To Spit or to Swallow - That is the Question! Carbohydrate Mouthrinse May Be Better Than Water, Yet Still Not an Option for Performance Oriented Athletes

Image 1: "You need carbs to fuel your workouts!" You know the whole litany... what may be news to you is that scientists are speculating that "intra workout carbs" do not necessarily have to be ingested to do their ergogenic magic.

Those of you, who already "friended" me on Facebook and are following what is going on on the SuppVersity Facebook page (just want to remind you that Facebook has now an option that allows you to be informed, whenever something new is posted), will probably remember the discussion revolving around "carbohydrate mouthrinsing" and whether or not it may be even more beneficial to spit and not to drink your Gatorade... now, all the health benefits of low-carbohydrate (when I am talking "low" I am not talking of Atkins type <80g) diets aside, it does seem pretty counter-intuitive that just swishing one of those carbohydrate-laden electrolyte drinks in between your teeth for a few seconds, to then spit it out again could actually have any merit. Yet, science, or I should say a handful of studies, do suggest otherwise.

As part of their recently published study into the effects of carbohydrate mouthrinsing on exercise capacity in the pre- and postprandial state (Fares. 2011), Elie-J. M. Fares and Bengt Kayser have compiled a list of the 8 hitherto published peer-reviewed papers on that subject. And if you just went by the column "increased perfomance", "yes or no", it appears like it was an established fact that carbohydrate mouthrinsing was highly ergogenic. After all, six out of the eight studies are marked with the tag "increased performance".

Figure 1: Performance increases and standard deviations of the respective measures from studies on the advantage of carbohydrate vs. artificially sweetened or plain water mouthrinse (data calculated based on summary in table 2 of (Fares. 2011)

If we do yet have a look at the quantity of those performance increases and the individual standard deviations (I compiled the respective data for you in figure 1), things begin to look less conclusive. I mean, there is obviously a standard deviation for both arms of each study and there also is a mean improvement (or decrease in performance), but if the "performance increment" is smaller than the standard deviation, for all but one study, this does make me feel uncomfortable with the statement that I would see "scientific evidence", let alone "conclusive scientific evidence" in support of carbohydrate mouth-rinses.

Mouthrinse vs. placebo = minimal (if any advantage), but what about vs. ingestion?

Regardless of what you think about the real world significance of an average performance increase of 1% (calculated based on the data from figure 1), for the small fraction of athletes for whom these minimal performance increases would actually count, i.e. high intensity endurance athletes, like time-trial Tour de France cyclists, the "control", or I should say the "benchmark" should not be plain or sweetened water, but rather one of these crab-, ah... pardon me, carb-loaden sugary electrolyte drinks these athletes are habitually consuming. I was thusly happy to see that Catherine Moss, a student of Sports and Exercise Sciences at the Massey University in Auckland, New Zealand has recently conducted an experiment for her thesis that has much more practical relevance for the high achieving athletes (Moss. 2011).

Table 1: Composition of the placebo and CHO supplement in the Moss study (adopted from Moss. 2011)

In a randomized, counter-balanced, double-blind study, Moss had eight recreationally trained cyclists perform a time trial (with a predetermined amount of work) in the course of which the cyclists ingested or rinsed (swirling 0.33ml/kg body weight of the solution for 8s) with either a placebo solution or a carbohydrate drink, whenever another 12.5% of the total work was done. In that it is worth mentioning that the composition of the CHO solutions differed for the one that was meant to be ingested and the one that was intended to be swished. With the former containing 7.5% and the latter 15% carbs, Moss mimicked solutions that had been used "successfully" previous studies. I do yet no idea, why the placebo did not contain electrolytes, as this could obviously have made a difference at least in the ingestion trials... I guess this is what distinguishes a thesis like this from a study that is worth being published in a peer-reviewed journal ;-)

Figure 2: Mean power output (in Watts) at different time points during time trial (data adapted from Moss. 2011).

As the performance data in figure 2 goes to show, only the ingestion of the carbohydrate led to significant improvements in mean power output, specifically at the later stages of the time trial. This "breakdown" may be explained by the "glycogen reduction exercise protocol" all participants had conducted the day before the time trial. So that after a "low carbohydrate" dinner, the participants were supposed to be glycogen depleted when they performed the time-trial on the subsequent morning.

Figure 3: Total time (in s) during time trial (data adapted from Moss. 2011).

In a way this is an unfair advantage, for the carb ingestion, which accordingly elicited way better time trial times. It does yet not lessen the significance of data on carbohydrate vs. water mouth rinse, which shows pretty conclusively that in a glycogen depleted state both forms of mouthrinsing (plain water or a 15% carbohydrate solution) are equally ineffective, when it comes to actual performance increases.

Figure 4: Pleasure / displeasure feeling during time trial (data adapted from Moss. 2011).

If you do however look at the pleasure/displeasure feeling scale data in figure 4, I would speculate that in a non-glycogen depleted state the carbohydrate-rinsers would have performed significantly better... I mean, without gas in the tank a car won't work even if it "wanted". In view of the fact that the carbohydrate ingestion group did yet pedal at a higher intensity, this would warrant further investigation.

