Oral Presentation 49th Nutrition Society of Australia Annual Scientific Meeting 2025

Impact of nutrient-dense spinach-enriched bread on postprandial glycaemia and satiety: a randomised controlled crossover trial in healthy adults (129926)

Ritnesh V Prasad 1 , Ulluwis HAJ Hewawansa 2 3 , Gary Williamson 2 3 4 , Elizabeth Barber 2 3
  1. Department of Primary Care and Nutrition, College of Medicine, Nursing & Health Sciences, Fiji National University, Tamavua, Suva, Fiji
  2. Department of Nutrition, Dietetics & Food, Monash University, BASE Facility, Notting Hill, Victoria, Australia
  3. Victorian Heart Institute, Monash University, Victorian Heart Hospital, Victoria, Australia
  4. School of Biological Sciences, Queen's University, Belfast, Northern Ireland, United Kingdom

Background: Declining intake of plant-based foods has contributed to rising global diet-related health problems(1). Incorporating sustainable vegetables into staple foods may improve nutrient intake without compromising sensory appeal. Spinach (Spinacia oleracea) is rich in polyphenols, fibre, vitamins, and minerals, making it a promising functional ingredient for improving bread quality(2).

Objective: To evaluate the nutritional enhancement, sensory acceptance, appetite regulation, and postprandial glycaemic and insulinaemic responses of a spinach-enriched bread compared with standard white bread in healthy adults.

Methods: A single-blinded, randomised crossover study was conducted in 15 healthy adults (8 males, 7 females; age 28 ± 7 years; BMI 28.0 ± 7.8 kg/m²). Participants consumed 107 g servings (equivalent to 50 g carbohydrates) of either control white bread or bread enriched with 20% (w/w) spinach after an overnight fast, with at least one week washout. Nutrient composition of the breads was analysed using Foodworks, and sensory properties assessed via hedonic scoring. Appetite ratings (hunger, satiety, fullness and prospective food consumption) were recorded over 3 hours using visual analogue scales to calculate a composite appetite score. Capillary glucose and plasma insulin were measured at regular intervals, and area under the curve (AUC) values were calculated using the trapezoidal rule.

Results: Spinach-enriched bread contained 60.6 mg/100 g more total polyphenols and higher fibre (+28%), folate (+58%), calcium (+78%), and iron (+90%) than white bread, with no significant differences in acceptance of appearance, taste, texture and aroma (p > 0.05). No significant treatment effects were observed for composite appetite scores (mean difference of hunger: −3.6 mm*min; 95% CI: −91.1, 83.9; p = 0.93, satiety: 1.1 mm*min; 95% CI: −76.3, 78.5; p = 0.97, fullness: 9.3 mm*min; 95% CI: −64.6, 83.2; p = 0.80, and prospective food consumption: 4.9 mm*min; 95% CI: −76.3, 86.1; p = 0.89). Peak postprandial glucose was similar for both breads (7.1 mmol*min/L). AUCglucose (mean difference: 25.5 mmol*min/L; 95% CI −137, 187; p = 0.68) and AUCinsulin (mean difference: 301 µU*min/L; 95% CI −12,384, 12,986; p = 0.77) were not significantly different between treatments. Interestingly, spinach bread delayed the time to peak insulin by 30 min (135.7 µU*min/mL at 60 min vs. 144.6 µU*min/mL at 30 min for white bread).

Conclusions: Incorporation of 20% (w/w) spinach into staple bread substantially improved its nutritional profile, particularly in polyphenols, fibre, folate, calcium, and iron, without compromising sensory acceptance. While overall postprandial glycaemic and appetite responses were unchanged (similar to findings with baobab(3) or pomegranate(4)), the delayed insulin peak suggests a potential benefit for glucose-insulin dynamics. Spinach-enriched bread may represent a sustainable, nutrient-dense option to support metabolic health. Further research in metabolically compromised populations is warranted.

  1. Xu X, et al (2025) BMC Medicine 23, 456.
  2. Lasya CS (2022) The Pharma Innovation Journal 11(8), 1232-1239.
  3. Coe S, Ryan L (2016) Nutrition Research 36 (2), 193-200.
  4. Garcia P, et al (2023) Foods 12 (14), 2798.