Chocolate milk: Yummy, but not special.

The ‘original’ chocolate milk study came out in 2006. And it seems like the whole chocolate milk thing just won’t die. Alas, document delivery has yet to deliver the article to my inbox yet (have I mentioned how much I love the Internet?), so I leapt forward in time to look at another study in the small puddle of chocolate milk studies.

This study doesn’t quite get at the question, “How important, exactly, is post-workout nutrition?” but rather, “How does chocolate milk compare to other forms of post-workout nutrition?”

Gilson SF, Saunder MJ, Moran CW et al. Effects of chocolate milk consumption on markers of muscle recovery following soccer training: a randomized cross-over study. Journal of the International Society of Sports Nutrition, 7:19, 2010.

Introduction

I think we would all like to believe the pre, intra and post-workout nutrition are very important. We’ve seen one example of how pre-workout protein probably doesn’t really make any difference large enough to warrant the extra cost of consuming it. While there have been studies supporting the idea that post-workout nutrition is important and results in better recovery (a fairly vaguely defined term) and better results (an even more vaguely defined term), the debate around WHAT to consume after a workout takes most of us down a path of debate that I believe counts as pure, unadulterated intellectual masturbatory minutae.

But, don’t let my opinion count for much of anything.

Let us assume for the purposes of this review, that post-workout nutrition DOES matter. And furthermore, let us assume that post-workout nutrition matters for the non-elite typical gym go-fer.

What do we know about chocolate milk? We know it contains both protein and carbohydrate. We know that in head-to-head comparisons, it tends to do just as well, or better than carbohydrate drinks alone. However, we’re not sure whether the fact that in previous comparisons, the drinks weren’t calorie controlled might explain why it did so well or whether it actually does affect recovery insofar as we can measure it.

Methods

This study was a randomized cross-over trial of chocolate milk vs. a calorie-equivalent carbohydrate beverage in NCAA Division I soccer players.

Players were tested at baseline on a Monday, and then tested again on Wednesday and then Friday. During this time, they were in the off-season, but had their training volume increased by 25% above their normal volume for this time of year. They took their blinded drink after each training session. Their baseline training schedule was between 45 and 90 minutes of training, seven days a week. The increased training schedule was between 90 and 120 minutes of training, 4 consecutive days in the week.

Players were asked to rate their muscle soreness from 0-100, and mental and physical fatigue on a formal questionnaire. Blood samples were drawn and measured for creatine kinase (a marker for inflammation), and myoglobin (which appears in the blood as muscle is broken down). The players also underwent maximal voluntary contraction testing and performance tests (t-drill and vertical jump).

The players went through a two-week wash-out period between the two, two-week trials.

Statistics

I’m not going to go into a lot of the statistics here, but there is a paragraph that is quite troublesome, “Preliminary statistical analyses were performed on 17 subjects who completed all testing. However, some subjects exhibited large variances in baseline measurements between the two treatment periods, possibly due to activities outside of the study during the two unsupervised days prior to [pre-testing]. This resulted in significant group differences in numerous [pre-testing] measurements…The exclusion criteria had the intended effect of eliminating all significant differences in [pre-testing] values between treatments, making the interpretation of the data simpler. However, it should be noted that exclusion of these subjects did not alter the outcomes of any hypothesis testing…”

[What worries me about this study is that they started with 22 soccer players, but lost 5 subjects due to incomplete testing or training with and without injuries, and “excluded” 4 more players from the statistical analysis because of “large variations in dependent measurements between baseline periods…” I’m sorry, but you don’t get to pick and choose who you analyze or don’t analyze. And if the exclusion doesn’t affect the final interpretation, why exclude at all then? That’s called selection bias.]

Results

The average age of the players in this study was 19 years (SD 0.3 years)

Overall, there weren’t any notable differences between the carb-only drink and chocolate milk. Creatine kinase levels rose (predictably) with both drinks, although it did not tend to rise as much when the players had chocolate milk instead. The players tended to perform just as well whether they had a carb-only drink or chocolate milk.

However, the investigators in this study did not succeed in creating a 25% increase in training duration in these athletes. While training duration increased equally between the two drink trials, an average increase of 10 minutes per four days is not a 25% training increase. It’s more like an 11% training increase. Less than half of intended effect. So what we don’t know is whether either of these drinks produces different results if the training duration is increased beyond 11%.

Discussion

The authors of this paper use these results to encourage more study–a conclusion with which I agree. They do state that a major limitation of the study is that there was no placebo or control group–with which I also agree.

So what can we take away from all of this?

I think there are a few points that most readers of this blog can take away:

1) Unless you’re a 19 year old Division I soccer player, this study shouldn’t be the reason why you choose to drink anything after your workouts.

2) Any study that excludes subjects after having already analyzed the data should be under high suspicion of biased information. In this case, it probably didn’t matter, but we’ll never _really_ know.

3) I suspect that it doesn’t really matter what you drink after your workouts, if anything at all. If there are any applicable links between this study and you, the numbers suggest that you can pretty much do what you want and you’ll still play and test about the same.

So in the end, there isn’t anything magical about chocolate milk. If you’re drinking it anyways, good for you. If you’re not, there’s no reason for you to rush out and get any. Just do what you’re doing. Simplfy what you can, and rest assured that you’re not missing out.