Yet another protein question

Catalonia

New Member
Hi.. I just read Bryan's bit on protein in his newsletter. I think I grasp it--but i'd like to be certain. If i'm taking a whey protein (with creatine and dextrose) prior to working out. It doesn't really matter that much what the 'quality' is so long as I can digest it? (and as long as I consume enough of it)
The second, and more important question is regarding 'casein' or calcium caseinate. is Hydrolyzed Casein truely superior in MEANINGFUL terms? I do not care at all if anything is superior in technical or abstract ways.
Thanks
 
Protein quantity will always make up for quality as long as the protein source has the full spectrum of amino acids at some level. The better the balance of amino acids, the less you need.

However, whith the typical bodybuilder diet, you will seldom be protein deficient.

Hydrolyzed casein (casein hydrolysate) is just casein that has been predigested using bovine digestive enzymes (from their gut). As long as you don't lose any amino acids in the process there will be no change in its nutrative value. the only thing that "might" change is that it won't be released as slowly. Casein is generally a "slow" protein, meaning it is time-released. Or has a sustained release pattern. When you pre-digest it, it will act more like whey.

However, remember one thing, hydrolysates of ANY kind taste absolutely aweful. So, if you are taking something that says it is made with hydrolysates, it will only actually have a tiny bit of it.
 
The Protein Digestibility–Corrected Amino Acid Score1
Gertjan Schaafsma

Center of Expertise Nutrition, DMV International-Campina Melkunie, 6700 AA, Wageningen, the Netherlands



ABSTRACT
TOP
ABSTRACT
INTRODUCTION
Validity of preschool-age child...
Validity of true fecal...
Truncation of PDCAAS values...
REFERENCES


The protein digestibility–corrected amino acid score (PDCAAS) has been adopted by FAO/WHO as the preferred method for the measurement of the protein value in human nutrition. The method is based on comparison of the concentration of the first limiting essential amino acid in the test protein with the concentration of that amino acid in a reference (scoring) pattern. This scoring pattern is derived from the essential amino acid requirements of the preschool-age child. The chemical score obtained in this way is corrected for true fecal digestibility of the test protein. PDCAAS values higher than 100% are not accepted as such but are truncated to 100%. Although the principle of the PDCAAS method has been widely accepted, critical questions have been raised in the scientific community about a number of issues. These questions relate to 1) the validity of the preschool-age child amino acid requirement values, 2) the validity of correction for fecal instead of ileal digestibility and 3) the truncation of PDCAAS values to 100%. At the time of the adoption of the PDCAAS method, only a few studies had been performed on the amino acid requirements of the preschool-age child, and there is still a need for validation of the scoring pattern. Also, the scoring pattern does not include conditionally indispensable amino acids. These amino acids also contribute to the nutrition value of a protein. There is strong evidence that ileal, and not fecal, digestibility is the right parameter for correction of the amino acid score. The use of fecal digestibility overestimates the nutritional value of a protein, because amino acid nitrogen entering the colon is lost for protein synthesis in the body and is, at least in part, excreted in urine as ammonia. The truncation of PDCAAS values to 100% can be defended only for the limited number of situations in which the protein is to be used as the sole source of protein in the diet. For evaluation of the nutritional significance of proteins as part of mixed diets, the truncated value should not be used. In those cases, a more detailed evaluation of the contribution of the protein to the amino acid composition of the mixed diet is required. From such an evaluation, it appears that milk proteins are superior to plant proteins in cereal-based diets.



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KEY WORDS: • protein quality • amino acid score • scoring pattern • digestibility • critical evaluation


INTRODUCTION
TOP
ABSTRACT
INTRODUCTION
Validity of preschool-age child...
Validity of true fecal...
Truncation of PDCAAS values...
REFERENCES


It is well accepted that the nutritional value of proteins may differ substantially depending on their (essential) amino acid composition and digestibility. For many years, bioassays, mainly with rats, were the methods of choice to assess the nutritional value of proteins. This value was expressed in parameters such as protein efficiency ratio, net protein utilization and biological value. In 1989, a joint FAO/WHO Expert Consultation on Protein Quality Evaluation (FAO/WHO 1990 ) concluded that protein quality could be assessed adequately by expressing the content of the first limiting essential amino acid of the test protein as a percentage of the content of the same amino acid in a reference pattern of essential amino acids. This reference pattern was based on the essential amino acid requirements of the preschool-age child as published in 1985 (FAO/WHO/UNU 1985 ) (Table 1 ). Subsequently, this percentage is corrected for the true fecal digestibility of the test protein, as measured in a rat assay. This scoring method, known as the protein digestibility–corrected amino acid score (PDCAAS),2 was adopted as the preferred method for measurement of the protein value in human nutrition. Proteins with PDCAAS values exceeding 100% were not considered to contribute additional benefit in humans and were truncated to 100%. The PDCAAS formula is shown later.








