Milk: An Essential Source of Vitamin B12
Vitamin B12 deficiency affects a large proportion of older adults, and its prevalence increases with age. Furthermore, recommended intakes may not be adequate to reach and maintain optimal vitamin B12 status.
Research Assistant at Université Laval
Sources and Functions
Vitamin B12, or cobalamin, is a water-soluble vitamin present in foods of animal origin, such as meat, poultry, fish, seafood, eggs and milk products. Some foods are also fortified with vitamin B12. With the exception of algae and miso, very few plants contain this vitamin. In addition, the quantities present in plants are low and in a form that may be inactive or not easily absorbed by the body.1
This vitamin is essential for neurological functions and the growth and division of cells, including red blood cells. Vitamin B12 deficiency is therefore associated with serious health problems2-4 that include the following:
- neurological and cognitive deficits (loss of feeling in the limbs, paralysis, mood disorders),
- stunted growth,
- congenital malformations, including neural tube malformations,
- hyperhomocysteinemia, a risk factor for atherosclerosis.
Vitamin B12 Deficiency
Vitamin B12 deficiency occurs when the body does not properly absorb the vitamin, or when a person's diet is lacking in a reliable food source, namely foods from animal origin. Vegetarians, especially vegans, older adults, pregnant women and people living in developing countries are more at risk of vitamin B12 deficiency.5,6
In Canada, intakes of vitamin B12 among the general population seem to be largely higher than the recommended intakes, or approximately twice the suggested daily amount of 2.4 µg.7 A number of researchers have indicated, however, that the Recommended Dietary Allowance is not adequate for reaching and maintaining an optimal vitamin B12 status, even for a young, healthy population. An intake of 4 to 7 µg per day would be preferable.8
Pregnant women have needs that are slightly higher than those of the general population; these women are therefore deemed to be more at risk of deficiency. A study conducted on 1,424 pregnant women in Newfoundland and Labrador showed that 43.6% had a deficiency in or marginal levels of vitamin B12.9
Between 5% and 20% of older adults have vitamin B12 deficiency,10 likely due to inadequate absorption, caused by either a Helicobacter pylori bacterial infection in the stomach, or atrophy of the gastric mucosal membrane. In both cases, acid production decreases, which affects gastric pH and consequently impedes absorption of vitamin B12 from foods.11 Absorption of the synthetic form contained in supplements seems to be less affected by this reduction in gastric acidity.11
Milk and Vitamin B12: The Evidence
Many studies indicate that vitamin B12 intakes correlate with the consumption of animal products.11,12 For example, the British landmark EPIC (European Prospective Investigation into Cancer and Nutrition) cohort study of over 500,000 participants showed that vitamin B12 intakes were proportional to the number of servings of animal foods, including milk products, that the study subjects consumed.12
The daily consumption of milk products can therefore contribute to the recommended intake of vitamin B12. In fact, milk is an excellent source of this vitamin, as a single 250 mL serving provides 1 µg of vitamin B12, or a little less than half of the Recommended Dietary Allowance.6,7 It has been estimated that the contribution of milk products to total vitamin B12 intake is about 30%.13 Yet the majority of Canadians, all ages combined, do not consume the recommended number of servings of milk products.14
Studies show that among individuals at risk of deficiency, the consumption of milk and milk products may increase vitamin B12 intake and consequently decrease the incidence of deficiency. A study involving healthy older adults showed that the consumption of 3 cups of milk per day for 12 weeks significantly increased vitamin B12 intakes compared to the group that did not receive milk supplementation.15 Similarly, a study carried out on children from an underprivileged environment in Kenya showed that supplementation of 200 mL to 250 mL of milk per day during the school year increased blood levels of vitamin B12 and helped lower the prevalence of vitamin B12 deficiency in children.16
A number of studies show a strong positive association between blood levels of vitamin B12 and the consumption of milk and milk products.17 Some studies have even demonstrated that among all food sources of vitamin B12, milk is characterized as having the best correlation with optimal blood values of this vitamin.13,18
The bioavailability of vitamin B12 from food sources varies, but healthy adults generally absorb 50% of the vitamin contained in foods.19 The absorption of vitamin B12 from eggs appears to be relatively low at a rate of less than 9%.1 However, the vitamin B12 from meat, poultry and fish is estimated to be absorbed at a rate of 42% to 61%; while the vitamin B12 contained in milk is estimated to be the most bioavailable, with approximately 51% to 79% absorption.18,19
Furthermore, Agriculture and Agri-Food Canada recognizes that vitamin B12 is better absorbed from cow’s milk than when taken in vitamin supplements. The organization also states that one glass of milk can provide 50% of an adult’s daily vitamin B12 requirement.20 In a Quebec study conducted on pigs, research scientists from the organization showed that the absorption of vitamin B12 naturally present in cow’s milk was twice higher than that of synthetic vitamin B12. In this study, pigs were used as a model since their digestive system shares many similarities with that of humans in terms of anatomy, physiology, absorption and metabolism.21
Numerous studies show a positive correlation between milk product consumption, especially milk consumption, and vitamin B12 intake and blood levels. Moreover, the form of vitamin B12 found in milk appears to be highly bioavailable. Consequently, milk and milk products are an excellent food source of vitamin B12, and daily consumption can aid in the prevention of vitamin B12 deficiency.
