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Abstract

Vitamin B12 (B12) is an essential nutrient required for optimal energy metabolism and nervous system functioning. Adults aged >50 years are at risk of impaired B12 digestion and absorption and are recommended to consume B12-fortified foods and/or supplements, i.e. sources of free B12. The general consensus is that B12 has high bioavailability from dairy sources; therefore, developing a fortified dairy product represents a promising strategy to fill a market niche and improve B12 status in older adults. This research thesis consists of three main phases, with the following objectives: (I) to identify the most suitable method for the analysis of added B12 in yoghurts; (II) to develop B12-fortified yoghurts and assess shelf-life stability; and (III) to assess the efficacy of consuming one daily portion of B12-fortified, versus unfortified yoghurt on the B12 status of healthy older adults. For objective I, I developed a High-Performance Liquid Chromatography method and compared its performance to that of RIDASCREEN®, an immunoassay. I found that RIDASCREEN® was the most suitable method for measuring B12 in yoghurt, given its lowest level of quantitation (0.5 μg/L). For objective II, the shelf-life stability of methylcobalamin (MeCB), a naturally-occurring B12 form, and cyanocobalamin (CnCB), the synthetic B12 form, added to yoghurts either in isolated or encapsulated form was tested by measuring total B12 concentrations in yoghurts for 8 weeks. Results indicated that CnCB was a stable fortificant throughout yoghurt shelf-life, and isolated MeCB was stable up until week 4. For objective III, I performed an 8-week double-blind, randomized controlled intervention trial. Yoghurts were fortified with 50 μg MeCB. B12 status was measured at baseline, weeks 4 and 8 using serum total B12 concentration. In a total of 66 participants (aged 50-74y), a significant time-treatment interaction was found (p