Introduction

Vitamin B12 (B12, cobalamin) is a driving force. It helps to make DNA and blood cells, and it is crucial to sustain a healthy brain and nervous system. The vitamin in its natural form is only present in foods of animal origin, such as milk, meat, and fish, and a well-balanced omnivorous diet is necessary to supply the recommended amount in humans (2.4 μg B12/day). This poses a challenge for the growing number of vegans worldwide. In most countries, vegans are encouraged to take daily B12 supplements to stay healthy. Traditionally, oral supplements contain 2.4–10 μg of synthetic cyano-B12 (CN-B12), and the manufactures recommends one pill per day. In comparison, food contains natural B12 forms, such as hydroxo-B12 (HO-B12), and it is ordinarily consumed repeatedly during the day. This distinction is important as the intestinal B12 absorptive system is saturated at 1–2 μg B12 per meal. Besides being used in oral supplements, CN-B12 is also used for food fortification purposes. The two forms of B12 (in their free form) are equally well absorbed in both man and rat, but recent rat studies suggest that HO-B12 is a superior B12 source for the tissues when compared with CN-B12, as it provides more active B12 coenzymes that are necessary for the B12 metabolism.¹

Figure 1 Characteristics of Vitamin B12

Experiments

Authors present data on 60 rats kept on a low-B12 diet for four weeks prior to two weeks intervention with either dietary Vitamin B12 (two groups) or a daily vitamin pill (two groups) or continuing on the low-B12 diet (one group). The dietary groups (“HO-diet” and “CN-diet”) received food with added HO-B12/CN-B12, while the supplementation groups (“CN-pill” and “CN-pill (4×)”) received a single daily dose of CN-B12 that was embedded in jelly. For the “CN-pill” group, the jelly beans contained the same B12 amount as the pre-estimated daily intake of B12 from these diets (0.72 μg/day, see method section). In the pilot study, we showed that B12 was equally well absorbed when being administered in water and in a jelly matrix.

Results

Liver, kidneys, brain, and muscle biopsies were measured for their content of Vitamin B12. Authors found that the HO-diet provided more B12 to the liver than the CN-diet, but no differences were observed for the other tissues that were examined. They did see a trend towards a higher kidney B12 for the “CN-diet” group, but this observation was not statistical significant. When compared with vitamin pills, dietary CN-B12 provided more than twice the amount of B12 to the kidneys, even when the pills contained a four times higher daily B12 dose than the diet. In fact, a fourfold increase of the B12 dose in the pills did not provide extra B12 to any tissue. However, they did find that the higher B12 dose in the vitamin pills (“CN-pill (4×)” group) caused a higher accumulation of B12 in the liver when compared with the “CN-diet”. In the brain, a small difference was observed between the “l(fā)ow-B12” group and the high-dose vitamin pill (“CN-pill (4×)”) (p = 0.006). No differences in muscle B12 were observed between any groups.

Conclusion

The studies in rats show that dietary B12 is better at rescuing a low Vitamin B12 status when compared with a daily vitamin pill, which is possibly due to a limited capacity of the B12 absorption system. This also explains why an increase in the vitamin pill dose did not provide more B12 to the body than vitamin pills with a lower dose. The results highlight the need for human studies to clarify whether food fortification is a better strategy than a daily vitamin pill, when it comes to an improvement of the B12 uptake in the vegan population.