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Wannabebig Round Table - Issue 3
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Nutrition
Q: Is it better to mix my post-workout shake with water or milk? I find that when I mix my shake with milk I feel bloated for several hours afterwards.
A: Blood & Iron:
First, let me get the obvious answer out of the way: if drinking a shake made with milk makes you feel crappy--due to lactose intolerance, or just by filling you up too much, or whatever--use water. Pretty simple. As long as you're training approach isn't too retarded, and you're eating in a manner to support your goals (i.e. a slight caloric deficit if you're dieting, or a moderate caloric excess if trying to gain) whether you mix your post-workout shake with water or milk is probably not going to make a whole lot of difference. That said, there are a couple of more interesting issues this question brings up, the first being whether you should be having a post-workout shake at all. Let me explain.
It's pretty standard dogma by now that one should always have a post-workout shake after training. In fact, this may be too late to optimally take advantage of the 'anabolic window' that occurs during and after training. Tipton et al. looked at muscle protein synthesis when a shake, which consisted of 35g of sucrose(AKA table sugar) and 6g of essential amino acids, was consumed either immediately prior to or immediately following a training session consisting of 10 sets of 8 repetitions of the leg press and 8 sets of 8 repetitions of the leg extension. (3) The researchers then looked at phenylalanine uptake (which is an indicator of muscle protein synthesis) across the leg to see which had the great anabolic effect. They found that consuming the shake prior to exercise resulted in over twice as much phenylalanine being taken up. By consuming the shake pre-workout, amino acids are available during a period of increased blood flow to the leg which results in greater delivery of those aminos to muscle tissue. I generally have both a shake prior to and following my workouts--and if you look at this study more carefully, the data supports this approach. If, however, you are only going to have one shake, I think it's clear that it is a much better idea to consume it pre-workout rather than post-workout. Unfortunately, it may cause stomach upset for some. If, however, you keep the shake small (As this study demonstrates it does not take much to significantly elevate protein synthesis--here it was only 6g of aminos and 35g of sugar.) and mix it with a minimal amount of liquid, it should not present too much of a problem.
The other issue that this question brings up is that of protein types. If you are having ONLY a pre-workout shake OR a post-workout shake, I would say adding milk is, in general, a bad idea. It will slow the absorption of amino acids in the gut during a period when you want a rapid increase in blood amino-acid levels. Milk protein is composed of two fractions, which are casein (accounting for approximately 80% of the protein in milk) and whey (which accounts for the remaining 20%) These have, respectively, been characterized as 'slow' and 'fast' proteins according to the rate at which they are digested and the speed at which amino-acids enter the bloodstream. (1) Whey results in a rapid, high spike in blood amino acid level which is highly anabolic, whereas casein results in a slow, steady increase in plasma amino-acid levels that is anti-catabolic in nature. (2) Mahe et al, who looked at the differences in digestion between casein and beta-lactoglobulin (which is the major subfraction in whey) found that casein clots in the acidic environment of the stomach, which delays gastric emptying, and results in a prolonged, steady released of amino-acids. Whey, in contrast, remains soluble in the stomach, and quickly makes its way further down the digestive track resulting in the characteristic rapid peak in blood amino levels.
Okay, back to the original question. Now, if you've followed the advice above, and switched to having a pre-workout shake, what you have as your post-workout shake will depend on how long you are going to go before your next meal. If you are not going to be able to eat for some time, it is probably better to mix your post-workout shake with milk. While some have inferred from the research that by consuming both casein and whey together you'll get both the anti-catabolic effects of casein along with the anabolism of whey, this is unlikely. As Lyle McDonald, and a number of others have pointed out, it is more likely that since casein clots in the gut, and slows gastric emptying, you'll be slowing down the whey, causing it to act much like casein. If you're not going to be eating for some time, this is exactly what you want: to curb catabolism until your next meal. If, however, you know you'll be having a protein rich meal within an hour or two after you training session, avoiding casein and using the 'anabolic window' again to cause a second rapid spike in blood aminos, may be to greater advantage.
A: Chicken Daddy:
Mixing your post-workout protein shake with milk is not a bad idea per se, but it’s sub-par. One of the functions that insulin works is by translocation of GLUT4 (‘glucose transporter 4’) receptors to the cell membrane (1). GLUT4 is basically one of the glucose receptors (there are others) that allow glucose uptake in the cell. Unfortunately, it does this not only in muscle cells, but also adipocytes (fat cells). Which explains how insulin can also be a ‘fattening’ hormone.
