Protein needs for exercise

The DRI (Dietary Reference Intake) guidelines for protein intake is 0.8 g / kg / day assuming relatively high protein bioavailability i.e. a diet including soy and/or animal-derived products (SEE MY POST ON THIS BY CLICKING HERE). The DRI conclusions are that there are NOT higher protein needs for endurance athletes (READ THEIR STATEMENT BY CLICKING HERE) or strength athletes (READ THEIR STATEMENT BY CLICKING HERE).

What do I think? The natural (i.e. no steroid use) maximum growth of muscle is about 1 lb per month (the rest is body fat, no matter how convinced an athlete is that it is muscle). That amount of muscle growth will taper off rapidly after the first one or two years of very intensive training. During this first intensive growth phase, the 1 lb of muscle per month corresponds to 1/30 lb of muscle per day. One pound is about 454 grams, so 1/30 lb is about 15 grams of muscle building per day, which equates to 60 Calories of protein being used per day to directly build muscle in addition to the regular every-day calories of protein needed for healthy tissue maintenance.

However, these 60 Calories of protein are being turned into muscle every second over the 24 hours in the day (on average 2 to 3 Calories per hour of protein being converted into muscle), not just right after we eat a meal with protein in it. As a result, we have to eat MORE than 60 Calories of protein at our 3 to 6 meals per day in order to ensure that those precious few Calories are available each and every hour, even when we are not eating. Our body can not store protein anywhere other than in muscle tissue itself, so excesses of protein at any one meal result in elimination of the nitrogen (i.e. protein) from the body. Therefore, the only way to ensure that protein is available to the body for as many hours of the day as possible is to consume it at regular intervals throughout the day AND to consume it in meals that digest as slow as possible so that the protein enters the bloodstream over a couple hours of digestion rather than quickly.

Protein powders enter the bloodstream quickly and are therefore NOT as good a protein source as natural protein food such as tofu, egg whites, meat, chicken, etc. Casein powder digests slower than whey powder, and for this reason has been shown to contribute to greater muscle growth than whey; this is also the reason that casein is thought of as a "slow release" or "night-time" protein source to be taken by bodybuilders before they go to sleep.

Although protein itself slows down digestion, in combination with healthy fats and fiber sources its digestion rate is slower still. As is the case with carbohydrate fueling of muscle, protein fueling of muscle is improved when a salad and healthy fat source is consumed with the protein.

However, no matter how slow the digestion of a meal and no matter how much protein you eat at any one time, within a couple hours digestion is complete, the excess protein is being excreted, and a couple hours after that the amino acid levels are dropping in the bloodstream. This induces the release of cortisol, which in turn stimulates the breakdown of muscle to provide the rest of the body's tissues with amino acids. In other words, catabolism instead of anabolism even though you might have eaten five chicken breasts or drank 500 Calories of protein shake earlier (and have the gas to prove it, meaning not all of it could be absorbed so microbes in your intestine digested it instead and they produced methane and other gases as a byproduct).

Assuming a 2-hour digestion for a HEALTHY meal (i.e. including healthy fats and vegetables) to slow down digestion, the protein in a meal thus has at most 4 hours to go to work on muscle building. That means you only need a dozen more calories than your basal needs every four hours. If you miss meals or snacks every 3-4 hours you lose muscle mass and cannot be made up for by eating more protein in the previous or subsequent meal or snack. Thus, assuming a meal or snack every 4 hours (even in the middle of the night when you wake up after your first 4 hour REM cycle to go to the bathroom), the MAXIMUM additional protein need that a strength athlete could use in their diet is about 12 extra Calories every 4 hours i.e. 12 Calories X 6 feedings per day = 72 Calories per day beyond their basal needs of 0.8-1 g / kg / day DRI or RDA (100 g or 400 Cal for a 100 kg i.e. 220 lb athlete). This additional 72 Calories of protein represents less than a 25% increase in protein needs even for a large athlete. For athletes ranging 100-250 lb, this corresponds to 181-454 Cal protein needs (by DRI guidelines) plus 72 Calories i.e. 250-520 Cal protein per day in the weight range. This obviously does not take into account different activity types, muscle mass of the athlete, level of intensity of training, whether or not the athlete is sleeping well or eating other macronutrients at sufficient levels to facilitate muscle growth, etc. But is a ballpark estimate of needs to at least serve as a basis for discussion. The TOTAL caloric needs of athletes in this weight range will be from 1500-4000 Calories per day depending on training load (duration and intensity) i.e. protein needs are about 15% of total calories. Below 10% would could assume that, even when eating highly bioavailable protein sources, protein intake is insufficient for not only performance but also for health. Note that protein needs for the population follow a Gaussian curve, so different people's needs will vary somewhat.

