Macronutrients 101: carbohydrates

What are carbohydrates and why do athletes need them?

Carbohydrates are our bodies’ chief source of energy. From a chemical standpoint, they are compounds of carbon, oxygen and hydrogen arranged in:

• Monosaccharides – a fancy term for our simplest carbohydrates, glucose, maltose and fructose (fruit sugar)
• Disaccharides – two or more disaccharides bound together – maltose, lactose (the sugar found in milk)
• Polysaccharides – glycogen (the stores of glycose in our muscles and liver) and starches (storage of glucose in plants). These are our complex sources of carbohydrates.

All complex compounds of carbohydrates can break down to and, in some way, yield glucose, which the body needs to fuel the work of most of its cells. Glucose is also necessary as it is the preferred source of energy for brain function, nerve cells and developing red blood cells.

So why are carbohydrates especially important for athletes?

1. The main source of energy for moderate to high intensity (e.g., 65–80% VO2max) endurance activities as well as resistance-based workouts (e.g., three to four sets using ~ 6–20 repetition maximum [RM] loads) are carbohydrates.
   Think of your body like a car, with different gears. If you don’t have enough carbohydrate available for training, you lose your extra “gears”. No matter what sport you do – the game-winning shot, the extra surge for a PB during a run, the extra push to lift heavier than ever before – is dependent on carbohydrates.
2. Carbohydrates are protein and muscle-sparing nutrients.
   If the body is not supplied with enough glucose to meet its needs, it will start to break down other compounds in the body – proteins (which is not ideal as proteins have their own roles to fulfil that can’t be provided by other nutrients) or fats. In the ISSN (International Society of Sports nutrition) position stand on nutrient timing, it is stated that “as glycogen levels decline, the ability of an athlete to maintain exercise intensity and work output also decreases while rates of tissue breakdown increase”. That is why carbohydrates are known as the “protein sparing nutrient” because it prevents gluconeogenesis, the process of breaking down muscle for energy. Because muscle mass is directly related to your metabolic rate, muscle breakdown for energy will decrease your metabolic rate.
3. Immunity:
   Did you know that carbohydrates play a role in the adaptive immune system It has been shown that athletes who do not get enough carbohydrates have increased bouts of illness, especially respiratory tract infections. Getting ill frequently can be detrimental to your training.
4. Sleep and mood:
   Most carbohydrate rich foods also contain tryptophan, which helps to produce the feel-good hormone serotonin in your brain. Without enough of this hormone, you are more likely to get depressed or have sleeping difficulties.
5. Weight:
   Choosing carbohydrates wisely and eating whole grain, low GI carbohydrates like brown rice, low GI bread, legumes and whole wheat pasta can help to manage weight. Complex carbohydrates contain fibre, which helps you feel fuller for longer, promotes bowel health and helps to regulate blood cholesterol. When fibre is fermented by your gut bacteria, it produces short chain fatty acids, which has been proven to promote weight loss.
6. Recovery:
   Eating carbohydrates after training (especially if you train twice a day or have sessions less than 8 hours apart) is important to replenish muscle glycogen stores and help you to be ready for the next training session.

Simple vs. complex carbohydrates:

A lot of infographics on the internet refer to carbs as “good” or “bad”. This is actually a very ineffective way to look at it if you are an athlete. While simple carbohydrates, or monosaccharides, may contain less nutrients than complex carbohydrates, both have their place in a well-structured nutrition protocol.

• Think of “complex carbohydrates” as “slow fuel”. Complex carbohydrates contain fibre, which helps to keep blood glucose levels steady, and provide energy over a long period of time. This includes whole grains like whole wheat bread, brown rice, and quinoa, as well as legumes like beans and lentils, some fruits and vegetables, and starchy vegetables like sweet potatoes.
• “Simple carbohydrates” are “quick fuel” for your muscles. During and after training, your muscles become like a sponge, incorporating the carbohydrates you eat into muscle glycogen. It is better to get in carbohydrates that are quickly digested in this time – for example energy drinks, dates, bananas, sports gels, or even something like honey during sessions. After sessions, combining quick carbohydrates with protein has been shown to improve recovery and muscle protein synthesis (which is why chocolate milk is such a popular option). Examples can be smoothies, chocolate milk, recovery drinks, fruit and milk/yogurt, etc.

How much carbohydrates do you need? Recommendations by the ISSN (Kersick et al., 2018)

Carbohydrates around training (International Olympic Committee and ISSN guidelines)

Carbohydrates and water

A lot of low-carb diets lead to great weight loss in the first week or two. This is because each gram of glycogen stored in muscle also stores 2.7g of water, and as the glycogen in the muscles become less, so does the water content. Likewise, the morning after you ate a high-carbohydrate meal or the morning after you had a higher intake of carbohydrates the previous day, you might weigh a little more due to having more water in your muscles, but as you use your muscles and the glycogen to live and train, this normalises.

The takeaway?

Carbs are an important part of a healthy diet for athletes, and by eating the right TYPE of carbohydrates in the correct portion sizes for your individual needs, and at the right time, you will be able to elevate your health and performance.

References

Kerksick C, Harvey T, Stout J, et al. 2008. International Society of Sports Nutrition position stand: nutrient timing. Journal of the International Society of Sports Nutrition. 5(17). Available from: http://www.jissn.com/content/pdf/1550-2783-5-17.pdf

Potgieter, S. 2013. Sport nutrition: A review of the latest guidelines for exercise and sport nutrition from the American College of Sport Nutrition, the International Olympic Committee and the International Society for Sports Nutrition. South African Journal of Clinical Nutrition. 26(1).