Study under review: Comparison of low- and high-carbohydrate diets for type 2 diabetes management: a randomized trial
Although some diet-related diseases are handled primarily with pharmacological medications, lifestyle interventions are a cornerstone of type 2 diabetes (T2D) management. In the past few issues of Study Deep Dives, we’ve covered recent research on blood sugar management, and Study Deep Dives issue #3 featured an op-ed by Stephan Guyenet on how T2D can be prevented.
But the most widely-debated topic concerning T2D prevention and treatment is probably carbohydrate intake. Traditionally, the American Diabetes Association does not recommend a lower carbohydrate diet for T2D management. However, they also acknowledge that the amount of carbohydrates in the diet is the primary determinant of the blood glucose response to eating.
Because relatively high-carbohydrate diets are often recommended for T2D patients who may be considered carbohydrate-intolerant, there has been growing interest in the use of low-carbohydrate diets that are higher in fat and protein. There is no shortage of research comparing low- and high-carbohydrate diets in various populations, but most use research designs that allow the participants to consume food freely, leading to differences in energy intake and weight change between dietary conditions. No doubt these studies have their advantages by being more applicable to what would occur in real-life, but they give us less information about the mechanisms behind the diets. Additionally, it has been established that caloric restriction and weight loss independently improve glycemic control, insulin resistance, and cardiovascular risk.
Another confounding variable of previous research is the consumption of saturated fat, which usually increases during low-carbohydrate diets, since people tend to replace carb-rich foods with food sources containing high levels of saturated fat, like fattier cuts of meat and dairy. Interestingly, a vegetable-based low-carbohydrate diet has been associated with lower all-cause and cardiovascular disease mortality rates when compared to an animal-based low-carbohydrate diet. Plant-based fats are composed primarily of mono- and polyunsaturated fatty acids, suggesting that the health effects of a low-carbohydrate diet may be influenced by fat type (or food quality!).
The study under review compared the long-term metabolic effects of a hypocaloric low-carbohydrate diet with a high unsaturated to saturated fatty acid ratio to an energy-matched high-carbohydrate diet based on the recommendations of the American Association of Clinical Endocrinologists (AACE) in obese people with T2D, as part of a holistic lifestyle modification program.
Hypocaloric diets for people with type 2 diabetes are known to provide some benefit. However, the ideal macronutrient ratios of such diets aren’t well-understood. Furthermore, studies involving various diets for people with type 2 diabetes are often confounded by an increase in saturated fat intake to compensate for lower carbohydrate intake. The goal of this study was to examine the effects of a calorie-matched hypocaloric low-carb diet with a high unsaturated to saturated fatty acid ratio compared to a high-carb diet in diabetics.
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.
- 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.
Carbs-protein or protein-carbs …
Does food order matter? Grandma always said “You have to eat your vegetables first if you want dessert!”. If you substitute “carbs” in for dessert, grandma might have hit another one out of the park. It’s possible that simply switching the order of what you eat might benefit blood sugar control, which would be a relatively easy way to address the thorny public health issue of type 2 diabetes