|Causes and Mechanisms of Linear Growth Retardation (International Dietary Energy Consultative Group - IDECG, 1993, 216 pages)|
|The mechanical factors which influence bone growth|
Of more importance to the practical study of the effects on the mechanical behaviour of bone is the apparent growth stimulation which can occur in normal adolescents, particularly females developing idiopathic scoliosis. The average height of these patients has been found to be significantly greater than that of a similar matched population (Ashcroft & Lovell, 1966). This association was first observed in Sweden (Willner, 1975).
Amongst the many parameters we have studied in the course of a general investigation centered around the aetiology of idiopathic scoliosis, the height, arm span, upper and lower body segments were routinely measured. The results were compared with those obtained on a similar group of normal Jamaican school children of the same age. There is no doubt that excessive growth occurs. There seems little else to which to attribute this other than a changing diet.
The scoliosis study began in 1956 and includes cases presenting earlier. We seem to have had an epidemic of the condition, which started around 1975, reached its peak between 1978 and 1984, and has begun to decline. This decline is particularly impressive when one takes into account the fact that the number of adolescent children at risk has been steadily increasing at a rate of about 1.7% p.a. since the study started. Although the deformity, in the idiopathic variety, does not usually manifest itself until puberty, the background of stimulation must start earlier in childhood. We have tried to investigate this and came up against great difficulties, for the obvious reason that the suppliers of animal feeds, which are known to contain anabolic agents, are very loath to give the details of the amount and type of additive used. The fear of litigation prevents them from cooperating and has prevented us obtaining conclusive evidence. Large amounts of oestrogens were added to the feed of broiler hens in the 1960s and early 1970s before it was prohibited. Anabolic agents are still added to animal feeds, although it seems that the quantity has been decreased and the actual types used have been altered.
If one allows ten years between the onset of our 'epidemic' and the time that these agents apparently began to be added to the animal feed in Jamaica, there seems to be a degree of correlation, if only a loose one (Golding, 1991). There may be some confirmation for the hypothesis that the idiopathic form of scoliosis has an association with diet in three unrelated facts:
Firstly, we found that estimates of social class and income groups in these patients suggested strongly that it was the better off town patients who were particularly liable to develop the condition. The country patients who eat natural, locally produced food were less likely to develop idiopathic scoliosis.
Secondly, measurements of leg length have shown that a leg length discrepancy of more than a quarter inch occurs in almost 25% of patients with idiopathic scoliosis compared with 4% of normal adolescent children.
Thirdly, the rare form of idiopathic scoliosis which develops in infancy rather than at puberty is commoner in Holland than in most of the rest of Europe, and is peculiarly rare in North America, suggesting that an environmental rather than a genetic factor is at work.