Protein is a vital and essential nutrient for an endurance athlete's diet that is used to help build proteins in our body we need to function. There are 20 different amino acids that if assembled into various chains will create proteins. There are eight essential amino acids that we must have come from our diet, while others are used more as a small bit of energy in training. Various types of proteins are needed to build connective tissue and muscle fibers/cells. With this nutrient being so critical, can you consume too much protein and if so what can happen? Well first we need to know how much protein a typical sedentary person should consume and then compare that to an endurance athlete. A non-active person should consume roughly .8g per kilogram of body weight (.36g per pound) of protein for their daily needs. This is much different when you apply hours of heavy training for an endurance athlete who needs to increase their protein intake to 1.2g per kilogram body weight (.55g per pound body weight). The increased amount of protein needs for athletes is primarily to provide amino acids for the repair of exercise-induced muscle damage while aiding in building new muscle from the training. Another reason for the larger amount of protein intake is to compensate for the amount of fuel and energy expenditure as well as aid in providing proper muscle recovery. Endurance athletes and strength athletes love the benefit of the amplified energy requirements that allows them to eat more than a sedentary individual and doing so allows for more protein and nutrients being taken-in.
Having established what is the proper amount of protein to consume daily let's look at what happens if you have too little or too much. Typically for an athlete or healthy person consuming less than 2 grams per kilogram body weight will most likely not cause for any problems or side effects. But once you begin to take in more than 2 g/kg body weight, the increased risk begins. Your kidneys may become overloaded trying to filter out ketones (by-product of stored energy in the body). The more your kidneys work to flush out these ketones before they become toxic, the greater the risk of dehydration occurring. Many athletes confuse this dehydration with weight loss. But basically as you are losing this water weight you are also excreting increased amounts of calcium in your urine, which is coming from a decrease in the amount of bone calcium. So if you are an athlete who already has a weak bone structure, it can do some serious damage and possibly lead to stress fractures. This is something that may happen more frequently in Females with a low-calorie diet combined with not menstruating may find this happening at a greater rate and be more detrimental. Having your kidneys filter the high amount of protein has also helped accelerate the progression of pre-existing kidney disease in some people. Some other side effects that may occur include dizziness, weakness, and bad breath which all typically begin with dehydration.
There is always the other side of the spectrum where some athletes do not consume enough protein. Typically this happens to athletes who are trying to stay at a specific weight or percent body fat level. Usually these athletes are restricting more than just the protein, including carbohydrates, fats and general caloric intake that is sufficient to help them perform. Picky eaters can fall into this territory as well. If you are on a vegan diet, be sure it is properly created as well as those athletes that are on a strictly carbohydrate diet. Without a continuation of amino acids being supplied to the muscles, which comes from protein in your diet, your body will break down your muscle in order to fulfill its needs. Not meeting protein needs can lead to loss of power, which will lead to detrimental performance outcomes, the risk of injury increases, and any training adaptations that normally would take place won't anymore.
Since we have now established some guidelines on what the proper levels of protein intake should be, athletes need to be able to identify what are good sources of protein and the timing on consuming them. Fish, chicken, eggs, lean cuts of red meat like beef, pork, lamb, eggs, and low-fat or non-fat dairy products including yogurt and cheese, nuts, and beans are items that will have a great source of protein in them. Best times to consume protein is immediately after exercise when muscle receptors in the body are at a heightened sensitivity to help retain amino acids that will help increase muscle adaptation from training and help facilitate a quicker recovery. There is the "thirty minute window" of when your body is at this high level of alertness for nutrients, but that alertness will typically be at its peak for roughly for four hours after exercise while still partially on an increased awareness for a full twenty-four hours. Now what we have learned is that taking in protein with carbohydrate will help stimulate your insulin which will also increase the amount of amino acids that are taken in by your muscles. My favorite snack after a good workout is chocolate milk or a similar like carbohydrate-protein shake. You need the proper nutrients to help rebuild your muscles and keep your muscle glycogen stores (stored energy) high throughout training in order to reap the full amount of benefits.
Athletes will usually get a sufficient amount of protein if they already are consuming the proper amount of calories to coincide with their training. There isn't a need to consume more and put yourself at risk. The best way to know if you are taking in too much or too little of anything is to keep a dietary log and monitor what you take in for nutrients, and its caloric content. Remember that as an endurance athlete you typically will only need about .55 grams of protein per pound of body weight per day. The best time to consume some of your daily intake of protein is within thirty minutes post exercise to help aid in muscle repair and recovery. Protein is great for post-exercise intake when combined with carbohydrate which will also help maintain your muscle glycogen stores to help your training and performance in the future.
References
American Dietetic Association. Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: nutrition and athletic performance. J Am Diet Assoc. 2000;100:1543-56.
Beals K, Houtkooper L. Disordered eating in athletes. In: Burke L, Deakin V, editors. Clinical Sports Nutrition. Sydney. Australia: McGraw-Hill; 2006. p. 201-26.
Biolo G, Maggi SP, Williams BD, Tipton KD, Wolfe RR. Increased rates of muscle protein turnover and amino acid transport after resistance exercise in humans. Am J Physiol. 1995;268:E514-20.
Burke L. Nutrition for recovery after training and competition. In: Burke L, Deakin V. Clinical Sports Nutrition. 3rd ed., McGraw-Hill. 2006;415–453.
