Intersection of Diabetes Mellitus, Metformin and Vitamin B12
Within Canada and the US, the Institute of Medicine convenes a panel of experts to review the literature and set recommendations for each nutrient. These recommendations are set for the general, healthy population. That is logical. It seems appropriate.
But what if you have a disease, a common disease, and your medication puts you at risk of a nutrient deficiency? A study published in Diabetes Care Journal reports that metformin, a medication prescribed for people with diabetes mellitus, may double the number of people who are vitamin B12 deficient. Unless you take a vitamin B12 dietary supplement. Use of supplements containing vitamin B12 was associated with a reduction in the prevalence of vitamin B12 deficiency.
This is an important study for two reasons:
1. Almost 26 million children and adults in the United States have diabetes, almost 1 out of 10 Americans. Almost 11 million of these are people over 65 years of age. Type 2 diabetes mellitus is the most common form.
2. According to the Canadian Diabetes Association, metformin is the recommended drug treatment when individuals with type 2 diabetes cannot achieve glycemic targets using lifestyle management.
The Recommended Daily Allowance (RDA) is expected to protect 97.5% of healthy persons from deficiency. For adults, the Institute of Medicine recommends that the vitamin B12 RDA of 2.4 ug be met by consuming synthetic vitamin B12 from fortified foods or dietary supplements. Using a serum B12 concentration of < 148 pmol/L (200 pg/mL) and homocysteine concentrations > 10 umol/L (135 mg/L) to define vitamin B12 deficiency, Evatt and colleagues reported 2.5% of persons over 50y of age to be deficient. This percentage is similar to that reported by Reinstatler and colleagues.
But for individuals with diabetes being prescribed metformin, vitamin B12 adequacy may be compromised unless they exceed the RDA. Vitamin B12 plays a key role in the normal functioning of the brain and nervous system. Because vitamin D status is important for memory and energy, eg fatigue and depression, physicians may need to address vitamin B12 requirements for their patients using metformin.