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Editor's Special Interest Articles
Protein: How much do athletes need? Are high protein diets safe?
Dr. Monte Hessler provides chiropractic treatment for low back pain, neck pain, sciatica and sports injuries among other musculoskeletal disorders.
He has practiced in Phoenix, Arizona for over 20 years.
Protein : How much protein do athletes need - and how safe are high-protein diets?
Protein is not just an essential nutrient, but the largest component in the body after water, typically representing about 15% of body weight. Most of this protein mass is found in skeletal muscle, which explains the importance of protein to athletes. However, proteins also play an important role in the following:
* Transport and storage of other nutrients;
* Catalysing biochemical reactions;
* Control of growth and differentiation;
* Immune protection;
* Providing our bodies with structural integrity.
Although the basic biochemistry and functional roles of protein in the body have long been understood, there’s still a huge amount of mythology and confusion surrounding protein nutrition, especially where athletes are concerned. This is partly because of general misconceptions about basic protein metabolism and partly because new research continues to throw up surprises about exactly what constitutes optimum protein nutrition!
The protein we eat is made up of around 20 amino acid ‘building blocks’. The process of digestion breaks down dietary protein into its constituent amino acid building blocks, which can then be absorbed into the body and reassembled to make various kinds of human protein, such as muscle, connective tissue, immune proteins, and so on.
Maintaining optimum protein status
An athlete has to move his or her body to perform, and this requires the muscles to generate force to accelerate body mass. As a rule of thumb, the greater an athlete’s power-to-weight ratio, the faster he or she can move, and (to a lesser extent) the longer he or she will be able to maintain any given speed of movement. Since all force and movement is generated by muscles, most power athletes benefit from maximising muscle mass and strength, while minimising the amount of superfluous body mass – ie fat.
And while out-and-out muscle strength is less important for endurance athletes, maintaining sufficient muscle mass is critically important, not least because high training volumes are known to increase the rate of protein oxidation from the amino acid pool, potentially leading to delayed recovery, a loss of muscle mass and consequent loss of power, and increased injury risk.
Given that athletic training is known to increase the demands on the amino acid pool, many athletes, particularly bodybuilders and strength athletes, adopt high-protein diets to maintain a positive nitrogen balance, or at least prevent catabolism and loss of muscle tissue. However, even today there remains much debate about how much protein athletes really need to optimise and maintain performance.
Protein v carbohydrate
There are other questions too. For example, should any extra protein be ingested at the expense of carbohydrate, the body’s preferred fuel for high-intensity training? And what about the possible health implications of high-protein diets, about which health professionals often express concerns?
Until recently the protein requirements of athletes were thought to be similar to those of sedentary people, and athletes were advised that they need only consume the recommended daily amount (RDA) of protein (currently set at 0.8- 1.0g of protein per kg of body weight per day) to maintain proper nitrogen balance. For a 70kg athlete, this would equate to 56-70g per day.
However, research over the past decade has indicated that athletes engaged in intense training actually need to ingest about 1.5-2 times the RDA in order to maintain a positive protein balance. This equates to 105-140g of protein per day for a 70kg athlete, which is equivalent to three to four medium-sized chicken breasts or 13-20oz of canned tuna per day! There is also evidence that training at altitude imposes an even higher demand for protein – perhaps as much as 2.2g per kg per day.
Unfortunately, these more recent findings on protein needs have not yet become widely accepted by some of the powers that be. For example, the UK’s Food Standards Agency website (in its section on sports nutrition) simply states that protein is important in the diet, especially ‘if you’re trying to build muscle’. It goes on to advise: ‘Try not to eat more protein than you need because your body won’t use it to build muscle. Instead it converts excess protein to fat, which is then stored, so try to make sure your protein intake is just right for your needs.’ However, it never actually states what those needs are.
Although foods like breads, cereals and legumes contain significant amounts of protein, which can add to that contributed by high-protein foods, such as meat, fish, milk and eggs, larger athletes, or those engaged in high volumes of training, may struggle to include the increased amounts of protein now recommended in a ‘normal’ diet; indeed, a number of nutritional surveys have indicated that protein insufficiency may be a problem for certain groups of athletes, including runners, cyclists, swimmers, triathletes, gymnasts, skaters and wrestlers.
