Protein is essential for growth and repair of tissues, but unless you are regularly participating in strenuous strength, speed or endurance exercise for more than an hour each day, then your protein needs are perhaps no greater than those recommended for a typical healthy, balanced running diet.
Proteins and amino acids
Protein is found primarily in muscle and is needed for the growth and repair of tissues. Proteins are broken down during the digestive process into smaller units called amino acids. There are 20 different amino acids, which can be combined to make many different proteins. Our bodies can make proteins from amino acids, but we are unable to produce nine of the amino acids, the essential amino acids, so these have to be supplied by your diet.
The table below shows all the foods that supply all the essential amino acids.
Table 1: Complete protein foods
|Milk and dairy products|
|Meat and poultry|
|Corn plus peas or beans|
|Rice plus beans|
|Lentils plus bread|
Only animal sources, such as eggs or fish, contain all the essential amino acids, but by combining different plant proteins, such as rice plus beans, you can also make complete protein foods. Strict vegetarians need to plan their diet carefully to ensure that their food combinations provide them with all the essential amino acids their body requires.
Protein quality is improved when dairy products are added to a plant food and when plant-based foods, such as wheat and beans, are mixed together. Good matches are muesli and milk, rice pudding, sesame seed bread, pitta bread and hummus, baked beans on toast or lentil curry and rice.
Protein needs for runners
The average daily protein requirements, expressed in grams per day for every kilogram you weigh (g/kg/d) is summarised later in Table 2.
For people who are sedentary or have low levels of activity, the daily protein requirement is equivalent to 0.75g per kg of body weight (0.34g per lb). So a person weighing 60kg (132.3lb) would need 45g (60 x 0.75 or 132.3 x 0.34) of protein per day.
If you are exercising more than an hour each day, then your daily requirement is slightly increased to 1 to 1.2g of protein per kg of body weight, that’s 60 to 72g of protein if you weigh 60kg. However, this requirement is still well within the amount that is typically consumed on average and therefore protein supplements are not necessary.
Experts recommend a further increase for athletes in the order of 1.2 to 1.4g/kg/d for endurance athletes and 1.6 to 1.7g/kg/d for strength athletes. When protein requirements are increased, for example, during heavy running endurance training, the amount can simply be achieved by increasing the overall energy intake of the diet without altering the proportion of protein consumed. Therefore, no adjustment is necessary to the foods or the composition of the normal diet.
Experts also state that there is no advantage (both in terms of performance or muscle size) to taking more than 2g of protein per kg of body weight per day providing carbohydrate needs are met. Commonly, athletes report excess intakes of 100g of protein per day. If this was all used for muscle protein synthesis, muscle mass would increase by about 500g/d. But, in reality, the extra protein is metabolised and excreted, rather than converted into muscle.
Table 2: Daily protein requirements of a runner
|Activity level||Protein g/kg/d|
|Sedentary to low levels of activity||0.75|
|Regular activity > 1 hour per day||1.0 - 1.2|
|Endurance athletes||1.2 - 1.4|
|Strength athletes||1.6 - 1.7|
In practice, providing you are eating enough food to meet your energy and carbohydrate requirements, achieving an adequate amount of protein is fairly easy. Table 3 (to follow) lists the protein content of some common foods.
Animal sources are richer in protein than vegetable sources and, therefore, a larger quantity of non-animal sources need to be consumed to provide the equivalent amounts of protein. This can be particularly problematic for vegetarian strength and endurance athletes due to the bulk of the fiber-rich vegetables that they need to eat to meet daily protein needs. In this situation a protein supplement may be advisable.
Table 3. Protein content of everyday foods
|Portion of food||Protein (g)|
|150g (5.3oz) lean meat or poultry||40|
|150g (5.3oz) fish||33|
|150g (5.3oz) soya beans||21|
|150g (5.3oz) tofu, lentils, kidney beans||12|
|135g (5.3oz) baked beans||10|
|284ml (9.6oz) milk||10|
|30g (1.06oz) cheddar cheese||8|
|2 slices of bread||6|
Protein and amino acid supplements
It is easy to meet your protein needs from your daily food intake, without having to resort to supplements. High-protein diets have long been associated with exercise training, in the mistaken belief that this will lead to greater muscle mass and strength, simply because muscle itself is protein. But all a protein or amino acid supplement will do is empty your pockets. It doesn’t matter if excess protein is obtained from food or a supplement, it still won’t be turned into muscle.
During running or other exercise, the body relies mainly on muscle glycogen, liver glycogen and fat stores for its fuel. Protein is used as muscle fuel only if glycogen stores are low. It is important to ensure that glycogen stores are kept well topped up to prevent muscle protein being used as fuel, and the best way to do this is to stock up on carbohydrates before, during and after exercise.