Figure 5: Respiratory exchange ratio (higher values = higher carbohydrate oxidation) during time trial (data adapted from Moss. 2011).

That being said, there was what I consider an interesting effect of carbohydrate rinsing on the respiratory exchange ratio (remember higher values = higher carb oxidation), which would suggest that the theory Fares and Kayser propose (Fares. 2011), according to which the activation of sweetness taste receptors cells (T1R2 and T1R3) in the mouth would explain the previously cited performance "increases" in other studies, may have its merits. What else than the sensation of incoming carbs could explain that the cyclists burned more carbs in the carb mouthrinse compared to the placebo mouthrinse trial (cf. figure 5) - and that in the absence of significant differences in blood glucose or insulin levels?

Spit it or suck it? What's right for you?

While we do not know whether it would make sense to mouthrinse in a glycogen repleted state (yeah, I know +1% ;-), for any athlete interested in maximal performance, simply ingesting his carb + electrolyte drink would certainly be the best option. The (intermittendly) fasting dieter, who wants to maximize his fatty acid oxidation in the course of say his "morning cardio", on the other hand, would be best off with a non-carby electrolyte drink that helps him avoid dehydration and does not compromise (even if the effect is minimal) fatty acid oxidation... what? You want to know who would  benefit from spitting his carbs out? Well, at least based on the current data, mostly the cleaning contractors of your local gym - after all, they would have to work overtime (and be paid overtime) to clean up the mess ;-)

Milk & Exercise a Perfect Match? A Summary of the Latest Scientific Studies on Its Ability to Sustain Muscle Growth, Protect from Muscle Damage, Binges and Dehydration

Is milk the perfect fluid replacement + anti-post-workout binge + muscle protector for gymrats, fitness junkies and professional athletes? 

It stands out of question. Compared to Coke and many of the so-called "sports-" or "energy drinks" that are in fact no much more than over-caffeinated liquid sugar bars, milk is a healthy beverage. Whether it's also a potent ergogenic though, is still intensely debated.

A recent study from the McMaster University in Hamilton, Ontaria, for example, indicates that the initial surge in post-workout protein synthesis cannot be sustained solely by the low amount of protein in regular milk (Volterman. 2015). Its inability to trigger longlasting increases in protein synthesis and thus to promote a positive whole body protein balance does yet not negate the already proven benefits milk and some of its less-known constituent (I am not talking about whey or casein!) may have for athletes and gymrats.

You can learn more about dairy at the SuppVersity

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You want to know what kind of advantages this may be? Well, here is a brief overview of the latest scientific evidence that is either directly or indirectly related to potential beneficial effects of milk:

• Consumption of 500 ml of milk post-exercise-induced muscle damage can limit decrements in muscle function in females, and limit increases in soreness and serum markers of muscle damage in females and males.
  
  That's not something I say, but something, scientists from the Institute of Technology in Carlow, Ireland, conclude based on their observations in 32 team sport players (male n = 16; female n = 16) who were randomly, but equally divided into four groups: male milk, male carbohydrate, female milk, and female carbohydrate. Immediately following muscle damaging exercise, participants consumed either 500 ml of milk or 500 ml of an energy-matched carbohydrate solution. Skeletal troponin I (sTnI), creatine kinase (CK), peak torque, counter movement jump height, 20 m sprint performance and passive and active soreness were recorded prior to and 24, 48 and 72 h post-exercise-induced muscle damage (EIMD).
  

  

  Figure 1: Brief overview of the most important facts (Rankin. 2015).

  What the scientists found was that the women experienced likely to very likely beneficial effect on attenuating losses in peak torque at 60°/s from baseline to 24, 48 and 72 h, and a likely beneficial effect in minimizing decrements in sprint performance and soreness over 72 h. Furthermore, the milk consumption was unlikely to have a negative effect on serum markers of damage from baseline to 48 and 72 h.
  
  For males, on the other hand, milk had an unclear effect on muscle function variables. Milk had a most likely/likely beneficial effect on limiting muscle soreness from baseline to 72 h, and a possible beneficial effect on attenuating increases in CK. The effect on sTnI was unlikely to be negative from baseline-72 h. In that, the female participants demonstrated smaller increases in sprint time, passive soreness, active soreness (non-dominant leg) and sTnI values and did thus benefit to a greater yet not significantly greater extent from the 500 ml of milk - that's a difference that could be both sex- and/or protein-specific; I mean, for a man, 500 ml of milk yield significantly less protein on a per kg body weight basis than the same 500 ml do for a woman. That's a difference that could well partly explain why women benefit more from milk vs. carbohydrates only compared to men.
• The consumption of skimmed milk following 30 min of moderate-vigorous cycling exercise reduces subsequent energy intake in female recreational exercisers.
  
  Obviously, working out will only help you shed body fat if the increased energy expenditure during the workout is not (over-)compensated by increased food intake after your workouts. Against that background the results from a recent study from the Northumbria University (Rumbold. 2015) are significant, because they indicate that 600 mL of skimmed milk have a significantly more pronounced "anti-binging" effect than 600 mL of an isocaloric orange drink when they are ingested immediately after a workout.
  

