Marathon season feels like Christmas for running enthusiasts. There is nothing like lacing up and enjoying every one of those 42.195 kilometres with the crowd cheering you on.
To feel your best, leave no loose ends in your nutrition planning. Complex carbohydrates play a key part in fuelling preparation and keeping your muscles ready to perform.
What are simple and complex carbohydrates?
Different types of carbohydrate are classified by their chemical structure.
Simple carbohydrates
Simple carbohydrates consist of one or two saccharides, or sugars. They are generally associated with rapid absorption, with carbohydrate sensing beginning in the mouth and digestion and absorption taking place further along the digestive tract.
- Monosaccharides include glucose, fructose and galactose.
- Disaccharides include lactose (glucose + galactose), sucrose (glucose + fructose) and maltose (glucose + glucose).
Complex carbohydrates
Complex carbohydrates contain more saccharides, or sugars, arranged in long chains. Breaking polysaccharides into monosaccharides takes time, allowing them to be digested and absorbed in the small intestine.
- Oligosaccharides are chains of 2 to 9 monosaccharides.
- Polysaccharides are chains of 10 or more monosaccharides.
Starch is the best-known example of a polysaccharide. Roughly half of the carbohydrate we eat is in the form of starch, found in rice, pasta, potatoes, pulses and other foods.
Do not confuse starch with resistant starch. The latter follows a different route, reaching the large intestine without being broken down by digestive processes and serving as a substrate for bacterial fermentation.
Properties and benefits of complex carbohydrates
Slower carbohydrate absorption can help moderate the release of insulin needed for glucose to enter cells, avoiding sharp insulin and blood glucose fluctuations.
Their absorption rate can also help maintain fullness for longer than simple carbohydrates.
This does not make simple carbohydrates unsuitable: they can be useful in certain situations. A sports nutritionist can design a nutrition plan tailored to your training and individual needs.
Why are complex carbohydrates important for runners?
As carbohydrate is a major fuel for runners, long-chain complex carbohydrates can help provide the required amounts. Consider the time between eating and training or competition, as digestion can take longer and cause discomfort if timing is unsuitable.
To keep your glycogen stores topped up, complex carbohydrates deserve a regular place in your diet.
What is glycogen? Simple. It is a store of glucose in the muscles and liver. When sufficient glycogen is available, the body can obtain energy through glycogenolysis, which breaks it down into glucose.
How much complex carbohydrate do marathon runners need?
There is no single figure for everyone. Training and rest schedules differ, and so does the amount of carbohydrate required. Needs depend on body composition, which can be assessed through anthropometry, as well as physical capacity, emotions and daily activity outside sport.
One principle remains: longer and more intense exercise generally requires more carbohydrate.
How does carbohydrate loading work?
Several strategies are used for carbohydrate loading before competition, from supercompensation after substantial muscle glycogen depletion earlier in the week to simply increasing daily carbohydrate intake one or two days before the race.
The depletion approach can involve greater fatigue, injury risk and hypoglycaemia during the low-carbohydrate phase.
In the second approach, the week’s carbohydrate intake remains matched to training, followed by a significant increase in this nutrient before competition, while keeping the overall macronutrient balance appropriate.
This does not mean eating enormous amounts of carbohydrate-rich food all day and feeling heavy or overfull on race day. Increase carbohydrate without an excessive rise in total calories.
The distribution of other macronutrients will therefore change. Your protein intake may fall temporarily, but a single day does not undo the rest of the week’s planning.
As race day approaches, nerves may increase. During carbohydrate loading, choose foods you tolerate well and familiar options for your fuel intake. Avoid high-fibre foods that cause gas or heavy digestion, and choose easily digested foods such as white rice or pasta, mashed potato and cereal porridge.
At this stage, more readily digested carbohydrate choices may be preferable to higher-fibre complex carbohydrate foods.
Sources of complex carbohydrates
Many foods rich in complex carbohydrates can fit into your nutrition plan.
- Brown rice
- Wholemeal pasta
- Quinoa
- Millet
- Buckwheat
- Wholemeal or rye bread
- Vegetables
These foods contain complex carbohydrates and can help maintain glycogen stores and supply energy.
Putting it together
Meal timing depends on your needs and training. A sports nutritionist can advise when to choose complex carbohydrates and when simple carbohydrates may be more useful.
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