β-glucan appears to depend both on daily intake and on physicochemical properties, such as molecular weight and viscosity. The objective of this study was to determine the effects of oat processing, genotype, and growing location on the physicochemical properties of β-glucan. Five oat genotypes (HiFi, Leggett, CDC Dancer, Marion, and CDC Morrison) grown in two locations (Saskatoon and Kernen) were dehulled (untreated) and processed in a pilot facility through kilning (kilned, not flaked) and subsequent steaming and flaking (kilned, flaked). Untreated groats gave a relatively low Rapid Visco Analyzer (RVA) apparent viscosity (164 cP) and a low extractable β-glucan molecular weight (332,440) but exhibited high β-glucan solubility (90.49%). Compared with untreated groats, the kilned (not flaked) samples had significantly increased RVA apparent viscosity (314 cP) and extractable β-glucan molecular weight (604,710). Additional processing into kilned and flaked products further increased RVA apparent viscosity (931 cP) and β-glucan molecular weight (1,221,760), but β-glucan solubility (63.83%) was significantly reduced. Genotype and growing environment also significantly affected β-glucan viscosity and molecular weight, but no significant interaction effects between processing, genotype, and environment were found. Results indicate that there is potential for processors to improve the physicochemical and nutritional properties of oat end products through processing of specific oat genotypes from selected growing locations.

Zurbau, A., Noronha, J. C., Khan, T. A., Sievenpiper, J. L., & Wolever, T. (2021). The effect of oat β-glucan on postprandial blood glucose and insulin responses: a systematic review and meta-analysis. European Journal of Clinical Nutrition, 10.1038/s41430-021-00875-9. doi:10.1038/s41430-021-00875-9

Abstract:

To determine the effect of oat β‑glucan (OBG) on acute glucose and insulin responses and identify significant effect modifiers we searched the MEDLINE, EMBASE, and Cochrane databases through October 27, 2020 for acute, crossover, controlled feeding trials investigating the effect of adding OBG (concentrate or oat-bran) to carbohydrate-containing test-meals compared to comparable or different carbohydrate-matched control-meals in humans regardless of health status. The primary outcome was glucose incremental area-under-the-curve (iAUC). Secondary outcomes were insulin iAUC, and glucose and insulin incremental peak-rise (iPeak). Two reviewers extracted the data and assessed risk-of-bias and certainty-of-evidence (GRADE). Data were pooled using generic inverse-variance with random-effects model and expressed as ratio-of-means with [95% CIs]. We included 103 trial comparisons (N = 538). OBG reduced glucose iAUC and iPeak by 23% (0.77 [0.74, 0.81]) and 28% (0.72 [0.64, 0.76]) and insulin by 22% (0.78 [0.72, 0.85]) and 24% (0.76 [0.65, 0.88]), respectively. Dose, molecular-weight, and comparator were significant effect modifiers of glucose iAUC and iPeak. Significant linear dose-response relationships were observed for all outcomes. OBG molecular-weight >300 kg/mol significantly reduced glucose iAUC and iPeak, whereas molecular-weight <300 kg/mol did not. Reductions in glucose iAUC (27 vs 20%, p = 0.03) and iPeak (39 vs 25%, p < 0.01) were significantly larger with different vs comparable control-meals. Outcomes were similar in participants with and without diabetes. All outcomes had high certainty-of-evidence. In conclusion, current evidence indicates that adding OBG to carbohydrate-containing meals reduces glycaemic and insulinaemic responses. However, the magnitude of glucose reduction depends on OBG dose, molecular-weight, and the comparator.

Wolever, T. M. S., Jenkins, A. L., Yang, J., Nisbet, M., . . . Pan, Y. (2019). An optimized, slowly digested savory cluster reduced postprandial glucose and insulin responses in healthy human subjects. Current Developments in Nutrition, 3(3), nzz006. doi:10.1093/cdn/nzz006

Abstract:

