Sports Nutrition and Carbohydrates

header carbs

 

Understanding Carbohydrates Part 1: ‘The Substrate King!’

Unless you have been recreating the legendary Forrest Gump’s run across America, then you may well have heard of the macronutrient, carbohydrate! The scientific carbohydrate debate has been gathering pace for years, and potentially will continue to split opinions among athletes, coaches, and academics alike for some time yet. With discussions on high carbohydrate diets, low carbohydrate diets such as ketogenic, and restrictive carbohydrate diets such as the FODMAPS…is there any wonder athletes struggle to understand nutrition!forrest carbs

but what are carbohydrates, and what do they do?…

…where do they come from, and why do we need them?

Carbohydrates, or saccharides as they are scientifically known, are groups of molecules which are created from carbon, hydrogen, and oxygen atoms, and are typically divided in to three major categories: monosaccharides, oligosaccharides, and polysaccharides. Monosaccharides are the simplest carbohydrate molecules and are classified as the base unit of all carbohydrates due to them only containing one single sub-unit of sugar (1). The three major monosaccharides are glucose, fructose, and galactose, with glucose being the most common transport mechanism in the body. It is naturally found in food, or is the end product of more complex carbohydrates being broken down. Glucose is easily broken down by the body and is typically used as an energy substrate, stored as glycogen, or converted to fat (triglycerides) and stored for later use. Fructose is generally identified as the sweetest monosaccharide, and is found in fresh fruits, and high fructose corn syrup (HFCS) products such as soft drinks, many desserts, and of course various branded energy gels. Galactose is not generally found in natural products, and consequently is needed to be combined with glucose so it can be utilized as a fuel source, or stored for later use.

p1 sproutWhen monosaccharides, are bound together, then more complex carbohydrates are produced, called oligosaccharides (sucrose, lactose, and maltose). The common table sugar (sucrose) is typically the most common oligosaccharide, with lactose, probably more well known for its potential difficulty to digest, leading to lactose intolerance issues. Maltose, is the product of sprouting seeds and is typically found in sprouted grains, malted cereals, malted milk, and some beers.

Polysaccharides, are regarded as complex carbohydrates, and are typically divided into starch and fiber (plant polysaccharides), and glycogen (animal polysaccharides). Polysaccharides are generally found in such foods as cereals, rice, wheat, corn, and potatoes, and are commonly broken down in to glucose for absorption, yet take much longer to digest than the simple carbohydrate sugars, of glucose and fructose, hence their presence in sports supplements, such as drinks, and gels. However, it is the more complex carbohydrates which should make up the bulk of an athlete’s diet.

Various sports nutrition companies, such as Mountain Fuel® are now producing performance supplements which contain various manufactured complex carbohydrates, such as maltodextrins, due to their high Glycemic Index (GI), which means energy is quickly available, their rapid digestibility (2), and their reduced risk of developing gastrointestinal issues during physical activity (2).  

Carbohydrates are contained in all living cells and we ingest the majority of them through plant sources, where they are then metabolised to form adenosine triphosphate (ATP), or energy. Carbohydrates’ primary role, is to provide energy to the working muscles, and is seen as the exercise substrate King, yet it also plays a major role in storing energy as glycogen, and also converting glucose in to fat, to store as a potential fuel substrate.

 Carbohydrate Metabolism:

With regards to metabolising carbohydrates, there are three basic pathways. The first two pathways (glycolysis and glycogenolysis) are anaerobic so require no oxygen to produce energy, whereas the third (oxidative metabolism) does rely on oxygen availability to be able to produce energy (1). The availability of energy which the body demands during exercise for anaerobic and aerobic activities, primarily depends on the exercise intensity, and the exercise duration. For example, generally, the shorter the exercise duration, the higher the intensity can be and therefore, energy availability is typically provided anaerobically ie: resistance training or sprinting for example. Conversely, the longer the exercise duration is, the lower the intensity, and consequently, energy provision demands then become less dependent on anaerobic metabolism, and the process of oxidative metabolism is then expected to be able to begin utilizing carbohydrates, and fat as exercise substrates, when exercise durations become much longer, and intensities become much lower ie: marathon running and cycling sportive events for example.p2 usain bolt

 

Types & Quantities of Carbohydrate:

Whether you have a scientific background or not; mid-pack week-end warrior, or are an elite athlete, it really helps to have at least a little basic knowledge and understanding of how food works once it is consumed, and it also helps in constructing a healthy nutritional and training framework (3).

Usually, athletes just want to know what to eat, how much to eat, and when to eat it…and I guess nutrition really is that easy…is it not?   

Just giving carbohydrates the sub-category titles of simple and complex is enough to confuse the average individual when it comes to attempting to fuel their training and/or competitive events.

