Vitamin B12, also known as cobalamin, is an important nutrient that the human body requires for several processes but cannot produce on its own. It plays a role in keeping blood and nerve cells healthy, contributing to red blood cell formation, and assisting in DNA synthesis. The recommended daily allowance for adults is typically 2.4 micrograms (mcg), although this amount can be higher for pregnant or nursing individuals. Milk, both dairy and fortified plant-based varieties, serves as a common dietary source of this vitamin.
Vitamin B12 in Dairy Milk
Dairy milk naturally contains vitamin B12, making it a significant source. A single 250 mL glass of cow’s milk can provide a substantial portion of the daily recommended dietary intake, often around 46% for adults over 13 years old.
The presence of vitamin B12 in dairy milk stems from its synthesis by microorganisms. Specifically, bacteria and archaea residing in the digestive tracts of ruminant animals like cows are responsible for producing this vitamin. These microbes require cobalt to synthesize vitamin B12, which is then absorbed by the animal and transferred to its milk.
The concentration of vitamin B12 in dairy milk can vary due to several factors. Research indicates that diet composition, ruminal conditions such as pH, and even animal characteristics like breed and lactation stage can influence the B12 content. For example, diets higher in acid detergent fiber, like grass, tend to encourage increased vitamin B12 concentrations in milk.
Vitamin B12 from dairy milk is considered to have good bioavailability, meaning the body can absorb and utilize it effectively. Studies using animal models, like pigs, suggest that the vitamin B12 in milk is absorbed more efficiently than the synthetic form, cyanocobalamin, found in many supplements. The efficiency of intestinal absorption of vitamin B12 from milk can range between 8% and 10%.
Vitamin B12 in Plant-Based Milks
Plant-based milk alternatives, such as soy, almond, oat, and rice milk, do not naturally contain vitamin B12. Therefore, for plant-based milks to contribute to B12 intake, they must be fortified with the vitamin.
Fortification involves adding synthetic vitamin B12 during the manufacturing process. This practice makes plant milks a viable source of the nutrient for individuals following vegetarian or vegan diets who may otherwise struggle to obtain sufficient B12. Consumers should always check the nutrition labels of plant-based milks to confirm B12 fortification and its amount.
The levels of vitamin B12 fortification in plant-based milks can differ significantly across brands and types. For instance, some fortified plant milks may provide 2.4 micrograms per cup, which aligns with the daily recommended amount for adults, while others might offer higher or lower amounts, or none at all. Soy milk is often fortified to levels comparable to dairy milk in terms of calcium, vitamin D, and B12.
While fortified plant milks can be a convenient source of vitamin B12, their overall nutritional profile compared to dairy milk varies. Some plant-based milks, especially unfortified varieties, may have lower levels of protein, zinc, phosphorus, and other vitamins. The bioavailability of synthetic B12 used in fortification can also be a consideration, though some fortified foods have shown a strong impact on B12 status.