Long distance runners training for a marathon require a balanced diet of carbohydrate, protein and fat (the macronutrients). Good nutrition is needed to get through the gruelling 26.2 miles of a marathon, and helps to ensure the race is finished without suffering any ill effects.
Carbohydrates and Marathon Training
Carbohydrates should make up 50-65% of the diet when training for a marathon in order to maintain energy levels. If a marathon runner does not consume enough carbohydrates, he or she may suffer from hypoglycaemia (a very low level of sugar in the blood) during training, or worse still, during the race.
Hypoglycaemia has some unpleasant (and sometimes fairly alarming) symptoms, including headaches, light-headedness, difficulty concentrating, confusion, heavy legs, wobbliness and shaking, dire fatigue and fainting.
Carbohydrates are the body’s preferred source of energy for high intensity sports such as marathon running. This is because carbohydrate stores can be readily converted to energy when fuel is needed, whereas the conversion of fat to energy takes longer. Carbohydrates are stored as glycogen in the liver and muscles. When running, glycogen is converted into glucose and released into the blood, and the blood transports it to the working muscles that need energy.
The best sources of carbohydrates are known as complex, or starchy carbohydrates, which release energy steadily and maintain stable blood sugar levels. Some examples of complex carbohydrates include pasta, potatoes, rice, wholegrain breads and cereals, oats, beans, lentils, nuts, seeds, fruits and vegetables.
The Importance of Protein and Fat in the Diet
Protein is important for rebuilding and repairing muscle tissue, and should make up 20-25% of the diet. Good sources of protein include fish, lean meat, skinless chicken, eggs, low fat dairy products, beans, pulses, nuts, seeds, tofu and other soya products, and various meat substitutes.
Fats should comprise 15-25% of total calories in the diet. Some important functions of fats include the absorption of fat soluble vitamins, joint lubrication, and energy production. The healthiest fats are unsaturated fats, good sources of which include oily fish, nuts, seeds, avocados and many cooking oils (including olive and sunflower).
Saturated fats occur in red meat, full fat animal products and hydrogenated vegetable oils, and should be eaten sparingly because they contribute to high cholesterol levels.
Fluid Intake for Long Distance Running
When training for a marathon, good hydration is essential. It is necessary to drink more than the recommended 6-8 glasses of water each day because more fluid than usual is lost via sweat and breathing during running.
Dehydration leads to a decrease in blood volume, causing the heart to beat faster in order to get an adequate supply of oxygen and nutrients to the muscles and remove waste products. Symptoms of dehydration include headaches, cramps, dizziness, fatigue, exhaustion, and a reduction in performance.
Isotonic sports drinks are recommended in addition to water. These replace electrolytes lost in sweat, such as sodium and potassium, which help the muscle cells to function efficiently. Sports drinks also provide energy in the form of glucose. It is important to take regular sips during a long distance run, and to top up fluid (and carbohydrate) levels after each training session.
Long distance runners who want to give their best performance at competition level should not underestimate the importance of good nutrition during their marathon training.
To learn more about carbohydrate intake when training for a marathon, the article Why do Marathon Runners Need Carbohydrates? may be of interest.
Resources:
- McArdle, W.D., Katch, K.I. and V.L. Katch. Exercise Physiology: Energy, Nutrition and Human Performance, 6th Ed. London: Lippincott Williams and Wilkins, 2007, 81-107
 |
 |
 |
 |
 |
