Revised D-A-CH Reference Values for the Intake of Vitamin B6

<b><i>Background:</i></b> The Nutrition Societies of Germany, Austria, and Switzerland as the joint editors of the “D-A-CH reference values for nutrient intake” have revised the reference values for vitamin B₆ in summer 2019. <b><i>Summary:</i></b> For women, the average requirement (AR) for vitamin B₆ intake was derived on the basis of balance studies using a pyridoxal-5′-phosphate (PLP) plasma concentration of ≥30 nmol/L as a biomarker of an adequate vitamin B₆ status. The recommended intake (RI) was derived considering a coefficient of variation of 10%. The RIs of vitamin B₆ for men, children, and adolescents were extrapolated from the vitamin B₆ requirement for women considering differences in body weight, an allometric exponent, growth factors as appropriate, and a coefficient of variation. For infants aged 0 to under 4 months, an estimated value was set based on the vitamin B₆ intake via breast feeding. The reference value for infants aged 4 to under 12 months was extrapolated from the estimated value for infants under 4 months of age and the average vitamin B₆ requirement for adults. The reference values for pregnant and lactating women consider the requirements for the foetus and the loss via breast milk. <b><i>Key Messages:</i></b> According to the combined analysis of 5 balance studies, the AR for vitamin B₆ to ensure a plasma PLP concentration of ≥30 nmol/L is 1.2 mg/day for adult females and the extrapolated AR for adult males is 1.3 mg/day. The corresponding RIs of vitamin B₆ are 1.4 mg/day for adult females and 1.6 mg/day for adult males, independent of age. For infants, the estimated value is 0.1 mg/day and 0.3 mg/day, depending on age. The AR of vitamin B₆ for children and adolescents ranges between 0.5 and 1.5 mg/day, and the RI is between 0.6 mg/day and 1.6 mg/day. During pregnancy, the AR is 1.3 mg/day in the first trimester and 1.5 mg/day in the second and third trimesters; the RI is 1.5 mg/day in the first trimester and 1.8 mg/day in the second and third trimesters. For lactating women, the AR is 1.3 mg/day and the RI is 1.6 mg/day.

Allometric Scaling of physiologically-relevant organoids

The functional and structural resemblance of organoids to mammalian organs suggests that they might follow the same allometric scaling rules. However, despite their remarkable likeness to downscaled organs, non-luminal organoids are often reported to possess necrotic cores due to oxygen diffusion limits. To assess their potential as physiologically relevant in vitro models, we determined the range of organoid masses in which quarter power scaling as well as a minimum threshold oxygen concentration is maintained. Using data on brain organoids as a reference, computational models were developed to estimate oxygen consumption and diffusion at different stages of growth. The results show that mature brain (or other non-luminal) organoids generated using current protocols must lie within a narrow range of masses to maintain both quarter power scaling and viable cores. However, micro-fluidic oxygen delivery methods could be designed to widen this range, ensuring a minimum viable oxygen threshold throughout the constructs and mass dependent metabolic scaling. The results provide new insights into the significance of the allometric exponent in systems without a resource-supplying network and may be used to guide the design of more predictive and physiologically relevant in vitro models, providing an effective alternative to animals in research.