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Current world supplies of and requirements for essential amino acids

Hoshiai Kazuo

Abstract

Correlations of GDP per capita per year with total protein supplies per capita per day and animal-protein ratios were computed by pooling data prom 164 countries. Average supplies for 1972-1974, 1975-1977, 1979-1981, and 1984-1986 were determined from FAO food balances sheets. Essential amino acid (EAA) supplies by country were computed using amino acid data for food commodities shown in FAO food balance sheets and other data. The EAA requirements for the four periods were estimated by country. When the latest amino acid requirement estimates are used, lysine is the limiting amino acid in all predominantly cereal diets.

Editor's note

Dr. Hoshiai has utilized the new essential amino acid pattern proposed by Vernon Young and collaborators using modern stable-isotope methodology. * For adults these values are much higher than those found by Rose and collaborators in the 1940s using the N-balance technique and still accepted as recently as the 1985 FAO/WHO/UNU Expert Consultation on Energy and Protein Requirements. Recently, however, an ad hoc expert consultation convened by the FAO has accepted in principle the conclusion of Young and collaborators that essential amino acid requirements per gram of protein are the same for adults as previously observed for children. Pending additional studies, the group recommended simply applying the essential amino acid pattern proposed in the 1985 report to all ages except infants. While the exact values differ slightly from those proposed by Young and collaborators, they are sufficiently similar that their use would not significantly alter the calculations in Dr. Hoshiai's article.

Introduction

In an earlier paper l reported semi-logarithmic correlations of gross domestic product (GDP) per capita per year in US dollars at 1975 prices with total protein per capita per day and animal protein ratios by country [1]. The data were calculated statistically for 164 countries at intervals of three years for the period 1966-1980. The future demand for total, vegetable' and animal protein was also statistically estimated from these values to the year 2000.

The balance between essential amino acid (EAA) supplies and requirements has relevance to fundamental problems in the utilization of protein-rich food. In 1973, EAA requirements were expressed in terms of a scoring pattern by FAO/WHO [2]. Revised requirements were published in 1985 by FAO/WHO/ UNU [3], with patterns (EAA mg/kg/day) given for different ages. On the basis of this revision, I subsequently studied the EAA imbalance by country and for the world, comparing the 1973 and 1985 patterns [4-6].

A newly proposed EAA pattern has been estimated on the basis of ¹³C-labelled amino acid tracer studies [7; 8]. This new pattern proposes much higher requirements for EAA for adults than the 1985 pattern. This is especially the case for lysine, with adult levels similar to those for pre-school children (25 year old).

Protein supplies and GDP by countries have also changed over the years. Therefore, I have undertaken to compute up-to-date world correlations of GDP (in US dollars at 1980 prices) with total protein supplies and animal-protein ratios for four three-year periods between 1972 and 1986. Related changes in the EAA nutritional balance were studied by comparing protein supplies with the 1973, 1985, and 1990 patterns by country and for the world. This paper summarizes the results in the hope that they will be of service in planning the improvement of world protein food supplies and intake.

Computations and findings

Correlations of GDP with protein supplies and animal-protein ratios

Semi-logarithmic correlations of GDP per capita per year in US dollars at 1980 prices [9] with total protein supplies per capita per day and animal-protein ratios were computed on a world basis by pooling the data from 164 countries for 1972-1974, 1975-1977, 19791981, and 1984-1986 from FAO food balance sheets and related information [10]. The computation was done by the least-squares method, with the data statistically weighted according to population. Recently corrected GDP and population figures were incorporated for calculating these linear regressions. These and related coefficients are shown in table 1. The slopes of the world correlations have moved a little to the left from those reported earlier [1] because of a change of the formula constants, primarily because protein food prices rise with inflationary tendency year by year.

Generally, protein nutrition, which corresponds to the quantity and quality of protein supplies, has improved in most countries. The correlation of GDP with total protein supplies implies that countries on the left of the world standard line, such as those classified as developed market economies, pay higher prices for protein-rich food. Countries on the right of the line, such as those in southern Asia and countries classified as centrally planned economies, pay lower prices.

Animal-protein ratios have closer correlation with GDP as well as the prices of animal-protein food because animal protein always costs more than vegetable protein. It is worth noting that the correlation coefficients between GDP and animal-protein ratios are higher than those between GDP and total protein supplies.

EAA supplies and requirements

The EAA supplies by country were computed using amino acid data [11-14] for food commodities shown in FAO food balance sheets and other data [9]. These publications include 381 items of food commodities in 162 countries in the 1972-1974 average, 444 items in 164 countries in the 1975- 1977 average, and 300 items in 146 countries in the 1979-1981 average. The most recent information consists of 220 items in 146 countries in the 1984-1986 average. The coverage for food compiled in each FAO publication is the same as the whole, although there are many differences in the number of items in each period. For a small number of food items for which amino acid data are not available, the EAA contents were estimated from other similar foods. EAA supplies by region and economic system, and for the world, were determined by summing the food commodities of related countries on the basis of FAO statistics.

