The effect of polyphenol-rich flaxseed muffins on glycaemic, insulinaemic and 24-hour glucose response in healthy adults
Flaxseed may be considered a functional food as it contains chemical and bioactive compounds, such as antioxidants, polyphenols and dietary fibre. These compounds help to prevent diseases, such as cardiovascular disease (CVD) and Type 2 Diabetes (T2D), and they enhance metabolic health. It is important to investigate the use of flaxseed as a functional ingredient in bakery products to provide health benefits, particularly through its effect on blood glucose. The main aim of this PhD was to evaluate the effect of flaxseed in different forms (whole and ground) incorporated into bakery products on the blood glucose profile of healthy individuals. Ground flaxseed produced significantly higher levels of total polyphenols (518.8 ± 101.1 μg GAE/g compared to 260.1 ± 25.7 μg GAE/g for the control muffins) and antioxidant capacity (1693.9 ± 78.6 μmol/l compared to 89.8 ± 25.7 μmol/l for the control muffins). Both flaxseed forms reduced the rapidly digestible starch (RDS) in the muffins, which may lead to lower blood glucose levels. Both flaxseed muffin types produced a significantly lower glycaemic response (GR) compared to standard glucose, but there were no significant differences between the flaxseed muffin types. Moreover, adding flaxseed lowered the Glycaemic Index (GI) value compared to the control muffins (64.3 ± 36.8 vs. 53.3 ± 13.2 and 42.2 ± 13 for the control, whole and ground flaxseed muffins respectively). The results for the incremental area under the curve (iAUC) for glucose and insulin showed that both the whole and ground flaxseed muffins significantly lowered the GR and insulinaemic response (IR) compared to the control muffins, at 60, 90 and 120 min (p < 0.001). There were no significant differences for the insulin iAUC 120 between the two flaxseed muffin types (p > 0.05). The results of the blood glucose profile over 24 hours demonstrated that the flaxseed muffins were effective at lowering and maintaining blood glucose levels over 24 hours whether consumed once or three times a day. The results for the iAUC for the blood glucose were significantly lower for both flaxseed treatments during 24 hours (p=0.014) and during the night (p=0.005) compared to the control muffin. Overall, the study found that flaxseed was effective amongst healthy individuals in relation to its effect on the glucose profile over 24 hours, gluco-regulation and insulin levels. These results add to the current body of evidence in the field of functional foods and support the use of such functional food ingredients in a healthy diet, specifically to improve the regulation of glucose in adults.
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