Study under review: Food Order Has a Significant Impact on Postprandial Glucose and Insulin Levels
The glycemic index gets a lot of attention. However, as you may have learned in Study Deep Dives #4, this focus may be potentially overrated as a tool for managing blood sugar levels. In its position statement on dietary carbohydrate and the prevention and management of type 2 diabetes, the American Diabetes Association (ADA) emphasizes that the amount of total carbohydrate in a meal is one of the strongest predictors of the blood glucose response. This is correct, but ignores the non-negligible influence of food order on the blood glucose response to meals.
Postprandial hyperglycemia refers to a state after consuming a meal in which blood glucose levels elevate beyond a healthy range. Normal blood sugar values after eating are between 120-140 mg/dl. For people with diabetes, the ADA recommends keeping postprandial glucose levels below 180 mg/dL, since those with diabetes can experience much higher than normal levels after eating (as shown in Figure 1). Observational as well as interventional studies have shown that postprandial hyperglycemia, yet not high fasting glucose levels, is an independent risk factor for vascular diseases, due in part to increased oxidative stress. Interestingly, even in people with normal glucose tolerance, having glucose levels greater than 155 mg/dL one hour after eating is correlated with an increased risk for nonalcoholic fatty liver disease as well as having early atherosclerosis.
Against that background, it is all the more important to know that the GI is not very useful in making food choices because it’s typically used for individual foods and not meals, and thus ignores the significant effect of fat and protein from mixed meals on postprandial glucose. It is well established that fiber, fat, and protein will all slow down gastric emptying and thus delay the rise in blood sugar following a meal. What has been missing, though, is data regarding the effect of food order on postprandial blood sugar responses in people with type 2 diabetes. This pilot study measured the effects of varying food order on the glucose and insulin responses to a meal in overweight and obese adults with type 2 diabetes.
The macronutrient content can change the way carbohydrates are absorbed by affecting the digestion process. This suggests the order in which macronutrients are consumed during a meal may affect blood sugar levels. This study explored this possibility as it applies to diabetic people.
Other Articles in Issue #10 (August 2015)
Put down the apple and have some chedda
Although both cheese and meat are lumped into the “watch out!” category in hearthealth recommendations, dairy products often show neutral or positive associations with cardiovascular health. But how do cheese-rich diets fare in randomized trials when compared to other diets? This trial tested three diets against each other in a highly controlled fashion: a cheese diet, meat diet, and high-carb diet.
All up in your krill: The story on krill
Oil thus far has been fairly simplistic: it’s better than fish oil and more expensive. But there’s a reason why you can’t draw conclusions based off few studies, and successful results in one condition don’t apply to other conditions. This trial gives some of the first pieces of evidence for possible negative metabolic effects of krill. oil.
Omega-3: kid-tested, mom approved?
While heart health gets much of the attention for fish oil benefits (which, incidentally, are often overstated), outcomes in children typically show more promise. This study, involving children and their parents living on the island of Mauritius, explored possible behavioral benefits to fish oil supplementation. And not just the childrens’ behavior, but the parents’ as well!
Priming the pump: carb levels for endurance exercise
If you run, cycle, or do anything long and sweaty, then you already know that carb intake is especially important for endurance activity. But recommended intakes range from around 30-60 grams, which is pretty broad. This trial can help you get to a more specific number, and possibly perform better.
A thorough trial of carb intake for diabetes
There are few conditions where carbs play as direct of a role as in type 2 diabetes. Yet the recommended carb intake levels for this condition aren’t so different than for the general population. That may change at some point, due to trials like this one, which is more highly controlled and thorough than previous lower-carb & diabetes studies.
- Interview: Elke Nelson PhD
- Interview: Marguerite McDonald, MD
“B” is for breakouts
B vitamins are commonly thought of as harmless, due to being water-soluble. As nutrition junkies know, that view lacks nuance, and B vitamins can indeed be harmful in certain situations. As an example, this elegant series of experiments sheds new light on the mechanism by which vitamin B12 may impact acne formation.
Wellness, Not Weight
By Cristen Harris, PhD
Salt in the wound
Science and mystery often go hand in hand, and this is a perfect example: when you have a skin infection, you tend to have more salt in the infected skin. But why is that? Well, where there’s smoke, there’s fire. The salt is probably doing something in regards to immune response, and it’s possible that how much salt you eat could also play a role. Resist the urge to skip to the end of this mystery -- the buildup is worth it.