First off, let’s clarify what carbohydrates are not:
Carbs have gotten a bad reputation in recent years with the increasing popularity of diets such as paleo and keto. Carbs are not bad. They will not make you gain weight if consumed and they are not these mythical little critters that turn to blubber if eaten after 8pm. So, what are they?
The primary role of carbohydrates is to serve as an energy source to the body. They supply an ergogenic effect and elevate muscle glycogen on aerobic performance, work output, and high intensity activity. They basically help you do everything in life at a higher level. Did you know that carbs are the only energy source utilized by brain tissue? This makes it the preferred energy source for nervous system functioning. Appropriate and adequate consumption of carbs allows for better muscle recruitment, better muscle growth, and greater fatigue resistance. There are three types of carbohydrates: monosaccharides, disaccharides, and polysaccharides. Today we’re going to be talking about the mono and disaccharides AKA the simple carbs or simple sugars.
Monosaccharides are single-sugar molecules, mono meaning one. These are our glucose, fructose, and galactose carbs. Glucose is our most common mono and the building block of larger sugars. It is the primary energy substrate for cells and composes glycogen. Glycogen is extremely important as it is stored in the cytoplasm of cells in muscle tissues and the liver until needed for ATP, which is what fast-acting energy is! You can consume glucose via intravenous fluids or some sport drinks in the form of dextrose. Fructose is our monosaccharide that is found naturally in fruits and vegetables. These carbs cause less insulin secretion than other sugars. Galactose is our mono that combines with glucose to make lactose, the sugar found in milk.
Disaccharides are made up of two simple sugars, di meaning two. These are our sucrose, lactose, and maltose carbs. Sucrose is a combination of glucose and fructose. This combo creates our most common table sugar and occurs naturally in most fruits. Maltose is two glucose molecules combined. Maltose normally occurs as a polysaccharide, also called a complex carbohydrate, and is broken down during digestion; however, maltose also occurs during fermentation and is the primary carbohydrate found in beer.
Pre-Exercise Simple Sugars Provide:
-Readily available fuel sources of energy
-Help fight fatigue to help you keep pushing through tough training sessions
-Help muscle contraction
Not all of your carbohydrate intake should come from simple carbohydrates, but we will discuss complex carbohydrates(polysaccharides) on another day. Simple sugars have been found to regulate muscle protein synthesis. Simply put, it helps stimulate and regulate muscular growth. This occurs by an increase in insulin secretion from the pancreas. The greater the insulin secretion, the greater the muscle growth. This is especially true when insulin levels are elevated when amino acids are present. Essentially, insulin is anabolic to muscle. Unfortunately, insulin is also anabolic to fat. Carbohydrates play an extremely important role in fueling the body for action and recovering after activity. Simple sugars in conjunction with amino acids from protein should be your go-to for recovering from a workout.
Post-Exercise Simple Sugars Help:
-Refuel depleted energy
-Stimulate insulin secretion for muscle growth
-Increase energy levels to keep you moving
Inadequate carbohydrate intake while exercising can have a detrimental effect. Individuals that partake in regular exercise or have active jobs may see a decrease in motivation and effort in blood glucose is too low. Inadequate carbohydrate intake for a prolonged period of time will likely cause decreases in single session and multi-session performance due to chronically low muscle glycogen. These individuals may also see a decrease in muscle growth due to the lack of insulin secretion and chronically low muscle glycogen. Thankfully, there seems to be no known effect on the body with too much carbohydrate intake if calories are properly balanced. So, what is the “optimal” carbohydrate intake?
Studies show that on non-training days under 0.5g/lb, light training days 1g/lb, moderate training days 1.5g/lb, and heavy training days 2g/lb is optimal for body composition purposes. Not all of your carbohydrates should be from simple sugars, however. Remember how simple sugars spike insulin levels? Our body only optimizes this insulin spike during or after a bout of exercise. Meaning, simple sugars are great for during and post-exercise or elevates bouts of activity, but aren’t essential throughout the rest of your day. The goal for the rest of your carbohydrate intake should be from complex carbs.
To sum it all up, simple sugars:
-aid in muscle growth
-supply fuel for fast-acting energy
-aid in recovery
-are great around high levels of activity, but are not necessary all day or even every day
References:
Baechle TR, Earle RW. Essentials of Strength Training and Conditioning. NSCA 3rd Ed. 2008. 208-211.
Burke LM, Kiens B, Ivy JL. Carbohydrates and Fat for Training and Recovery. J Sports Sci. 2004 Jan; 22(1): 15-30.
Burke LM, Loucks AB, Broad N. Energy and Carbohydrate for Training and Recovery. J Sports Sci. 2006 July: 24(7): 675-685.
Garthe I, Raastad T, Refsnes PE, Koivisto A,, Sundgot-Borgen J. Effect of Two Different Weight-loss Rates on Body Composition and Strength and Power-related Performance in Elite Athletes. Int J Sport Nutr Exerc Metab. 2011 April; 21(2):97-104.
Howarth KR, Phillips SM, MacDonald MJ, Richards D, Moreau NA, Gibala MJ. Effect of Glycogen Availability of Human Skeletal Muscle Protein Turnover During Exercise and Recovery. 2010 Aug. https://doi.org/10.1152/japplphysiol.00108.2009.
Kenney WL, Wilmore JH, Costill DL. Physiology of Sport and Exercise 5th Ed. 2012. 50-52.