Protein

Protein requirements have been well researched and in recent years, while scientists are starting to agree on some key issues much more research is to be done before we fully understand this diverse nutrient. Public opinion however, tends to move in cycles with opinion being influenced by the media, the internet and pseudo-scientists. It's no wonder many athletes are struggling to decide just how much protein they actually require?

Why is protein important?

Protein is an essential nutrient in the diet, being used to manufacture body proteins that have important structural and functional roles. Structural proteins are needed to build connective tissue, cell membranes and muscle cells. Regulatory proteins act as enzymes or transport vehicles. Proteins are made up of various sequences of about 20 different amino acids. Eight of these amino acids are essential and must come from the diet. Some amino acids are used as a minor fuel source during exercise.

Do athletes require more protein?

In the last 20 years, detailed research has enabled scientists to measure protein metabolism during exercise and recovery, and to monitor protein balance in athletes. Endurance athletes in heavy training require extra protein to cover a small proportion of the energy costs of their training and to assist in the repair and recovery process after exercise. Strength athletes, who are interested in gaining muscle size and function, require more protein in the early stages of very intensive resistance exercise. However, strength athlete’s muscles seem to adapt to the stress of resistance exercise, so that the protein requirements to maintain protein balance in very well-trained athletes are only marginally greater than those of generally active people. Athletes, who are growing, such as adolescents, have additional protein requirements. The table below summarises protein requirements for different types of athletes or exercise activities. Since athletes come in various shapes and sizes, it is easier to keep track of these requirements by relating them to the size (body mass or BM) of the athlete.

Table 1: Estimated protein requirements for athletes

Group Protein intake (g/kg/day)

Sedentary men and women

0.8-1.0

Elite male endurance athletes

1.6

Moderate-intensity endurance athletes (a)

1.2

Recreational endurance athletes (b)

0.8-1.0

Football, power sports

1.4-1.7

Resistance athletes (early training)

1.5-1.7

Resistance athletes (steady state)

1.0-1.2

Female athletes

~15% lower than male athletes

(a) Exercising approximately four to five times per week for 45-60 min
(b) Exercising four to five times per week for 30 min at <55% VO2peak

Source: Burke and Deakin, Clinical Sports Nutrition, 3rd Edition, McGraw-Hill Australia Pty Ltd, 2006

Do athletes need to eat more protein-rich foods?

Even if an athlete has a higher requirement for protein than a sedentary individual, do they need to change their eating practices to increase their protein serves? In particular, do they need to focus only on very high protein foods, or take protein supplements? Generally, athletes enjoy the advantage of increased energy requirements that make it possible to consume even larger amounts of protein and other nutrients than the sedentary person. Numerous dietary surveys show that the dietary patterns reported by various groups of athletes provide protein intakes that are well in excess of 2.0 g/kg body mass per day - especially in the case of strength-training athletes. Therefore, there is little scientific justification for special high protein eating strategies for sport.

  Quantity of food required to provide needs for a 70 kg athlete Amount of protein (g)

Breakfast

2 cups cereal
300 ml milk
2 slices toast
2 tablespoons jam
1 cup juice

6
12
8
0
2

Lunch

2 bread rolls each with 50 g chicken + salad
1 banana
1 fruit bun
250 ml flavoured low fat milk

41
2
6
13

Dinner

Stir-fry with 2 cups pasta + 100 g meat + 1 cup vegetables
1 cup jelly + 1 cup custard

50
13

Snacks

750 ml sports drink
1 carton yoghurt
1 piece fruit
1 cereal bar

0
10
1
2

Analysis

 

166 g
(2.3 g/kg)

How does timing and teamwork of protein and with other nutrients work?

Recovery after each workout or competition is a challenge for the athlete with a busy timetable. Recovery processes are complex and include refueling, rehydrating and repairing. Muscle and body protein metabolism is a constant balance between protein breakdown and protein rebuilding. During exercise the balance shifts towards protein breakdown, while during the recovery period after exercise the balance tips in the opposite direction. By consuming protein immediately after exercise it enhances muscle uptake and retention of amino acids, and promotes a more positive protein balance. This heightened state of protein metabolism seems to last for up to 24 hours and it is important for athletes to look at their protein spread throughout the rest of the day as well as immediately after exercise. The most important news is that the effect of post-exercise protein intake is best seen when the protein is combined with carbohydrate. Carbohydrate intake stimulates an increase in the hormone insulin, which in turn, stimulates the muscle to take up the amino acids. A protein-carbohydrate snack or meal after a workout makes good sense - not only for muscle repair and adaptation to training, but to provide carbohydrate fuel to restore muscle glycogen levels. Snacks or light meals that achieve this team-work include:

  • Flavoured yoghurt
  • Flavoured milk drinks
  • Fruit smoothies
  • Liquid meal supplements (e.g. Sustagen Sport)
  • Sandwiches with meat, cheese, chicken or peanut butter fillings
  • Breakfast cereal and milk
  • Sports bars 
  • Sports bars

Can athletes have too much protein?

