FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS	ESN: FAO/WHO/UNU EPR/81/31A August 1981
	WORLD HEALTH ORGANIZATION
	THE UNITED NATIONS UNIVERSITY

Provisional Agenda Item 3.2.3

Joint FAO/WHO/UNU Expert Consultation on
Energy and Protein Requirements

Rome, 5 to 17 October 1981

VARIOUS COMMENTS RELATED TO AMINO ACID SCORING PATTERNS

by

C.E. Bodwell
USDA
Beltsville
Maryland

Working paper on amino acid scoring patterns. Dr. Harper (1) has presented a thoughtful analyses as to why certain differences exist between the FAO/WHO (2) and NRC (3) provisional amino acid scoring patterns and has made a recommendation that the sulfur amino acid level, in particular, should probably be lowered in any revision of the FAO/WHO provisional scoring pattern. This suggestion is based on data of Foman (detailed by Dr. Harper, ref. 1) and of more recent data based on estimates of essential amino acid requirements of children studied at INCAP (4,5). It should be noted that the “INCAP scoring pattern” listed in Table 14 of Dr. Harper's paper is based on preliminary calculations reported by Torun et al. and not on the final values as published (5). Specifically, instead of all 3 values for lysine being similar as stated by Dr. Harper, it should be noted that the final value for lysine suggested by Torun et al. (5) is much higher than the values used in either the FAO/WHO or NRC scoring patterns. As noted by Dr. Harper, the INCAP values for valine and isoleucine are lower than either the FAO/WHO or the NRC values while the INCAP value for total sulfur amino acids is lower than the FAO/WHO value but similar to the NRC value.

It would seem prudent for the committee to carefully consider the possibility that the value for total sulfur amino acids in the FAO/WHO provisional scoring pattern may be too high. Whether the present values for valine and isoleucine should be retained (despite the lower values suggested by the INCAP data) as suggested by Dr. Harper is obviously a decision which the committee will have to make. Likewise, the higher lysine value suggested by the INCAP data must be considered.

Inconsistencies In Patterns Of Requirements. As shown in Table 13 of Dr. Harper's (1) paper, the estimated levels of amino acids required, expressed as mg/kg body weight/day, decrease with age. This is a welT-known and accepted fact or concept which is biologically “logical.” It is also logical, however, to expect a general consistency in the level of any single essential amino acid as a proportion (percentage) of the sum of all of the essential amino acids. That is, it seems unlikely that there are non-uniform changes in the relative amounts of specific essential amino acids with changes in age. However, the requirement levels suggested by both FAO/WHO (2) and NRC (3) show such fluctuations as is illustrated by the data shown in Tables 1 and 2. As an example, it seems highly unlikely that lysine comprises 14.5% of the total essential amino acids required in infancy, 23.0% in childhood, and 14.5% in adulthood as indicated in Table 1. These and other similar “inconsistencies” are circled in Tables 1 and 2. This would seem to be a problem which the committee may wish to address.

Consistency Of Percentage Distribution Of Essential Amino Acids In Estimates Of Requirements And In Amino Acid Scoring Patterns. It is useful to compare the percentage distribution of each of the essential amino acids in the various estimates of requirements with similar percentage distributions in the provisional amino acid scoring patterns. Detailed data are included in Tables 1, 2 and 3 and a summary is given in Table 4. Although specific values (circled) are exceptions, the most striking fact is that of the degree of general agreement between the values shown (Table 4). The data is suggestive of the concept that if quite accurate estimates of essential amino acid requirements were available, the distribution patterns would be identical for all ages. In any case, comparisons such as that given in Table 4 may be useful in deliberations as to the validity of the current provisional FAO/WHO amino acid scoring pattern.

Estimates Of Protein Nutritive Value Obtained By Use Of Amino Acid Scores. Simple amino acid scores can only be expected to give a general indication of protein nutritive value since other factors may also be important (amino acid bioavailability, nitrogen digestibility, etc.). However, various scores appear to give reasonable estimates of protein nutritive value (5,7). One of the limitations of most scoring procedures (which are based on only the first limiting amino acid) is that no information is given about the nutritive value of the protein source when it is combined with other sources (as is the case in practice). The use of a score based on the single most limiting amino acid without question has value. However, the “scoring” of a protein for 3 or 4 selected amino acids (e.g., lysine, methionine plus cystine, tryptophan) has been suggested (7) and would give considerably more information than a simple score based on the level of one amino acid.

Nitrogen To Protein Conversion Factors. The 1973 report (2) noted that the factor of 6.25 was used throughout the report for converting nitrogen (N) to protein (i.e., N × 6.25 = protein). By listing various conversion factors for different protein sources, etc. In the Appendices, however, the report appeared to endorse the use and validity of the factors given. A committee for the AOAC (Association of Official Analytical Chemists) was convened in 1980 to address the question of the accuracy and application of the various factors suggested for different protein sources. The AOAC committee concluded that accurate factors do not exist and recommended that the use of only percent nitrogen values can be scientifically justified Attachment 1). The conclusions reached by the AOAC committee were based on a consideration of a large body of data (an example is shown in Attachment 2). It would seem prudent to avoid any implied endorsement of the use of the various factors as was done in the 1973 FAO/WHO report.

