Consumption of fluid skim milk promotes greater muscle protein accretion ............

[3XL]

Consumption of fluid skim milk promotes greater muscle protein accretion after resistance exercise than does consumption of an isonitrogenous and isoenergetic soy-protein beverage1,2,3
Sarah B Wilkinson, Mark A Tarnopolsky, Maureen J MacDonald, Jay R MacDonald, David Armstrong and Stuart M Phillips

1 From the Exercise Metabolism Research Group, Department of Kinesiology (SBW, MJM, and SMP), the Departments of Pediatrics and Neurology (MAT and JRM), and the Department of Gastroenterology (DA), McMaster University, Hamilton, Canada


Background:Resistance exercise leads to net muscle protein accretion through a synergistic interaction of exercise and feeding. Proteins from different sources may differ in their ability to support muscle protein accretion because of different patterns of postprandial hyperaminoacidemia.

Objective:We examined the effect of consuming isonitrogenous, isoenergetic, and macronutrient-matched soy or milk beverages (18 g protein, 750 kJ) on protein kinetics and net muscle protein balance after resistance exercise in healthy young men. Our hypothesis was that soy ingestion would result in larger but transient hyperaminoacidemia compared with milk and that milk would promote a greater net balance because of lower but prolonged hyperaminoacidemia.

Design:Arterial-venous amino acid balance and muscle fractional synthesis rates were measured in young men who consumed fluid milk or a soy-protein beverage in a crossover design after a bout of resistance exercise.

Results:Ingestion of both soy and milk resulted in a positive net protein balance. Analysis of area under the net balance curves indicated an overall greater net balance after milk ingestion (P < 0.05). The fractional synthesis rate in muscle was also greater after milk consumption (0.10 * 0.01%/h) than after soy consumption (0.07 * 0.01%/h; P = 0.05).

Conclusions:Milk-based proteins promote muscle protein accretion to a greater extent than do soy-based proteins when consumed after resistance exercise. The consumption of either milk or soy protein with resistance training promotes muscle mass maintenance and gains, but chronic consumption of milk proteins after resistance exercise likely supports a more rapid lean mass accrual.

[3XL]

Wat commentaar van Lyle McDonald


My comments: In recent years, there has been an explosion of research looking at optimal nutrition around resistance training. While earlier research focused only on endurance training (and primarily looked at how to optimize glycogen resynthesis), recent studies have looked at how different nutrients, or combinations of nutrients, impact on resistance training.

Earlier studies, more concerned with physiological details tended to use solutions of essential amino acids either alone or combined with pure sucrose; more recent research has begun to examine either real foods or protein powders in terms of how they impact on the stimulation of protein synthesis (or the inhibition of protein breakdown) following training.

This study continues in that vein, examining the impact of either skim milk or a soy beverage following resistance training on the promotion of protein synthesis/gain following resistance training. Soy, like whey, is a fast protein, digesting rapidly (flooding the bloodstream with amino acids); milk, containing a mixture of whey and casein (in a roughly 20:80 ratio) combined both a fast and slow protein.

The study recruited eight healthy men who were tested on two different occasions, once with the soy beverage and one with the milk beverage. Their 1 repetition maximum was tested on leg press, leg curl and leg extension to set training loads.

Prior to the workout, all subjects received a standard breakfast, 2.5 hours later they reported to the lab where they were set up for measurement and training. I think it's important to note that a lot of previous research has used fasted subjects which I think colors the results; the impact of meals consumed prior to training affects overall metabolism. By giving the subjects a standardized breakfast before the workout, I think it better models real world training practices.

The subjects performed 4 sets of one leg leg press, leg curl and leg extension at 80% of 1 rep max. the first. The first three sets were stopped at 10 reps, the last set was taken to exhaustion and the rest interval between sets was 2 minutes. The research choose 1 leg exercise to make it easier to examine the impact of training and nutrition on protein synthesis.

After a set of blood measurements and a muscle biopsy, the subjects were given either a skim milk or soy based beverage containing 18.2 grams protein, 1.5 grams fat and 23 grams carbs as either lactose from the milk or maltodextrin in the soy drink.

The study used a combination of blood data and muscle biopsy to examine the impact of the different drinks on protein synthesis, looking primarily at the uptake of phenylalanine which was used to calculate the fractional synthetic rate of muscle protein following training. A number of other parameters including blood glucose and insulin, muscle blood flow, and amino acid kinetics was also examined.

The study showed that blood glucose and insulin levels rose 60 minutes after training but were back to the same level as during exercise at the 120 minute mark. As has been seen in other studies, blood flow to the trained muscles was increased immediately after training and decreased back to normal by 60 minutes after the drink was given. At the 30 minute mark, although both milk and soy protein showed a peak in terms of total amino acids, the soy protein showed a higher peak consistent with it being a fast protein compared to the milk. Blood amino acids returned to normal by the three hour mark after consumption.

Of most interest, fractional synthetic rate in the trained muscles was measured for 3 hours following training and was found to be 34% greater for the milk trial compared to the soy trial. That is, milk protein generated a significantly larger stimulation of protein synthesis compared to the soy drink.

Since both soy and milk provide equal amounts of the essential amino acids, the researchers concluded that that could not be the cause of the difference. Since blood glucose and insulin changed more or less identically for both proteins, that couldn't explain it either.

The most logical conclusion, and other research has suggested this previously, is that the digestion rate of the proteins were the determining factor. Previous research supports this idea. In this study, soy generated a faster peak in amino acid levels followed by a relatively faster drop while the milk generated a more even and sustained increase in amino acid levels. Previous research by Phillips suggests that consumption of milk proteins following training leads to greater LBM gains than soy in the long-term as well

Interestingly, the difference between soy and milk occurred despite the presence of other nutrients (fats/carbs) in the drink; I say interestingly because previous research comparing whey and casein found less of a difference when the whey was consumed with other nutrients.

However, this doesn't seem to be the case following training, at least not with the amounts of other nutrients given (perhaps more fat would have slowed down the soy and minimized the impact).

In any case, I think this study raises some interesting questions about the optimality of consuming a fast protein (such as whey) immediately after training. My personal current belief is that whey should be consumed before and/or during training and something like milk protein isolate (or simply milk) would be better following training; this study would seem to support that belief

[g-men]

Je zou denken dat hoe sneller de proteine des te beter na de training.

Soy proteine is sneller als melk proteine (gemeten na 30 minuten een grotere piek van soy) maar toch is de toename van LBM groter bij Melk proteine.

Ik heb hier nog wel vraagtekens over, hoe sneller de proteine des te eerder kan het herstel toch beginnen zou je zeggen?

Daarna is het blijkbaar goed om iets langzamere proteine te hebben zoals caseine om het lichaam voor een langere periode van proteine te voorzien.

Het lijkt mij dan ideaal om je wheyproteine te mixxen met melk voor na je training. Veel snel en veel langzaam.


Toch wordt dit meestal weer afgeraden.

[DutchVince]

Het zit 'm hierin denk ik:

In this study, soy generated a faster peak in amino acid levels followed by a relatively faster drop while the milk generated a more even and sustained increase in amino acid levels.

De snelle soja proteïne piekt snel maar valt snel terug.
Het melk proteïne nivo stijgt langzamer maar blijft daarna langer op een hoger nivo.