• Assessment
    What is the vitamin B-12 status of children of vegetarians, as measured by methylmalonic acid (MMA)?
    • Conclusion

      Based on data from two studies, there is limited, though consistent, evidence that small children of parents who follow very restrictive vegetarian diets are likely to be deficient in vitamin B-12 as measured by MMA. The proportion of these children who were vitamin B-12 deficient ranged from 55% to 85%.

    • Grade: III
      • Grade I means there is Good/Strong evidence supporting the statement;
      • Grade II is Fair;
      • Grade III is Limited/Weak;
      • Grade IV is Expert Opinion Only;
      • Grade V is Not Assignable.
      • High (A) means we are very confident that the true effect lies close to that of the estimate of the effect;
      • Moderate (B) means we are moderately confident in the effect estimate;
      • Low (C) means our confidence in the effect estimate is limited;
      • Very Low (D) means we have very little confidence in the effect estimate.
      • Ungraded means a grade is not assignable.
    What is the vitamin B-12 status among adolescent vegetarians, as measured by methylmalonic acid (MMA)?
    • Conclusion

      Adolescent vegetarians who followed restrictive diets in childhood may be at risk for vitamin B-12 deficiency. Based on two studies of the same group of subjects, vegetarian (LOV/LV) or omnivorous adolescents who had followed a very restrictive (macrobiotic) vegetarian diet early in life were likely to be vitamin B-12 deficient. Forty-one percent of adolescents had MMA >290nmol/L and 21% had MMA >410nmol/L.

    • Grade: III
      • Grade I means there is Good/Strong evidence supporting the statement;
      • Grade II is Fair;
      • Grade III is Limited/Weak;
      • Grade IV is Expert Opinion Only;
      • Grade V is Not Assignable.
      • High (A) means we are very confident that the true effect lies close to that of the estimate of the effect;
      • Moderate (B) means we are moderately confident in the effect estimate;
      • Low (C) means our confidence in the effect estimate is limited;
      • Very Low (D) means we have very little confidence in the effect estimate.
      • Ungraded means a grade is not assignable.
    What is the vitamin B12 status among adult vegetarians, as measured by methylmalonic acid (MMA)?
    • Conclusion

      Among healthy adults, vegetarians consistently had a significantly higher prevalence of vitamin B-12 deficiency (as measured by elevated MMA levels) than omnivores. Depending on the criteria used to define vitamin B-12 deficiency and sample differences, prevalence of B-12 deficiency among adult vegetarians ranged from 30% to 86%. When vegans and LOV/LV vegetarians were analyzed separately, vegans had even higher proportions of vitamin B-12 deficiency (43% to 88%).

    • Grade: I
      • Grade I means there is Good/Strong evidence supporting the statement;
      • Grade II is Fair;
      • Grade III is Limited/Weak;
      • Grade IV is Expert Opinion Only;
      • Grade V is Not Assignable.
      • High (A) means we are very confident that the true effect lies close to that of the estimate of the effect;
      • Moderate (B) means we are moderately confident in the effect estimate;
      • Low (C) means our confidence in the effect estimate is limited;
      • Very Low (D) means we have very little confidence in the effect estimate.
      • Ungraded means a grade is not assignable.
    What is the vitamin B-12 status among vegetarian older adults (>55 years) as measured by methylmalonic acid (MMA)?
    • Conclusion

      Research on the vitamin B-12 status among vegetarians older than 55 years is limited to only two neutral quality studies of Chinese women. Based on these studies, the proportion of older adult vegetarians who are vitamin B-12 deficient ranges from 46.9% to 68%.

    • Grade: III
      • Grade I means there is Good/Strong evidence supporting the statement;
      • Grade II is Fair;
      • Grade III is Limited/Weak;
      • Grade IV is Expert Opinion Only;
      • Grade V is Not Assignable.
      • High (A) means we are very confident that the true effect lies close to that of the estimate of the effect;
      • Moderate (B) means we are moderately confident in the effect estimate;
      • Low (C) means our confidence in the effect estimate is limited;
      • Very Low (D) means we have very little confidence in the effect estimate.
      • Ungraded means a grade is not assignable.