(I) Interaction between vitamin B1 and calcium or magnesium -animal experiments- Effects of calcium and magnesium deficiencies on vitamin B1 metabolism: (a) In rats fed a calciumdeficient diet for 4 weeks, the concentration of thiamin in synaptosomal and myelin-membrane fractions in the brain was decreased and the ratio of free thiamin to total thiamin and the amount of nonprotein-bound thiamin were increased in the brain. In rats fed a magnesium-deficient diet for 4 weeks, the concentration of thiamin in liver and the activities of thiamin-dependent enzymes in the liver were decreased. (b) In rats fed a calcium-deficient, low-thiamin (20μg/100g diet) diet, typical neurological symptoms of thiamin deficiency occurred and sometimes the rats died. When thiamin was administered to these rats, they recovered quickly. In these rats, growth, body temperature, blood pressure and heart rate were decreased, and the thiamin level in the nervous system and heart was also decreased the level of calcium in the telencephalon was decreased only in these rats. These results indicate that calcium plays a role in the binding of thiamin to nerve membrane structures, thus playing a specific role in the process of nervous conduction. In contrast, magnesium has little effect on thiamin in nerve tissues, but may play an important role in thiamin-dependent enzyme systems in the liver. (II) Survey of nutrient intake and vitamin B1 status of farm villagers in northeast Thailand To clarify the health and nutritional (especially vitamin B1) status of inhabitants in rural Thailand, a medical survey study and a survey of food habits were carried out in a farm village with a population of about 1, 000 in northeast Thailand. In this report, the food intake, thiamin status and biochemical blood status of farm villagers and company employees are presented. (1) From the results of the food survey, it was apparent that a) foods for these villagers were mainly glutinous rice and immature papaya, with some fish, chicken, chilli and leaf vegetables, b) intakes of calcium, vitamin B1 and vitamin B2 were deficient in this group compared with the recommended values for Thailand, c) the sources of nutrients were mainly glutinous rice and the most potent source of retinol was chilli. (2) From the results of biochemical plasma and blood examinations, spread of infections diseases including chronic hepatitis was evident in inhabitants of this area, especially in company employees, and there were many marginal nutritional deficiencies, especially in the villagers. (3) Thiamin intake and blood thiamin levels were very low. From these results, it is postulated that many diseases will be induced by these nutritional deficiencies.
Forty healthy female college students underwent gustatory function tests for salt (discrimination of salt concentration, salt taste threshold), biochemical parameter measurements (plasma Zn, plasma Na, plasma retinol, plasma retinol-binding protein (RBP)) and a five-day dietary consumption survey. In the tests, performed six times, individuals, rate of correct discrimination (RCD) between 0.6% and 0.7% NaCl concentration was 51.2+28.7%. Only eleven (28%) subjects were able to make a correct discrimination. No significant association was found between the RCD and either the detection or recognition threshold for salt. Plasma Zn, retinol and RBP levels were lower in the present subjects than in our previous studies. Plasma Zn level in 20% of the subjects was lower than 0.7 μg/ml. Correlations among plasma Zn, retinol and RBP were positively significant. From these associations and the finding that Zn is indispensable for the biosynthesis of RBP, it can be postulated that Zn influences vitamin A metabolism. These subjects showed low energy and nutrient intake (per kg body weight) levels except for protein. There was a significant correlation between Zn intake (per kg body weight) and the plasma Zn level. The RCD was correlated positively with plasma Zn. Although the level of significance did not exceed 0.05 (r=0.282, p=0.078), this tendency indicates that the plasma Zn level is related to RCD. There was a significant difference in plasma Zn level between the high and low RCD groups. With regard to the RCD, only the plasma Zn level showed a marginally significant partial regression coefficient (p=0.096) in multiple regression analysis. Thus, it was suggested that the plasma Zn level might have influenced the discrimination of salt concentration.