Background: Slowly digested carbohydrates are perceived as beneficial by some consumers, and various regulatory bodies have published specific criteria defining lower postprandial glycemic response. We developed an optimized savory cluster snack containing slowly digested starch. Objective: We compared the glucose and insulin responses elicited by the optimized (test-) cluster, a control-cluster, and an available-carbohydrate-matched portion of white bread in healthy individuals. The primary outcome was blood-glucose peak rise. We tested healthy individuals (n = 25) on 3 occasions using a randomized crossover design. On each occasion, the participants provided fasting blood samples and then consumed 1 serving of test-cluster, control-cluster, or white bread. We then measured the participants’ blood-glucose and serum-insulin concentrations over the next 4 h. Results: The test-cluster elicited a significantly lower blood-glucose peak rise (mean ± SEM: 1.24 ± 0.09 mmol/L) and incremental area under the curve (iAUC; 67 ± 8 mmol × min/L) than the control-cluster (2.27 ± 0.13 mmol/L and 117 ± 10 mmol × min/L, respectively) and white bread (2.27 ± 0.16 mmol/L and 114 ± 9 mmol × min/L, respectively). The serum-insulin peak rise and iAUC elicited by the test-cluster (128 ± 13 pmol/L and 6.10 ± 0.73 nmol × min/L, respectively) and white bread (141 ± 20 pmol/L and 6.47 ± 1.11 nmol × min/L, respectively) were significantly lower than those elicited by the control-cluster (205 ± 26 pmol/L and 9.60 ± 1.31 nmol × min/L, respectively). Conclusion: The test-cluster elicited lower glucose and insulin responses than the control-cluster. The results support the hypothesis that the carbohydrates in the test-cluster are digested and absorbed slowly in vivo.

Wolever, T. M. S., Jones, P. J. H., Jenkins, A. L., Mollard, R. C., . . . Chu, Y. F. (2019). Glycaemic and insulinaemic impact of oats soaked overnight in milk vs. cream of rice with and without sugar, nuts, and seeds: A randomized, controlled trial. European Journal of Clinical Nutrition, 73(1), 86-93. doi:10.1038/s41430-018-0329-1

Abstract:

Background/Objectives: Soaking oats overnight in milk renders them ready to eat the next morning, however, it is unknown whether oats prepared this way will retain its relatively low glycaemic and insulinaemic impact. Therefore, we compared the glycaemic, insulinaemic and subjective hunger responses elicited by oats soaked overnight in 110 g skim-milk (ONO) vs. cooked cream of rice cereal (CR), both with and without inclusions. Subjects/Methods: The project was performed at two research centers (Toronto, Winnipeg) as two separate studies each using a randomized, cross-over design with similar methods. The glycaemic and insulinaemic responses of overnight-fasted participants without diabetes (males:females: Toronto, 24:16; Winnipeg, 20:20) were measured for 3 h after consuming CR and ONO fed alone (Toronto) or with added sugar, nuts, and seeds (CRsns and ONOsns) (Winnipeg). Participants rated subjective hunger using visual analog scales. Data were analyzed by paired t-test. The primary endpoint was 0–2 h incremental area under the curve (iAUC) for glucose. Results: Mean glucose iAUC was 33% less, after ONO than CR (mean difference was 39 (51–27) mmol × min/l, p < 0.0001) and 24% less, after ONOsns than CRsns (mean difference was 43 (65–21) mmol × min/l, p = 0.0003). Serum-insulin iAUC was 33% less, after ONO than CR (mean difference 57 (81–40) pmol × hl, p < 0.0001) and 32% less, after ONOsns than CRsns (966 (1360–572) pmol × h/l, p < 0.0001). In both Toronto and Winnipeg, subjective hunger ratings were similar across the two treatments. Conclusions: Oats prepared by soaking overnight in skimmed milk without and with inclusions retain their relatively low glycaemic and insulinaemic impact.

Wolever, T. M. S., Johnson, J., Jenkins, A. L., Campbell, J. C., . . . Chu, Y. (2019). Impact of oat processing on glycaemic and insulinaemic responses in healthy humans: A randomised clinical trial. British Journal of Nutrition, 121(11), 1264-1270. doi:10.1017/S0007114519000370

Abstract:

Oats can be processed in a variety of ways ranging from minimally processed such as steel-cut oats (SCO), to mildly processed such as large-flake oats (old fashioned oats, OFO), moderately processed such as instant oats (IO) or highly processed in ready-to-eat oat cereals such as Honey Nut Cheerios (HNC). Although processing is believed to increase glycaemic and insulinaemic responses, the effect of oat processing in these respects is unclear. Thus, we compared the glycaemic and insulinaemic responses elicited by 628 kJ portions of SCO, OFO, IO and HNC and a portion of Cream of Rice cereal (CR) containing the same amount of available-carbohydrate (23 g) as the oatmeals. Healthy males (n 18) and females (n 12) completed this randomised, cross-over trial. Blood was taken fasting and at intervals for 3 h following test-meal consumption. Glucose and insulin peak-rises and incremental AUC (iAUC) were subjected to repeated-measures ANOVA using Tukey’s test (two-sided P<0·05) to compare individual means. Glucose peak-rise (primary endpoint, mean (SEM) mmol/l) after OFO, 2·19 (SEM 0·11), was significantly less than after CR, 2·61 (SEM 0·13); and glucose peak-rise after SCO, 1·93 (SEM 0·13), was significantly less than after CR, HNC, 2·49 (SEM 0·13) and IO 2·47 (SEM 0·13). Glucose iAUC was significantly lower after SCO than CR and HNC. Insulin peak rise was similar among the test meals, but insulin iAUC was significantly less after SCO than IO. Thus, the results show that oat processing affects glycaemic and insulinaemic responses with lower responses associated with less processing.

