The recommended intakes of many minerals and vitamins are controversial and in many cases based on early inappropriate experimental work. For example, the early vitamin D requirement for adults was based on anecdotal evidence from cod liver oil supplementation in children. Calcium too has had recommended levels based on data from inappropriate studies, with the initial data on calcium requirements in adults collected from Norwegian prisoners who had managed to adapt to low calcium requirements from poor diet. In this study, no account was made of the possible liberation of calcium from bone to plasma, making the data meaningless for long-term calcium requirements in healthy adults. More recent data has resulted in increases in the recommended requirement for calcium and other minerals, but data still suggests that the recommended daily intakes in many Western nations is too low for optimal nutrition.
Because many of the studies on calcium are based on data from soon after the second World War, researchers1 have attempted to investigate the calcium requirement of adult men using calcium balance studies previously published. A review of the literature revealed 157 suitable individual cases in men under the age of 59 years with intakes of less than 1100 mg of calcium. The results of the analysis showed that the calcium intake at which the urine calcium plus the skin calcium losses were equal to the net absorption, was around 750 mg per day. Based on the 750 mg per day rounded figure, it was calculated that the recommended intake for calcium should be 900 mg per day in order to prevent deficiency in the majority of the population. The current UK RDA is 800 mg for an adult, which suggests that the current recommendations do not supply adequate calcium.
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