Abstract

Vitamin B12 (B12) is present in foods of animal origin, and vegans are encouraged to take supplements with synthetic B12 in order to ensure a sufficient uptake. Recent rat studies suggest that natural (hydroxo-B12, HO-B12) and synthetic (cyano-B12, CN-B12) B12 behave differently in the body. Here, we test if a daily vitamin pill matches dietary B12 in ability to restore a low B12 status in rats. B12-depleted male Wistar rats (n = 60) were divided into five groups (n = 12 in each) and subjected to two weeks intervention with various schemes of B12 supplementation. Two "dietary" groups received a low-B12 chow that was fortified with either HO-B12 or CN-B12 providing a continuous supply. Two "pill" groups received a single daily dose of CN-B12, where the vitamin content either matched or exceeded by factor four the provisions for the "dietary" groups. A control group received the low-B12 chow without B12 fortification. B12 was measured in plasma and tissues. Dietary B12 provides 35% more B12 to the tissues than an equivalent single daily dose (p < 0.0001). Natural B12 delivers 25% more B12 to the liver than synthetic B12 (p = 0.0007). A fourfold increase in B12, supplemented as a single daily dose, does not provide any extra B12 to the tissues (p = 0.45). We conclude that dietary B12 is better at rescuing a low B12 status than a daily vitamin pill.