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Table 1. FAO/WHO/UNU amino acid requirement pattern based on amino acid requirements of preschool-age child1




Table 2 shows values for protein efficiency ratio, true fecal digestibility, amino acid score and nontruncated PDCAAS for some selected proteins.



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Table 2. True fecal digestibility, amino acid score and PDCAAS for selected proteins1




Now, after ~10 y of experience with the PDCAAS method, it can be concluded that the method has been adopted widely. On the other hand, critical questions have been raised in the scientific community (Dutch Dairy Foundation on Nutrition and Health 1995 , Darragh et al. 1998 ) about the following three PDCAAS issues: 1) the validity of the preschool-age child amino acid scoring pattern, 2) the validity of the true fecal digestibility correction and 3) the truncation of PDCAAS values to 100%.
These issues are discussed later; it is concluded that it is timely to evaluate the PDCAAS method in its current form.


Validity of preschool-age child amino acid scoring pattern
TOP
ABSTRACT
INTRODUCTION
Validity of preschool-age child...
Validity of true fecal...
Truncation of PDCAAS values...
REFERENCES


This reference scoring pattern (Table 1) is based on amino acid balance studies performed ~20 y ago by Torun et al. (1981) and Pineda et al., 1981 ) in a limited number of 2-y-old children. These children were recovering from malnutrition and thus not representing normal healthy preschool-age children. The results of these studies, which so far have not yet been published in peer-reviewed international journals, were expressed in mg/kg of body weight/d and were assumed to include a safety margin of the same magnitude as that of the FAO/WHO safe level of high quality protein (meat, fish, egg, milk) intake for this particular group of children. The reference pattern was obtained by computing the ratios between the essential amino acid requirement values (mg/kg body weight/d) and this safe level of high quality protein intake (g/kg body weight/d), thus resulting in values of mg/g of protein for each essential amino acid.

Although there is no evidence to reject the assumption that both numerator and denominator of these ratios include similar margins of safety, this has not been validated. A difference in safety margins of nominator and denominator would result in an incorrect reference pattern with underestimated or overestimated values.

Another issue is that the current reference pattern is restricted to the indispensable amino acids and does not include amino acids that become indispensable under specific physiological or pathological conditions, such as cystine, tyrosine, taurine, glycine, arginine, glutamine and proline. This implies that these latter amino acids should also contribute to the nutritional value of a protein (van Hooydonk 1994 ).

These considerations plead for a critical contemplation of the current scoring pattern.


Validity of true fecal digestibility correction
TOP
ABSTRACT
INTRODUCTION
Validity of preschool-age child...
Validity of true fecal...
Truncation of PDCAAS values...
REFERENCES


As recognized by the FAO/WHO Expert Consultation on protein quality evaluation (1990), the intestinal flow of amino acids beyond the terminal ileum is an important route for bacterial metabolic consumption of amino acids. Amino acids that appear in the colon are most probably lost for body protein synthesis. Therefore, ileal rather than fecal digestibility is the critical biologically relevant parameter for amino acid or protein digestibility. The Expert Consultation recognized the shortcomings of the true fecal digestibility correction and recommended methodological studies to resolve uncertainties about the contribution and variation of endogenous amino acid losses at the terminal ileum before the determination of ileal digestibility could be recommended to replace fecal digestibility. Since then, several studies in this field were published (e.g., Caine et al. 1997a and 1997b , Huisman et al. 1993 , Rowan et al. 1994 , Van Leeuwen et al. 1996 ) indicating that antinutritional factors associated with dietary proteins may enhance substantially endogenous losses of amino acids and therefore decrease the nutritional value of the protein. Only true ileal digestibility of amino acids will take these losses into account (Darragh et al. 1998 ), and it is therefore timely to consider the use of ileal instead of fecal digestibility values.


