A recent study evaluated the relationship between intake of vitamin B6 and vitamin B12 and risk of hip fracture among postmenopausal women. According to the findings, a higher than recommended intake of combined vitamins B6 and B12 could increase the likelihood of sustaining a hip fracture.
Previous research has found that more than half of the United States population uses some kind of dietary supplement (of note, evidence has tied supplements including Herbalife, Hydroxycut, and garcinia cambogia to increased risk of liver failure). Further, the study authors noted, “Both insufficient and excess intakes of a nutrient may be harmful. According to randomized clinical trials (RCTs), high-dose vitamin supplementation may lead to unexpected adverse effects.”
Researchers used data from the Nurses’ Health Study (NHS) to conduct their study. NHS data for the current study went back to June 1984. The women filled out a survey via mail pertaining to their medical history, lifestyle, and disease risk factors; follow-up surveys were conducted every two years. The women were followed through May 2014; final analysis included responses from 75,864 postmenopausal women. After excluding 117 fractures related to cancer or traumatic events, 2,304 hip fractures were recorded.
Characteristics of Fracture Patients
Among the 2,304 hip fractures, median age at the time of fracture was 75.8 years, and mean body mass index (BMI) was 24.3 kg/m2. The median cumulative average intake of total vitamin B6 was 3.6 mg/d, and vitamin B12 was 12.1 μg/d. The reference group for vitamin B6 analysis was those with a daily intake < 2 mg/d, and for vitamin B12 was < 5 μg/d.
BMI did not significantly differ across high and low vitamin intake groups. However, in both vitamins B6 and B12 groups, the higher intake cohorts had increased levels of physical activity and lower rates of smoking. Women with higher intakes of vitamins B6 and B12 also had higher intakes of other micronutrients, and a lower consumption of caffeine and alcohol. The low vitamin B12 intake group had lower rates of functional limitations, chronic diseases, and medication use; middle and high intakes had similar rates. This association was weaker in the vitamin B6 groups.
The women were followed for a mean 20.9 years. After adjusting for covariates, compared to the reference group, the highest vitamin B6 overall intake (diet and supplements) group had a relative risk (RR) for hip fracture of 1.29 (95% CI, 1.04-1.59; P = .06 for linear trend). When comparing groups based on vitamin B6 intake from supplements only, the highest intake group’s RR was 1.41 (95% CI, 1.10-1.80; P = .09 for linear trend).
“For total vitamin B12, intakes at least 30 μg/d were associated with a nonsignificant increased risk of hip fracture compared with intakes less than 5 μg/d (RR, 1.25; 95% CI, 0.98-1.58), and risk increased linearly with increasing intake (RR, 1.01; 95% CI, 1.00-1.03 per 10-μg/d increase in total intake; P for linear trend = .02),” the researchers observed.
An increased intake of both vitamins was significantly associated with increased hip fracture risk compared to a reference category of a low intake of both vitamins (RR, 1.47; 95% CI, 1.15-1.89). most women did not have a high intake of one and a low intake of the other. Women with a medium intake for both vitamins did not have a significantly greater risk for hip fracture (RR, 1.18; 95% CI, 0.98-1.42).
For women aged 19 to 50 years old, the National Institutes for Health (NIH)’s recommended daily allowance (RDA) for vitamin B6 is 1.3 mg; for women aged older than 50 years, NIH recommends a 1.5 mg dose. The NIH’s vitamin B12 recommendation is 2.4 μg for women aged 14 years and older.
“The RDAs are established to meet the nutritional requirements of almost the entire population. Despite that, use of high-dose vitamin supplementation far exceeding the RDAs is common, often without any definite indication and in the absence of clear evidence of benefit,” the study authors observed. They suggested that caution be applied when taking supplements, “because adverse events can occur.”