- Watanabe F. Vitamin B12 sources and bioavailability. Exp Biol Med 2007;232:1266-1274.
- Smith AD and Refsum H. Vitamin B-12 and cognition in the elderly. Am J Clin Nutr 2009;89:707S-711S.
- Thompson MD et al. Vitamin B-12 and neural tube defects: the Canadian experience. Am J Clin Nutr 2009;89:697S-701S.
- Appel LJ et al. Effect of dietary patterns on serum homocysteine: results of a randomized, controlled feeding study. Circulation 2000;102:852-857.
- Antony AC. Vegetarianism and vitamin B-12 (cobalamin) deficiency. Am J Clin Nutr 2003;78:3-6.
- Stabler SP and Allen RH. Vitamin B12 deficiency as a worldwide problem. Annu Rev Nutr 2004;24:299-326.
- Institute of Medicine. Dietary reference intakes for thiamine, riboflavin, niacin, vitamin b6, folate, vitamin B12, pantothenic acid, biotin and choline. Chapter 9: Vitamin B12. Washington, DC: National Academies Press. 2000.
- Bor MV et al. Daily intake of 4 to 7µg dietary vitamin B-12 is associated with steady concentrations of vitamin B-12-related biomarkers in a healthy young population. Am J Clin Nutr 2010;91:571-577.
- House JD et al. Folate and vitamin B12 status of women in Newfoundland at their first prenatal visit. CMAJ 2000;162:1557-1559.
- Park S and Johnson MA. What is an adequate dose of oral vitamin B12 in older people with poor vitamin B12 status. Nutr Rev 2006;64:373-378.
- Allen LH. How common is vitamin B-12 deficiency. Am J Clin Nutr 2009;89:693S-696S.
- Davey GK et al. EPIC-Oxford: lifestyle characteristics and nutrient intakes in a cohort of 33 883 meat-eaters and 31 546 non meat-eaters in the UK. Public Health Nutr 2003;6:259-269.
- Vogiatzoglou A et al. Dietary sources of vitamin B-12 and their association with plasma vitamin B-12 concentrations in the general population: the Hordaland Homocysteine Study. Am J Clin Nutr 2009;89:1078-1087.
- Garriguet D. 2004. Nutrition: Findings from the Canadian Community Health Survey – Overview of Canadians' Eating Habits. www.statcan.gc.ca. Accessed January 28, 2015.
- Barr SI et al. Effects of increased consumption of fluid milk on energy and nutrient intake, body weight, and cardiovascular risk factors in healthy older adults. J Am Diet Assoc 2000;100:810-817.
- Siekmann JH et al. Kenyan school children have multiple micronutrient deficiencies, but the increased plasma vitamin B-12 is the only detectable micronutrient response to meat or milk supplementation. J Nutr 2003;133:3972S-3980S.
- Villamor E et al. Vitamin B-12 status is associated with socioeconomic level and adherence to an animal food dietary pattern in Colombian school children. J Nutr 2008;138:1391-1398.
- Tucker KL et al. Plasma vitamin B-12 concentrations relate to intake source in the Framingham Offspring Study. Am J Clin Nutr 2000;71:514-522.
- Russell RM et al. Older men and women efficiency absorb vitamin B-12 from milk and fortified bread. J Nutr 2001;131:291-293.
- Agriculture and Agri-Food Canada. 2014. It is a proven fact that vitamin B12 is better absorbed from cow’s milk. www.agr.gc.ca. Accessed December 24, 2014.
- Matte JJ et al. Bioavailability of vitamin B12 in cows’ milk. Br J Nutr 2012;107:61-66.