Added the following:
B Vitamin Supplementation Increases Stroke and Kidney DamageA study published in JAMA in April 2010 asked whether giving supplemental B vitamins to people with diabetes would improve their kidneys because they were known to have low levels of homocysteine. What the study found was very disturbing: people with diabetes who were given a single daily tablet of B vitamins containing folic acid (2.5 mg/d), vitamin B6 (25 mg/d), and vitamin B12 (1 mg/d) ended up with significantly worse kidney function as measured by GFR and also in a higher incidence of stroke. This suggests B Vitamin supplementation is harmful to people with kidney problems.
Effect of B-Vitamin Therapy on Progression of Diabetic Nephropathy. A Randomized Controlled Trial. Andrew A. House et al. JAMA Vol. 303 No. 16, April 28, 2010.