Truncation of PDCAAS values to 100%
TOP
ABSTRACT
INTRODUCTION
Validity of preschool-age child...
Validity of true fecal...
Truncation of PDCAAS values...
REFERENCES


According to the current PDCAAS method, values that are higher than 100% are truncated to 100%, arguing that digestible essential amino acid concentrations in a protein in excess of those in the preschool-age child reference pattern do not provide additional nutritional benefit. This statement is correct when the protein in question is the sole source of protein in the human diet, as occurs in infant feeding practices and under special conditions, like enteral feeding. However, under all other conditions, humans consume mixed diets with proteins from a variety of sources. Under such conditions, the power of high quality proteins to balance the amino acid pattern of the mixed diet is extremely relevant. A classic and widely accepted example in this regard is the combination of milk and wheat, in which the relatively high lysine concentration of milk proteins compensates for the low concentration of this essential amino acid in wheat. So it can easily be computed that 1.2 g of casein can balance 1 g of wheat protein, whereas 6.2 g of soy protein would be needed to do so (Table 3 ). The truncation of PDCAAS values thus largely eliminates the differences in the power of high quality proteins to balance the amino acid composition of inferior proteins. This is highly relevant, not only for the low lysine content of cereals but also for the low content of S-containing amino acids and threonine of many plant protein sources. Thus, truncated PDCAAS values do not provide information about the potency of a protein to balance inferior proteins, and a solution for this problem should be found.




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Table 3. Amount of protein needed to upgrade 1 g of wheat protein to obtain the preschool-age child’s lysine requirement level of 58 mg/g mixed crude protein




The questions about the validity of the amino acid scoring pattern and the application of the true fecal rather than the true ileal digestibility correction as well as the truncation of PDCAAS values warrant a critical evaluation of PDCAAS in its current form as a measure of protein quality in human diets.


FOOTNOTES

1 Presented at the symposium "Criteria and Significance of Dietary Protein Sources in Humans," held in San Francisco, CA, on October 4, 1999. The symposium was sponsored by the National Dairy Council; International Dairy Federation; United Kingdom Dairy Association; Dairy Farmers of Canada; Davisco Foods International, Inc., New Zealand Milk; CAMPINA MELKUNIE, Zaltbommel, The Netherlands; Land O’Lakes; and CERIN. Published as a supplement to The Journal of Nutrition. Guest editors for this publication were Gregory D. Miller, National Dairy Council, Rosemont, IL, and Daniel Tome, Institut National Agronomique, Paris, France.

2 Abbreviation used: PDCAAS, protein digestibility–corrected amino acid score.


REFERENCES
TOP
ABSTRACT
INTRODUCTION
Validity of preschool-age child...
Validity of true fecal...
Truncation of PDCAAS values...
REFERENCES




1. Caine W. R., Sauer W. C., Tamminga S., Verstegen M.W.A., Schulze H. Apparent ileal digestibilities of amino acids in newly weaned piglets and fed diets with protease-treated soybean meal. J. Anim. Sci. 1997a;75:2962-2969[Abstract/Free Full Text]
2. Caine W. R., Tamminga S., Verstegen M.W.A., Sauer W. C., Schulze H. Endogenous recoveries of true ileal digestibilities of amino acids in newly weaned piglets fed diets with protease-treated soybean meal. J. Anim. Sci. 1997b;75:2970-2979[Abstract/Free Full Text]

3. Darragh A. J., Schaafsma G., and Moughan P. J. Impact of amino acid availability on the protein digestibility corrected amino acid score. Proceedings of the Nutrition Week of the International Dairy Federation, Wellington, New Zealand, March 9–11, 1998 1998

4. Dutch Dairy Foundation on Nutrition and Health Proceedings of the International Workshop on Nutritional Aspects of Milk Proteins in Comparison with Other Proteins, organized by the Dutch Foundation on Nutrition and Health, Utrecht, the Netherlands, March 13–14, 1995 1995

5. European Dairy Association Nutritional Quality of Proteins 1997 European Dairy Association Brussels, Belgium.

6. FAO/WHO Expert Consultation Protein Quality Evaluation 1990 Food and Agricultural Organization of the United Nations FAO Food and Nutrition Paper 51, Rome.

7. FAO/WHO/ÚNU Expert Consultation Energy and Protein Requirements. Technical Report Series 724 1985 World Health Organization Geneva

8. Huisman J., Verstegen M.W.A., Van Leeuwen P., Tamminga S. Reduction of N pollution by decrease of the excretion of endogenous N in pigs. Nitrogen Flow in Pig Production and Environmental Consequences 1993:55-61 Pudoc Scientific Publishers Wageningen, the Netherlands.

9. Pineda O., Torun B., Viteri F. E., Arroyave G. Protein quality in relation to estimates of essential amino acid requirements. Bodwell C. E. Adkins J. S. Hopkins D. T. eds. Protein Quality in Humans 1981:29-42 AVI Publishing Company Westport, CT.

