Table 1.

Experimental evidence on B vitamins and bone health.

References	Study Model	Treatment (T) vs. Control (C)	Bone Outcomes	Main Findings
Murray et al. 1977 [10]	Chick cartilage in vitro	T: Isonicotinic acid hydrazide vs. C: (G-31H) pyridoxine hydrochloride to chick embryos	Lysyl oxidase activity	Decreased lysyl oxidase activity in cartilage and aorta in treatment chicks vs. controls.
Fujii et al. 1978 [11]	Rats	T: B6 deficient diet vs. C: 30 mg/100 g B6 fed diet	Collagen cross-linking formation	B6-deficient rats had more soluble bone collagens, lower amount of aldehydes and collagen formation.
Bird et al. 1982 [12]	In vitro embryotic chick aorta	T: PLP added C: no treatment to illuminated lysyl oxidase	Lysyl oxidase activity	The presence of PLP increased enzyme activity. The removal of PLP decreased enzyme activity.
Dodds et al. 1986 [13]	Rats	T: B6 deficient diet vs. C: 6 mg/kg pyridoxine hydrochloride	Bone formation	Vitamin B6-deficiency reduced G6PD activity in bone formation and callus development. B6-deficient fed rats had more osteoporotic bones with cavities and less new bones.
Masse et al. 1994 [14]	Chicks	T: 0.4 mg/kg vs. C: 3 mg/kg B6 to young chicks	Bone mechanical property	Deficient chicks had decreased cortical thickness, osteoid in trabecular bone, reduced secondary ossification centers and coarse trabeculation.
Masse et al. 1996 [15]	Chicks	T: 0.4 mg/kg vs. C: 3 mg/kg of B6	Bone mechanical property and collagen cross-linking	Deficient chicks had decreased fracture load and offset yield load, and increased collagen solubility.
Herrmann et al. 2009 [16]	Rats	T: a folate- and B12-deficient diet vs. C: standard diet for 12 weeks	Homocysteine level, bone strength (femoral neck compression), bone area, BTM: OC and CTx	Higher plasma homocysteine level in T group vs. controls, but no difference for homocysteine concentration in the bone tissue. No difference in bone strength, bone area, or BTM.
Herrmann et al. 2007 [17]	Human osteoblasts	Three B vitamins, B6 and folate (µg/L), B12 (ng/L) at various concentrations (0, 0.1, 10, 100, 1000)	Alkaline phosphatase, OC, and P1NP activity; Mineral matrix for formation	No significant difference for BTM levels or mineral matrix among different concentrations of a mix of three B vitamins. Homocysteine level is significantly higher in all concentrations except at the highest concentration of three B vitamins.
Herrmann et al. 2007 [18]	Human osteoclasts	Three B vitamins, B6 and folate (μg/L), B12 (ng/L): B6 (0, 2, 4, 6, 35); folate (0, 1, 2.5, 5, 15); B12 (0, 25, 100, 250, 500)	DRA for osteoclast activity, TRAP, and CK activity	Low concentration of the B vitamins combined or alone increased resorption activity significantly vs. the highest concentration.
Holstein et al. 2010 [19]	Mice	T: folate and B12-deficient diet vs. C: control diet for 9 weeks.	Homocysteine, folate, B12, BTM: OC and CTx callus stiffness, size and composition	Folate- and B12-deficient mice showed significantly lower serum folate and B12 but higher serum homocysteine. No significant difference in OC, CTx, callus stiffness and size.

Abbreviations: BTM: Bone turnover biomarker; CK: Cathepsin K; CTx: Carboxyterminal cross-linking telopeptide; DRA: Dentine resorption activity; G6PD: Glucose 6-phosphate dehydrogenase; OC: Osteocalcin; PLP: Pyridoxal phosphate; P1NP: Procollagen type I N propeptide; TRAP: Tartrate-resistant acid phosphatase.