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Protein is the building block of muscles and essential for repair and growth of muscle after exercise. Whenever you exercise, and particularly during resistance exercise, you cause microscopic damage to the myofibrils of muscle fiber (myofibrils are small protein filaments in the muscle fiber that help the muscle contract). This isn't the type of damage that you go to the doctor for, but normal biological damage called catabolism. The effect creates a stimulus and environment for muscle repair and growth. The body responds to the damage by sending nutrients, including protein and other growth factors like testosterone, to the muscle to help it grow. And just for the record, and contrary to what many people think, protein is not used by the muscles for fuel unless the circumstances are extreme (for example, starvation). Instead, fat and carbohydrate are the main fuels.
Research shows that protein consumed before exercise and within 30 minutes of finishing your workout will help with growth and recovery. The guideline for protein consumption after exercise is 1 gram for every 3-4 grams of carbohydrate. Peanut butter has 9 grams of protein per 2 tablespoons. Yogurt is another good source of protein. The guidelines for quantity of protein before exercise are not as clear as after, but you can experiment and see if you notice any difference.
You probably won't notice much difference using protein supplements unless you are malnourished or an elite athlete doing tremendous amounts of aerobic or resistance exercise. That's because most Americans, including athletes, get enough protein in their diets. Excess protein is not used by the body; instead, it is excreted in urine. The RDA recommendation for protein is 0.8 g/kg in healthy adults. Athletes, pregnant women, and individuals with certain medical conditions may need as much as 1.2-1.7 g/kg. Extra protein intake should be discussed with a doctor or registered dietitian.
Do the following math to calculate your protein needs:
- Divide your weight by 2.2 to calculate your weight in kilograms.
- Multiply your weight in kilograms by 0.8-1.7 gm/kg (depending on factors mentioned above). Here's an example if you weigh 200 pounds and consistently do heavy resistance exercise:
200/2.2 = 91 kg
91 kg x 1.4 = 127 grams of protein per day
Again, keep in mind that most Americans get enough protein in their diets. The supplement industry is a multibillion-dollar industry which is unregulated by the federal government. They want to sell you their product and so they will tell you what you want to hear. Unless you really need the extra protein, I recommend saving your money. Buy some exercise equipment instead!
You ought to add up all the protein you eat in a typical day to get some objective data to make decisions with, and then if you have specific nutrition questions related to your protein intake or other nutrients, see a registered dietitian (your doctor can refer you or you can check www.eatright.org), or check in with Betty Kovacs, the MedicineNet registered dietitian, for authoritative information.
Medically reviewed by Robert Bargar, MD; Board Certification in Public Health & General Preventive Medicine
"Effects of protein supplements on muscle damage, soreness and recovery of muscle function and physical performance: a systematic review."
Pasiakos SM, Lieberman HR, McLellan TM
Sports Medicine May, 2014