What is a protein shake?

Protein shakesA protein shake is a high protein beverage, usually prepared by mixing a specially formulated, high-protein powder with liquid (e.g. water, milk or fruit juice). There are many brands of protein shake with slightly different compositions; however, the key ingredients are protein hydrosolates. These are proteins that have already been broken down, so your body absorbs them more readily than non-hydrolysed (intact) proteins. Many protein shake powders also contain added amino acids and sugary carbohydrates. The sugars raise the body’s insulin level, in turn stimulating the body to turn protein into muscles. This process is known as protein synthesis. Amino acids help the body to synthesise proteins more rapidly, as protein synthesis is dependent upon the availability of amino acids.

Why do people drink protein shakes?

Most people drink protein shakes because they want their muscles to grow bigger. Muscles grow when your body synthesises proteins into muscle tissue. Exercising stimulates the protein synthesis process, which occurs most rapidly in the period of rest following exercise. However the extent to which muscles grow is also influenced by the amount of protein available in your body.

Protein shakes are an excellent source of protein and people usually drink them after exercising (when protein synthesis is occurring most rapidly) to maximise the benefits of exercise. Muscular development is also dependent on the levels of insulin and amino acids, which stimulate the process of protein synthesis. This is why many protein shakes also contain added amino acids and glucose rich carbohydrates.

Do protein shakes work?

Studies show that protein shakes increase muscle anabolism (i.e. the process of muscle development) when consumed immediately following exercise. However, not all protein powders are the same. It appears that formulas with added amino acids and glucose rich carbohydrates are more effective than those containing only proteins.

What happens to excess protein?

Like the energy and nutrients you consume when eating, the protein you consume in a shake must be digested by your body. Despite popular myth, there is no evidence that the additional protein consumed through protein shakes damages the kidneys. If protein is not converted to muscle, it will be converted into and stored by your body as fat.

Benefits of protein shakes

Protein shakesIn terms of muscle development, the benefits of protein shakes include:

  • They contain quantities of protein which are difficult to consume quickly through eating alone.
  • They can be consumed immediately after exercise without suppressing appetite or causing bloating.

In addition, there is evidence that consuming protein shakes after exercise may:

  • Counteract the immune suppression effect (i.e. the tendency for the body’s immune system to become less effective in protecting against disease) which can occur after intensive exercise;
  • Aid bone formation;
  • Reduce the risk of muscular and joint injuries;
  • Reduce the risk of viral and bacterial infections;
  • Reduce the risk of heat exhaustion;and
  • Reduce muscular soreness following exercise, probably due to the anti-inflammatory effect of increased insulin.

Risks of protein shakes

There is no scientific evidence of increased health risks resulting from the consumption of high protein beverages.

Limitations of protein shakes

While there are few adverse health risks, there are a number of limitations of protein shakes.

  • They do not address other factors which reduce muscle anabolism. For example, post-exercise hypo-hydration, which, if not corrected (e.g. by drinking milk following a workout) can compromise performance in subsequent exercise sessions;
  • They contain almost exclusively protein. Other essential nutrients (e.g. carbohydrates, oils, vitamins and minerals) and micronutrients (e.g. iodine, calcium, vitamin A) contained in dietary sources of protein are generally absent;
  • Protein shakes may have a bitter taste;
  • A protein shake is not an armchair workout! They maximise the effects of resistance exercise, but do not work in the absence of it.

Alternatives to protein shakes

Protein shakesProtein shakes are a convenient way of increasing protein levels after exercise. However, they can be relatively expensive and they lack the additional benefits found in dietary sources of protein (e.g. the combination of nutrients and micronutrients).

For professional and amateur athletes, body builders, and others who wish to rapidly increase muscle density, the benefits of protein shakes may outweigh the costs. As there are no known health risks, the financial costs appear to be the main concern. However, maintaining a generally healthy diet that is low in fat, alcohol, salt and refined sugars is also an important part of maximising exercise benefits.

For individuals who simply want to develop healthy muscle tone, eating a well-balanced but protein rich diet is probably sufficient. Such a diet will ensure the availability of protein for synthesis following exercise. Good sources of dietary protein include:

  1. Lean meat: Lean chicken and fish are lower in fat than pork, lamb, beef and other meats.
  2. Low fat dairy products, particularly low fat milk: Milk also has a positive effect on post exercise rehydration, which has been shown to optimise exercise efficiency.
  3. Beans, legumes and nuts: Good sources of vegetable protein, but remember that nuts are high in fat and should only be eaten in small handfuls.

More information

Food types For more information on food groups and components, see Types and Composition of Food.
For more information on nutrition, including information on nutrition and people, conditions related to nutrition, and diets and recipes, as well as some useful videos and tools, see Nutrition.
For more information on fitness and exercise, including stretches, types of exercise, exercise recovery and exercise with health conditions, as well as some useful videos, see Fitness and Exercise.


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