Implications

Note: At normal calcium absorption, the intercept of urinary plus skin calcium meets absorbed calcium at an intake of 840 mg as in Figure 14. A 10 percent reduction in calcium absorption raises the intercept and requirement to 1150 mg and a 10 percent increase in calcium absorption reduces it to 680 mg.

FAO/WHO and other Nutritionists...verbatim.

The major reduction in theoretical calcium requirement which follows animal protein restriction has led us to attempt to show in Table 33 how the calcium allowances recommended in Table 31 could be modified to apply to nations where the animal protein intake per capita is around 20–40 g rather than around the 60–80 g in developed countries.

Dibba, B., Prentice, A., Ceesay, M., Stirling, D.M., Cole, T.J. & Poskitt, E.M.E. 2000. Effect of calcium supplementation on bone mineral accretion in Gambian children accustomed to a low calcium diet. Am. J. Clin.. Nutr., 71: 544-549.

These hypothetical allowances take into account the need to protect children, in whom skeletal needs are much more important determinants of calcium requirement than are urinary losses and in whom calcium supplementation had a beneficial effect in the Gambia. However, adjustment for animal protein intake has a major effect on the recommended calcium allowances for adults as the table shows. It also brings the allowances nearer to what the actual calcium intakes are in many parts of the world.

If sodium intakes were also lower in developing than developed nations or urinary sodium were reduced for other reasons such as increased sweat losses, the calcium requirement might be even lower, for example, 450 mg (Figure 18).

Fairweather-Tait, S., Prentice, A., Heumann, K.G. et al. 1995. Effect of calcium supplements and stage of lactation on the calcium absorption efficiency of lactating women accustomed to low calcium intakes. Am. J. Clin. Nutr., 62:1188-1192.

Aspray, T.J., Prentice, A., Cole, T.J., Saw, Y., Reeve, J. & Francis, R.M. 1996. Low bone mineral content is common but osteoporotic fractures are rare in elderly rural Gambian women. J. Bone Miner. Res., 11: 1019-1025.

This would be reduced still further by any increase in calcium absorption, whether resulting from better vitamin D status because of increased sunlight exposure or for other reasons, as illustrated in Figure 19. Because the increase in calcium absorption in the Gambia is much more than 10 percent, this is likely to have a major – although not at present calculable – effect on calcium requirement there. However, the adjusted bone mineral density in Gambian women is reported to be some 20 percent lower in the spine (but not in the forearm) than in British women, which emphasises the need for more data from developing countries.