Translocation of GLUT4 can also occur due to muscular contractions (2). So, weight lifting alone increases muscular insulin sensitivity - called insulin independent glucose uptake. Because of this fact, this time is ideal to take advantage of the nutrient partitioning (basically means where the nutrients go) effects of training. So, ideally we’re looking at a quick digesting carbohydrate to replenish the glycogen used while training and a quicker digesting protein to provide amino acids due to the increased protein synthesis that comes after training (for up to 36 hours (3)). The quickest digesting carbohydrate, glucose - also known as dextrose or corn sugar or even grape sugar - is probably the best idea. It’s also very cheap, especially if bought in bulk. Maltodextrin is also a good available source. It is known as a ‘complex carbohydrate’, purely on the grounds that it is a glucose polymer consisting of about 3-8 molecules. It is therefore too long to be classed as ‘simple’, and since there is no mid-classification, complex it is. This doesn’t stop it from digesting very quickly and doing the same job to insulin that glucose does. Maltodextrin is also a carbohydrate exploited by supplement companies for this very reason. They can claim it is a complex carb and it’s great in their MRPs. In all truth, it is the guar gum that they put in these products that slow digestion, not the maltodextrin. Any other time of day, just like glucose, it is a poor choice.
Once you’ve got the basic idea of a simple sugar post-workout, then you can experiment using different combinations of glucose and maltodextrin. It is usually recommended to make a 50/50 mix of the two, based on the differing absorption rates of the two carbs. Glucose requires no digestion and so once in the intestinal tract can pass straight through the wall lining. Maltodextrin, however, requires a bit of digestion to split it into the glucose molecules that make it up. The difference of digestion is not really that much in the way of time, but can make a big difference. This is because glucose enters the cell via active transport (4) and only so much can get through at any one time once the receptors are all being utilised. By taking in maltodextrin, the longer digestion and absorption rate means the glucose from the malto is getting to the cell more or less once the first glucose molecules are in. So you’re basically ‘lining the glucose up’.
For protein, a quick-digesting source like hydrolysed whey or whey isolate fits the bill. Hydrolysed is a more expensive route to take and not absolutely necessary. Isolate will suffice.
You want quick absorption of this shake, so avoid fat in this ‘meal’. While something like oil may very well simply sit on top of the liquid in the stomach (5), it’s a different story when the fat is actually part of the food itself, which is the case with milk. The fat present will slow the digestion and absorption rates which is something you are actually trying to avoid in this time frame. As well, casein is the predominant protein that milk consists of (about 80% or so, with about 20% being whey). Casein actually forms clots in the stomach during digestion, forming a sort of paste that slows digestion further. Again, this is not something you’re striving for, so milk consumption during this time is not the obvious choice. There is some degree of controversy in the whey versus casein debate, but that is for another day.
So what I’ll say is that if you need the calories from the milk, drink it after your post-workout shake, about 90 minutes after is good, or as soon as you feel hungry if it is before this 90 minute bracket. Ideally, a simple sugar, quick-digesting protein is more suited for the post-workout window.
References:
(1) Need for GLUT4 activation to reach maximum effect of insulin-mediated glucose uptake in brown adipocytes isolated from GLUT4myc-expressing mice.
Diabetes. 2002 Sep;51(9):2719-26.
(2) Intracellular mechanisms underlying increases in glucose uptake in response to insulin or exercise in skeletal muscle.
Acta Physiol Scand. 2001 Mar;171(3):249-57
(3) The time course for elevated muscle protein synthesis following heavy resistance exercise.
Can J Appl Physiol. 1995 Dec;20(4):480-6.
(4) Post-ischemic stimulation of 2-deoxyglucose uptake in rat myocardium: role of translocation of Glut-4.
J Mol Cell Cardiol. 1998 Feb;30(2):393-403.
(5) Gastic emptying and intragastric distribution of lipids in man. A new scintigraphic method of study. Dig Dis Sci (1982) 27 (8): 705-711.
(6) In vivo and in vitro gastric emptying of milk replacers containing soybean proteins. J Dairy Sci. 1994 Feb;77(2):533-40.