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Sunday
Jul192009

The Power of Protein - Part 3: Amounts & Sources

Written by Tom Nikkola - Director of Nutrition & Weight Management

In the first two parts of this series, we looked at health concerns related to protein intake, and what research says about protein intake and body composition. To wrap up the series, today we'll look at recommended intakes, and some general differences among protein sources.

Recommended Protein Intake

The dietary guidelines suggest a daily intake of .8 grams per kilogram of body weight. For a sedentary individual, with no interest in optimal health or body composition, it's possible that the RDA will be sufficient. As was discussed in the section on protein intake and body composition, this still may not be ideal. For a sedentary individual that consumes protein at the lower end of the recommended intake, he or she may not benefit from the satiating effect of protein. In this case, a sedentary individual can end up overeating carbohydrates and fat, and gain excess weight.

For exercising individuals, the International Society of Sports Nutrition recommends protein intakes in the range of 1.4 to 2.0 grams of protein per kilogram of body weight. Though research has not shown a benefit for intakes higher than these ranges, some individuals such as bodybuilders and strength athletes consume amounts higher than 2.0 grams per kilogram with no ill effect. Some long-term studies are currently being conducted on active individuals who have been eating upwards of 4 grams kilogram body weight for many years, but it will be some time before the studies are completed. For the purpose of gaining lean body mass, evidence today does not suggest it is necessary to consume more than 2.0 grams per kilogram. However, metabolisms vary, and some individuals can benefit from higher intakes.

Aside from exercise recovery, it is also important for those on a reduced-calorie or a weight loss diet to consume protein on the higher end of recommended ranges. When people eat less calories than their body needs, the body not only reduces fat stores but lean body mass as well. Strength training and higher protein intakes can help prevent or reduce the amount of lean mass lost. Weight management is not about calories alone. It is common for people on reduced calorie diets to focus solely on the number of calories they eat, and not where those calories are coming from.  Most of the time, the lowest calorie foods, are low-fat, low-protein, higher-carbohydrate foods. It is possible to lose weightby simply reducing calories, but if protein needs are not met, the percentage of body fat the individual carries may not change much.

One last point to consider for recommended intakes is how the amount is determined. Many nutrition protocols are based on a certain percentageof calories coming from each of the three macronutrients such as 55% carbohydrates, 25% fat and 25% protein. The trouble with using only percentages is, as calories go down, the actual intake of protein goes down.

The following is an example using a 150 pound female. For the example, we'll use 10 calories per pound for a weight loss calorie amount, and 15 calories per pound for a weight maintenance goal*. If we continue using 2 grams per kilogram of body weight as a protein recommendation, that gives us 136 grams as a daily target.

Weight Loss nutrition plan at 10 calories per pound body weight*

1500 calories

25% of calories from protein = 94 grams of protein

Weight maintenance nutrition plan at 15 calories per pound body weight*

2250 calories

25% of calories from protein = 140grams of protein

That is quite a variance in protein intake! Now let's look at this example a different way, and calculate protein based on body weight:

Weight Loss nutrition plan at 10 calories per pound body weight*

1500 calories

2 grams of protein per kilogram body weight = 136 grams of protein (36% of total calories)

Weight maintenance nutrition plan at 15 calories per pound body weight*

2250 calories

2 grams of protein per kilogram body weight = 136 grams of protein (24% of total calories)

*Calorie amounts are very rough estimates. For accurate, personal caloric needs, be sure to do a CaloriePoint

In the example above, for the weight loss goals, 36% of the calories coming from protein may be considered a higher protein diet. However, because the protein recommendation was based on body weight, it is actually a reasonable amount for this individual's goals. Protein is a building block for many parts of the body.  The requirements for carbohydrate and fat can vary tremendously based on activity level and training goals, but it is not wise to reduce protein in the same way.

Protein Sources

The last big piece of the puzzle is deciding on where to get your protein from. Protein sources are sometimes divided between complete and incomplete proteins, which is a way of defining the amino acid content of protein. The terms are not perfect. Generally, plant sources are considered incomplete and animal sources complete proteins. In the case of incomplete proteins, at least a couple of different sources need to be eaten together in order to provide the body with all of its amino acid needs. Animal-based proteins are considered complete proteins as they provide all of the necessary amino acids. It is possible to mix plant sources of protein to make complete protein sources. Because of their high carbohydrate content, it's possible to overeat carbohydrates and calories when trying to achieve a sufficient protein intake on a plant-based diet. The choice to eat or avoid animal protein is a personal one.

Avoiding animal proteins increases the risk of nutrient deficiencies, and it can be more challenging to meet ideal protein intake, but it is still possible, if necessary, to meet protein needs with a vegetarian diet. The difference between a vegetarian diet and non-vegetarian diets deserves much more space than is available here, and will be addressed in the future. As we discussed in the first post in this series, there is not any reason to fear animal protein sources, unless they are heavily processed, or if they come from commercial farms. It is best to choose free-range, pastured, grass-fed, organic sources of animal protein.

In future articles, we'll look at individual protein sources, such as soy, whey, casein, egg, milk, and additional protein sources. Many of these sources deserve their own post in order to weigh out the pros, cons, and ideal use of each. Whey, egg, and milk protein seem to be the best sources from a physiological standpoint. We'll look at this on a deeper level in the future.

Go to: Part 1 - Protein and Health Concerns

Go to: Part 2 - Protein and Body Composition

Written By: Tom Nikkola, CSCS, CSSN 

References:

Dietary Reference Intakes: Recommended Intakes for Individuals (PDF|87 KB) National Academy of Sciences. Institute of Medicine. Food and Nutrition Board.

Campbell B, Kreider RB, Ziegenfuss T, La Bounty P, Roberts M, Burke D, Landis J, Lopez H, Antonio J. International Society of Sports Nutrition Position Stand: Protein and Exercise. J Int Soc Sports Nutr. 2007, 4:8

Layman DK, Evans E, Baum JI, Erickson DJ, Boileau RA. Dietary Protein and Exercise Have Additive Effects on Body Composition during Weight Loss in Adult Women. J. Nutr. 135:1903-1910, 2005

Westerterp-Plantenga MS, Rolland V, Wilson SA, Westerterp KR. Satiety related to 24 h diet-induced thermogenesis during high protein/carbohydrate vs high fat diets measured in a respiration chamber. Eur J Clin Nutr. 1999;53:495–50

Lowery LM, Devia L. Dietary protein safety and resistance exercise: what do we really know? J of the Int Soc Spo Nut. 2009; 6:3

Clifton PM, Keogh JB, Noakes M. Long-term effects of a high-protein weight-loss diet. Am J Clin Nutr. 2008;87:23-9

Krieger JW, Sitren HS, Daniels MJ, Langkamp-Henken B. Effects of variation in protein and carbohydrate intake on body mass and composition during energy restriction: a meta-regression. Am J Clin Nutr. 2006; 83:260-74

Layman DK, Evans EM, Erickson D, Seyler J, Weber J, Bagshaw D, Griel A, Psota T, Kris-Etherton P. A moderate-protein diet produces sustained weight loss and long-term changes in body composition and blood lipids in obese adults. J Nutr. 2009 139: 514-21

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