Rethinking sports drinks

Is it necessary to spike insulin post workout? Generally no, or at least not to the degree that I was once taught. Sugar based sports drinks (Gatorade, Powerade, etc) are based off a simple concept –they rescue your blood sugar during a crash that usually occurs during high intensity sporting events and/or exercise sessions. They also will provide the fluids and minerals to support hydration and electrolyte balance. Most importantly, sugar-based sports drinks make the body rely on carbohydrate as a fuel while suppressing the breakdown of fat. What we really want is a postworkout drink that will provide a slower release of carbohydrate to give us a continuous source of fuel while also allowing the breakdown and utilization of fat. This is exactly what the Generation UCan pre/post-exercise supplement does.

Generation UCan for pre and post exercise.

This is a chart showing some of the downsides of a sugar-based sports drinks that is from the low-carb expert Jeff Volek (co-author of the Atkins Diet).
High osmolarity-Slows gastric emptying, increases gastric distress, limits amount of carbohydrate that can be provided
Rapidly increases blood glucose- requires you to drink it more, possible for rebound hypoglycemia (you get a sugar rush after drinking followed by below baseline blood sugar level)
Rapidly increases blood insulin– blocks fat breakdown, blocks fat oxidation, increased reliance on carb as a fuel, and chronic negative implications on body composition and health.

Alan Aragon’s research review from 2008 provides several articles providing information regarding the topic of insulin. We want to maximize muscle synthesis while minimizing protein breakdown after our workouts. Having high insulin levels (from the sugar based sports drink) does not minimize protein breakdown, in fact, no higher than insulin’s basal/resting levels. What we have failed to realize is that a pre-exercise meal does more than enough spiking to our insulin levels enough so that it is elevated up to 1 hour post exercise. To quote from Alan’s research review, “Rennie & colleagues found that even during a sustained high blood level of amino acids, no further inhibition of muscle protein breakdown occurred beyond insulin elevation to approx. 15 mU/l (slightly above normal resting levels). In more recent work by Greenhaff, a higher maximal anabolic threshold was found; an insulin level of 30 mU/l decreased muscle protein breakdown by half. Further insulin elevations failed to reduce muscle protein breakdown or increase anabolic signalling (again easily achieved from a pre-workout meal) (3).

Take home messages from the research…

  • Insulin levels beyond small-moderate amounts (15-30 mU/l) does not further inhibit muscle protein breakdown.  Moderate sized meals (pre-training) can easily double insulin levels up to 1 hr after training. (1) (2) (3)
  • Another study found the whole milk was superior for increasing net protein balance compared to its fat-free counterpart despite the fat free milk containing 81% more protein. (4)
  • Anabolic phase post workout (30-60 min window) is not dependent upon insulin
  • Spiking insulin is not necessary considering maximal effects for recovery are seen at minimal elevations.  Multiple training bouts (think: tournaments where multiple games per day) may be the exception where sugar based sports drinks should be consumed.

Resources:

(1) Rennie MJ, et al. Branched-chain amino acids as fuels and anabolic signals in human muscle. J Nutr. 2006 Jan;136 (1 Supple):254S-8S.

(2) Greenhaff PL, et al. Disassociation between the effects of amino acids and insulin on signaling, ubiquitin ligases, and protein turnover in human muscle. Am J Physiol Endocrinol Metab. 2008 Sep;295(3):E595-604

(3) Tipton KD, et al. Timing of amino acids-carbohydrate ingestion alters anabolic response of muscle to resistance exercise. Am J Physiol Endocrinol Metab. 2001 Aug;281(2):E197-206

(4) Elliot TA, et al. Milk ingestion stimulates net muscle protein synthesis following resistance exercise. Med Sci Sports Exerc. 2006 Apr;38(4):667-7



Categories: Nutrition, Strength Training, Uncategorized

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