By Michael Lohre MS, HFI

Recently, chocolate milk has received a substantial amount of publicity as a recovery drink. As a scientist and endurance athlete who has religiously used recovery formulas for 10+ years, I chose to take a closer look at chocolate milk for meeting an athlete’s post-workout needs.

Chocolate milk is familiar, affordable and delicious. No wonder it has become popular with endurance athletes looking for a tasty and convenient recovery drink. But the question we want to answer is whether or not chocolate milk is indeed a superior recovery formula. We are not disputing its price, taste, or its nutritional value. So let’s compare an athlete’s nutritional recovery needs after a workout to what chocolate milk actually provides.

The main goal of a post-exercise recovery drink is to promote muscle glycogen synthesis and fluid recovery. After a workout, your body needs three things quickly:

1.  Rehydration with fluids to replace those lost during exercise.
2.  Replenishment of carbohydrate calories to replace used energy stores (glycogen).
3.  Quality protein to repair and prevent muscle breakdown.

 

First, let’s consider rehydration. Dehydration is an unavoidable result of prolonged physical exercise. Recovery begins with replenishment of lost fluids to quickly reverse the negative effects of dehydration. Rehydration reduces acidity of the stomach, cools core temperature, increases blood flow to muscles and skin, and removes cellular waste while delivering cellular metabolites. These metabolic activities are the foundation of your recovery. Muscle cramps and post-event injuries are often the result of an athlete failing to rehydrate in a timely fashion. Research has shown that the most quickly absorbed fluid in the gut is cool water (1).  The addition of carbohydrates, protein and especially fats, will slow the absorption rate of any liquid.  Therefore, the challenge to recovery nutrition is to provide calories while maintaining a high absorption rate for the liquid. 

I was only able to find one study investigating low-fat milk as a rehydration beverage (no additional studies seem to exist using chocolate milk) (2). Interestingly enough, almost all articles written about the benefits of chocolate milk as a recovery drink refer back to this one study!

This study compared the effectiveness of low-fat milk, a sports drink, and water at restoring fluid lost after exercise in a hot environment. The author of this study concluded that milk was superior to the sports drink and water in promoting rehydration due to lower total urinary output in a 1 to 2 hour time period post-workout. Relative to the amount of liquid consumed, those subjects that drank milk produced the least urine, which means milk proved to be superior in fluid retention 1-2 hours post-workout. Although this fluid retention may suggest recovery potential, fluid retention does little for hydration if the fluid remains in the gut and doesn’t reach the circulation. The author of the study did infer that milk’s slower rate of absorption probably accounted for the reduced urinary output but failed to discuss how this slower absorption rate may be detrimental to rehydration and recovery.

Unfortunately, science can be leveraged for an agenda and I speculate that the dairy industry provided funding for this research. Why would an educated researcher choose to include a slow absorbing liquid like milk in a rehydration study? If Exon/Mobile were to have funded this research using the same experimental design they may have shown that motor oil was the superior rehydration beverage because after consuming motor oil, no fluid would leave the gut and urinary output would be greatly reduced. Obviously, motor oil is toxic and is not a recovery beverage, and of course, milk provides nutrition and fluids whereas motor oil does not. But to my point, decreased urinary output itself does not tell us if the fluid is being shuttled to recovery processes within the body. Touting retained fluid or decreased urinary output as “better rehydration” is a guess at best, since the fluid could easily be gridlocked in the gut due to slow absorption.

Numerous other studies have examined rehydration (3). The consensus of these findings indicates that fluid absorption through the intestine must be maximized to support optimal rehydration. The fluid in milk, instead of being available within the circulation, is delayed in the gut. Milk has a high fluid concentration and, like any palatable liquid, will contribute to hydration. However, a proper recovery drink should maximize absorption rate through the gut wall to quickly restore fluid balance to dehydrated muscles. For rehydration, milk is better than not consuming any fluid at all, but milk can’t compete with water or properly designed sports drinks.

Second, let’s discuss glycogen replenishment. Glycogen is the carbohydrate stored in human muscle and liver tissue and is the premier fuel for athletic activity. Muscle glycogen storage levels present before a bout of exercise are the best predictor of athletic performance. In restoring lost glycogen post-workout, time is of the essence. The enzyme responsible for synthesizing glycogen (glycogen synthase) is relatively inactive except for a short time window immediately after exercise. To maximize glycogen synthesis you must begin your recovery nutrition immediately after the cessation of exercise. Two hours post-workout, your ability to store glycogen is reduced by 50% (4). If you fail to provide glycogen synthase with sufficient carbohydrate in a timely fashion, you will not recover effectively and subsequent workouts will suffer (5).

Controlled studies that measure milk’s effect on muscle glycogen recovery following prolonged endurance exercise do not exist. However, a few decades of research have examined the most effective nutrients for promoting glycogen replenishment. A mixture of high-glycemic carbohydrates and protein in a 4:1 ratio has proven to be most effective (6). Many commercial recovery formulas approximate this ratio of carbohydrates and protein as does chocolate milk. Glycemic index is a measure for how quickly a carbohydrate enters the blood as glucose. High glycemic index carbohydrates are rapidly absorbed and create a strong insulin response. A strong insulin response is favorable post-workout because it facilitates glycogen formation, increases muscle blood flow and increases amino acid uptake into muscle cells (7). Foods are assigned a glycemic index value between 0 and 100. Foods with higher values enter the blood as glucose quicker than foods with a lower value. Remember, glucose is the substrate for glycogen synthesis so high glycemic carbohydrates are ideal for time-sensitive glycogen replenishment after exercise.

