Do refined grains spike blood sugar?

controlled trial · 2008

“The barley or rye kernel breakfasts resulted in significantly lower blood glucose peaks (1.5 ± 0.2 mmol/L and 1.6 ± 0.2 mmol/L, respectively, based on individual peak increment) than did breakfasts of WWB (3.2 ± 0.4 mmol/L; P < 0.0001), whole-grain barley porridge (2.9 ± 0.3 mmol/L, barley/rye; P < 0.001 and P < 0.01, respectively), or oat kernels (2.7 ± 0.2 mmol/L, barley/rye; P < 0.01 and P < 0.05, respectively).”

Effect of cereal test breakfasts differing in glycemic index and content of indigestible carbohydrates on daylong glucose tolerance in healthy subjects. Am J Clin Nutr
Who: 12 healthy adults (5 women, 7 men) aged 21-41 with normal BMI, Lund, Sweden
PMID 18326603

controlled trial · 2025

“The wholegrain rye-based diet resulted in 30% ( P < 0.001) lower whole-day glucose iAUC as compared with the wheat-based diet ( Table 5 ).”

Postprandial Effects of Four Test Meals Containing Wholegrain Rye or Refined Wheat Foods on Circulating Incretins, Ghrelin, Glucose, and Inflammatory Markers. J Nutr
Who: adults aged 30-70 with BMI 27-35 (overweight/obesity), 72% female
PMID 39515756

controlled trial · 2008

“Breakfast cereals ranged from low (≤55) to high GI (≥70), with the majority having a moderate GI of around 60-65.”

Determination of the glycaemic index of various staple carbohydrate-rich foods in the UK diet. Eur J Clin Nutr
Who: Healthy adult volunteers without diabetes or gastrointestinal disorders, Cambridge, UK
PMID 17426747

controlled trial · 2013

“Following consumption of the biscuits breakfast, glycemia was significantly lower during the first part of the morning (times 30, 40, 60, 75, and 90 minutes) than after the extruded cereals breakfast (Fig. 5A).”

Cereal processing influences postprandial glucose metabolism as well as the GI effect. J Am Coll Nutr
Who: 25 healthy men aged 18-40 with BMI 20-25 (12 isotope part in Lyon, 13 glycaemic part in Sydney)
PMID 24015715

controlled trial · 2010

“In fact, glucose peaks and glycaemia curves between T30 and T180 min were significantly lower in the LGI group than in the HGI group (glucose peak: 7·06 (SEM 0·29) mmol/l in the LGI group v. 7·85 (SEM 0·17) mmol/l in the HGI group).”

Effect of postprandial modulation of glucose availability: short- and long-term analysis. Br J Nutr
Who: 38 healthy overweight non-diabetic adults (19 men, 19 premenopausal women) aged 20-60, BMI 25-30, Lyon
PMID 20030904

other primary study · 2002 · landmark

“Even in large amounts, these foods when eaten alone are not likely to induce a significant rise in blood glucose.”

International table of glycemic index and glycemic load values: 2002. Am J Clin Nutr
Who: Compiled GI tests in healthy and diabetic subjects from published and unpublished sources, 1981–2001
PMID 12081815

other primary study · 2008 · landmark

“Breads, breakfast cereals, rice, and snack products, including whole-grain versions, are available in both high- (70 or greater) and low-GI forms.”

International tables of glycemic index and glycemic load values: 2008. Diabetes Care
Who: published and unpublished GI tests in human subjects (mostly healthy adults, some with diabetes), MEDLINE 1981-2007
PMID 18835944

controlled trial · 2016

“In this study, a red meat/refined grain meal resulted in significantly higher postprandial insulin secretion than a dairy/chicken/nuts/wholegrain meal after a similar chronic dietary pattern but did not alter postprandial glucose concentrations.”

Differential Effects of Red Meat/Refined Grain Diet and Dairy/Chicken/Nuts/Whole Grain Diet on Glucose, Insulin and Triglyceride in a Randomized Crossover Study. Nutrients
Who: Adults without type 2 diabetes, BMI 18-45, 15 men and 36 women, mean age 35, 34 with IFG/IGT
PMID 27809219