不很清楚，文中這樣講

Possible Mechanisms

A possible biological explanation for the findings in the present study is not clear. The magnitude of intakes of vitamins B₆ andB₁₂ associated with an increased risk of hip fracture in our study far exceeded the recommended dietary allowances (RDAs) (1.3-1.7 mg/d for vitamin B₆ and 2.4 μg/d for vitamin B₁₂).¹⁵

Possible adverse effects of high-dose vitamin B₆ supplementation have previously been suggested.^24,25 High doses (≥500 mg/d) might increase the risk of falling because neurological symptoms, including ataxia, neuropathy, and decreased muscle tone, have been reported, and milder neurological symptoms have been observed at doses of approximately 100 mg/d as adverse effects.²⁶ Preliminary work suggested that high vitamin B₆ concentrations might accelerate bone loss by counteracting the modulating influence of estrogens on steroid receptors.²⁷ A recent paradox theory proposes that large doses of pyridoxine, the inactive form of vitamin B₆ included in supplements and found in foods, inhibits the active form pyridoxal phosphate.²⁸

We do not have an explanation for the mechanism by which vitamin B₁₂ may contribute to increased fracture risk.