Lactose is the predominant carbohydrate in milk. Lactose has a very low glycemic index (digests slowly) as does low-fat skim milk with a glycemic index value of 32. Commercial chocolate milk also contains high-fructose corn syrup (HFCS) which contributes to total carbohydrate content. Unfortunately, HFCS also has a low-glycemic index and consequently chocolate milk’s glycemic index is only 24. This is one of the lowest values of any carbohydrate containing food that has been tested! For comparison, most commercial recovery products contain maltodextrin or dextrose, both having a glycemic index of 100. For more information about glycemic index and a chart of glycemic index for common foods visit: (8)
Chocolate milk’s low glycemic index makes it a poor choice for replacing glycogen stores after training. However, except for that brief window of time immediately after training when one is most interested in restoring glycogen and promoting insulin secretion, an athlete should normally consume low glycemic index carbohydrate foods such as milk. Eating low glycemic meals between workouts results in lower blood sugar spikes and more sustained levels of blood glucose. The health benefits of eating a diet rich in complex, low-glycemic index carbohydrates is well documented. Milk also has a desirable ratio of carbohydrates to protein and may be a quality source of additional calories for meals other than your immediate post-workout nutrition.

Third, let’s discuss quality protein. Stimulation of protein synthesis is essential to all athletes for rebuilding and repairing muscle tissue. Protein synthesis is activated by an elevated blood amino acid level, which is accomplished with protein consumption. Your ability to synthesize protein after exercise is three times greater than at rest if you sufficiently raise your blood amino acids levels (9).

Milk is composed of both whey and casein proteins. Both proteins are high quality and provide the muscles with the ideal combinations of amino acids. However, milk’s slow absorption rate from the gut delays these amino acids from entering the blood stream. In addition to this delay, casein makes up a significant percentage of the protein in milk and has a very slow digestion rate. If your goal is to supply amino acids to repair the muscles as quickly as possible, then milk is a poor choice for delivery. Delivery of protein in a whey concentrate, hyrdolysate, or isolate form, not milk, will best support your recovery.

In addition to slow absorption rates and providing low glycemic index carbohydrates, milk has two other deficiencies that make it less than ideal as a recovery drink. First, a large proportion of the population is lactose intolerant. Lactose intolerance differs between races with those of Caucasian heritage less likely to be lactose intolerant than those of Asian or African descent. However, the incidence of lactose intolerance among adults is significant and one source suggests that as high as 90% of the world’s adult population may be intolerant (10). If you are lactose intolerant and have trouble digesting milk, you should not use milk as a recovery formula. Secondly, milk is prone to spoil, has a short shelf life, and must be kept cold. If you need a recovery drink immediately after a workout, you may have trouble keeping milk readily available and usable.

In conclusion, although low-fat milk is a nutritious beverage and better than nothing if consumed post-workout, it is far from an ideal recovery drink. The optimal recovery formula should “dump” water, glucose, and amino acids into the circulation, taking advantage of the unique biochemical conditions that exist post-workout to synthesize glycogen and muscle protein. Although milk does contain both high-quality proteins and carbohydrates, these nutrients are difficult to digest and absorb. They “trickle” into the blood stream and are circulated too slowly to provide the nutrition in a timely fashion to optimize recovery. The same properties that preclude milk from being a superior recovery drink may make it an ideal addition to the diet for meals other than your recovery nutrition. Slowly released carbohydrates and proteins are ideal any time other than post-workout, as they provide cells with a steady supply of macronutrients.

If milk isn’t the answer, then what is a good recovery formula? There are a handful of quality recovery drinks on the market and many sports supplement companies manufacture their own recovery blend. Look at the ingredients when selecting a product. The first ingredient should be a high glycemic index carbohydrate, most often taking the form of maltodextrin or dextrose. Whey protein should accompany these ingredients and make up around 20% of total calories. Do not purchase a product whose first ingredient is high-fructose corn syrup or sucrose (table sugar). These sugars, although sweet and inexpensive, have low glycemic indexes, delivering glucose too slowly for efficient glycogen synthesis after exercise.

One downfall of commercial mixes, especially in comparison to milk, is their relative cost per serving. Commercial formulas are usually two to three times as expensive as the equivalent caloric amount of chocolate milk. I started producing  Mike’s Mix Recovery Drink as an alternative to the more expensive commercial formulas. Mike’s Mix if formulated in accordance with the research on recovery nutrition. It’s made from all-natural ingredients and is offered at a price to fit every athlete’s budget. You won’t find a more effective product at a better price. Mike’s Mix is still a bit more expensive than chocolate milk ($1.10 compared to $.80 for equal caloric servings), but for an extra 30 cents you are getting a superior recovery product. Mike’s Mix is quickly absorbed and easy on the stomach. It maximizes glycogen synthesis by providing the optimal ratio of high-glycemic carbohydrate and offers 20 grams of quickly digesting whey protein. Also, it mixes instantly and tastes great. You work hard when you train, make sure that your nutrition is also working hard for you.