Nutrition Q &A: Protein Intake

Q: I read with interest your Diet Guidelines Handout. Your summary of daily intakes and so on makes a lot of sense.  I did have one question about your recommendation of 1/4 to 1/3 g protein per pound of body weight you want to keep per day.  For me at a target weight of 160 lbs that is about 0.1 lb/day of protein.  That seems low. I would have thought at least double that and maybe more.  Am I overdoing the protein? ~ David

A: This question is asked frequently today since there is an array of high protein diets reported in numerous magazines and books.   Individuals may think they require much more protein than they need.  First, I need to define my audience, and that is you the athlete.  Athletes in endurance sports such as running and cycling require the majority of their daily calories in the form of carbohydrates.  However, during training and racing there is some muscle protein breakdown making intake of protein necessary as well.

Keep in mind that even when the body breaks down protein during exercise that only a small amount of that protein is actually used to fuel the body.  Most often, it is used as a fuel only when the training bout is at a high intensity level or when calories and carbohydrates are not being consumed at a level necessary to match the calories burned.  Even when used for energy, protein only accounts for 1-6% of the calories to support a 65% VO2 Max effort.  Furthermore, most of the protein the body breaks down is reused and made into new proteins following exercise.

The question remains as to how much protein the athlete needs for muscular adaptations, repair, and general health.  The average non-exercising American over age 18 should consume 0.36 g of protein per pound of body weight.  The athlete does require a little more due to that 1-6% loss of protein that occurs during training and competition.  The recommendations vary depending on the type of exercise and are listed below based on the position statements of the American Dietetic Association and the American College of Sports Medicine.

 Daily Energy and Protein for a 5’9”, 160-lb, 24-yr old male 
Type of AthleteGrams per pound of body weightGrams per day% of Total Daily Calories
 Non-Exercising0.3657.6 g/day~ 9%
Endurance (>50% VO2Max effort)0.55 – 0.6488 – 102.4 g/day~ 10-11%
Strength (during early training)0.73 – 0.77116.8 – 123.2 g/day~ 15-16%
NOTE:  The daily energy needs listed are theoretical based on some exercise assumptions and do not apply to all 160-lb male athletes.

Daily Energy and Protein for a 5’ 4”, 120-lb, 24-yr old female

Type of AthleteGrams per pound of body weightGrams per day% of Total Daily Calories
Non-Exercising0.3643.2 g/day~ 9%
Endurance (>50% VO2Max effort)0.55 – 0.6466 – 76.8 g/day~10-11%
Strength (during early training)0.73 – 0.7787.6 – 92.4 g/day~ 15-16%
NOTE:  The daily energy needs listed are theoretical based on some exercise assumptions and do not apply to all 120-lb female athletes.

Just because you eat more protein does not mean your body is going to keep building more and more muscle.  If this scenario were true we could just eat our way through the off-season and never touch weights (I assure you that your coach does not recommend this method of building muscle).  Several things occur when you consume protein above the recommended amounts for your activity.  First, it can result in extra calories above your daily needs.  Extra calories, even in the form of protein can result in additional fat mass.  Second, additional protein will be excreted but with no additional production of muscle (so you may waste money).  Third,  you may be trading off calories that body could actually use in the form of carbohydrates and healthy fats to sustain endurance.  Fourth, consuming too much protein for the athlete may result in an increase in urinary loss of calcium.  Combine that with the fact that cyclists take part in a non-weight bearing sport and you might increase your risk of osteoporosis.

So, in summary, keep in mind that the majority (not all) of the sedentary population as well as athletes more than meet the above requirements through daily intake and rarely need additional supplementation – the exception are those who are on very restrictive diets.  Even the highly trained athlete does not require protein levels above the recommendations.  In fact, the more trained the individual, the more efficient the body becomes.  Notice the additional protein needs of the strength athlete.  The additional protein is usually only needed during the early period of training when their muscles are growing in size.  However, as they get to a maintenance training level their dietary protein needs decrease to that of the endurance athlete or even a little less.