  

  Figure 2: Absolute and relative energy intake during the milk vs. orange juice trials (Rumbold. 2015).

  As the data in Figure 2 indicates the 9 female recreational exercisers (19.7 ± 1.3 years) who completed a standardized exercise regimen consisting of an VO2 peak test and 30 min of moderate-vigorous exercise (65% V̇O2peak) consumed 25.2% ± 16.6% less energy on an ad-libitum pasta meal that was served 60 minutes after the workout.
  
  If we assume that they women didn't compensate for the "missing" 25% of the energy later during the day and assuming that they did the workout 2x per week, the 169kcal per workout would yield a total fat loss of 1.9kg per 6 months - well, if the 7,000kcal deficit per 1kg of fat equation actually held ;-)
• Milk-based drinks are more effective rehydration options compared with traditional sports drinks. The additional energy, protein, and sodium in a milk-based liquid meal supplement facilitate superior fluid recovery following exercise.
  
  The aim of a recent study from the Griffith University study was to compare the rehydration potential of a carbohydrate-electrolyte beverage with several varieties of milk following exercise-induced fluid losses. Fifteen male participants (age 24.9 ± 5.5 years, height 179.3 ± 4.9 cm, body mass 75.8 ± 6.6 kg (mean ± SD)) lost 2.0% ± 0.2% body mass through intermittent cycling before consuming a different beverage on 4 separate occasions.
  
  The drinks that were tested included cow's milk (286 kJ·100 mL(-1)), soy milk (273 kJ·100 mL(-1)), a milk-based liquid meal supplement (Sustagen Sport (Nestle); 417 kJ·100 mL(-1)), and a sports drink (Powerade (Coca Cola Ltd); 129 kJ·100 mL(-1)). Beverages were consumed over 1 h in volumes equivalent to 150% of body mass loss. Body mass, blood and urine samples, and measures of gastrointestinal tolerance were obtained before and hourly for 4 h after beverage consumption.
  

  

  Figure 3: Overview of the most important study results (Desbrow. 2014).

  The results show that the net body mass at the conclusion of each trial was significantly less with Powerade (-1.37 ± 0.3 kg) than with cow's milk (-0.92 ± 0.48 kg), soy milk (-0.78 ± 0.37 kg), and Sustagen Sport (-0.48 ± 0.39 kg). Net body mass was also significantly greater for Sustagen Sport compared with cow's milk trials, but not soy milk. Upon completion of trials, the percentage of beverage retained was Sustagen Sport 65.1% ± 14.7%, soy milk 46.9% ± 19.9%, cow's milk 40.0% ± 24.9%, and Powerade 16.6% ± 16.5%.
  
  If it were not for the fact that some of the subjects were complaining over increased bloating and fullnessduring all milk trials compared with Powerade, there would thus be no reason to go for the "classic" high carb + electrolyte solutions.

Are the hormonal side effects of dairy and its cancerous consequences even worse than they're painted by the steadily growing anti-dairy lobby? Find the answer to this and related questions in a previous SuppVersity article from January 2014 | read more.

Not all that glitters white like milk is gold, though. Only recently scientists from the Tokyo Metropolitan Institute of Gerontology had to realize that milk fat globule membranes, of which previous studies have shown that they may help avoiding metabolic syndrome (Pfeuffer. 2007), do not boost the already beneficial effects of exercise on the frailty status of elderly men and women (Kim. 2015).

Just like the previously discussed disappointing results of the Volterman (2014) study, the results Kim et al. present in their latest study do not negate the existing beneficial effects on satiety / anti-binging, muscle damage and function in response to muscle damaging exercise and rehydration discussed in this article | Comment on Facebook!

References:

• Desbrow, Ben, et al. "Comparing the rehydration potential of different milk-based drinks to a carbohydrate–electrolyte beverage." Applied Physiology, Nutrition, and Metabolism 39.12 (2014): 1366-1372.
• Kim H, Suzuki T, Kim M, Kojima N, Ota N, Shimotoyodome A, Hase T, Hosoi E, Yoshida H. "Effects of Exercise and Milk Fat Globule Membrane (MFGM) Supplementation on Body Composition, Physical Function, and Hematological Parameters in Community-Dwelling Frail Japanese Women: A Randomized Double Blind, Placebo-Controlled, Follow-Up Trial." PLoS One 6;10.2 (2015):e0116256.
• Pfeuffer, M., and J. Schrezenmeir. "Milk and the metabolic syndrome." Obesity reviews 8.2 (2007): 109-118.
• Rankin P, Stevenson E, Cockburn E. "The effect of milk on the attenuation of exercise-induced muscle damage in males and females. Eur J Appl Physiol. (2015): Feb 12. [Epub ahead of print] 
• Rumbold, Penny, et al. "Milk Consumption Following Exercise Reduces Subsequent Energy Intake in Female Recreational Exercisers." Nutrients 7.1 (2015): 293-305.
• Volterman, Kimberly A., et al. "Effects of postexercise milk consumption on whole body protein balance in youth." Journal of Applied Physiology 117.10 (2014): 1165-1169.