Vitamin B12: A secondary analysis of status, biomarkers and other determinants in young and elderly women.
Cocker, Jason Paul
Background/Aim: Vitamin B12 has multiple functions within the human body, including roles as a co-factor for both the one carbon metabolism cycle and methylmalonyl CoA mutase. Vitamin B12 deficiency can have serious lifelong consequences. The aim of this study is to explore the associations between markers of vitamin B12 status and other biochemical, dietary and physical measures. Methods: Three data sets composed of either young omnivore women (n=65; age 24.5 ± 4.4 y; mean ± SD), randomly selected young women (n=305; age 22.5 ± 3.9) and elderly women (n=44; age 80.5 ± 7.6) were examined. Associations between vitamin B12 biomarkers and other selected biomarkers of nutritional status (i.e. serum folate, erythrocyte folate), lifestyle factors such as; dietary intake, alcohol intake, oral contraceptive pill (OCP) use (in the non-elderly groups), and other factors such as BMI were examined using mixed effects regression, accounting for study clusters. Results: Serum vitamin B12 stratification (low, medium or high) was not associated with likelihood of being classed as having a raised methylmalonic acid (MMA) and/or homocysteine (tHcy) (p=0.316). Younger women who used the OCP had serum vitamin B12 concentrations that were 72.3 (SE=12.4) pmol/L lower than non-users (p<0.001), there was however no associations between OCP use and tHcy (p=0.669) or MMA (p=0.595) concentrations. Serum vitamin B12 concentration (pmol/L) was related positively to both serum folate (nmol/L) (β=0.018 95% CI: 0.009, 0.026, p<0.001) and erythrocyte folate (nmol/L) (β =0.456 95% CI: 0.164, 0.747, p<0.01). Vitamin B12 was marginally associated with the intake of protein (p<0.05) and negatively associated with alcohol intake (p<0.001). Conclusions: The lack of an association between serum vitamin B12 stratifications and metabolite cut-offs suggest that you are not more likely to have raised metabolites in conjunction with any of the three serum vitamin B12 cut-offs. The lack of negative metabolite consequences in those who use the OCP suggest that the decreased serum vitamin B12 is possibly inconsequential. This, however, suggests that in populations who are frequent users of the OCP, serum vitamin B12 may not be suitable as a primary measure of vitamin B12 status. Alcohol use in Australia females is above the global average and suggests that this group are at increased risk of decreased vitamin B12 status due to alcohol intake. Serum vitamin B12 proved less than ideal throughout this study as a primary marker of vitamin B12 status. It was unable to show concordance with MMA and tHcy cut-offs and demonstrated it was unsuitable as a primary marker in OCP users. This suggests that it is time for a new primary marker of status with holo-transcobalamin II being the likely successor. Research needs to be focused on this marker of status in the future to determine the factors which affect it so we can be better suited to use it as a primary marker of status.
Advisor: Samman, Samir
Degree Name: Master of Dietetics
Degree Discipline: Department of Human Nutrition
Publisher: University of Otago
Keywords: Vitamin; B12; Biomarkers; Young; Elderly; Women
Research Type: Thesis