Bioavailability of vitamin B₁₂ in cows' milk

Br J Nutr. 2012 Jan;107(1):61-6. doi: 10.1017/S0007114511002364. Epub 2011 Jun 27.


The natural source of vitamin B₁₂ in human diets comes from animal products. For example, one glass (250 ml) of milk provides approximately 50 % of the RDA (2·4 μg/d). It was hypothesised that the provision of vitamin B₁₂ from milk is more efficiently absorbed than the synthetic form used in vitamin supplements. Pigs (n 10) were used as a model for intestinal absorption of vitamin B₁₂ in humans to compare the net fluxes of vitamin B₁₂ across the portal-drained viscera (PDV; an indicator of intestinal absorption) after ingestion of meals complemented with conventional and vitamin B₁₂-enriched (via injections to cows) milk (raw, pasteurised or microfiltrated) or with equivalent amounts of cyanocobalamin, the synthetic form used in supplements or unsupplemented. Net flux of vitamin B₁₂ across PDV after the ingestion of milk was positive, though not influenced by milk enrichment (P>0·3) or technological processes (P = 0·8) and was greater than after ingestion of equivalent amounts of cyanocobalamin (cyanocobalamin v. all milk, P ≤ 0·003). In fact, net fluxes of this vitamin were not different from 0 after either cyanocobalamin or the meal devoid of vitamin B₁₂ (unsupplemented v. cyanocobalamin, P = 0·7). The cumulative PDV fluxes during the 24 h following ingestion of meals complemented with milk varied from 5·5 to 6·8 μg. These values correspond to an efficiency of intestinal absorption of vitamin B₁₂ from milk varying between 8 and 10 %. Therefore, vitamin B₁₂, which is abundant in cows' milk, is also substantially more available than the most commonly used synthetic form of this vitamin.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Biological Availability
  • Cattle
  • Crosses, Genetic
  • Diet / adverse effects
  • Dietary Supplements / analysis
  • Female
  • Food Preservation / methods*
  • Food, Fortified / analysis
  • Intestinal Absorption*
  • Milk / chemistry*
  • Milk / metabolism
  • Nutritive Value
  • Portal System / metabolism
  • Sus scrofa
  • Vitamin B 12 / administration & dosage
  • Vitamin B 12 / analysis
  • Vitamin B 12 / blood
  • Vitamin B 12 / metabolism*
  • Vitamin B 12 Deficiency / prevention & control
  • Weaning


  • Vitamin B 12