The role of age on B12 biomarker response to dietary intakes of vitamin B12 and Implications for dietary intake recommendations

Abstract

Background: Despite having dietary intakes that typically greatly exceed current recommendations, 10–40% elderly population are affected by low vitamin B12 biomarker status as a result of atrophic gastritis (Pfeiffer et al., 2007), leading to an age-related decline in gastric acid secretion necessary for B12 separation from food protein. Despite its mild, non-specific clinical manifestation, this condition may contribute to the development of several diseases of ageing such as cardiovascular disease, dementia and osteoporosis (Hoey et al., 2007). However, B12 dietary intake recommendations remain uniform across adult age groups and there is as yet no evidence to support a revision of the recommendations specifically for older adults who are at increased risk of developing atrophic gastritis. This study aimed to investigate the role of ageing in the relationship between dietary B12 intake and biomarker status, and to provide scientific evidence to support the development of age-specific B12 dietary intake recommendations. Methods: The present research comprised new statistical analysis of a previous cross-sectional study of n250 older (≥60 years) and n191 younger participants who provided a blood sample analysed for B12 biomarkers (holotranscobalamin (holoTC); methylmalonic acid; total homocysteine and serum total B12); and gastric function biomarkers Pepsingonen I:II (Hoey et al., 2007). B12 Dietary intake was assessed using a 4 day food diary completed in conjunction with a semi-quantitative food frequency questionnaire used to identify fortified food consumers. Data were statistically analysed using chi-square, Pearson's correlation and independent samples t-tests as appropriate. Results: Mean dietary B12 intakes were higher amongst elderly participants (4.1 μg day−1 (SD 3.3 μg) versus 3.6 μg day−1 (SD 2.0 μg) amongst those aged <60 years; P = 0.01). However, atrophic gastritis (defined as Pepsinogen I:II ratio <3) was significantly more prevalent in older (14%) versus younger (2%) participants (P < 0.001) and was associated with lower B12 biomarker status compared to those with normal gastric function (P < 0.001). The B12 biomarker holoTC correlated more strongly and significantly with dietary B12 intake in both age groups (r = 0.22; P < 0.01) compared with the other B12 biomarkers. Over two thirds of the total sample were fortified food consumers but the effect of fortified food consumption on total dietary B12 intake was minimal, providing only 0.3 μg day−1 (SD 0.4 μg) free B12. Discussion: Findings support emerging evidence that holoTC, the biologically active fraction of B12, may be the most sensitive marker of B12 intake and status (Hermann et al., 2005). Previous studies have suggested that mean intakes of 6–15 μg B12 are associated with optimum biomarker status (Bor et al., 2006), indicating that fortification at a higher level than that currently used may be associated with the most optimal B12 biomarker status amongst this population subgroup. Conclusion: B12 dietary intake recommendations for older persons (aged ≥60 years) should be tailored to meet their increased physiological requirements. At current levels of fortification, regular consumption of B12 fortified food failed to significantly improve B12 status, but in the future, advice regarding the dietary inclusion of fortified foods or supplements at a dose close to dietary levels may be incorporated into such recommendations.