The current RDA in Europe is only 1 micrograms for adults, while the US dietary reference intake (DRI) is 2.4 micrograms. In order to correct all vitamin B12-related variables a RDA of 6 micrograms is needed, according to research published in the January 2006 issue of the American Journal of Clinical Nutrition (Vol. 83, pp. 52-58).
Vitamin B12, found in meat, dairy products and eggs, is essential for life, working with folate in the production of red blood cells, as well as helping the body in the use of fatty acids and certain amino acids.
"When establishing the RDA, a major concern is to ensure the minimum of the vitamin required to avoid the risk of developing vitamin deficiency," wrote lead researcher Vakur Bor.
The current study calculated dietary and supplemental intake of vitamin B12 for 98 post-menopausal women with an average age of 57 using three-day diet records, a method that does not rely heavily on memory and widely believed to give the most valid estimated of intake.
After dividing the volunteers into quintiles depending on B12 intake, the researchers measured four different vitamin B12-related serum markers.
Despite the range of intake varying from three to 15 micrograms, the researchers observed that the curves leveled off at a daily intake of about six micrograms for all the variables analysed.
"A daily vitamin B12 intake of six micrograms appears to be sufficient to normalize all of the vitamin B12-related variables, which suggests that this dose might be more adequate for the general adult population than the current RDA," concluded Bor.
The results may have implications for vitamin producers and supplement makers. Average commercial multivitamin supplements in Denmark contain only 1 microgram of vitamin B12, while in the Netherlands the average is 2 micrograms. Some multivitamin formulations in the UK contain as little as 0.5 micrograms.
Vitamin B12 deficiency is believed to be rare, except amongst vegetarians. A balanced western diet normally contains five to seven micrograms of the vitamin. Vegetarian and vegan diets however require vitamin B12 supplements to maintain healthy levels. According to a 2002 Datamonitor study there are approximately 13 million vegetarians in Europe.