Daily protein intakes under 2 g/kg BM in healthy people are unlikely to cause side effects. Less is known about the long-term side effects of protein intakes above 2 g/kg BM. High protein intakes can increase the amount of calcium excreted in the urine. This may cause problems with athletes at risk of weakened bones - for example, female athletes with low energy intakes who are not menstruating. High protein intakes are also known to accelerate the progression of pre-existing kidney disease.
From a nutritional point of view, excessive intakes of protein tend to be expensive especially if protein supplements are used. High protein intakes based on the consumption of large amounts of animal foods (e.g. meat and dairy foods) can result in a greater fat intake. High protein intakes may increase fluid requirements. However, the main concern is that excessive focus on high protein foods may displace other valuable foods (e.g. fruit and vegetables) or other important nutrients such as carbohydrate and fibre from the diet.

Can athletes have too little protein?

Although the majority of athletes eat more protein than is required to meet their special needs for sport, there are some athletes who may eat diets inadequate in protein. These athletes include:

  • Athletes on low energy diets trying to achieve or maintain a lower body mass/body fat level, especially those undertaking extreme restriction to lose weight rapidly.
  • Athletes restricting dietary variety, especially those cutting out large numbers of food groups. This includes fussy eaters and people with extensive allergies or food intolerances, athletes travelling to places with a restricted food supply, and athletes following extreme carbohydrate-rich diets or poorly constructed vegetarian diets. Athletes with eating disorders or disordered eating problems, and those following fad diets (e.g. the Cabbage soup diet, or long-term juice and vegetable fasts) are also at risk of sub-optimal protein intake among other nutrient inadequacies

Failure to consume sufficient protein on a regular basis may cause muscle to be broken down to ensure a continual supply of essential amino acids in the body. This will lead to loss of strength and power, or a failure to make optimal gains from training.

Which are the best foods to provide protein?

The following table gives examples of many basic foods that provide 10g of protein per serve. Many people typically turn to meat, poultry and dairy products to obtain protein. These food sources are considered to be of high value due to the protein in the food containing all the essential amino acids required to build muscle tissue. Don't forget that plant foods such as bread, pasta, rice, breakfast cereal, legumes, lentils and nuts also contribute significant amounts of protein to the overall diet. These protein sources are incomplete and are missing some important amino acids. It is important to mix these incomplete proteins together to ensure adequate amino acid balance. Remember also that many common foods or mixed dishes are made up of these basic ingredients. For example, we sometimes forget that custard or rice pudding is made with milk, or that meat or chicken are in the sandwich filling, or pasta sauce. Mixing and matching foods is a good way to team up protein, carbohydrate and other nutrients. Ideally, a mixture of protein sources should be included in the diet, and distributed at each meal and snack over the day, to ensure the full complement of amino acids is consumed on a regular basis.

Table 2: Protein rich foods for athletes. Each of the following foods provides approximately 10 g of protein. These foods have moderate to low fat contents and are rich in other nutrients. 

Animal Foods Plant Foods

2 small eggs
30 g (1.5 slices) reduced fat cheese
70 g cottage cheese
1 cup (250 ml) low-fat milk
35 g lean beef, lamb or pork (cooked weight)
40 g lean chicken (cooked weight)
50 g grilled fish
50 g canned tuna or salmon
200 g reduced fat yoghurt
150 g light fromage frais

4 slices (120 g) wholemeal bread
3 cups (90 g) wholegrain cereal
2 cups (330 g) cooked pasta
3 cups (400 g) cooked rice
3/4 cup (150 g) lentils or kidney beans
200 g baked beans
120 g tofu
60 g nuts or seeds
300 ml soy milk
100 g soy meat

Are protein supplements useful?

Generally, athletes can obtain all the protein they require from a good mixed diet. Occasionally, an athlete may require a supplement when a practical way to consume sufficient food cannot be found. Many protein supplements are very expensive due primarily to the amount of marketing that accompanies products and the processing required to extract the protein from cow’s milk. They tend to provide very large amounts of protein and little other nutrients. There is no need for the amount of protein provided by many supplements and there is certainly no justification for the extra cost. The most suitable supplement is one that provides both protein and carbohydrate. Good alternatives to protein supplements include homemade fruit smoothies, liquid meal supplements such as PowerBar Protein Plus powder and 20 g skim milk powder added to regular milk.

Does increasing protein intake assist with weight loss?

Although high protein diets are the current trend in weight loss nutrition it is not advised that athletes undertake such high protein low carbohydrate meal plans. However if an athlete is trying to change body composition and reduce weight more protein may help. Protein can reduce appetite when its volume is increased in meals. Athletes trying to maintain body shape or those that have reduced training volume dramatically through injury or during taper and are finding it difficult to reduce dietary intake may benefit from a slightly higher protein content to help reduce hunger. This slight increase in protein intake will help them reduce their intake and control their energy intake.

Written by AIS Sports Nutrition, last updated June 2009. © Australian Sports Commission.

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