High intake of vitamin B6 and B12 may increase the risk of hip fracture in postmenopausal women, according to the results of a recently published prospective cohort study.

To better understand the impact of vitamin B6 and B12 intake on hip fracture risk, the study authors analyzed data of 75,864 postmenopausal women who participated in the Nurses’ Health Study. Data on hip fracture and potential confounders were collected at baseline as well as every other year using follow-up questionnaires. Additionally, a semiquantitative food frequency questionnaire was collected every 4 years in order to obtain extensive dietary information. “Relative risks (RRs) were calculated by Cox proportional hazards regression, with cumulative average intakes of vitamins B6 and B12 as main exposures, adjusting for potential confounders,” the study authors explained.

Of the total women included in the study, 2304 had a hip fracture (median [range] age at hip fracture: 75.8 [46.7 to 93.0]; mean [SD] BMI: 24.3 [4.6]). The analysis revealed a median (interquartile range) cumulative average intake of 3.6 (4.8)mg/d for total vitamin B6 and  12.1 (11.7)μg/d for total vitamin B12.

“Both vitamin B6 (RR, 1.29; 95% CI, 1.04-1.59 for an intake of ≥ 35 vs <2mg/d; P =.06 for linear trend) and vitamin B12 (RR, 1.25; 95% CI, 0.98-1.58 for an intake of ≥ 30 vs <5μg/d; P =.02 for linear trend) were associated with increased fracture risk,” the study authors stated. Additionally, the results showed that women who consumed high combined vitamin intakes (B6 ≥35mg/d and B12 ≥20μg/d) had a nearly 50% increased risk of hip fracture (RR: 1.47; 95% CI: 1.15, 1.89) vs women with low combined vitamin intake (B6 <2mg/d and B12 <10μg/d).

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The authors concluded that while the intakes observed in the study far exceeded recommended dietary allowances, the findings “add to the evidence suggesting that caution should be used in vitamin supplementation when there is no apparent deficiency.”

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