A new consensus report was issued this month by a committee from the American Diabetes Association (ADA) regarding medical nutrition therapy for adults with diabetes or prediabetes. The report includes reiteration of some previous recommendations but also introduces important new guidelines that may be of interest to doctors and nutritionists using dietary interventions for individuals with these conditions.
It’s noteworthy that the report “is intended to provide clinical professionals with evidence-based guidance about individualizing nutrition therapy for adults with diabetes or prediabetes.” This is important to be aware of because, in the past, medical and nutrition professionals who ran afoul of officially approved guidelines by recommending “outside the box” approaches for patients or clients risked professional criticism and potentially even legal action. (For example, a dietitian in Australia was de-registered by the Dietitians Association of Australia for advising her clients with type 2 diabetes or insulin resistance to follow a low-carb diet. And an orthopedic surgeon in Tasmania was banned from giving nutrition advice to patients after also recommending low-carb, high-fat diets to those at risk of losing limbs from diabetic complications. [The Australian Health Practitioner’s Regulation Agency later dropped all charges against him and issued a full apology.])
A notable point from the report is that there is no ideal, across-the-board percentage of calories from protein, fat, or carbohydrate, so blanket recommendations are out and macronutrient composition may be based on individual preferences and goals. This opens the way for any number of approaches that may be effective for improving glycemic control and insulin sensitivity, such as a vegetarian diet, Mediterranean diet, low-fat diet, low-carb or very low-carb diet. Evidence for efficacy of each of these approaches came from randomized controlled trials, meta-analyses, observational studies, and other types of studies conducted between 2014-2018.
These disparate approaches are quite different, but the consensus committee identified some broad similarities that make sense not just for those with diabetes or prediabetes, but for anyone concerned about overall metabolic health: the committee recommends an emphasis on non-starchy vegetables, minimizing added sugars and refined grains, and choosing whole foods over highly processed foods as much as possible. Not exactly earth-shattering suggestions, but now that new food labels require the disclosure of added sugar rather than just total sugars, consumers can make more informed choices. The American Heart Association claims this information “could prevent nearly a million cases of cardiovascular disease and Type 2 diabetes in the United States and save tens of billions of dollars in health care costs.” An overly optimistic estimate, perhaps, but cutting back on packaged foods with excessive amounts of added sugar will likely result in at least some reduction in health care costs associated with conditions driven primarily by hyperglycemia and/or hyperinsulinemia, and their metabolic sequelae.
Considering the disciplinary action taken in the past against health care professionals for recommending low-carb approaches for those with diabetes, it’s a welcome development to see the following in the evidence-based consensus report:
The report also suggests that achieving glycemic targets should “include individualized guidance on self-monitoring carbohydrate intake to optimize meal timing and food choices…” The good news here is, increased availability of home glucometers allows people to monitor their own blood glucose and have feedback literally at their fingertips. Some insurance plans may also cover continuous glucose monitors for individuals with diabetes or prediabetes, and this information can be instrumental for people to learn about how certain foods affect their blood glucose in near-real-time.
Nutrition professionals and the general public alike may be drawn to the glycemic index as a proxy for how carbohydrates affect people. However, there’s a great deal of individual variability with regard to response to carbohydrate-containing foods: As we wrote about in the past, one person’s high-fiber bran cereal is another’s grape jam on white bread. With this in mind, it’s refreshing to see the report acknowledge the weaknesses of using glycemic index and glycemic load in guiding food choices for people with diabetes: “Two systematic reviews of the literature regarding GI and GL in individuals with diabetes and at risk for diabetes reported no significant impact on A1C and mixed results on fasting glucose.” With individual response varying so much, definitions of low, medium, and high GI foods are much less reliable than is generally appreciated.
Another noteworthy point the committee addressed is that individuals with diabetic kidney disease who are not on dialysis do not need to restrict protein intake to less than average (about 1-1.5 g/kg body weight per day, or 20% of calories). We previously addressed the issue of protein intake with regard to kidney function, noting that evidence does not support a causative role for protein in kidney disease. In a paper covering more than 13 risk factors for chronic kidney disease, high protein intake was not among the factors, and neither the National Kidney Foundation nor the National Institutes of Health list high protein intake as a factor either. Diabetes itself is one of the top two causes of kidney damage, along with hypertension—not dietary protein.
The ADA consensus report indicated that overall, diets higher in protein and fiber (especially from whole foods, rather than fiber supplements) generally resulted in greater weight loss and improvements in HbA1c compared to other diets. The consensus also acknowledges that eating patterns in which certain carbohydrate foods are replaced with higher fat foods show greater improvements in glycemia and certain CVD risk factors, and that dietary cholesterol intake does not correlate well with cardiovascular disease events. These points are in line with the 2015 Dietary Guidelines for Americans, which officially de-listed cholesterol as a “nutrient of concern” and removed limitations on total fat consumption. (These government guidelines are issued every five years; a committee has been selected to create the next iteration, for 2020-2025.)
A somewhat disappointing part of the report is the committee’s negative stance toward the role of nutritional or herbal supplementation as an adjunct to dietary intervention. The consensus acknowledges that B12 supplementation may be warranted in some individuals taking metformin (which is known to affect B12 levels in some individuals). Beyond that, though, they don’t recommend supplementation with berberine, alpha-lipoic acid, chromium and biotin, or any other compounds with substantial evidence supporting their beneficial effects in those with diabetes.
That last point aside, this consensus report is quite heartening and gives health care professionals flexibility to recommend a number of different potentially helpful strategies and to help patients individualize their diets as necessary.