The myths and mysteries of optimal dietary protein intake

It has been a long posed question as to whether elite and recreation athletes alike require an increase amount of protein within their diets in order to optimise training gains. This article will discuss the need for protein within an athletic diet, its optimal dosage, and overall guidelines that can be applied to an individualized nutritional programme.

We know that the average individual contains approximately 12kg protein, much of this is contractile skeletal muscle and the remainder resides as free amino acids found either in the circulation or intracellularly within muscle fibres. A continual bodily protein turnover shows that humans require a regular and adequate level of protein intake in order to carry out basic biological functioning and that this level of intake is somewhat increased for active individuals. Such a consensus was reached due to an observed increased in leucine oxidation during exercise, as well as multiple studies showing greater protein intake results in an improved muscle mass and muscular strength.

It is also clear that exercise causes increases in muscle protein synthesis alongside muscle protein breakdown, however exercise alone does not result in a positive net muscle protein balance. It is essential exercise is coupled with amino acid ingestion, as this will stimulate muscle protein synthesis and inhibit exercise induced protein down. This way muscle mass will gradually increase (hypertrophy). At the other end of the spectrum, inactivity will lead to an inhibition of protein synthesis and actually stimulate the breakdown of proteins, resulting in a net loss of muscle mass (atrophy) and decreased muscular strength. Although it has been shown that just a minimal amount of resistance training can prevent the inhibition of protein synthesis, this is of greater importance during periods of recovery or injury when muscle wastage is most likely to occur.

Now to perhaps the key question; how much protein do athletes  actually need to consume? Firstly, it should be noted that specific recommendations are extremely difficult to determine due to the variation in parameters such as age, sex, sport, playing position and the individuals training status. However, ingesting 20 grams of egg or whey protein can be said to be the general guideline of consumption to maximise the anabolic response of the muscles to exercise. There is little need to consume more than 20 grams of protein following a bout of physical activity, since the body is unable to utilise further amounts and so it will be either oxidised or excreted. No metabolic window exists for this consumption, as muscle protein synthesis experiences no change whether intake occurs immediately following training or three hours later. Although eating immediately after exercise is necessary to optimise recovery with regards to other substances such as glycogen.

Depending on the nature of one's nutritional goals some individuals may benefit from excess protein intake.  This is true of those with a primary aim of gaining lean mass and muscular strength where carbohydrate intake is not an concern. It may also be of benefit to those on a hypocaloric diet for weight loss, as a high protein diet will prevent the loss of lean tissue. The main concern here resides with the notion that excessive protein consumption may compromise the intake of other macronutrients such as carbohydrate.

Another key argument with regards to protein is whether there is a real need for its supplementation. It has been shown that training actually increases protein balance, which allows for enhanced reutilization of amino acids and thus reduces intake requirements. Therefore more ample amounts of protein are consumed in the diet and so there is little need for supplements. Despite this many do still seek further means of protein intake, with whey being a very popular choice. Compared to other supplements such as casein or soy, whey protein stimulates a superior anabolic response of muscle protein synthesis. This is because it contains greater amounts of leucine, an important essential amino acid.

With reference to the possible dangers of a high protein intake, evidence is at best equivocal that it will lead to negative health effects. Kidney problems and bone loss in healthy individuals are almost uncertain, let alone those who are physically active. It is however important that an increased amino acids intake does not override that of other essential nutrients.

When applying the contents of this article to your own nutritional programme the following guidelines may be followed; although it is probably not necessary whey protein is the best supplement option. 20 grams of protein is sufficient to stimulate optimal muscle protein synthesis following exercise and can increase strength by 40-50%. However this should only be used as a general figure and individually tailored with regards to age, sex, sport and training status.