Table 1.

Estimated maximal % of daily reference intake (DRI) of B vitamins that could be provided by the gut microbiota (from Magnusdottir et al. [56])

Vitamin	Intracellular concentration (mmol/gDW)	DRIa (mg/day)	HGMratio	%DRI from HGM
Biotin	9.0 × 10− 7	0.03	0.40	4.5
Cobalamin	8.5 × 10−8	0.0024	0.42	31
Folateb	5.0 × 10−5	0.4	0.43	37
Niacinb	3.3 × 10−3	15	0.63	27
Pantothenate	2.3 × 10−6	5	0.51	0.078
Pyridoxineb	5.8 × 10−4	1.3	0.50	86
Riboflavin	9.0 × 10−6	1.2	0.65	2.8
Thiaminb	8.7 × 10−6	1.15	0.56	2.3

^aDietary reference intakes (Standing Committee on the Scientific Evaluation of Dietary Reference Intakes and Its Panel on Folate, Other B Vitamins, and Choline, 1998). Values averaged for male and female references intakes (ages 19–50)

^bAtomic mass for dihydrofolic acid, nicotinic acid, pyridoxine 5′-phosphate, and thiamine monophosphate