"Identification of risk factors for metformin-related vitamin B12 deficiency has major potential implications regarding the management of diabetes mellitus," wrote Rose Zhao-Wei Ting, MBBS, from Prince of Wales Hospital, the Chinese University of Hong Kong in Sha Tin, and colleagues. "First, there is likely to be an improved yield of detecting vitamin B12 deficiency if high-risk individuals can be identified. Second, subjects identified as having substantial risk for metformin-related vitamin B12 deficiency might benefit from empirical screening or primary prevention with other means such as calcium supplementation."
The researchers identified 155 diabetes patients in the study who had a vitamin B12 deficiency, and 310 members of a control group who did not suffer B12 deficiency after taking metformin. The study authors noted that the increased risk of B12 deficiency was observed even when adjustments were made for "confounders" such as age and weight.
"The risk factors identified have implications for planning screening or prevention strategies in metformin-treated patients," the researchers reported. "Enough concerns exist to call attention to the value of vitamin B12 screening, particularly among at-risk patients receiving metformin. Our data underscore the need for monitoring subjects undergoing high-dose and/or prolonged-course metformin therapy."
The scientists said that, so far, the mechanism that causes B12 deficiency in metformin-treated diabetes patients is unknown. They also noted that some of the hospital medication records were imprecise, some patients' exposure may have been misclassified, and that the study used serum vitamin B12 concentration to define vitamin B12 deficiency.
"Virtually all prescription drugs cause the depletion of one or more nutrients," said Mike Adams, a consumer health advocate. "And yet patients are almost never told about the urgent need to replenish those nutrients through supplementation. As a result, people who take prescription drugs suffer from chronic nutritional deficiencies that cause serious harm to their health and ultimately raise the risk of premature death."
Another difficulty that may have affected the scientists' information is that, according to recent research, vitamin B12 deficiency can also be mistaken for mental decline, sleeplessness or nervous system disorders. The study found that long-term undiagnosed vitamin B12 deficiency has caused brain damage in 39 percent of elderly participants who were not able to recover after B12 supplementation, but the remaining 61 percent were able to make a complete recovery through supplementation.
Vegetarians were advised by the study results to supplement their diet with vitamin B12 to avoid deficiency, as meat tends to be one of the richest sources of the vitamin.