[Influence of foods on the posterior longitudinal ligament of the cervical spine and serum sex hormones].

To investigate the involvement of sex hormones as a potential cause of ossification in the posterior longitudinal ligament (OPLL) of the cervical spine, we experimentally examined the influence of ingested foods on the serum levels of sex hormones and changes in the spinal ligament. Castrated rabbits were administered a sex hormone and raised with special feed. Assay of the serum sex hormone levels, analysis of the carbon and nitrogen isotope ratios in body hairs, and histological studies were carried out. In the group administered soybeans and highly concentrated saline solution, the serum estrogen level was high, the serum testosterone level was low and the delta 15N value of the body hairs was also low. Histologically, a group of newly formed chondroblasts was seen in the posterior longitudinal ligament in the angular region of a narrowed intervertebral disc, and many fibroblasts were detected by assay using a microspectrophotometer (MSP) in this group. These findings suggested that a diet high in vegetable protein, consisting mainly of beans, and foods high in salt may lead to an unbalanced state for sex hormones and cause histological changes in the spinal ligament. This, as well as other general ossifying factors of ligament, may play a role in the etiology of ossification.