I have changed my vitamin B12 recommendations.
A 2010 paper by Bor et al., showed that in healthy people aged 18-50, a vitamin B12 intake of 4 to 7 mcg/day was associated with the lowest methylmalonic acid and homocysteine levels (1). They reviewed other research from the past 10 years, primarily on older populations, that reinforces this finding.
My previous recommendations were 1.5 – 2.5 µg twice per day. I have changed that to 2.0 to 3.5 µg twice per day. For supplements, I raised the lower end of the range from 10 µg to 25 µg. The daily range is now 25 to 100 µg.
You can read an explanation of my recommendations here under Step 2.
1. Bor MV, von Castel-Roberts KM, Kauwell GP, Stabler SP, Allen RH, Maneval DR, Bailey LB, Nexo E. Daily intake of 4 to 7 microg dietary vitamin B-12 is associated with steady concentrations of vitamin B-12-related biomarkers in a healthy young population. Am J Clin Nutr. 2010 Mar;91(3):571-7.
