SuomiIron deficiency is common among children under 3 years and main causes of iron deficiency are increased iron need, small amount of iron from food and big consumption of cow milk products, especially consuming cow milk together with food [1]. Nutrition therapist and Estonian Nutrition Therapy Association´s member of board Triin Muiste reminds that milk is food, not a drink. A lot of parents give their children cow milk as a drink together with food and consume dairy products with meals themselves – the most important drink is water and parents should start practicing giving water to their children as early as possible.
Milk anemia can be defined as iron deficiency anemia triggered by heavy consumption of dairy products.
HOW DOES THE CONSUMPTION OF DAIRY PRODUCTS PROMOTE IRON DEFICIENCY?
Cow milk and dairy products contain in addition to a lot of calcium also a protein called casein. Calcium as well as casein both decrease iron absorption. The main forms of casein in cow milk are β-caseins and αs-caseins. It has been found in clinical studies that caseinphosphopeptides (peptides that are formed from casein in our digestive process) from β-caseins promote iron absorption and increase iron´s bioavailability, but caseinphosphopeptides from αs-caseins and whole caseins decrease iron absorption. Human breast milk contains β-caseins and does not contain αs-caseins that explains better absorption of iron from human breast milk – 7–10 times better compared to cow milk [2].
Residues of phosphoserine (ingredients of many proteins) in casein-protein strongly bind iron.Therefore, for humans casein from cow milk decreases iron absorption. To some extent the decrease in iron absorption may be reduced by protein hydrolysis [2].
A lot of different research has been done regarding consumption of calcium and iron absorption. It has mainly been found that during a longer period of time the consumption of calcium does not decrease iron absorption significantly. Different results have been found for iron absorption and consumption of calcium for a shorter period of time.
Calcium inhibits iron absorption in case of shorter periods of time, when calcium is consumed in greater amounts together with iron-rich food. Therefore, water or juice are preferred drinks together with meals instead of consuming dairy products to get the most benefits from iron from food [3]. It is also a well-known fact that iron supplements should not be taken with dairy products. For iron to get absorbed, you should avoid dairy products and calcium supplements at least 1 hour before and after taking iron supplements or eating iron-rich food.
Compared to cow milk, iron from breast milk is absorbed much better, 50–70% vs 5–10% from milk substitutes. Milk substitutes for infants contain iron many times more compared to breast milk due to low absorption [4]. Human breast milk contains calcium about 30 mg per 100 ml, cow milk contains calcium about 125 ml per 100 ml – the difference is four-fold. In addition, cow milk contains a certain casein that is not found in human breast milk that also explains the weak absorption of iron from cow milk.
Cow milk and dairy products can also damage the intestinal mucosa. Absorption of nutrients, minerals and vitamins is weak from damaged intestinal mucosa. Intestinal mucosa recovers when the disturbing factors have been removed or decreased from food (e.g. intestinal mucosa recovers during celiac disease, when a person ditches gluten) [5]. Children under 1 year are not advised to consume dairy products in order to decrease the risk for iron deficiency anemia. It has been found that as much as 40% of otherwise healthy infants suffer from intestinal blood loss due to consumption of dairy products [6].
Sources:
[1] A.Aro, M.Mutanen, M.Uusitupa. Ravitsemustiede, 4.-7.köide, 2017.
[2] Kibangou, I., Bouhallab, S., Henry, G. et al. Milk Proteins and Iron Absorption: Contrasting Effects of Different Caseinophosphopeptides. Pediatr Res 58, 731–734 (2005).
[3] Dawson-Hughes, B & Seligson, F.H. & Hughes, Virginia. (1986). Effects of calcium carbonate and hydroxyapatite on zinc and iron retention in postmenopausal women. The American journal of clinical nutrition. 44. 83-8. 10.1093/ajcn/44.1.83.
[4] Tampere University of Applied Sciences. 2020.
[5] Lapsen Raudanpuuteanemia. Potilan Lääkärilehti. 31.1.2020 5/2020 vsk 75 s. 254 – 257
[6] E. Ziegler. Consumption of cow’s milk as a cause of iron deficiency in infants and toddlers. Nutrition Reviews, Volume 69, Issue suppl_1, 1 November 2011, Pages S37–S42.
