VITAMIN [B.sub.12] CONCENTRATIONS AND INTAKE SOURCE

Nutrition Research Newsletter, March, 2000

Recent news about the fortification of foods with folic acid has focused attention on Vitamin [B.sub.12] deficiency and its symptoms of megaloblastic anemia and neurological complications. A big argument used in the fight against folic acid fortification has been that an increased risk of neurological damage from unidentified vitamin [B.sub.12] deficiency can be masked by the partial hematologic response to folate. In addition to masking megaloblastic anemia, fortification with folic acid can worsen the progression of vitamin [B.sub.12]-related effects.

Recent studies have also found that vitamin [B.sub.12] deficiency is more prevalent among the elderly than previously thought. Since many studies have focused on the elderly, a team of researchers from Tuffs University recently used the Framingham Offspring Cohort to explore the relationship between vitamin [B.sub.12] intake and plasma concentrations. These researchers hypothesized that the prevalence of low vitamin [B.sub.12] concentrations would increase with age and that vitamin [B.sub.12] levels vary according to intake source.

Subjects included 2999 children of the original Framingham Study cohort, a study designed to examine heart disease risk factors. Plasma vitamin [B.sub.12] levels were obtained and separated into groups ([is less than] 148, 185, and 258 pmol/L) so they could be examined by age group (26-49, 50-64, and 65-83 years), supplement use, and food intake sources of fortified breakfast cereal, dairy products, and meat.

Mean serum vitamin [B.sub.12] concentration was 329 pmol/L. A commonly used clinical cutoff for low vitamin [B.sub.12] status is 148 pmol/L. Nine percent of the population fell below this cutoff point. All groups obtained the majority of their vitamin [B.sub.12] intake from meat. Those with lower [B.sub.12] levels obtained significantly more of their vitamin [B.sub.12] intake from meat compared with those with higher [B.sub.12] levels. Twenty-eight percent of the population took supplements containing vitamin [B.sub.12]. Non-supplement users were likely to have significantly more vitamin [B.sub.12] concentrations below 185 pmol/L as compared to supplement users, 20% vs. 8%, respectively.

The researchers also examined the relationship between vitamin [B.sub.12] levels and fortified breakfast cereals. Among non-supplement users, those consuming cereal more than four times per week had significantly higher plasma vitamin [B.sub.12] concentrations than those who did not eat cereal. Forty-one percent of the subjects who neither took supplements nor consumed fortified cereal had the highest prevalence of vitamin [B.sub.12] levels below 185 pmol/L. Despite the initial hypothesis, there were no significant differences between plasma concentrations and age. However, there was a trend toward lower plasma concentrations and age.

These findings have important implications, since people with vitamin [B.sub.12] concentrations of 258 pmol/L have been shown to be at some risk for neurological symptoms of vitamin [B.sub.12] deficiency. Sixty-three percent of the subjects had concentrations greater than 258 pmol/L. This study provides proof for the need of improved diagnoses and treatment of vitamin [B.sub.12] deficiency in adult populations. Researchers are also working on better identifying those persons more at risk for vitamin [B.sub.12] deficiency, i.e., those with H.pylori infection and chronic users of medication that suppresses gastric acidity.

Katherine L Tucker, Sharon Rich, Irwin Rosenberg, et al., Plasma Vitamin [B.sub.12] Concentrations Relate to Intake Source in the Framingham Offspring Study, Am J Clin Nutr 71: 514- 522 (February 2000) [Correspondence: K. L. Tucker, Jean Mayer USDA Human Nutrition Research Center on Aging at Tuffs University, 711 Washington St., Boston, MA 02111. E-mail: tucker@hnrc.tufts.edu.]