Wolever, T. M. S., Jenkins, A. L., Prudence, K., Johnson, J., . . . Steinert, R. E. (2018). Effect of adding oat bran to instant oatmeal on glycaemic response in humans - A study to establish the minimum effective dose of oat β-glucan. Food and Function, 9(3), 1692-1700. doi:10.1039/c7fo01768e

Abstract:

Reducing the glycaemic response to carbohydrate-containing foods may have desirable physiological effects for many people. Here, we aimed to determine the minimum amount of oat β-glucan from oat-bran which, when added to instant-oatmeal, would reduce the glycaemic response by 20% compared to a β-glucan-free cereal. Therefore, the glycaemic responses elicited by one serving (27 g) instant-oatmeal plus 247 g 2% milk (IO, 28 g available-carbohydrate, 1.2 g β-glucan) or IO plus 0.2, 0.4, 0.8 or 1.6 g oat β-glucan (OBG) from oat-bran, or an available-carbohydrate matched portion of cream of rice (CR) plus milk were measured over 2 h in n = 40 subjects using a randomized, cross-over design. The primary endpoint was incremental area under the curve (iAUC). The secondary endpoint was glucose peak-rise. The results showed that grams OBG consumed were significantly correlated with mean iAUC (p = 0.009) and with mean glucose peak-rise (p = 0.002). Each gram of OBG reduced iAUC by 7% and peak-rise by 15%. Thus, to achieve a ≥20% reduction in iAUC relative to CR, 1.6 g OBG had to be added to IO (74 ± 7 vs. 93 ± 6 mmol min L−1, p < 0.05), but, to achieve a 20% reduction in peak-rise, only 0.4 g OBG was required (2.00 ± 0.1 vs. 2.40 ± 0.1 mmol, p < 0.05). We conclude that adding OBG to IO flattened postprandial glycaemic responses in a dose-dependent fashion; 1.6 g OBG was required to reduce iAUC by ≥20% versus CR, but a 20% reduction in peak-rise required only 0.4 g. The greater effect of OGB on peak-rise than iAUC presumably reflects the way viscous dietary fibres modulate glucose absorption kinetics.

Musa-Veloso, K., Poon, T., Harkness, L. S., O'Shea, M., & Chu, Y. (2018). The effects of whole-grain compared with refined wheat, rice, and rye on the postprandial blood glucose response: A systematic review and meta-analysis of randomized controlled trials. American Journal of Clinical Nutrition, 108(4), 759-774. doi:10.1093/ajcn/nqy112

Abstract:

Background: Whole grains are often referred to collectively, despite differences in their composition, physical structure, processing, and potential health benefits. Objective: The aim of this study was to compare the postprandial blood glucose response of whole-grain with refined wheat, rice, or rye, while controlling for the food delivery matrix and the processing of the grain (e.g., grinding, germination). Design: Eleven electronic databases were systematically searched to identify studies published up to and including November 2017. Randomized controlled trials comparing the effects of whole-grain wheat, rice, or rye with those of each grain's refined counterpart on postprandial blood glucose area under the curve (AUC) were included. Pooled effect sizes were computed by using the difference in the blood glucose AUC after the consumption of the whole compared with the refined grain. Results: Twenty publications were included, with 10, 14, and 5 strata (or active-control comparisons) on whole-grain wheat, rice, and rye, respectively. The consumption of ground (wholemeal) wheat, compared with white wheat, was not associated with a significant reduction in blood glucose AUC (−6.7 mmol/L ⋅ min; 95% CI: −25.1, 11.7 mmol/L ⋅ min; P = 0.477). The consumption of wholemeal rye, compared with endosperm rye, was not associated with a significant reduction in blood glucose AUC (−5.5 mmol/L ⋅ min; 95% CI: −24.8, 13.8 mmol/L ⋅ min; P = 0.576). The consumption of intact (whole-grain) rice, compared with white rice, was associated with a significant reduction in blood glucose AUC (−40.5 mmol/L ⋅ min; 95% CI: −59.6, −21.3 mmol/L ⋅ min; P < 0.001). Conclusions: Compared with white rice, whole-grain rice significantly attenuates the postprandial blood glucose response. In most of the studies on wheat and rye, the postprandial blood glucose responses to foods formulated with wholemeal compared with refined flours were compared. Whether reductions in the blood glucose AUC can be achieved with whole-grain (as opposed to wholemeal) wheat and rye requires further investigation.

