Diet for Marathon Runners – Protein

What is protein?

  • Protein is made up of a combination of 20 amino acids that are like the body’s building blocks.
  • Nine of the amino acids are essential as they cannot be made in the human body and must be provided by the diet. To read more about amino acids click here
  • Protein can come from animal and plant sources.
  • Protein from animal sources contains all essential amino acids.
  • Protein from plant sources lacks one or more of the essential amino acids. Vegetarians need to plan carefully to ensure all the essential amino acids are provided in their diet.

Why do you need protein?

You need protein to:

  • Grow
  • Develop strong muscles and tissues.
  • Carry oxygen around the body.
  • Help to prevent illness (antibodies and a healthy immune system).
  • Trigger reactions in your body (enzymes and hormones).

Some protein in the post-training and post-competition meals can help improve muscle glycogen restoration by increasing the rate glucose is taken into muscles, help in the repair of muscle tissue, and may help optimize gains in lean body mass. The recommended amount of protein post training is 10-20g.
Protein has a small role in providing energy when glycogen stores have been exhausted. When protein is used for energy it cannot be used for the important roles of muscle growth, repair and recovery. By having good glycogen stores you actually spare protein.

How much protein do you need?

The results of scientific studies suggest that athletes should consume 15% of their energy from protein (0.8 – 1.7g per kg of body weight per day).
It is common for us to eat more protein than needed so it is not usually difficult to meet protein requirements. When athletes increase their energy intake they often automatically increase their protein intake.
When you want to gain muscle mass it is important to ensure you consume enough energy, predominantly from carbohydrate. If you do not increase your energy and carbohydrate intake you will actually use some of your body protein to provide energy – you can lose muscle!

Can you have too much protein?

Yes! Too much protein is associated with the following risks:

  • If you eat too much protein you will not be getting enough carbohydrate to meet your energy needs and your body will use the protein as an energy source – this is wasteful!
  • You will need to urinate more often to get rid of the waste products of protein breakdown. This means many trips to the toilet, an extra strain on your kidneys and the risk of dehydration.
  • High-protein foods are often high-fat foods.
  • Protein foods, especially animal protein, tend to be expensive.
  • A diet high in protein may increase calcium loss.

How can you work out your daily protein needs?

As an athlete you should aim for a protein intake of 1.2–1.4g per kg of body weight per day.
Protein needs per day = body weight x 1.2–1.4g
Marathon runners need an increased protein intake to repair the muscle damage caused by distance running.