The drive to eat more protein than this due to information from the supplement industry and from anecdotal information from athletes using steroids is overwhelming. Therefore, many athletes simply don't feel right unless they eat significantly more protein while training. I completely understand this. Coming at the problem from this direction, the question should be posed COMPLETELY differently. Instead, lets ask the question: "At what point does the amount of protein in the diet have a negative impact on muscle growth or on health?"

It turns out that Exceeding 20-30% of total Calories in the diet as protein has the following negative effects:
*Lowers testosterone dramatically down to only 1/4 its starting levels in men [Volek JS et al., J Appl Physiol, 82 (1997) 49],
*Raises cortisol [Slag MF, Metabolism 30 (1981) 1104],
*Raises the activity of enzymes that break down protein [Peters JC & Harper, J Nutr 115 (1985) 383 and Block KP, J Clin Invest 79 (1987) 1349],
*Reduces the rate at which muscle can absorb carbohydrate by 30-50% [Terruzzi I et al., Mol Cell Endocrin 190 (2002) 135 and Tremblay F & Andre Marette, J Bio Chem 41 (2001) 38052]
*Reduces glycogen recovery [Moundras C et al.,Gastrointest Liver Physiol 27 (1993) G1057] and
*Has been shown by the American Heart Association to significantly increase the risk of many diseases [1956-2000 Meta-Analysis, Circulation, 104 (2001) 1869].

Therefore, the percentage of calories that are protein in an athletes diet should be a MINIMUM of 10%, a MAXIMUM of 25%, and an average of 15-20%.

For a 50 kg athlete (110 lb) requiring 2000 Cal / day, 20% of calories corresponds to 400 Cal of protein i.e. 100 g of protein, which is 2 g protein per kg athlete i.e. 1 g protein per lb body weight. Twice the DRI. The athlete might not need this much, but eating that much will not harm their performance or health. NOTE that if the athlete did NOT need 2000 Cal per day, 20% of a smaller number is LESS protein, meaning they would need LESS than 1 g protein / lb body weight. In fact, their needs might only be the standard DRI or RDA recommendations.

For a 100 kg athlete (220 lb) requiring 4000 Cal / day during heavy training versus only 2000 Cal / day when not training for weeks at a time, protein needs will go from 800 Cal i.e. 200 g (about 1 g / lb body weight per day) down to 400 Cal i.e. 100 g (about 0.5 g / lb body weight, i.e. 1 g / kg body weight, close to the RDA).

BOTTOM LINE: Dramatically increased protein needs with training are a myth. Overconsuming protein at any one time can not make up for frequent small feedings. Eating meals that digest slowly due to including healthy fats and vegetables increases protein availability to muscle. If an athlete wants to increase their protein needs they should do so in a way that does not reduce testosterone, glycogen and health, meaning limit protein intake to 20% in general. Protein intake of ~20% corresponds to 1 g protein / kg body weight during weeks of no training, 1 g / lg body weight during periods of intensive training, and somewhere inbetween when training is intermediate.

Comments

[Mike Turken]

Hi, Dr. Clyde.

Love the blog! About this entry on protein needs - how do you factor in the body's need for protein for non-muscle-building processes, such as cell turnover and intracellular protein synthesis? Are these needs at all increased in athletes?

Thanks,

Mike Turken