Micronutrient status, with special reference to vitamin B6

Objective: To assess the adequacy of micronutrient status among the adult population, with special reference to vitamin B-6 status. Design and subjects: Micronutrient status was assessed among a random sample of the adult Dutch population (reference group, n = 300), aged 20-79 y, stratified for age and gender, and among a group with a low vitamin B-6 intake (n = 144). Results: Low vitamin B-6 groups had lower mean levels of erythrocyte and plasma pyridoxal (PL) and pyridoxal-5'-phosphate (PLP), urinary excretion of 4-pyridoxic acid, basal and stimulated erythrocyte aspartate aminotransferase (EAST) and erythrocyte alanine aminotransferase (EALT) activities and EAST stimulation coefficients but not of EALT stimulation coefficients, handgripstrength and 24 h homocysteine excretion before and after a methionin load test. Besides, plasma levels of vitamin C, B-12 and folate were lower among low B-6 than among reference groups indicating a combined low vitamin status. Direct biomarkers of vitamin B-6 intake (plasma PLP and 4-pyridoxic acid excretion) were significantly related to more functional parameters (EAST, EALT and alpha-EAST). Among random reference groups the prevalence of plasma PLP values below 19 nmol/l was 3-7% for different age-gender groups, with the highest value of 16% among men aged 50-79 years. The prevalence of high values of erythrocyte glutathion reductase stimulation coefficient (alpha-EGR) and low levels of serum vitamin B-12 and C was not more than 5% among different age-gender reference groups. Conclusions: Direct biomarkers of vitamin B6 intake confirmed the preselection of a group with a low vitamin B-6 intake. The results suggest that the sensitivity of vitamin B-6 status parameters for low vitamin B-6 intake was highest for the direct vitamin B-6 status parameters and lowest for handgripstrength and homocysteine excretion after a methionin load; results for enzyme stimulation coefficients were intermediate. The prevalence of below adequate status parameters for vitamin B-2 B-6, B-12 and C was not more than 7% among the different age-gender groups, with the exception of a value of 16% for plasma PLP levels below 19 nmol/l among men aged 50-79.