CARBOHYDRATE SUPPLEMENTS - DO YOU REALLY NEED THEM?

 

There's LOW GI (Glycemic index) carbohydrates, that we get via our diets from foods like sweet potato, brown rice, and oatmeal, and HIGH GI carbohydrates, such as donuts and glucose (aka dextrose) - the major ingredient in a powdered carbohydrate supplement.

 

GI is a ranking of foods in relation to their measured blood glucose response.

 

Effectively, a LOW GI food produces a sustained and smaller release of glucose, in comparison to a HIGH GI food, that will trigger a shorter but larger glucose release.

 

• HIGH GI: 70 of MORE
• MEDIUM GI: 56-69
• LOW GI: 55 or LESS

Essentially - your diet should be made up of LOW GI carbohydates primarily, because of the benefits that come with the fibre. 

 

However, you can safely enjoy both types of carbs and still lose weight, providing you're in a calorie deficit. You don't have to eat squeaky clean all day! FURTHER READING IN RELATION TO THIS HERE.

 

Also, a low GI diet has been seen to improve blood sugar levels and high blood cholesterol (1).

 

But to be at your healthiest - try and favour the LOW GI carbs to the HIGH option!

 

However, HIGH GI foods can also be enjoyed form time to time, but only in moderation, remembering that a long-term consumption of a high GI diet is associated with an increase or coronary heart disease and Type 2 diabetes (2).

 

 

The research behind a carbohydrate supplement before resistance training is mixed - however, one study (3) into resistance trained females found carbohydrates prior to leg training increased time to exhaustion.

 

For the endurance athlete, a carbohydrate supplement taken 30-60 minutes before training for endurance athletes has mixed scientific data, and different results for a variety of people.

 

 

For resistance training, if your workout exceeds 1 hour - it's recommended you ingest a glucose/electrolyte drink to keep blood glucose levels steady, spare muscle glycogen, fight off dehydration, and bolster your immune system, that can weaken due to intense training (4).

 

Leg day comes to mind, although you shouldn't be training for much longer than an hour anyway.

 

For endurance athletes, the research behind carbohydrates taken DURING activity is very promising.

 

One study (5) into 7 well-trained male cyclists, cycling for up to 3 hours at different speeds, found that muscle glycogen was spared when carbohydrates were taken during the bout. 

 

It's recommended that 45-60 grams of carbohydrates be taken per hour during endurance training, with it acceptable to begin dosages 30-40 minutes before the onset of fatigue. 

 

And as far as team sports go - football (soccer) players have shown improved performance, following a carbohydrate supplement before and during the game (6).

 

 

Glycogen is simply thousands of GLUCOSE molecules in chains, stored within skeletal muscle for energy. 

 

So taking glucose CAN give you two petrol tanks instead of one! 

 

THE FIRST TANK: The ingested glucose from your carbohydrate supplement

 

THE SECOND TANK: Your stored glycogen - resulting from the carbohydrates you have recently ingested (e.g your morning oats).

 

For the resistance trainer, a carbohydrate supplement after training is not vital.

 

Research (7) into resistance training has found that carbohydrates post-workout replenishes muscle glycogen to the level of 91%, whilst plain water boosts it to a level of 71%.

 

The resistance trainer can very simply replenish glycogen via whole-food carbohydrate sources in the meals scheduled for after the workout. 

 

Some bodybuilders are shocked at the hard science behind carbohydrates post-workout, but a lot of opinions over the years have been formed from studies into endurance athletes, with chinese whispers kicking them along even further. 

 

Now the above relates to glycogen re-synthesis, but what about muscle protein synthesis, and muscle protein breakdown?

 

Other research (8) has examined this.

 

9 men performed a leg extension workout twice, receiving a carbohydrate (50g) supplement together with a whey protein (25g) drink for one of the workouts, and just the whey drink post-workout for another.

 

To quote from the paper, the researchers found: "ingestion of 50 g of carbohydrates with 25 g of protein did not stimulate mixed muscle protein synthesis or inhibit muscle protein breakdown more than 25 g of protein alone either at rest or after resistance exercise."

 

However - it's different for the endurance athlete, with suggestions glycogen synthesis is superior when taken immediately after exercise, as opposed to waiting several hours (9).

 

Further research suggests that supplementing carbohydrates together with a protein supplement (that accelerates glycogen synthesis) at a rate of about 1.2-1.6 g/kg of body weight, is effective for glycogen synthesis (10).

 

Those training with weights will benefit from carbohydrates WHILST training for longer than an hour, and will see a 16% increase in muscle glycogen synthesis following training, but no additional muscle growth.

 

Pre-workout carbohydrates may also not be beneficial, as they research suggests mixed results.

 

However, an endurance athlete will benefit far more from carbohydrates DURING training or after an event, and will also see favourable glycogen synthesis outcomes when supplementing with carbohydrates after training. 

 

 

 

 

 

(1) Jenkins DJ, Kendall CW, Augustin LS, et al. Glycemic index: overview of implications in health and disease. Am J Clin Nutr 2002;76(1):266S-273S.

 

(2) Liu S, Willett WC, Stampfer MJ, et al. A prospective study of dietary glycemic load, carbohydrate intake, and risk of coronary heart disease in US women. Am J Clin Nutr 2000;71(6):1455-1461.

 

(3) Wax B, et al. Effects of carbohydrate supplementation on force output and time to exhaustion during static leg contractions superimposed with electromyostimulation. Journal of Strength and Conditioning Research. 2012;26(6):1717-1723.

 

(4) Sherman WM, Jacobs KA, Leenders N. Carbohydrate metabolism during endurance exercise. In: Kreider R, Fry AC, O'Toole ML, eds. Overtraining in sport. Champaign, IL: Human Kinetics Publishers; 1998:289-308.

 

(5) Yaspelkis BB 3rd, Patterson JG, Anderla PA, Ding Z, Ivy JL. Carbohydrate supplementation spares muscle glycogen during variable-intensity exercise. J Appl Physiol. 1993 Oct;75(4):1477-85.

 

(6) Leatt PB, Jacobs l. Effect of glucose polymer ingestion on glycogen depletion during a soccer match. Can J Sport Sci. 1989 Jun;14(2):112-6.

 

(7) Ivy JL, Katz AL, Cutler CL, Sherman WM, Coyle EF. Muscle glycogen synthesis after exercise: effect of time of carbohydrate ingestion. J Appl Physiol 1988 Apr;64(4):1480-5.

 

(8) Staples AW, et al. Carbohydrate does not augment exercise-induced protein accretion versus protein alone. Med Sci Sports Exerc. 2011 Jul;43(7):1154-61.

 

(9) Doyle JA, Sherman WM, Strauss RL. Effects of eccentric and concentric exercise on muscle glycogen replenishment. J Appl Physiol 1993 Apr;74(4):1848-55.

 

(10) Van Loon LJ, Saris WH, Kruijshoop M, Wagenmakers AJ. Maximizing postexercise muscle glycogen synthesis: carbohydrate supplementation and the application of amino acid or protein hydrolysate mixtures. Am J Clin Nutr. 2000 Jul;72(1):106-11.