Wolever, T. M. S., van Klinken, B. J., Spruill, S. E., Jenkins, A. L., . . . Harkness, L. (2016). Effect of serving size and addition of sugar on the glycemic response elicited by oatmeal: A randomized, cross-over study. Clinical Nutrition ESPEN, 16, 48-54. doi:10.1016/j.clnesp.2016.07.003

Abstract:

Background & aims We aimed to determine the impact of serving size and addition of sucrose on the glycemic response elicited by oatmeal. Methods We studied 38 healthy subjects (mean ± SD age 40 ± 12 yr, BMI 26.4 ± 3.6 kg/m²) on 8 separate days using a randomized, cross-over design. Capillary blood-glucose responses over 2hr after consuming 30, 40 and 60 g Classic Quaker Quick Oats (18, 24 and 36 g available-carbohydrate [avCHO], respectively) and 30 g Oats plus 9 g sucrose (27 g avCHO) were compared with those after avCHO-matched servings of Cream of Rice cereal (Control) (22, 29, 44 and 33 g cereal, respectively). Blood-glucose incremental area under the curve (iAUC), peak-rise, rate-of-decline, time-to-peak and time-to-baseline were calculated. Results As serving size increased, iAUC, peak-rise, rate-of-decline and time-to-baseline increased significantly for both cereals, but the rate of increase was significantly greater for Control than for Oats. Time-to-peak increased significantly with serving size only for Oats. Compared to avCHO-matched servings of Control, mean (95%CI) iAUC, peak-rise and rate-of-decline, respectively were 22 (16, 27)%, 22 (19, 26)% and 23 (18, 27)% lower after consuming Oats without sucrose and 26 (18, 34)%, 14 (9, 20)% and 16 (9, 24)% lower after consuming Oats plus sucrose. Conclusions Oatmeal elicited a significantly lower glycemic response than avCHO-matched servings of Cream of Rice, even when sucrose was added to the oatmeal. Measures of glycemic response tended to increase with increased serving size; although the pattern of change varied between cereal types. These results suggest that oatmeal may be a good choice for minimizing postprandial glycemia.

Tosh, S. M., & Chu, Y. (2015). Systematic review of the effect of processing of whole-grain oat cereals on glycaemic response. British Journal of Nutrition, 114(8), 1256-1262. doi:10.1017/S0007114515002895

Abstract:

Whole-grain oats have been identified as a type of food that blunts blood glucose increase after a meal. However, processing of oats changes the physical characteristics of the grain, which may influence human glycaemic response. Therefore, the effect of different processes on acute postprandial glycaemic response, quantified using glycaemic index (GI) measurements, was investigated in a systematic review. A review of the literature identified twenty publications containing fifty-six individual tests. An additional seventeen unpublished tests were found in an online database. Of the seventy-two measurements included in the review, two were for steel-cut oats, eleven for large-flake oats, seven for quick-cooking (small flake) oats, nine for instant oatmeal and twenty-eight for muesli or granola. One granola measurement was identified as an outlier and was removed from the statistical analysis. In all, fifteen clinical tests were reported for rolled oat porridge that did not specify the type of oats used, and thus the effect of processing could not be assessed. Steel-cut oats (GI=55 (SE 2·5)), large-flake oats (GI=53 (SE 2·0)) and muesli and granola (GI=56 (SE 1·7)) elicited low to medium glycaemic response. Quick-cooking oats and instant oatmeal produced significantly higher glycaemic response (GI=71 (SE 2·7) and 75 (SE 2·8), respectively) than did muesli and granola or large-flake oatmeal porridge. The analysis establishes that differences in processing protocols and cooking practices modify the glycaemic response to foods made with whole-grain oats. Smaller particle size and increased starch gelatinisation appear to increase the glycaemic response.

Bordenave, N., Kock, L. B., Abernathy, M., Parcon, J. C., . . . Kasturi, P. (2015). Toward a more standardised and accurate evaluation of glycemic response to foods: Recommendations for portion size calculation. Food Chemistry, 167, 229-235. doi:10.1016/j.foodchem.2014.06.124

Abstract:

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.