What is Protein? Do I really need it?
In the human body, proteins are a part of every cell and tissue, including our muscle. Our bodies are constantly recycling proteins on a daily basis. The proteins that we eat in our diet can be used to replace broken down proteins in order to maintain balance. Proteins contain essential and non-essential amino acids. Amino acids are the building blocks for all our proteins in the body.
Protein can be found in relatively high concentrations in the following foods: • meats, poultry, and fish • legumes (dry beans and peas) • tofu • eggs • nuts and seeds • milk and milk products (cheese and yogurt) • grains, some vegetables and some fruits (provide only small amounts of protein relative to other sources)
Protein intake from animal sources rather than plant-based sources tend to have better absorption rates. However, even vegetarians can achieve adequate protein intake when a variety of plant sources are included ensuring intake of all essential amino acids. Here are some practical protein equivalents in common foods: • One cup of milk has eight grams of protein • One cup of soy milk has about seven grams of protein • One egg has six grams of protein • A three ounce piece of meat has about 21 grams of protein • One cup of dry beans has about 16 grams of protein • An eight ounce container of yogurt has about 11 grams of protein Recommended Intakes of Protein In general, it is recommended that 10-35 percent of your daily energy intake comes from protein. If you consume 2,000 calories per day, this would work out to be between 200 to 700 calories of protein per day. The recommended daily intakes (RDIs) can also be calculated by a person’s body weight. The Academy of Nutrition and Dietetics recommends that the average individual should consume 0.8 grams of protein per kilogram or 0.35 grams per pound of body weight per day for general health. So a person that weighs 75 kg (165 pounds) should consume an average of 60 grams of protein per day. Since there are approximately four calories per gram of protein, 60 grams of protein would result in the intake of 240 calories.
How much protein builds muscle?
Muscle mass is built when the net protein balance is positive: muscle protein synthesis exceeds muscle protein breakdown. Research shows muscle protein turnover is the greatest after working out. Additionally, it has been shown that muscle mass increases over time when resistance exercise (i.e. weight lifting, body weight exercises, etc) is combined with nutrient intake.
However, as we age, we need to increase our protein intake. Around 50 years of age, we need to increase the protein in our diets to one gram per kilogram of our body weight to maintain muscle mass. People that exercise regularly also need to eat more protein than the recommended daily intake. To increase muscle mass in combination with physical activity, it is recommended that a person that lifts weights regularly or is training for a running or cycling event eat a range of 1.2-1.7 grams of protein per kilogram of body weight per day, or 0.5 to 0.8 grams per pound of body weight. Consequently, the same 75 kilogram individual should increase their protein intake to 75 grams (300 calories) to 128 grams (512 calories) in order to gain muscle mass. This level of intake can generally be met through diet alone and without additional protein and amino acid supplementation.
When Should I Consume My Protein?
The process of protein turnover is increased with resistance training and can remain elevated for up to 48 hours in people beginning a new resistance training program. Therefore it is important to provide enough energy including protein so there is a sufficient pool of amino acids available to repair and build new muscle. Of course, you do not want to exercise on an empty stomach. In fact, exercising in an unfed state leads to an increase in protein loss making it more difficult for the body to both repair and build muscle. Research suggests there are several benefits to pre-exercise protein supplementation.
Pre-exercise protein supplementation helps to improve body composition by increasing resting energy expenditure up to 48 hours after exercise. This is important because it suggests that pre-exercise protein ingestion will not only help increase lean muscle mass and thus strength, but will also simultaneously reduce fat mass. However, the most scientifically supported and most significant benefits of consuming protein prior to exercise may be improved recovery and hypertrophy. This is thought to occur because of improved amino acid delivery. Protein supplementation after exercise may have a more profound impact on skeletal muscle hypertrophy. Several studies have demonstrated that protein ingestion following an acute bout of resistance training stimulates muscle protein synthesis for up to three hours. In contrast, failing to eat after exercise may limit protein synthesis and therefore limit potential progress in lean muscle tissue development. Research actually suggests there may be an “anabolic window” such that protein intake within an hour of exercise has the greatest influence on resistance training adaptations. Sign up for a FIT Formula Semi-Private Training session to learn how to combine good nutrition with a great fitness program!
Reference: Donna Cataldo, Ph.D. and Matthew Blair, B.S., and is a product of ACSM’s Consumer Information Committee.