A protein-enriched diet is considered a beneficial strategy for weight management and weight loss.
As obesity is a known risk factor for Type 2 Diabetes (T2D) development, balancing diet with increased protein intake might be beneficial for T2D prevention.
Several short-term studies report a positive effect of a protein-enriched diet on weight loss and some metabolic markers, however, until now, no long-term studies have evaluated the effect of protein-enriched diet on the incidence of T2D.
There is some indication that proteins from different sources have different effects on the risk of T2D.
Generally, consumption of red or processed meat is associated with increased risk, whereas dairy fermented products are associated with decreased risk of T2D.
A study published in the British Journal of Nutrition evaluated the effect of dietary protein intake on the incidence of T2D and on additional parameters associated with the risk of T2D (such as BMI, fasting glucose level, and insulin level) in a group of 2332 randomly selected men from Finland, aged 42–60 years.
This study was part of a larger study – The Kuopio Ischemic Heart Disease Risk Factor Study (KIHD) which was designed to investigate risk factors for cardiovascular diseases, atherosclerosis, and other related outcomes.
The recruitment and baseline measurements were obtained between 1984 and 1989 and the follow-up continued for 19 years. Patients with initial T2D, or unknown diabetic status were excluded.
Blood samples and other parameters were obtained at the beginning of the study and at follow-up visits.
To obtain dietary records at the baseline, patients completed a food record form for 4 days, including the weekend. To assist with record keeping, each participant was provided with a picture book that included the most popular meals consumed in Finland during the 80s and illustrations of possible sizes of meals.
To increase accuracy each participant had a session with a nutritionist to go over the completed form. Each meal was dissected to nutrient composition and protein (animal or plant), carbohydrates uptake and energy-adjustment have been calculated.
During the follow-up of 19.3 years, 432 T2D cases were identified. Analysis of dietary records didn’t show a correlation between protein intake from red meat and fish and the incidence of type 2 diabetes.
However, an increased risk of T2D was associated with protein intake from processed meat. Plant protein intake was associated with a decreased risk of T2D and this association remained statistically significant after multivariable adjustments.
Simulation of substitution of 1% energy from carbohydrates or from animal protein (except proteins from eggs) with the same amount of energy from plant-based proteins was associated with a 14-20% decreased risk of developing T2D.
Replacing carbohydrates with protein from other sources was not associated with decreased risk.
Taken together, the study results imply that a diet enriched with plant and egg protein is associated with a decreased risk of T2D. Why plant proteins are more beneficial in preventing T2D is not clear.
It might be related to glucose metabolism since plasma glucose concentrations were lower in patients favoring a plant-enriched diet.
Additional trials in a more diverse population are needed to confirm these benefits.
Written By: Bella Groisman, PhD