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Soya protein + HMB has same anabolic effect as whey

There are now a respectable number of studies that show that whey has a slighter stronger anabolic effect than soya protein. But researchers at Aarhus University Hospital in Denmark have discovered that you can boost the anabolic effect of soya proteins up to the level of whey by combining soya protein with 3 g HMB.

The researchers got eight healthy men to fast for a day and a half on four different occasions, and then got them to drink four different shakes in small quantities spread over a period of four hours. On one occasion the shake contained only carbohydrates [CHO], on another only whey [LWH], on the third occasion soya protein [SOY] and the fourth time soya protein plus 3 g HMB [HMB].

During the experiment the researchers administered labelled phenylalanine to the participants through a drip. They also took samples of cells from the subjects' leg muscles before and after given them the shakes.

The researchers were able to estimate the amount of growth that took place in the participants' muscle cells by looking at the amount of labelled phenylalanine that they absorbed. The figure below shows that the whey resulted in a higher level of anabolism than the soya protein and carbohydrates. But the addition of HMB to the soya protein resulted in the same anabolic effect as from the whey.

Soya protein + HMB has same anabolic effect as whey

Whey increased the activity of anabolic molecules such as mTOR and 4EBP1 in the subjects' muscle cells. This was less so for soya protein. But adding HMB to the soya protein boosted the activity of mTOR and 4EBP1, although it didn't reach the level of activity that the researchers observed in the whey group.

Soya protein + HMB has same anabolic effect as whey

"We found that protein beverages containing either leucine-rich whey protein or soy protein enriched with 3 g HMB improved the net balance of phenylalanine in muscle to a larger extent than beverages containing isocaloric carbohydrates or isonitrogenous soy proteins during fasting-induced catabolic conditions", the researchers summarised. "Leucine-rich whey protein distinctly activated the mTOR signaling pathway in muscle tissue samples."

"These findings are novel and support the use of tailor-made protein preparations to target protein preservation during fasting induced catabolism; whether this also applies to protein preservation in patients with catabolic illnesses is uncertain and awaits the outcome of future studies."

Clin Nutr. 2016 May 25. pii: S0261-5614(16)30096-6. [Epub ahead of print].

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