References

1. Harper, A. E. Working paper on “Amino Acid Scoring Patterns.”

2. FAO/WHO (Food and Agriculture Organization/World Health Organization). 1973. Energy and Protein Requirements. Report of a Joint FAO/WHO Ad Hoc Expert Committee. WHO Tech. Report Series 522, FAO Nutrition Meetings Report Series 52, Rome, Italy.

3. NRC (National Research Council). 1974. Improvement of Protein Nutriture. Committee on Amino Acids, Food and Nutrition Board, NRC. National Academy of Sciences, Washington, DC, 201 p.

4. Pineda, O., B. Torun, F. E. Viteri, and G. Arroyave. 1981. Protein Quality in relation to estimates of essential amino acids requirements. In “Protein Quality In Humans: Assessment and In Vitro Estimation,” C. E. Bodwell, J. S. Adkins and D. T. Hopkins (Eds.), AVI Publishing Co., Inc., Westport, Conn., pp. 29–42.

5. Torun, B., O. Pineda, F. E. Viteri, and G. Arroyave. 1981. 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. In “Protein Quality In Humans: Assessment and In Vitro Estimation,” C. E. Bodwell, J. S. Adkins, and D. T. Hopkins (Eds.), AVI Publishing Co., Inc., Westport, Conn., pp. 374–393.

6. Bodwell, C. E. 1977. Application of Animal Data to Human Protein Nutrition: A Review. Cereal Chem. 54: 958–983.

7. Bodwell, C. E. 1931. Use of amino acid data to predict protein nutritive value for adults. In “Protein Quality In Humans: Assessment and In Vitro Estimation,” C. E. Bodwell, J. S. Adkins, and D. T. Hopkins (Eds.), AVI Publishing Co., Inc., Westport, Conn., pp. 340–373.

^aRequirements for arginine and histidine for the rat and for histidine for humans not included incalculations.
^bSource: FAO WHO (3) assuming safe levels of protein intake of 2.0.0.8. and 0.55 g protein kg body wt day for infants. children (10–12 years of age). and adults. respectively.
^cCalculated from requirement levels for lysine given by Stockland et al. (7) and for all other amino acids by Rama Rao et al. (8). assuming a total protein requirement equivalent to 10% dietary protein. protein.
^dCalculated from requirement levels given by Said and Hegsted (9). who assumed a protein requirement equivalent to 3.2% of the diet. by wt.
^eCalculated from requirement levels given by Ashida and Yoshida (10). who assumed a protein requirement equivalent to 5% of the diet. by wt: the estimates of requirement levels by these authors are probably in error, since the assumed protein requirement is probably too high.

^aExcluding histidine; based on the NRC estimates of protein requirements (1.5, 0.75 and 0.47 gm protein/kg/day for 4–6 month infants, children and adults, respectively).

^aHistidine not included; INCAP values are from Torun et al. (1981).

Attachment I

The Referee

FEBRUARY 1981

VOL. 4, NO. 5

Ten issues per year published by the

1111 N. Nineteenth St.—Suite 210
Arlington. VA 22209

Cecilia Cassidy, Editor

Ad Hoc Committee Calls For Comments On Nitrogen-To-Protein Conversion Factor

The Nitrogen-to-Protein Conversion Factor Committee met on December 17, 1980. They concluded that accurate factors for converting nitrogen to protein do not exist, and made the following recommendations:

1. All analyses report the percentage nitrogen in the sample.
2. If the percentage of protein is reported, the nitrogen-to-protein conversion factor used shall be specified in the report.
3. As desired, the traditional and customary nitrogen-to-protein conversion factors may be used as listed in Section 14.063 in the 12th Edition of Official Methods of Analysis OR Section 14.068 of the 13th Edition modified to read as follows:

2.057 Protein = nitrogen × 6.25 except for wheat and its products in which protein equals N × 5.7."

Other traditional and customary factors are 5.18 for almonds; 5.46 for peanuts and brazil nuts; 5.30 for tree nuts and coconut; 6.38 for dairy products.

Modification of 14.068 was approved interim official first action in March, 1980. Committee D gave official first action approval at the October, 1980 meeting, and the 6.25 factor approved in October will appear in “Changes in Methods” in March, 1981. It should be made clear that this “change” is actually a reversion to the factors as published in the 12th Edition of Official Methods of Analysis.

Comments on this recommendation should be sent to Doris Baker, General Referee for Cereal Foods, via the AOAC office. The committee's recommendations will then be forwarded to eleven General Referees and then to Committees A, C, and D.

Attachment II

From “pre-print” supplied by Sosulski et. al.; Canadian Journal of Plant Science.

Table 4.8 AA composition (mg/g N), N distribution (mg/g N), N-P factors and chemical scores for fifteen sources of animal proteins

1.FAO, 1970.
2.Owusu-Domfeh et al., 1970.
3.Rubin, 1972.
4.Alexander and Elvehjem, 1956.
5.Holt and Sosulski, 1974.
6.WHO (1973) provisional pattern.
7.Personal data.
8.Corrected for AAN recovery.