Goodness of dairy 2Milk and milk products contribute to the daily intake of several vitamins, including vitamins A, B2 and B12.

Vitamin B2 and B12

Vitamin B2 – riboflavin – and B12 – cobalamin – are both water soluble and naturally present in milk and milk products. Meat and fish are other sources of riboflavin, and certain fruits and vegetables, particularly dark-green vegetables, contain reasonable concentrations. Vitamin B12 is the only vitamin in our food supply not directly, or via precursors, available from plant sources. Natural vitamin B12 is exclusively supplied by animal proteins found in milk and milk products, meat, fish and eggs. The reported bioavailability of B12 from various animal sources may vary.1,2  Typical B2 and B12 values of milk and milk products, and selected other food sources, are provided in the table below.

Table 1: Dairy and selected other sources of vitamin B2 and B123,4

Food sources Vitamin B2 (mg/100g) | %RDA Vitamin B12  (mcg/100g) | %RDA
Milk, semi skimmed 0.24 | 20 0.40 | 17
Cheese, Gouda 0.30 | 25 1.70 | 71
Egg, raw 0.47 | 40 2.50 | 104
Salmon, raw 0.13 | 11 4.00 | 167
Rump steak, raw 0.23 | 20 2.00 | 83
Mushrooms, common 0.31 | 26 0.00 | 0
Mixed nuts 0.22 | 19 0.00 | 0

Note: The US Recommended Dietary Allowances (RDAs), which are used in this table, are set to meet the needs of almost all (97 to 98 percent) individuals in a group. The RDAs are based on adults (average males-females), aged 19-70 years.

Functions within the human body

Vitamin B2 and B12 have many functions in the human body. Vitamin B2 plays a role in the proper functioning of the nervous system and energy-yielding metabolism. Vitamin B12 contributes to mechanisms such as: energy-yielding metabolism, cell division and red blood cell formation. Similar to other B-vitamins, sufficient intake of vitamin B2 and B12 also reduces tiredness. Although vitamin B12-deficiency is rare, mild subclinical deficiencies are common. Studies show that vegans, their children and elderly are especially at risk of displaying low levels of vitamin B12.2  In strict vegan diets a low B2 intake can also be a risk factor.5,6

Vitamin A and D

Vitamin A and D are both fat soluble and present in multiple forms. Vitamin A is naturally present in milk fat that typically contains approximately 10 µg retinol (preformed vitamin A) and 6 µg carotenoids (provitamin A) per gram of fat. While plant foods don’t supply retinol, they do provide high levels of carotenoids. These can be converted into vitamin A in the body. The most important carotenoid in our diets is ß-carotene.7  Vitamin A is most often expressed in Retinol Activity Equivalent (RAEs), accounting for the bioactivity of retinol and the less efficient carotenoid sources, however different calculation methods exist.8

Dietary sources of vitamin D account for around 10% of our body’s supply, as vitamin D is also synthesized in the skin by exposure to sunshine. Dietary vitamin D comes in two major forms: vitamin D2 (ergocalciferol – typical form in plants) and vitamin D3 (cholecalciferol – from animal foods in the diet). Milk and milk products have relatively low natural levels of vitamin D, however they are generally considered suitable products for fortification. The typical vitamin A and D values of several food sources are shown in the table below.

Table 2: Vitamin A and D in dairy and other food sources3,9,10

Food sources Retinol

(mcg/100g)

ß-carotene equivalents

(mcg/100g)

RAE

(mcg/100g) | %RDA

Vitamin D (mcg/100 g) | %RDA
Milk, semi skimmed 19 9 20    | 2 Tr. | 0
Milk, whole vitamin D fortified 33 20 46    | 6 1.3 | 9
Butter 958 608 1007 | 128 0.9 | 6
Cheese, Gouda 258 139 270   | 35 0.2 | 1
Egg, raw 190 Trb 190   | 24 1.8 | 12
Salmon 13a Tr 13     | 2 5.9 | 49
Mango 0 696 58     | 7 0.0 | 0
Curly kale, raw 0 3145 262   | 33 0.0 | 0

Note: The US Recommended Dietary Allowances (RDAs), which are used in this table, are set to meet the needs of almost all (97 to 98 percent) individuals in a group. The RDAs are based on adults (average males-females), aged 19-70 years.

a Value for Atlantic salmon; b Traces.

Functions within the human body

Vitamin A and D have many functions in the human body. Vitamin A contributes to the proper functioning of the immune system and maintaining normal vision.11  Vitamin D contributes to bone growth and maintenance, as it plays a key role in the uptake and availability of calcium. Furthermore, it plays a role in proper functioning of the immune system and muscles, and may be linked to improved insulin sensitivity and mediation of inflammation.12

References

  1. F. Watanabe, Vitamin B12 sources and bioavailability. Exp Biol Med (Maywood). 2007. 232(10): p. 1266-74.
  2. O’Leary and S. Samman, Vitamin B12 in health and disease. Nutrients., 2010. 2(3): p. 299-316.
  3. R.A. McCance and E.M. Widdowson, McCance and Widdowson’s The composition of Foods. Sixth summary ed. 2002: Cambridge: Royal Society of Chemistry.
  4. Institute Of Medicine, Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. 2001.
  5. D Majchrzak, et al., B-vitamin status and concentrations of homocysteine in Austrian omnivores, vegetarians and vegans. Ann Nutr Metab., 2006. 50(6): p. 485-91.
  6. A Waldmann, et al., Dietary intakes and lifestyle factors of a vegan population in Germany: results from the German Vegan Study. European Journal of Clinical Nutrition, 2003. 57: p. 947–955.
  7. D. Weber, The contribution of ß-carotene to vitamin A supply of humans. Mol Nutr Food Res, 2012. 56(2): p. 251-9.
  8. C.A. van Loo-Bouwman, T.H. Naber, and G Schaafsma, A review of vitamin A equivalency of β-carotene in various food matrices for human consumption. Br J Nutr. , 2014. 11: p. 1-14.
  9. Agriculture, A.R.S.U.S.D.o. National Nutrient Database for Standard Reference Release 26. Available from: http://ndb.nal.usda.gov/ndb/foods/show/70?fg=&man=&lfacet=&format=Abridged&count=&max=25&offset=0&sort=&qlookup=milk%2C+whole.
  10. Institute Of Medicine, Dietary Reference Intakes for Calcium and Vitamin D/DRI Values. 2010.
  11. National Institutes of Health; Office of Dietary Supplements. Vitamin A; Fact Sheet for Health Professionals. 2013 [cited 2014 20 May]; Available from: http://ods.od.nih.gov/.
  12. C.E. Chagas et al., Focus on vitamin D, inflammation and type 2 diabetes. Nutrients, 2012. 4(1): p. 52-67.