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Current balances between EAA supplies and requirements

Table 5 summarizes recent balances between EAA supplies and requirements for 26 countries with populations of more than 35 million among the 164 countries for which protein supply data in 1987-89 were studied, on the basis of the four scoring patterns. It also shows the deficiencies of the first LAA relative to the second in tons per year and the ratios of supplies to requirements for the first LAA (S: R ratio).

As found earlier [1], the first LAAs in the higher-GDP countries on the basis of the 1973, 1985, and Young patterns are threonine (Thr), sulphur-containing amino acids (SAA), and leucine (Leu) respectively; tryptophan (Trp) becomes the first LAA on the basis of the 1989 FAD/WHO pattern. In the lower-GDP countries, on the other hand, the first LAA is mainly lysine (Lys) for all four patterns. In some countries with a medium GDP, the first LAA shows a tendency to move from Lys to Thr, SAA, Leu, or Trp.

The deficiency of Lys in the 1987-89 average is estimated to reach approximately 1.2 million metric tons, and it is larger for the 1989 FAD/WHO pattern than for the Young pattern.

The S:R ratios for the first LAA range from 0.33 in Viet Nam to 2.06 in France for the 1989 FAO/ WHO scoring pattern, noticeably smaller than for the Young pattern. The ratios will improve as the APRs increase, as shown in figure 1. The linear regression is represented by the following formula as a world standard, based on pooling the data statistically weighted according to population from 161 countries for the 1987-89 average.

S: R ratio = 0.0204 APR + 0.6355.

For this formula, APR is the animal protein ratio expressed as percentage, and the correlation coefficient is 0.902. In most countries where Lys is the first LAA, the S:R ratios are below about 1.5 and the animal protein ratios are below about 50%.

Table 6 presents average protein supplies and EAA balances in 1987-89 by region and economic level and for the world. The first LAA for the world changes from Thr for the 1973 scoring pattern to SAA for the 1985 pattern and to Lys for the Young and 1989 FAD/WHO patterns. However, the imbalance index of 0.748 for Lys throughout the world according to the 1989 pattern is smaller than that of 0.836 according to the Young pattern; i.e., the degree of imbalance is greater. Although the S: R ratio for Lys is 1.31 on an average for the world, the ratio for all developed countries is 1.93, indicating an abundant excess, and that for all developing countries is 1.05, indicating little excess over the requirement on average. Therefore, it appears that the deficiency of Lys in many of these developing regions is serious, especially in Africa and the Far East, where the S:R ratios are often below 1.00.

TABLE 7. Differences in the first limiting amino acids according to the 1989 scoring patterns and past scoring patterns in countries with populations of more than I million (1987-89 averages)

a. Averages of total protein supplies per capita.
b. Averages of animal-protein ratios.
c. Averages of ratios of supply of the first limiting amino acids to requirements.

Table 7 shows the differences between the first LAA for the 1989 FAD/WHO pattern and those for the earlier patterns in 127 countries with populations of more than 1 million in 1987-89. It shows that the total number of countries where Lys is the first LAA increased substantially for the 1989 FAO/ WHO scoring pattern.

In that respect, to change favourably from Lys as the first LAA to Trp according to the 1989 scoring pattern, it is generally expected that total dietary protein supplies would have to increase to approximately 80 g per capita per day and APRs would have to rise to approximately 50% (excluding some countries where a variety of vegetable protein sources besides cereals are consumed). In most countries where Lys as the first LAA is very deficient, the S:R ratios are below 1.00. Therefore, it would appear that a great part of the population in these countries may be consuming diets low in available protein. The severity of protein malnutrition would, of course, be greatest for children.

Among 164 countries throughout the world for which an EAA imbalance was computed for the 1987-89 data, 121 were indicated to be deficient in Lys. These countries are mainly in developing regions, and the total Lys deficiency amounts to 1.15 million metric tons per year. As a result, the total unavailable EAA for these countries is estimated to be 11 million metric tons per year, or about one-third of the total EAA supply of approximately 33 million metric tons per year for 1987-89. If the supply of Lys in these countries were supplemented by 1.15 million tons per year, bringing it to the level of the second LAA, the additional EAAs that would be made nutritionally available would amount to approximately 6.5 million tons, more than five times the amount of the supplemental Lys. With that, the total protein (EAAs and non-EAAs) that could be used effectively would increase by approximately 17 million tons, approximately 20% of the 85 million tons of total protein supplies.

In 1987-89, world protein and EAA supplies were approximately 132 and 53 million tons per year respectively. The additional amount of protein and EAAs that would be made available with the Lys supplement would amount to approximately 12% of these supplies. Therefore, Lys supplementation could potentially effect an economical improvement of protein nutrition in underdeveloped parts of the world. It is anticipated that the imbalance of Lys could be greatly improved either by fortifying cereals and other foods with lysine or by breeding acceptable plant sources of protein higher in lysine, as well as by greater use of locally available high-lysine plant foods such as legumes.

Dynamic relationship between EAA I.I.s and APRs

Figure 2 plots the shifts in EAA I.I.s for the first LAA relative to APRs according to the 1989 FAO/ WHO scoring pattern in 23 major countries for 1972-74, 1975-77, 1979-81, 1984-86, and 198789. A change in the first LAA from Lys in countries with low APRs to Trp in those at higher APR levels is shown in an upward belt zone. The world correlations of GDP and S: R ratios with APRs for 1972 to 1989 are also shown.

FIG. 2. Relation between imbalance indexes for the first limiting amino acids and animal-protein ratios in accordance with the 1989 FAO/WHO scoring pattern in 23 major countries for 1972-1989

Conclusion

Re-evaluation of the deta on protein supply from 1972 to 1989 according to the 1989 FAO/WHO scoring pattern reveals a significant change in the calculated world imbalance of EAA compared with estimates based on the 1985 FAO/WHO/UNU pattern. Furthermore, the 1989 FAO/WHO pattern suggests even higher levels of Lys and Trp than proposed in 1989 [4]. Thus, on the basis of the 1989 FAO/WHO scoring pattern, of the 164 countries studied for 1987-89, deficiencies of Lys as the first LAA are estimated at a total of 1.15 million metric tons for the 121 developing countries having low APRs.

In contrast, the first LAA for the majority of industrialized countries having higher APRs is Trp.

Improvement of protein nutrition in the developing countries hinges on measures to increase their lysine intake, either by fortification of lysine-deficient staple foods or by increased use of legumes or other high-lysine plant foods.

Acknowledgements

I would like to express my gratitude to the Statistics Division of FAO, the Statistical Division of the United Nations, and the Economic and Social Data Division of the World Bank for providing access to the latest statistical information on world food balance and economics.

References

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