Folate, vitamin B<sub>6</sub>, and vitamin B<sub>12</sub> status in European adolescents : associations with homocysteine as well as communicable and non-communicable factors

Field: Medicine (Health Sciences)

Adolescence implies important psychological, social, and physiological changes. Apart from the first year of life, both energy and nutrient requirements are greatest during adolescence. To ensure physiological growth during this critical period, an adequate intake of folate, vitamin B<sub>6</sub>, and vitamin B<sub>12</sub> is mandatory. These B-vitamins are closely connected with homocysteine a well-known risk factor for cardiovascular diseases. In adolescents, a change towards an increasing consumption of energy dense but nutrient poor food is observed. Simultaneously, detrimental factors e.g. a sedentary lifestyle are implemented. Blood B vitamin and homocysteine reference values for adolescents do not exist. Therefore, the assessment of B-vitamin and homocysteine concentrations is not yet possible, but still needed. A prerequisite for the development of reference values is to record the present situation and to elucidate the influencing factors of B-vitamin status and homocysteine concentrations. Underlying data were taken from the HELENA study (“Healthy Lifestyle in Europe by Nutrition in Adolescence”). Overall, the present work elucidated several associations and provided potential reference data that might be a starting point for the further development of sound reference values.<br /> The relation of folate, vitamin B<sub>6</sub>, vitamin B<sub>12</sub> status and homocysteine levels with selected non-communicable factors gender, age, sexual maturity, and the methylenetetrahydrofolate reductase 677C/T as well as selected communicable factors body composition, supplement use, and smoking were investigated. Cobalamin and homocysteine levels varied between genders. Higher age was related with increased homocysteine concentrations. Sexual maturity was inversely associated with folate, red blood cell folate, and holo-transcobalamin concentrations. Analogue to age, homocysteine concentrations were positively associated with sexual maturity. The methylenetetrahydrofolate reductase 677C/T polymorphism was associated with folate, red blood cell folate, cobalamin, holo transcobalamin, and homocysteine concentrations. Normal weight adolescents displayed higher folate and cobalamin concentrations than overweight adolescents. Supplement users had higher folate, red blood cell folate, and cobalamin concentrations compared with non-users and homocysteine concentrations were lower in supplement users than in non-users. Smoking was associated with lower folate, red blood cell folate, cobalamin, and pyridoxal-5-phosphate concentrations. <br /> Furthermore, homocysteine and its association with the communicable factors physical activity, cardiovascular fitness, and fatness was examined. Few studies have targeted this relationship sofar. Subjects were mostly adults and studies on adolescents display inconsistent results. In the present study homocysteine concentrations were not significantly associated with physical activity, cardiovascular fitness, or fatness after controlling for potential confounders, neither in males nor females. <br /> Based on observing patients with homocystinuria suffering also from premature osteoporosis and fractures, it is hypothesised that also folate, vitamin B<sub>6</sub>, and vitamin B<sub>12</sub> status as well as homocysteine levels are associated with bone mineral density. However, in adolescents variations in bone mineral content and -density could not be explained by folate, vitamin B<sub>6</sub>, vitamin B<sub>12</sub> status, and homocysteine levels.