Nutrition Therapy Recommendations for the Management of Adults With Diabetes, Diabetes Care, Published online ahead of print, 9 October 2013.This post focuses on protein. (A previous post focused on carbohydrate. That post summarized the grading system they used to rate their evidence.)
The panel did not designate a particular amount of protein to consume, either in grams or percentage of calories, other than noting that people with diabetes eat about 45% of their calories from carbohydrate, 36-40% from fat, and 16-18% from protein:
Evidence suggests that there is not an ideal percentage of calories from carbohydrate, protein, and fat for all people with diabetes. Grade BDiabetes is the most common cause of kidney failure in the US. Even when a person's diabetes is controlled, they can still develop chronic kidney disease.
Macronutrient distribution should be based on individualized assessment of current eating patterns, preferences, and metabolic goals. Grade E
One job of the kidney is the removal of excess nitrogen or nitrogenous waste. Protein is the primary source of nitrogen in our diet. (The other macronutrients - fat, carbohydrate, and fiber - do not, by themselves, contain nitrogen. However, natural foods usually contain a combination of macronutrients.)
About protein consumption, the National Institutes of Health, NIDDK, say:
"In people with diabetes, excessive consumption of protein may be harmful. Experts recommend that people with kidney disease of diabetes consume the recommended dietary allowance for protein, but avoid high-protein diets. For people with greatly reduced kidney function, a diet containing reduced amounts of protein may help delay the onset of kidney failure."The ADA panel said:
For people with diabetes and no evidence of diabetic kidney disease, evidence is inconclusive to recommend an ideal amount of protein intake for optimizing glycemic control or improving one or more [cardiovascular disease] risk measures; therefore, goals should be individualized. Grade CThere appears to be some disagreement in these recommendations. Do people with diabetes and kidney disease reduce their protein intake or not? The best course of action may be to have kidney function checked regularly and individualize protein intake based on those measurements.
For people with diabetes and diabetic kidney disease (either micro- or macroalbuminuria), reducing the amount of dietary protein below usual intake is not recommended because it does not alter glycemic measures, cardiovascular risk measures, or the course of GFR* decline. Grade A
The term "protein" conjures meat and other animal-based foods. However, plant-based foods also provide protein. Here is what the ADA panel said about soy:
"For individuals with diabetic kidney disease and microalbuminuria, changing the source of protein to be more soy-based may improve [cardiovascular disease] risk factors but does not appear to alter proteinuria."They cited the following 2 studies as a basis for that statement, both of which found that intake of soy protein improved serum cholesterol levels and markers of kidney function, including proteinuria, "and may be beneficial for type 2 diabetic patients with nephropathy [kidney disease]":
Isolated Soy Protein Consumption Reduces Urinary Albumin Excretion and Improves the Serum Lipid Profile in Men with Type 2 Diabetes Mellitus and Nephropathy, Journal of Nutrition, August 2004Lastly, the following recommendation by the ADA stands out:
Soy Protein Intake, Cardiorenal Indices, and C-Reactive Protein in Type 2 Diabetes With Nephropathy, A longitudinal randomized clinical trial, Diabetes Care, April 2008
In individuals with type 2 diabetes, ingested protein appears to increase insulin response without increasing plasma glucose concentrations. Therefore, carbohydrate sources high in protein should not be used to treat or prevent hypoglycemia. Grade B
* GFR is Glomerular Filtration Rate, a measure of kidney function. Higher numbers are better. A normal, healthy kidney has a GFR above 90 (the unit is mL/min/1.73m2) with no protein, such as albumin, found in urine.