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The Milk Debate

By: Jovana K.

Over the past decade the use of low fat milk has become more prominent than the use of whole milk because there is substantial scientific evidence that consumption of foods high in fat causes weight gain and increases the risk of heart disease and cancer. However, there is some controversy over whether processed low-fat pasteurized milk can meet the needs of developing offspring and whether it should be consumed during pregnancy and development.

Milk Consumption During Pregnancy

Human brain development involves increased incorporation of long-chain polyunsaturated fatty acids (LCPUFA) in brain phospholipids. From the third trimester through to second year of postnatal life LCPUFA (i.e. docosahexaenoic acid (DHA) and arachidonic acid (AA)) are actively incorporated into the developing brain. The proportion of DHA and AA that the infant has reflects the presence of these fatty acids in the maternal diet. Dietary sources of LCPUFA include fish, fish oil and DHA fortified dairy including milk.

Naturally, cow’s milk does not provide a rich source of DHA however in North America whole milk and partially skimmed milk (2%) are fortified with DHA by adding DHA rich feed additive to cattle’s diet. Skim milk or low fat milk (1%) cannot be fortified with DHA because DHA is contained in the milk fat. The DHA-fortified milk products may allow mothers who do not eat large quantities of fish to obtain the levels of DHA that their baby needs for brain and central nervous system development.

Milk Consumption During Postnatal Development

The American Academy of Paediatrics recommends that toddlers drink whole milk because fatty acids are helpful for brain and bone development. However, some doctors recommend low fat or skim milk to overweight or obese children. Whether low fat or skim milk protects children from weight gain is under debate.

According to a cohort study of 12,829 US children aged 9 to 14 years, weight gain is associated with excess calorie intake and consumption of low fat or skim milk, but is not associated with drinking whole milk products. This finding although surprising is consistent with some animal findings. Pigs fed reduced-fat milk gain weight easily while pigs fed whole milk stay lean. Male rats fed whole milk had significantly lower concentrations of plasma triglycerides, very low-density lipoproteins and apolipoprotein B than rats fed low fat milk. The effects of whole milk on lipid profile and body composition are not well understood, but the process of removing fat from milk may in part be responsible for some of the observed effects.

Milk is an emulsion of butterfat globules and water-based fluid. Butterfat contains unique nutrients that support thyroid function and help the body develop muscle rather than fat. The butterfat properties of whole milk are different from that of low fat or skim milk, which may help to explain the effects of whole milk on body composition. Future studies should explore the mechanism by which whole milk may protect infants from gaining weight.