Protein Requirement: and Need During Exercise
By Zoë G Nance
There is a lot of information available about protein. Sources will both be similar and contradictory and having someone interpret the data and incorporate it into performance is extremely beneficial. There are contradictions with daily protein intake requirements and recommendations. There is also varying data in support to supplementation during exercise.
There are both incomplete and complete proteins. Incomplete proteins are common in non-animal sources: examples are beans and corn. However, when beans are combined with rice or corn with lime they become a complete protein. It is a good idea to have vegetable and animal sources of protein in a well balanced diet. Non-animal sources are considered, beans, corn, nuts, and legumes, an average serving is ¼ cup. Animal sources are meat, eggs and dairy, such as yogurt, milk, ice cream and cheese. A serving of yogurt and milk is one cup while the cheese serving size is 1 oz. One serving of protein is generally 7 g. While typically we should ingest over 20 grams of protein per meal. That would be at least 3 oz meat, 3 eggs or alternate for 21 g of protein at each meal, or 3 times per day.
The RDA for protein is .8-1.2 g of protein per kilogram of body weight per day. The RDA for an endurance/strength athlete is 1.2-1.5 g of protein per kilogram of body weight. So, take your body weight and divide that by 2.2 to convert pounds to kilograms. After the conversion take the number and multiply it by the numbers appropriate for your activity level. If you then, divide by three you will have a better number to gauge your protein per meal.
Protein is critical for the regulation of human metabolism. Insulin, hemoglobin and the oxidative enzymes in the mitochondria are all proteins that have important roles in regulating metabolism. Protein is important in the maintenance of water balance, acid-base balance, and prevention of infection. Proteins are also carriers for nutrients to the blood, such as free fatty acids (FFA) and lipoproteins and help transport nutrients into the body’s cell. Excess dietary protein can be converted to carbohydrate and fat and then enter the metabolic pathway for energy production or storage.
In most exercise tasks protein accounts for less than 5 percent of total energy cost. In the latter stages of longer endurance events protein could contribute to 15 percent of total energy costs. Even a brief session of exercise lowers the rate of protein synthesis and speeds up protein break down. The oxidation of leucine increases during exercise and the by-products eventually combine with pyruvate in the muscle cell; which eventually breaks down and part gets sent back to the liver for a conversion to glucose, at which point it can also be used as an energy source or excreted as urea.
Exercise causes an increase in protein in the urine with the potential of it also being lost through sweat. Protein content in sweat can be 1 gram per liter, which is a relatively small amount. And depending on individual sweat losses can be 2-4 grams of protein. The changes in protein synthesis that occur with training can also serve as a means to preserve carbohydrate stores when supply is short.
Ammonia is formed in the muscle from amino groups’; removal of the amino groups by alanine or glutamine may help to decrease ammonia production and delay the onset of fatigue. In the early stages of training a condition called sports anemia can develop and be prevented by an increase of protein intake during the early stages of training. Protein deficiency may also contribute to the onset of amenorrhea.
Fueling for an event
Some people support decreasing carbohydrates 2-4 weeks before an event and then add carbohydrates back into the diet 3 days before an event. There are consequences in attempting a low carbohydrate diet prior to a major event: excess fatigue, improper recovery, and moodiness are likely to occur. And research shows that there are no benefits of doing carbohydrate depletion.
All sources recommend eating 3-4 hours prior to an event. Ned Overend suggests light meals including fruit, oatmeal, yogurt and bagels. Chris Charmichael has 24 hour pre- race meal plan that looks like this:
Breakfast: 2 cups of multigrain cereal with one cup of skim milk, a banana, two eggs, 2 slices of whole wheat toast, coffee and OJ.
Snack: vegetable protein; like hummus, grain and one cup veggies
Lunch: 3 oz turkey, 2 servings of whole grain, piles of veggies one and ½ cups of brown or wild rice and a salad
Snack: Bar, a piece of fruit, coffee
Dinner: 3 oz of meat, 2 cups of pasta and one cup of vegetables
Pre Race Breakfast: One cup whole grain cereal, most experts suggest oatmeal, Carmichael suggests adding walnuts and raisins, I prefer raisins, honey and cinnamon. My cereal choice is brown rice, two eggs, I like mine with 1/4 TBSP cream cheese, two slices of whole wheat toast with two tablespoons peanut butter plus coffee and orange juice.
Most sources actually recommend a very similar plan.
All sources suggest that within 45 minutes of a race start ingesting a high carbohydrate gel or sugar, I always like brown rice syrup mixed with a little espresso and chocolate syrup. During exercise caloric replacement is vital for preventing the catabolic breakdown of muscle or using muscle as an energy source. Carbohydrate ingestion alone will prevent this. The human body will actually choose to breakdown muscle versus fat in the absence of carbohydrate because the breakdown of protein is easier. Carbohydrate ingestion every 45 minutes will keep you fueled for your event. It is recommended to ingest protein every two hours in an endurance event for the reasons listed above.
Sources: Sports Nutrition: a guide for the professional working with active people; second edition, Dan Benardot, PhD, RD.
Mountain Bike like a Champion; Ned Overend