Throughout scientific research, it is suggested that 1-1.1g of carbohydrate, or ~60g/hr can be oxidized by the body, whether this is via solid foods, liquids and/or energy gels or bars, however there has been athletes who can oxidize and utilize upwards of this amount, and closer to 90g/hr, however, this does take some training the gut to be able to do this, and not suffer any gastrointestinal issues.

As a healthy guideline, the recommended daily intake for the average adult male is 3-5g/kg of body weight/day, this equates to ~45-65% of total daily Kcals (4). Females should be consuming ~45-60%. However, for the more active individual with a more moderate to high intensity training program, this would be expected to increase to 5-8g/kg.bw/d (250-1200g of carbohydrate per day), and even up to ~10g/kg.bw/day during extreme periods of training (1). For individuals who may struggle to consume this amount of carbohydrates through food alone (see Table 1), liquid carbohydrate supplements would be advisable.

Other than rice, potatoes, and grains, a huge emphasis should be placed on consuming fresh fruits & vegetables for their carbohydrate content, but also for their great health benefits as past studies have shown that eating more fruit & vegetables can reduce the risks of heart disease, stroke, and some types of cancer (3).

Carbohydrate Periodization:

So, now we know what carbohydrates are, what they do, the types of foods that they are in, and the amounts we are typically recommended to consume…the next big question is… when, when do we consume them with regards to training and competition? Nutrient periodization does not need to be complex. The basis of periodizing nutrient intake should follow alongside an existing exercise training program, and as long as eating patterns and behaviours alter with the energy expenditure of training to match the set goals, performance should be optimal (5). The periodization of all nutrients, not only carbohydrates is key to a healthy, and successful training and competitive career, however the topic of nutrition periodization is not within the scope of this article and will be discussed in a future issue.

Key Points:

  • Carbohydrates are the ‘King of exercise substrates’ during prolonged intense bouts of training
  • Carbohydrates are typically sub-categorised in to simple and complex dependant on their make-up
  • Glucose is the base-unit of carbohydrates and is the easiest to digest
  • Energy demands during exercise for anaerobic and aerobic activities, primarily depends on the exercise intensity, and the exercise duration
  • The average adult male is recommended to consume ~45-65% of total daily Kcals from carbohydrates, and females ~45-60%
  • Fruit & vegetables should be part of your daily carbohydrate intake, as well as rice, potatoes, and grains
  • Carbohydrate periodization is key to a healthy & successful athlete

Next time: Understanding Protein ‘The Power of the Building Block’

Table 1: 50g Portions of Carbohydrates

Table 1: Portions of Carbohydrates Pre-and During Events

Food Items Portion Serving Carbohydrate Content
 

Pre-Race (~16hrs)

Uncooked rice

Uncooked pasta

Boiled potatoes

Mashed potato

Baked potato

Pitta bread

Baked beans

 

 

60g

70g

300g

325g

1 x medium

1

325g/8 tbsp

 

 

50g

50g

50g

50g

50g

50g

50g

 

Pre-Race (~12hrs)

Mountain Fuel Night Fuel

Banana

Muesli

 

 

50g

1 x large

70g

 

 

25g

25g

50g

 

Pre-Race (2-4hrs)

Mountain Fuel Morning Fuel

Porridge oats

Cornflakes

 

 

50g

150g

120g

 

 

35g

100g

100g

 

Pre-Race (30mins)

Mountain Fuel Xtreme Energy

 

 

50g

 

 

40g

During (per 60mins =
~30-60g/CHO)
 
Mountain Fuel Xtreme Energy

Raisins

Banana

Nutrigrain bar

50g

70g

1 x large

1

40g

50g

25g

25g

 

                                                                                                     

 

 References:

1– Haff, G.G. (2013). Essentials of Sports Nutrition and Supplements: Carbohydrates. NJ, USA, Humana Press

2-Jeukendrup, A. E. Carbohydrate Intake during Exercise and Performance. Nutrition. 20 (7), 669-677 (2004)

3– Ryan. M. (2012) Sports Nutrition for Endurance Athletes (3rd Ed.). Colorado, USA, Velo Press

4– Kreider, R.B; Wilborn, C.D; Taylor, L; Campbell, B; Almada, A.L; Collins, R; Cooke, M; Earnest, C.P; Greenwood, M; Kalman, D.S; Kerksick1, C.M; Kleiner, S.M; Leutholtz, B; Lopez, H; Lowery, L.M; Mendel, R; Smith, A; Spano, M; Wildman, R; Willoughby, D.S; Ziegenfuss, T.N and Antonio, J. ISSN Exercise & Sport Nutrition Review: Research & Recommendations. Journal of the International Society of Sports Nutrition. 7:7 (2010)

5– Seebohar, B. (2011). Nutrition Periodization for Athletes. (Second Ed.) CO, USA, Bull Publishing Company

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