Food Sequencing, an Idea Gaining Ground in Type 2 Nutrition
Studies are preliminary, but results so far are noteworthy.
It has long been understood that an important therapeutic target for all people with diabetes is meal time glucose control, and that the quantity of carbohydrates taken in at a meal or a snack is a reliable predictor of the insulin response. For people who have T1D, the carb count, or load, drives the calculation of a bolus injection or an adjustment of an insulin pump. For people who have T2D, that load is a predictor of how hard the pancreas will have to work to deliver insulin to metabolise incoming sugars. There’s evidence now that “pre-loading” lipids and proteins in the course of eating a meal and leaving carbohydrates for last helps the body to use insulin more efficiently than if one starts off with, say, a more traditional sequence of bread or rolls and a glass of fruit juice and then moves on to meat and vegetables.
Findings of two small group studies of T2D participants at Weill Cornell Medical College and the University of Pisa, published in 2015 and 2016 respectively, appear to support the proposition that beginning a meal with fats and proteins and ending with carbohydrates results in lower post-prandial — after a meal — blood glucose levels and improved insulin sensitivity. The study reports don’t explain in detail how this happens in the digestive process, but it’s thought that pre-loading with the slower-to-digest foods, such as meat and oils, slows emptying of the stomach contents into the small intestine, where nutrients are absorbed, and allows the body to deploy insulin at a time when it can work more efficiently to help tissue benefit from nutrition supplied by carbohydrates in potatoes, green vegetables, fruits, and bread.
Nutritionists tell us that as we begin to digest a meal, what we eat interacts with the linings of the stomach and intestines to trigger secretion of gut peptides. Some of these peptides interact directly with food, and others make their way into the blood stream to remote tissue, such as the liver, pancreas, and brain. Peptides getting to the brain will trigger signals telling the body when it’s reached satiety, or the feeling of fullness and satisfaction. Consider that we can have a bit of high protein yogurt in mid-afternoon and feel pretty satisfied until supper time. But how many of us can have one or two Oreos in the afternoon and beat the craving for another? So one plausible explanation for the food sequencing benefit lies in timing the journey of digestive peptides through the body to achieve an efficient use of nutrients, or quickly ridding the body of what it does not need. For people whose T2D has come on from obesity, this may be a significant piece of the puzzle.
Signals from the brain also control the mixture of enzymes the body adds to ingested food, in the appropriate sequence along the digestive tract, and at the appropriate speeds, to deliver nutrition to all the organs and tissue in the body. For people who have T2D, the liver, releasing glucose, and the pancreas, manufacturing insulin, are critical targets for these gut peptides. So, one plausible explanation for food sequencing — as a means to optimize the timing of the insulin response — may lie in how the brain orders the liver and pancreas to work at balancing glucose in the system, or reaching what’s known as homeostasis. For people with T2N, this is a question of having enough glucose circulating to nourish the body and at the same time preventing insulin from being deployed when it’s less useful.
The 2015 Cornell investigation, reported in Diabetes Care in July 2015, followed eleven middle-aged people with a mean A1c of 6.5, treating with metformin. Participants switched between loading carbohydrates first and proteins and lipids first, typically eating a meal of chicken, steamed vegetables, salad with a low-fat dressing, and bread. The protein/lipid pre-load sequence yielded a mean drop of 28.6% in post-prandial glucose level.
Researchers at the University of Pisa picked up on the Cornell study, publishing in August 2016 the results for twenty participants aged 50 to 75, also with well-controlled A1c, using metformin or metformin and a gliptin. As with the Cornell group, those who began lunch and the evening meal with lipids and proteins and saved carbohydrates for last experienced improvement in post-meal glycemic control.
What’s most revealing in the two results is that participants in neither group altered their daily intakes of calories or carbohydrates, or their daily activities — only the order in which they ate the portions of their two main daily meals. Moreover, both studies were “real life” as distinguished from being closely supervised in residential clinic settings. The researchers logged baseline fasting glucose levels for participants going into each study, but following the baseline measurements, daily fasting and post-prandial glucose tests were self-reported. Three were dropped from the Pisa group for not complying with the study protocol, a rate of attrition not seen as significant in light of the consistency of results. Even with the limited numbers of participants, both teams of researchers reported that their results should be considered substantial enough to justify further investigation.
The University of Pisa researchers’ report notes that even considering the “variability inherent to the real-life setting and the small populations,” self-monitoring of blood glucose by the participants showed overall reductions in glucose levels within a month which could be sustained an additional month merely by following the meat-vegetable-carbohydrate sequence. All this certainly suggests that food sequencing, as part of a consistently followed daily health routine, can be a safe, effective, and inexpensive path toward achieving good blood glucose control.
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