Am J Clin Nutr (August 19, 2009). doi:10.3945/ajcn.2009.27548
© 2009 American Society for Clinical Nutrition

Hydrolyzed dietary casein as compared with the intact protein reduces postprandial peripheral, but not whole-body, uptake of nitrogen in humans1,2,3,4

Amélie Deglaire, Claire Fromentin, Hélène Fouillet, Gheorghe Airinei, Claire Gaudichon, Claire Boutry, Robert Benamouzig, Paul J Moughan, Daniel Tomé and Cécile Bos
1 From the INRA, CRNH-IdF, UMR914 Nutrition Physiology and Ingestive Behavior, Paris, France (AD, CF, HF, CG, C Boutry, RB, DT, and C Bos); AgroParisTech, CRNH-IdF, UMR914 Nutrition Physiology and Ingestive Behavior, Paris, France (AD, CF, HF, CG, C Boutry, RB, DT, and C Bos); Riddet Institute, Massey University, Palmerston North, New Zealand (AD and PJM); and the Department of Gastroenterology, Avicenne Hospital, CRNH-IdF, Bobigny, France (GA and RB).

2 Presented in part in abstract form at Experimental Biology, San Diego, CA, 4–9 April 2008.

3 Supported by grants from the INRA (France) and the Riddet Institute (NZ).

4 Address correspondence to C Bos, UMR914 INRA-AgroParisTech Nutrition Physiology and Ingestive Behavior, AgroParisTech, 16 rue Claude Bernard, F-75005 Paris, France. E-mail address: cecile.bos@agroparistech.fr.

ABSTRACT

Background: Compared with slow proteins, fast proteins are more completely extracted in the splanchnic bed but contribute less to peripheral protein accretion; however, the independent influence of absorption kinetics and the amino acid (AA) pattern of dietary protein on AA anabolism in individual tissues remains unknown.

Objective: We aimed to compare the postprandial regional utilization of proteins with similar AA profiles but different absorption kinetics by coupling clinical experiments with compartmental modeling.

Design: Experimental data pertaining to the intestine, blood, and urine for dietary nitrogen kinetics after a 15N-labeled intact (IC) or hydrolyzed (HC) casein meal were obtained in parallel groups of healthy adults (n = 21) and were analyzed by using a 13-compartment model to predict the cascade of dietary nitrogen absorption and regional metabolism.

Results: IC and HC elicited a similar whole-body postprandial retention of dietary nitrogen, but HC was associated with a faster rate of absorption than was IC, resulting in earlier and stronger hyperaminoacidemia and hyperinsulinemia. An enhancement of both catabolic (26%) and anabolic (37%) utilization of dietary nitrogen occurred in the splanchnic bed at the expense of its further peripheral availability, which reached 18% and 11% of ingested nitrogen, respectively, 8 h after the IC and HC meals.

Conclusions: The form of delivery of dietary AAs constituted an independent factor of modulation of their postprandial regional metabolism, with a fast supply favoring the splanchnic dietary nitrogen uptake over its peripheral anabolic use. These results question a possible effect of ingestion of protein hydrolysates on tissue nitrogen metabolism and accretion. This trial was registered at clinicaltrials.gov as NCTNCT00873951.

Received for publication January 27, 2009. Accepted for publication August 3, 2009.

Alex wrote:Ease of digestion may be a better indication around workout as you wouldn't want some of the body's resources being used to digest when they could be utilised for training. I would sau other than during this period then fast acting makes little odds.

My Comments: Ever since the pioneering work in the 90’s on fast and slow proteins, there has been continued interest in the digestion speed of proteins and how that impacts on metabolism, performance and, of course, muscle growth. In recent years, there have been many claims made for the superiority of faster proteins to slower in terms of ’speeding amino acids to muscle’ in terms of promoting growth.

As well, as many may note, a recent commercial product (T-nations Anaconda), who’s anabolic claims were analyzed in perhaps the most commented article on the site in Alan’s Aragon’s guest article Supplement Marketing on Steroids, has recently been released to the market.

For background, hydrolysates are simply whole proteins that have been pre-digested (through the addition of enzymes during production) to some degree. The theory being that, due to this pre-digestion, the hydrolysate will be digested in the stomach faster, getting aminos into the bloodstream faster and, presumably, having a better effect on skeletal muscle than slower proteins.

But is it true? Guess.

The above study examined this issue by feeding 21 subjects 2 test meals containing either intact casein or it’s hydrolysate; the protein had been marked with radioactive nitrogen so that it’s fate after ingestion could be tracked over the next 8 hours. The test meals also contained 96 grams of carbohydrate and 23 grams of fat; this is worth noting as adding other nutrients to fast proteins often makes them behave more like slow proteins. I’ll spare you the methodology, sufficed to say that tracking protein after it enters the body is brutally complicated and involves a lot of modelling and various measurements of blood amino acid levels and such.

Here’s what the study found. Over the time course studied (8 hours after ingestion), the hydrolyzed casein product showed greater losses from digestion (that is, less was absorbed). As well, a greater amount of the hydrolysate was oxidized for energy through deamination (a process by which the amino group is stripped off the carbon backbone). Finally, a larger amount of the casein hydrolysate was used by the splanchnic bed (gut and intestines) with significantly LESS of the total protein reaching the bloodstream or peripheral tissues (muscles).

To quote the researchers:

Despite similar overall net postprandial protein utilization, our results indicate important differences in metabolic partitioning and kinetics between protein sources characterized by a preferential utilization of dietary nitrogen by for splanchnic protein syntheses after HC [hydrolyzed casein] ingestion at the expense of the incorporation into peripheral tissues.

Translating that into English: hydrolyzed casein is digested more poorly, get burned for energy to a greater degree and gets used more by the gut than intact casein; the end result of this is that hydrolyzed casein provides LESS amino acids to skeletal muscle after ingestion than intact casein protein.

So not only is the claim that hydrolysates are better at providing aminos faster to skeletal muscle wrong, the reality is actually exactly reversed: intact casein is better for providing aminos to the muscle. I’d note that other studies have found this as well: in one, intact protein provided MORE branched-chain amino acids into the bloodstream than a hydrolyzed form.

I’d add to this that, as I discussed in The Protein Book, other data supports the idea that slower proteins may actually be superior to faster proteins for muscle growth; in one set of studies, for example, milk protein (a mix of slow and fast proteins) resulted in greater hypertophy than soy (a fast protein) over 8 weeks of training and supplementation. As well hydrolyzed proteins tend to taste like bleach; it’s no coincidence that Anaconda has to come with a separate flavoring intensifier: hydrolysates are gag-inducing. They can’t be consumed straight.

Summing up: Hydrolysates are not only not superior to intact protein in terms of providing amino acids to skeletal muscle, they are distinctly inferior. Their fast digestion speed leads to greater digestive losses, more oxidation via deamination and provides less amino acids to skeletal muscle. That’s on top of tasting like vomit. Or at least making you want to.

Craig wrote:

kp1512 wrote:another thing that needs to be mentioned is capitlising on the body and what it needs via peak hormonal responses. that was clear also from that other article on sythetek I linked - but outside of that - more obvious

I need to read that when I'm in the right frame of mind

Craig wrote:The important part of using fast aminos or hydro at the right time is the hormonal effect and the change in amino levels, the whole idea of comparing these two protein sources is retarded. Its like complaining that a Lambo can't hold as many passengers as a estate car.