The Fast vs. Slow Protein Craze..
The use of fasted subjects in nutrition studies illustrates how researchers can end up with results that may not apply well to the real world. As the name implies, the study subjects are a group of people who have not eaten for an extended period of time. In many cases, they haven’t eaten for 8 – 10 hours or more, which of course does not reflect how the average person eats, at let alone how the average athlete eats—especially bodybuilders looking to add muscle mass.
Enter stage right, the “fast vs. slow” protein craze. The study that got this craze rolling was called “Slow and fast dietary proteins differently modulate postprandial protein accretion” and was responsible for causing a resurgence of interest in casein. The basic premise of this much-touted study was that the speed of absorption of dietary amino acids (from ingested proteins) varies according to the type of dietary protein a person eats.
The researchers wanted to see if the type of protein eaten would affect postprandial (e.g., after a meal) protein synthesis, breakdown, and deposition. To test the hypothesis, they fed casein (CAS) and whey protein (WP) to a group of healthy adults, a single meal of casein (CAS) or whey WP following an overnight fast (10 h). Using this specific study design, they found:
•WP induced a dramatic but short increase of plasma amino acids.
•CAS induced a prolonged plateau of a moderate increase in amino acids (hyperaminoacidemia)
•Whole body protein breakdown was inhibited by 34% after CAS ingestion but not after WP ingestion.
•Postprandial protein synthesis was stimulated by 68% with the WP meal and to a lesser extent (+31%) with the CAS meal.
The basic non-science summary is: the study found that CAS was good at preventing protein breakdown (proteolysis), but was not so good for increasing protein synthesis. WP had basically the opposite effects: it increased protein synthesis but didn’t prevent protein breakdown. The problem is that they were using fasted subjects for a single meal. ***
Keep that in mind as we move along here…
So far so good right? So what can we conclude from this study and how useful are the results? Like so many studies, the results were interesting—and of little use to people in the real world. Do these results hold up under more “real world” conditions where people are eating every few hours and/or mixing the proteins with other macronutrients (i.e., carbs and fats)?
The answer is probably not, which is exactly what the researchers found when they attempted to mimic a more realistic eating pattern of multiple meals and or the addition of other macronutrients. The follow up study was called “The digestion rate of protein is an independent regulating factor of postprandial protein retention.” Four groups of five to six healthy young men received:
• a single meal of slowly digested casein (CAS).
• a single meal of free amino acids mimicking the composition of casein (AA).
• a single meal of rapidly digested whey proteins (WP).
• repeated meals of whey proteins (RPT-WP) mimicking slow digestion rate of casein (i.e., reflecting how people really eat).
So what did they find? In a nut shell, giving people multiple doses of whey—which more closely mimics how people really eat-—had basically the same effects as a single dose of casein, and mixing either with fats and proteins pretty much nullified any big differences between the two proteins.
Even that’s not the end of the story, however, as multiple follow up studies done by the same group and others found these effects could also be different in older versus younger people and male versus female! How messed up is that?! So how much press did these follow up studies get? Little or none, as I recall.
Now, a later study did attempt to examine the actual net amino acid uptake after resistance training with whey vs. casein, and found both proteins had essentially the same effects on net muscle protein synthesis after exercise despite different patterns of blood amino acid responses.
Does that put to rest the issue or debate of one protein vs. the other post-workout? No, as there are yet more conflicting studies out there and my bet is still on whey as the superior post-workout protein, but it’s important to realize the answer is far from established at this time.
Got Milk?
Milk: nature’s original MRP. Despite all the fancy proteins out there all claiming to be the next step in the evolution of proteins that “will blast you past your plateaus in the gym,” good old milk seems to be competing—and winning—against some “high tech” products on the market. We have various studies finding increased protein synthesis and other positive effects when a purified protein supplement (e.g., whey, soy, casein, etc.) ingested right after or before a workout—usually in conjunction with carbohydrates—but what about good old milk, a “real” food?
One recent study found good old milk to be an effective post-workout drink that increased net muscle protein synthesis after resistance training. Yet another recent study compared 2 cups of skim milk as a post workout drink compared to a soy drink and a “sports drink.”
In this study, the milk and soy drinks were matched for basic macronutrient ratios and calories and all three were matched for total calories. 56 male volunteers were split into three groups, with all put on a resistance training program for 12 weeks. The volunteers were then randomly assigned one of the three drinks to consume as a post workout drink and again one hour after the workouts.
Although no major differences were found in strength between the 3 groups, the group getting the milk had the greatest increase in muscle mass (via increases in Type I and II fibers) with researchers concluding
“…chronic postexercise consumption of milk promotes greater hypertrophy during the early stages of resistance training in novice weightlifters when compared with isoenergetic soy or carbohydrate consumption.”
But it gets better: how about our favorite childhood drink, chocolate milk? How about chocolate milk vs. two commercial energy/fluid replacement drinks, such as Gatorade and Endurox R4?
One recent study—albeit a small one—found chocolate milk as effective as Gatorade, and more effective than Endurox, as a recovery drink for trained cyclists between exhaustive bouts of endurance exercise.
Now is this a condemnation of sports drinks and an endorsement for milk/chocolate milk as the last word on post-workout drinks? Not at all: remember those essential questions I mentioned above? You have to look at such a study in context—in other words, at the experimental design and how that applies to the “real world.” The subjects fasted for 10 - 12 h prior to the chocolate milk experiment, and these drinks were the only food these guys had for 14 - 16 hours. The results may have been quite different had they been following their normal eating patterns.
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