Abstract
Purpose: Flaxseed can be effective at lowering and stabilising blood glucose responses. The aim of this study was to determine whether flaxseed could lower blood glucose response more effectively when consumed as a single portion of 30 g, or a split portion consumed three times per day (10 g flaxseed per portion). Methods: The study was a randomised, repeated measures, cross-over design. Fifteen healthy participants consumed either (1) three flaxseed muffins containing a total of 30 g of flaxseed once in the morning, (2) three flaxseed muffins consumed at three different timepoints across the day (10 g flaxseed per muffin) or (3) three control muffins consumed at three different timepoints across the day (0 g flaxseed). The 24-h blood glucose response was measured using a continuous glucose monitor. Results: The results of this study demonstrated that flaxseed muffins given three times a day were effective at lowering and maintaining blood glucose levels over 24 h, compared to the control muffins and that both flaxseed treatments resulting in a lower blood glucose iAUC during the night. Conclusion: The results of this study indicated that adding flaxseed to a daily diet produced a lower glucose profile over 24 h in a free-living context compared to the control muffins.
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Key Points
There is a considerable body of evidence indicating that the consumption of low glycemic index (GI) foods reduces blood glucose fluctuations, and benefits the management and prevention of diabetes and prediabetes. Epidemiological evidence suggests that postprandial blood glucose levels are more strongly related to cardiovascular events than fasting blood glucose in individuals with diabetes. Current eating patterns can mean that a high proportion of the day is spent in the postprandial state, which produces the highest plasma glucose levels. This study investigated the effect of splitting a portion of flaxseed on blood glucose control, or whether the flaxseed is more effective administered in a single or split portion. The flaxseed portion was split over the three meals, which may cause a lower blood glucose post each of the three meals. The aim of this study, therefore, was to determine the most effective timing of flaxseed consumption to lower blood glucose response in healthy participants. This study used a single and a split portion regimen and investigated the blood glucose response over a 24-h period using a CGMS to determine whether flaxseed was more effective when consumed as a single portion of 30 g or as a split portion consumed three times per day (10 g flaxseed per portion).
The results of this study demonstrated that flaxseed muffins given 3 times a day were effective at lowering and maintaining blood glucose levels over 24 h, compared to the control muffins and that both flaxseed treatments resulting in a lower blood glucose iAUC during the night.
The flaxseed muffins contained 4.9 g/100 g of fibre, which could be one of the main reasons for the changes in blood glucose seen in the current study. Flaxseed contains n-3 fatty acids alpha-linolenic acid has which has previously been shown to have a positive impact upon glycaemic control. It has been shown that flaxseed lignan secoisolariciresinol diglucoside restricts expression of the phosphoenolpyruvate carboxykinase gene, which is considered the main enzyme in glucose synthesis in the liver. Finally, the protein in the flaxseed may also cause an increased insulin secretion resulting in decreased blood glucose. It is likely that the reductions in blood glucose observed in the current study are due to the cumulative effects of all of these components and their associated mechanism; however, further clinical trials are required to confirm this.
The results of this study indicated that adding flaxseed to the diet can produce a lower glucose profile over 24 h in a free-living context compared to the control muffins. Furthermore, flaxseeds were effective in improving the blood glucose profile over the 24 h; however, to improve blood glucose both over 24 h and overnight flaxseeds are better consumed in smaller amounts dispersed throughout the day. This study provides important data about adding flaxseed to the diet for healthy individuals, which can improve glycaemic response throughout the day and overnight.