Forty years ago, it was protein that dominated the thoughts of power athletes and bodybuilders. Employing the simple logic that muscles are made of protein, and that to build muscle you need lots of protein, steak-and-egg diets were the order of the day! But as the importance of carbohydrates in supplying energy and driving the insulin system (the most anabolic hormone in the body) became clearer, the emphasis gradually shifted.
This shift in emphasis was encouraged by an appreciation of the health benefits of dietary fibre present in unrefined carbohydrates, and also by research suggesting that very high protein intakes simply resulted in increased protein oxidation, imposing an additional load on the liver and kidneys. A scientific consensus began to form around the notion that diets containing substantially more than 1.0g of protein per kg per day were not only wasteful but potentially harmful, increasing the risk of kidney and liver problems, cardiac disease and even loss of bone density.
However, the recent meteoric rise in popularity of high-protein diets, such as Zone and Atkins, for slimmers has ignited a fierce debate about the safety and efficacy of high-protein diets, which is also relevant for athletes who routinely consume high-protein diets. In 2001, the American Heart Association’s nutrition committee published a statement on dietary protein intakes, claiming that: ‘Individuals who follow these [high-protein] diets are at risk for potential cardiac, renal, bone and liver abnormalities overall.
These conclusions have also been confirmed by other researchers; healthy athletes should not, therefore, be dissuaded from increasing their protein intake to up to three times the RDA level if they so wish.
High-protein diets and hydration
There’s a fairly linear relationship between protein intake and urea production, which means that high protein diets increase the amount of urea the kidneys have to excrete. With this elevated production of urea comes an increase in the obligatory water requirement of the kidneys to do their job, and that in turn has raised the question of whether athletes (whose fluids needs are already increased) on high-protein diets are at increased risk of dehydration.
To answer this question, scientists at the University of Connecticut compared the hydration levels of athletes consuming low (0.8g per kg per day), medium (1.8g) and high (3.6g) protein diets, each containing the same number of calories. Analysis of the results showed that, while there were significant increases in urine and plasma urea on the high-protein diet, the effects of increasing dietary protein on fluid status was minimal.
Moreover, to date there have been no studies conclusively demonstrating that increased protein intake leads to a loss in total body water. However, the researchers pointed out that the subjects in their study probably consumed enough water to meet any increased requirement, which explains – at least in part – why their hydration status was not compromised. They also concluded that more research is needed. In the meantime, however, it seems prudent to recommend that all athletes on high-protein diets should drink plenty of extra fluid, especially in warm conditions.
For many athletes, power-to-weight ratio is more important than outright power for optimum performance, and this explains why reducing excess body fat is often beneficial. New evidence is now emerging that high-protein diets might actually help in this process. Although research indicates that, providing the same number of calories are eaten, the relative proportions of protein and carbohydrate in the diet do not affect the amount or composition of weight loss in a reduced calorie regime, these ratios do affect appetite, with subjects tending to be more hungry on higher carbohydrate intakes and less hungry on higher protein intakes.
In summary, there is good evidence that athletes need a plentiful supply of protein in their diets and that, contrary to previous recommendations, they do need substantially more protein than their sedentary counterparts – at least 50% and possibly up to 120% more. For a 70kg athlete, this can mean up to 150g of pure protein per day.
However, the role of carbohydrates in supplying energy for fuel and recovery remain as important as ever, which means the diet must contain high-quality, low-fat sources of protein in order to enable adequate carbohydrate intake without an overall excess of calories. Simply assuming that because you eat more food than the average person you’ll be consuming adequate protein is not good enough!
There is no evidence that routinely exceeding the recommended protein intake has any additional benefits on nitrogen balance, unless this extra protein is consumed as a protein/ carbohydrate drink before, during or after training – something we’ll tackle in the next article (see below). However, there is evidence that even higher protein intakes may help suppress appetite, control hunger and reduce lean tissue loss during restricted calorie routines, which may be useful for athletes needing to reduce or maintain body weight, although such diets are not really compatible with high-volume training routines.
Finally, despite what you may have read elsewhere, healthy athletes can rest assured that high protein diets containing up to three times the current RDA for protein are perfectly safe, although it is important to remain well hydrated on such diets.
www.drmontehessler.com
- Updated: September 26, 2008
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Dr. Monte Hessler, along with all information provided,
is for educational purposes only and is not an attempt to replace the need to seek healthcare services
or to provide specific healthcare advice. We strongly encourage users to consult with their chiropractor
or other qualified healthcare professionals for personal healthcare attention and answers to personal
questions.
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