Contents
Are protein requirements different for athletes?
The explosion of sports supplements
Are protein shakes detrimental to health?
Why is protein important?
Protein is an important nutrient that is required for muscle growth and repair. The recommended intake for adults is 0.8g per kg of body weight per day. (1)
Therefore, a person weighing 10 stone requires 51g of protein a day. It can be seen from Table 1 below that a well-balanced diet that includes protein with every meal e.g. milk/yogurt with breakfast, chicken with lunch and fish with dinner would easily exceed this.
|
Per 100g |
Protein in grams |
|
Chicken breast |
32g |
|
Fillet steak |
21g |
|
Venison |
22g |
|
Lamb |
22g |
|
Salmon |
20g |
|
Cod |
18g |
|
Prawns |
18g |
|
Eggs |
12g |
|
Almonds |
21g |
|
Red Lentils |
24g |
|
Milk |
3g |
Table 1 Grams of protein in 100g of various foods
Are protein requirements different for athletes?
It has been a commonly held view for many hundreds of years that the protein requirements for athletes, (both endurance and strength), must be considerably higher than the norm. Protein intake of 4-5 g/ kg weight /day is thought to be common in some athlete groups. However, there is little scientific evidence to support the need for such high protein intake. Therefore, many countries and organisations including the WHO and US Department of Health and Human Services do not recommended a higher protein intake for athletes (2).
Whilst the body of scientific evidence does not support higher protein requirements in athletes a small number of research studies have concluded that protein requirements are raised by between 50 – 100% (3, 4, 5). If this is correct then the requirements rise to 1.6g/kg/day. Using a requirement of 1.6g for a 10 stone person equates to 102g of protein (102g protein = 408 kcals) which can still easily be obtained from a normal food based diet.
It is also important to note that this research relates to athletes who regularly train for 4-6 hours a day, not enthusiastic amateurs who may train for an hour a couple of times a week.
Eating large amounts of protein does not result in big, strong muscles. Muscle growth and development arise from an increase in the size of muscle fibres and an increase in the number of muscle fibres created by muscle usage. When the intake of protein is above that needed for muscle repair, resynthesis and energy it simply turns to fat.
The explosion of sports supplements
Over recent decades there has been an explosion of sports supplements being offered in the market place, including ‘protein shakes’. Protein shakes are powders with high protein content (usually between 10 – 50g per serving) that are mixed with water (or other liquids). Some also contain added vitamins and minerals. The type of protein most efficiently absorbed by muscle and thereby best able to repair muscle the fastest is whey protein. Whey protein can be found naturally in dairy products and this is often the type of protein found in supplements.
Protein shakes are aimed at people wanting to increase muscle mass and provide an easy,convenient way to consume high dosages of protein. Protein powders benefit from being easily portable to consume prior to or immediately after training.
Are protein shakes detrimental to health?
Protein shakes are not only an expensive way to consume protein but if misused can be detrimental to health. Over use of protein shakes creates a high protein diet which can impact both liver and kidney function. The liver plays a vital role in breaking down protein into amino acids and during this process nitrogen is released which then forms urea. Urea is filtered from the blood in the kidneys and is then excreted from the body. High protein intake therefore requires the liver and kidneys to work harder. Whilst this is less of a concern for people with no underlying kidney or liver condition in extreme cases it could potentially lead to liver or kidney failure.
In addition, high protein diets are commonly offset with low carbohydrate intake. The body’s preferred method of energy creation utilises glucose and glycogen, which derive from carbohydrate, however if this is not available the body is able to create energy by metabolising larger amounts of fat (and protein). The creation of energy from fatty acids produces ketones as a waste product. High levels of ketones cause ketosis. The kidneys are responsible for filtering ketones out of the blood, and as with urea this increases the work load on the kidneys.
Other negative implications of a low carbohydrate diet are symptoms of glycaemia, when blood sugar levels fall. Symptoms include dizziness, headaches, nausea, trembling and lack of energy.
High protein diets can also cause osteoporosis and kidney stones. The reason for this is that an increase in amino acids raises acidity levels in the blood and in order to neutralise this bones release calcium. Women are more at risk of osteoporosis but this can also affect men.
A further consideration for anyone who consumes a diet heavily reliant on protein shakes is whether the body is receiving all of the vitamins and minerals needed to support overall health and wellbeing, plus the fibre needed to maintain gut health.
In conclusion, there is little scientific evidence to support the need for a very high protein intake for building muscle but there is a much stronger argument that very high protein diets can be detrimental to health. A healthy balanced diet is all that is needed.