TABLE 1. Correlation formulas and related coefficients

X = GDP (US dollars per capita per year al 1981 prices).
Y = total protein supplies (grams per capita per day).\
Z = animal-protein ratio ( % ).
1. At 1980 prices [1].

The EAA requirements by country for the four periods were estimated using the three requirement patterns shown in table 2. For the 1985 pattern, the requirements at ages 0, 1, 6-9, and 13-17 years were interpolated curvilinearly from those at ages 0, 2-5, 10-12, and over 18 years shown by FAO/WHO/UNU [3]. The figures for the 0-year and 1-year age groups include not only the requirements for infants themselves but also those for their lactating mothers in some measure. Practically, however, the requirements for infants have little influence on the overall imbalance of EAA by country because the body weights of infants are small. For the new pattern, EAA requirements for everyone from children over two years old to adults are determined by accepting a protein requirement of 0.75 g per kilogram [7] as a safe conversion level from milligrams of EAA per gram of protein to milligrams of EAA per kilogram of body weight. Age distributions for each country in relation to the time periods and also to average changes in body weight of both sexes were estimated from published data [15-19]. For the estimates of changes in body weight, two categories were used - people of European or American descent, and those of African, Asian, or Mediterranean descent (table 3) - because detailed statistical data for all countries in the world are not available. The EAA requirements by region and economic system and for the world were calculated in the same way as the EAA supplies.

TABLE 2. Requirement patterns for essential amino acids (milligrams per kilogram of body weight)

a. Ref. 2.
b. Ref. 3. In designating age groups, "1," for example, represents an average for the range 1.0-1.99 years.
c. Interpolated curvilinearly from the values in ref. 3.
d. Ref. 5. Requirements for the ages 0-1 are the same as in the 1985 pattern.

TABLE 3. Assumed body weights (kilograms) by age group

Imbalance indexes (I.I.) representing the quantitative balance of the supply of individual essential amino acids relative to their requirement were calculated for countries, for regions, and for the world on the basis of the 1973, 1985, and new requirement patterns. A perfect balance would be indicated by an I.I. of 1.0; an I.I. less than 1.0 shows a relative deficiency, and one of more than 1.0 a relative excess.

The formula for the index using the 1973 pattern is

where S_a and R_a are respectively the supply and the requirement according to the 1973 pattern for each EAA, and S_total is the total EAA Supply' with all values on the right-hand side of the equation in milligrams per gram of protein.

For the 1985 and new patterns, the formula is

where S and R again represent supply and requirement according to the relevant pattern, with the values in this case being in tons (or any convenient weight unit) per year. The supply of each EAA is calculated by summing the quantities of the EAA from a variety of protein sources. and the requirement by summing the quantities determined using the requirement pattern and body weights by age group.

Current balances between EAA supplies and requirements

Table 4 and summarizes protein supplies and EAA balances for 23 countries with populations of more than 35 million from among the 146 countries for which 1984-1986 data were studied. Remarkable differences between the 1973, 1985, and new EAA patterns are seen in the first and second limiting amino acids (LAAs). By the 1973 pattern, threonine (Tier) and lysine (Lys) are the predominant first LAAs in countries with higher and lower GDPs respectively. By the 1985 pattern' sulfur-containing amino acids (SAAB) and Lys predominate as the first LAA under the same GDP conditions. By the new pattern, leucine (Leu) is the first LAA in the higher-GDP countries, and the relative deficiency of Lys increases noticeably in the lower-GDP countries. Countries where Lys is the first LAA are mostly in Asia and areas around the Mediterranean where animal-protein ratios are comparatively low as a consequence of high cereal intake.

TABLE 4. Protein supplies per capita and essential amino acid balances in countries with populations of more than 35 million (1984-1986 averages)

a. Deficiency of first limiting amino acid (LAA) relative to second LAA, in tons per year.
b. Ratio of supply of first LAA to requirement.

The ratios of supplies to requirements (S:R ratios) for the first LAA range from 2.0 to 5.3 for the 1985 EAA pattern but fall to 1.2-3.4 for the new pattern. It is supposed that an LAA S:R ratio below 2.0 may cause a deficiency of protein intake because the practical protein supplies are influenced by season, locality, income distribution, and so on. The countries with ratios below 2.0 all have Lys as their first LAA. Accordingly, these countries may be in an especially precarious state.

Table 5 and presents protein supplies and EAA balances in 1984- 1986 by regions and economic systems and for the world. The first LAA for the world would be Thr by the 1973 EAA pattern and SAA by the 1985 pattern, but is Lys by the new pattern. The deficiencies in the first LAA are estimated at 200,000 tons per year for Thr, 380,000 tons for SAA, and I million tons for Lys.

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