10. Renner E. Milk and Dairy Products in Human Nutrition 1983:90-130 W-Gmbh Volkswirtschaftlicher Verlag München.

11. Rowan A. M., Moughan P. J., Wilson P. J., Maher K., Tasman-Jones C. Comparison of ileal and fecal digestibilities of dietary amino acids in adult humans and evaluation of the pig as a model for animal digestion studies in man. Br. J. Nutr. 1994;71:29-42[Medline]

12. Torun B., Pineda O., Viteri F. E., Arroyave G. Use of amino acid composition data to predict protein nutritive value for children with specific reference to new estimates of their essential amino acid requirements. Bodwell C. E. Adkins J. S. Hopkins D. T. eds. Protein Quality in Humans 1981:374-393 AVI Publishing Company Westport, CT.

13. Van Hooydonk A.C.M. Definition of the nutritional value of dietary proteins. Protein Definition. Proceedings of the 1st IDF Symposium, Minneapolis, MN, October 1993. International Dairy Federation, Brussels 1994

14. Van Leeuwen P., Veldman A., Boisen S., Deuring K., Kempen G.J.M., Derksen G. B., Verstegen M.W.A., Schaafsma G. Apparent ileal dry matter and crude protein digestibilty of rations fed to pigs and determined with the use of chromium oxide (Cr2O3) and acid-insoluble ash as digestive markers. Br. J. Nutr. 1996;76:551-562[Medline]


You might want to look up this review also.

Functional properties of whey, whey components, and essential amino acids: mechanisms underlying health benefits for active people (review).

Ha E, Zemel MB.

Functional Ingredients Research, Inc, Twin Falls, Idaho, USA.

Whey proteins and amino acid supplements have a strong position in the sports nutrition market based on the purported quality of proteins and amino acids they provide. Recent studies employing stable isotope methodology demonstrate the ability of whey proteins or amino acid mixtures of similar composition to promote whole body and muscle protein synthesis. Other developing avenues of research explore health benefits of whey that extend beyond protein and basic nutrition. Many bioactive components derived from whey are under study for their ability to offer specific health benefits. These functions are being investigated predominantly in tissue culture systems and animal models. The capacity of these compounds to modulate adiposity, and to enhance immune function and anti-oxidant activity presents new applications potentially suited to the needs of those individuals with active lifestyles. This paper will review the recent literature that describes functional properties of essential amino acids, whey proteins, whey-derived minerals and other compounds and the mechanisms by which they may confer benefits to active people in the context that exercise is a form of metabolic stress. The response to this stress can be positive, as with the accretion of more muscle and improved functionality or greater strength. However, overall benefits may be compromised if immune function or general health is challenged in response to the stress. From a mechanistic standpoint, whey proteins, their composite amino acids, and/or associated compounds may be able to provide substrate and bioactive components to extend the overall benefits of physical activity.

Publication Types:
Review
Review, Tutorial

PMID: 12832028 [PubMed - indexed for MEDLINE]


Heres another good one

Protein supplements and exercise1,2,3,4
Robert R Wolfe
1 From the Shriners Burns Institute, Metabolism Unit, University of Texas Medical Branch, Galveston.

2 Presented at the workshop Role of Dietary Supplements for Physically Active People, held in Bethesda, MD, June 3–4, 1996.

3 Supported by grant 38010 from the National Institutes of Health.

4 Address reprint requests to RR Wolfe, Shriners Burns Institute, Metabolism Unit, 815 Market Street, Galveston, TX 77550.



ABSTRACT
TOP
ABSTRACT
INTRODUCTION
SCIENTIFIC RATIONALE FOR...
DIRECTIONS FOR FUTURE RESEARCH
CONCLUSION
REFERENCES


Active persons ingest protein supplements primarily to promote muscle strength, function, and possibly size. Currently, it is not possible to form a consensus position regarding the benefit of protein or amino acid supplements in exercise training. Determination of whether supplements are beneficial has been hampered by the failure to select appropriate endpoints for evaluation of a positive effect. Furthermore, studies focused at a more basic level have failed to agree on the response of protein metabolism to exercise. An additional complication of dietary studies that is not often taken into account is amount of energy intake. Because of these and other complications, studies at the whole body level have not yielded a clear picture of the need for, or response to, dietary protein or amino acid supplements. Consequently, it is necessary to examine this issue at the tissue level. In untrained subjects, both muscle protein breakdown and synthesis are increased in response to exercise. Amino acid intake further stimulates muscle protein synthesis after exercise as a consequence of stimulating amino acid transport into the intramuscular compartment. The stimulatory effect of amino acids after exercise is greater than the effect of amino acids on muscle protein synthesis when given at rest. These data suggest that not only may the exact composition and amount of an amino acid supplement be important, but the timing of ingestion of the supplement in relation to the exercise must be considered in designing future studies to evaluate the efficacy of amino acid supplements.

Full Version Here

http://www.ajcn.org/cgi/content/full/72/2/551S
 
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