How Much Protein Should You Consume?

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What is the optimal protein intake required for weightlifters, bodybuilders, strength trainers and other athletes?

The Role of Protein:

Proteins are physically and functionally complex macromolecules that have very important roles:

1. They make up the cytoskeleton (internal cellular network) that maintains the cellular shape and physical integrity. 

2. Actin and myosin filaments are proteins that form the contractile machinery of muscle. 

3. Hemoglobin transports oxygen while circulating antibodies search out foreign invaders. 

4. Enzymes catalyze reactions that generate energy, synthesize and degrade biomolecules, replicate and transcribe genes, process mRNAs, etc.

5. Receptors enable cells to sense and respond to hormones and other environmental cues.

Protein Intake - How Much Should You Consume?:

1. According to FDA: the RDA (Recommended Dietary Allowance) is 0.8 grams of protein per kilogram of lean bodyweight (1 kilogram=2.2 pounds). Example: if you weigh 70kg, you should consume (acc. to RDA) 56g of protein per day. This is the general protein requirement for sedentary adults, which is just enough that if one follows this guideline they will supply themselves with enough amino acids to replace each day's loss without allowing for exercise and the growth of muscle tissue. 

2. According to Dr Peter Lemon: according to Lemon, RDA doesn't appear to meet the needs of exercising adults. Dr Peter Lemon (researcher in the field) stated that, "the RDA for those engaged in strength training should be about 1.7 - 1.8 grams of protein per kilogram of body mass per day".

3. According to researchers at Kent University: their results showed that 1.4 grams resulted in protein synthesis.

4. According to the Letterman Army Institute of Research in San Francisco: their study showed that subjects on a higher protein intake (2.8 g/kg/day), coupled with intense strength training, gained 3.28 kg of lean mass. The study was done over a 40-day period and the subjects were trained to near exhaustion. Another study of weightlifters over a 3 month period, with the protein increased from 2.2g/kg/day to 3.5 g/kg/ day, resulted in a 6% increase in muscle mass and a 5% increase in strength.

The Bad Effects of Protein Consumtion:

Inflammation of the kidneys (lower back pain; flank pain) and feelings of malaise are symptoms to watch for. Most of the time the body does a good job of sorting and using protein, so most people will not run into this problem. One has to remember that some ingested amino acids are used for protein biosynthesis, while others are converted to glucose, which may lead to fat conversion.

Conclusion - So How Much Should You Take?
You should probably ingest between 1.4 grams of protein per kilogram of bodyweight or more. This can be beneficial if you are involved in an intense training program.

References:

1. Recommended Dietary Allowances, 10th Edition. Washington, D.C.: National Academy Press, 1989.
2. Consolazio GF, et al. Protein metabolism during intensive physical training in the young adult. Am J Clin Nutr 1975; 28:29-35
3. Dragan GI, Vasiliu A, Georgescu E. Effects of increased supply of protein on elite weightlifters. In: Galesloot TE, Tinbergen BJ, eds. Milk Proteins. Pudoc, Wageningen, The Netherlands 1985:99-103
4. A high ratio of dietary animal to vegetable protein increases the rate of bone loss and the risk of fracture in postmenopausal women. DE Sellmeyer, KL Stone, A Sebastian, SR Cummings. American Journal of Clinical Nutrition, 2001, Vol 73, Iss 1, pp 118-122.
5. Guyton M.D., Arthur C. Human Physiology and Mechanisms of Disease; 1992.
6. Arnal MA, Mosoni L, Boirie Y, Houlier ML, Morin L, Verdier E, Ritz P, Antoine JM, Prugnaud J, Beaufrere B, Mirand PP. Protein pulse feeding improves protein retention in elderly women. American Journal of Clinical Nutrition. 1999 Jun;69(6):1202-8. 
7.  Robert K. Murray. Harper's Illustrated Biochemistry. McGraw-Hill Medical; 27 edition (June 13, 2006)

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