There has been a large growth in recent years in the number of people using sports nutrition products, in particular proteinCompounds that form the structure of muscles and other tissues in the body, as well as comprising enzymes and hormones. supplements. However, in light of the fact that high levels of additional protein can have a damaging effect on the body this article asks whether protein shakes are really necessary.
Protein is an important nutrient that is required for muscleTissue made up of cells that can contract to bring about movement. 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.
Protein in grams
Table 1 Grams of protein in 100g of various foods
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 fatOne of the three main food constituents (with carbohydrate and protein), and the main form in which energy is stored in the body..
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.
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 liverA large abdominal organ that has many important roles including the production of bile and clotting factors, detoxification, and the metabolism of proteins, carbohydrates and fats. and kidneyOne of two bean-shaped organs that are located on either side of the body, below the ribcage. The main role of the kidneys is to filter out waste products from the blood. function. The liver plays a vital role in breaking down protein into amino acids and during this process nitrogen is released which then forms ureaA waste product formed from the breakdown of proteins.. Urea is filtered from the bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. 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 glucoseA simple sugar that is an important source of energy in the body. 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 ketonesA group of compounds that are produced by fat metabolism. as a waste product. High levels of ketonesAcidic chemicals formed when body fat is used for fuel at times when there is insufficient insulin to allow normal carbohydrate metabolism. cause ketosisIncreased levels of ketones in the blood resulting in their excretion in sweat, urine and breath, giving a classic smell like pear drops or nail polish remover. It occurs as a result of metabolic changes during prolonged fasting or starvation and is also common in poorly-controlled diabetes.. 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 osteoporosisA condition resulting in brittle bones due to loss of bony tissue. 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 calciumAn element that forms the structure of bones and teeth and is essential to many of the body's functions.. 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.
1 Department of Health, Dietary Reference Values for Food Energy and Nutrients for the United Kingdom 1991; HMSO
2 Lemon PWR, chapter 5 Protein and Amino Acids, Sports and exercise nutrition 2011; Wiley and Black
3 Lemon PW, Nagle FJ, Effects of exercise on protein and amini acid metabolismThe chemical reactions necessary to sustain life.. Med Sci Sports Exerc 1981; 13: 141 -149
4 Lemon PWR, Protein and exercise: update Med Sci Sport Exerc 1987; 19 (5 Suppl) S179- S190
5 Lemon PW, Effects of exercise on dietary protein requirements, Intl J Sports Nutr 1998; 8: 426-447