New research has found that taking high doses of vitamin B6 and B12 supplements could increase the risk of hip fractures in postmenopausal women.
Carried out by researchers at the University of Oslo, Norway, along with Harvard T.H. Chan School of Public Health in the USA, the new large-scale study looked at data collected from 75,864 US postmenopausal women over a period of 30 years.
The researchers recorded information on the incidence of hip fractures among the participants at the start of the study, and collected extensive information on the women's diet and use of dietary supplements every four years.
The findings, published in the journal JAMA Network Open, showed that after taking into account potentially influencing factors, taking vitamin B6 and vitamin B12 supplements were both associated with an increased risk of hip fracture. The risk was highest for women who took high doses of vitamin B6 together with high doses of B12, with these women showing an almost 50 percent increased risk of hip fracture compared with women who took a low intake of both vitamins.
The researchers noted that the vitamin intakes in this study were far higher than the recommended dietary allowances.
The results are also in line with previous Norwegian research, which found an increased risk of hip fracture in participants taking high doses of vitamin B6.
"The study is transferable to Norway, even though American women use a good deal more supplements than their Norwegian counterparts," commented lead author Professor Haakon E. Meyer.
The authors point out that many healthy individuals take high doses of vitamin B supplements, thinking that they are good for their health. However, only those with a vitamin B deficiency need to take a supplement. The results suggest that vitamin supplements should be used cautiously, with the authors adding that both insufficient and excess intakes of a nutrient can be harmful to health.
However, Professor Meyer also points out that some elderly people need extra vitamin B12 supplements, and there is no evidence that vitamin B12 alone results in increased risk of hip fracture.