Rat study finds whey protein hydrolysates effective in suppressing muscle mass loss

Compared to whey protein amino acids, whey protein concentrate, and whey protein hydrolysates, the latter was observed to be the most effective in suppressing muscle weight loss in rats fed a diet to simulate aged and malnourished muscles, researchers found.

The study, published in the Journal of Nutrition & Intermediary Metabolism​​ by researchers from the Morinaga Milk Industry Co. and the Faculty of Agriculture at Iwate University, sought to find solutions that can combat muscle degradation in patients with nutrition deficiencies. “Few studies have investigated the effect of whey protein and whey protein hydrolysates on muscle mass during chronic malnutrition,” ​the researchers said.

According to the researchers, amino acids have a track record of benefiting muscle mass for malnourished populations, but it can be costly. Hence, the study observed “which forms of whey protein are the most effective in preventing muscle mass loss during chronic muscle protein degradation.”​

The protein free diet​

Wistar rats were fed a 20% casein diet for a week to acclimatize them for the rest of the study. Then, the rats were divided into four groups: Rats that continued with the 20% casein diet as a control group, rats on a protein-free diet supplemented with whey protein amino acids, rats on a protein-free diet supplemented with whey protein concentrate, and rats on a protein-free diet supplemented with whey protein hydrolysates.

The protein free diets were chosen because it causes malnutrition and a decrease in body weight and muscle mass, thus simulating the sarcopenia of older demographics.

The supplementation for each group was administered orally once a day for seven consecutive days. The whey protein concentrate was provided by Millei Co., while the hydrolysate was provided by Morinaga Milk Industry, Co.

Muscle mass of hydrolysate group highest​

The researchers measured body weight and muscle mass of the rats after the dietary program. They found that feeding the rats a protein-free diet for seven days reduced body weight—all protein free fed rat groups experienced weight loss, while the casein group’s average weight increased. However, there was no significant difference between the whey protein groups.

Additionally, the researchers removed and measured the size of the rats’ extensor digitorum longus and soleus muscles (both on the leg). They found that the muscle mass of the casein diet group was significantly more than that of the whey protein groups.

However, the hydrolysate group experienced the least muscle reduction compared to the other whey protein groups. The researchers also pointed out that the hydrolysate group’s muscles experienced a higher increase in plasma EEAA, BCAA, and leucine.

“In conclusion, we showed that [seven] days [whey protein hydrolysate] supplementation protected extensor digitorum longus muscle mass loss induced by a [protein free diet],” ​the researchers wrote, adding that the finding suggests supplementation in elderly humans or other malnourished humans may be beneficial.

Source: Journal of Nutrition & Intermediary Metabolism​​
Published online ahead of print, doi:10.1016/j.jnim.2016.03.001
“Supplementation of protein-free diet with whey protein hydrolysates prevents skeletal muscle mass loss in rats”​
Authors: Yodai Kobayashi, et al.