Kashin-Beck Disease: evaluation of mineral intake in young Tibetan children from endemic areas

Kashin-Beck disease is an endemic and chronic osteochondropathy. This disease principally occurs in the Tibet Autonomous Region and in several provinces of the People’s Republic of China. Although many studies have already been conducted and many others are still underway, its ethiology remains unknown. A multifactorial hypothesis has been proposed: selenium deficiency, high concentration of organic matters in drinking water (fulvic acids) and mycotoxin poisoning by fungi infecting cereals. This original study aimed to measure the mineral contents of the food most often consumed in severe endemic regions and then to evaluate the daily intake of minerals in young Tibetan children from endemic areas. The mineral elements were selected in relation to their implications in bone metabolism. A sampling campaign split up into two time periods (winter and spring) was carried out. Ten families from two distinct regions were selected based on three criteria: they live in endemic areas; they include a 3 to 5 year-old child; this child has a KBD brother or sister. At the same time, a nutritional survey was made by the means of a prospective questionnaire in order to list the 24h food intake of the 3 to 5 year-old child. This survey highlighted the extremely monotonous cereal-based Tibetan diet. An analytical method for the minerals was developed as follows: mineralization of samples performed by microwave-assisted wet process; mineralized solutions measured by several atomic absorption or emission spectrometric methods and molecular absorption spectrometric methods. The analytical method was validated by mean of certified reference materials. Mean food contents were calculated and compared to food composition reference tables. High iron contents and selenium deficiencies were highlighted in several foods. Daily intakes were estimated combining mineral measurements and nutritional survey results. These were compared to dietary reference intakes from reference tables. This estimation reveals some crucial points: we confirm a marked deficiency in calcium; Ca/P ratios are always low; iron and copper intakes are excessive; zinc is the most probably deficient; while selenium could be deficient; manganese intakes often exceed toxicity thresholds. Nevertheless, this study encounters some limits. The bioavailability of minerals is a critical point that deserves further investigations. Moreover, a larger study over a longer term covering both endemic and non-endemic regions is required for definite conclusions to be reached.