Sustained effects of a protein ‘preload’ on glycaemia and gastric emptying over 4 weeks in patients with type-2 diabetes: A randomized clinical trial

Abstract: We have shown that the capacity of 25 g whey preloads to slow gastric emptying and reduce postprandial glycaemia persists after 4 weeks regular exposure in patients with diet-controlled type 2 diabetes. This dietary strategy therefore appears feasible for larger clinical trials to evaluate beneficial effects on long-term glycemic control.


Alex’s Notes: When it comes to managing blood glucose, drinking a giant whey protein shake before eating a meal is not the first idea that comes to mind. But maybe it should be. The researchers of the current study had previously shown that a 55 g whey protein preload, given 30 min before a high carbohydrate meal, slowed gastric emptying and greatly reduced postprandial blood glucose in patients with type-2 diabetes. These results were later replicated by another group of researchers using a considerably smaller amount of whey (17g) in combination with a low-dose of guar gum fiber (5g).

However, both these studies were a one-time deal, and it has been shown that the gastric emptying rate is adaptive. For instance, it has been shown that consuming a high-fat diet for two weeks significantly increases the gastric emptying rate, thereby negating one of the benefits commonly attributed to this diet. This has also been demonstrated with carbohydrates, and thus it stands to reason that perhaps it would occur with whey protein as well.

As such, the current study recruited seven 60 year old, obese, diet-controlled type-2 diabetics to undergo a 4-week randomized, single-blind, and cross-over protocol. The participants consumed a chocolate-flavored preload (100 ml water with either 25 g whey protein isolate or 25 g chocolate-flavored diet sauce as a placebo) 30 minutes before each of the three main meals for 4 weeks, followed by a 2 week washout, and then the alternative preload for 4 weeks.

After an overnight fast on the first and last day of each 4-week period, the participants consumed a mashed potato meal (total carbohydrates 62 g; 314 kcal) with a tracer to assess gastric emptying over the following 240 minutes, and also had some blood-borne measurements made.

Contrary to research concerning fat and carbohydrates, it was indeed shown that gastric slowing was present after 4-weeks of treatment with whey preloads. As could be expected, post-prandial blood glucose levels were also consistently lower for the whey group at the beginning and end of the interventions. Notably, there was no difference in body weight seen in either group.

This latter finding is in stark contrast to a previous study of obese middle-aged men, which found that drinking 54g of whey protein once per day before their largest meal was able to reduce appetite, caloric intake, weight, waist circumference, and body fat percentage, and increase lean body mass over the course of 12 weeks. Thus, perhaps the timeframe of the current study was not large enough.

Bottom line

It is important to keep in mind that these results apply only to individuals with poor glucose control. Thus, if you are a diabetic or prediabetic, consider adding some whey to your arsenal.

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