Non-cow's milk, which includes goat’s milk and plant-based beverages made from soy, rice, almonds, and coconut, has become increasingly popular in recent years due to milk protein allergies, lactose intolerance, and the perceived health benefits. Yet, these alternative milk beverages do not match cow’s milk in one crucial way: Children who drink non-cow's milk have lower levels of vitamin D in their blood when compared with those drinking fortified cow's milk, a new study finds.

An essential nutrient, vitamin D is made by our bodies when sunlight touches our skin. It is also found in eggs and oily fish, such as sardines and salmon. The sunshine vitamin is necessary to strengthen immunity and to support muscles, heart, lungs, and brain health. It also plays an important role in the development and strengthening of bones. In children, low levels of vitamin D can cause bone weakness and, in severe cases, rickets — a condition which in some cases can lead to deformities.

Fortified Milk

In both the United States and Canada, where the current study was conducted, cow’s milk products are required to contain about 40 units of vitamin D per 100 mL, making it a major dietary source of vitamin D for children. While non-cow’s milk also might be fortified with vitamin D, it is voluntary in both countries. This, then, may present some challenges when it comes to maintaining healthy vitamin D levels for the nearly 2.5 percent of all children who are allergic to milk.

To understand how non-cow’s milk stacks up against the everyday stuff, a team of researchers conducted a study on healthy, urban preschool-aged children attending routinely scheduled well-child visits in Toronto. The researchers recruited a total of 2,831 children between ages 1 and 6 from seven pediatric or family medicine primary care practices between December 2008 and September 2013. The researchers excluded those children with a condition affecting their growth or a chronic illness (other than asthma).

On a regular basis, 87 percent of the kids drank cow's milk, while 13 percent drank non-cow's milk. Children drinking only non-cow's milk were more than twice as likely to be vitamin D deficient as children drinking only cow's milk. Among children who drank both types of milk — perhaps the sibling of a child with a milk allergy — every additional cup of non-cow's milk was associated with a five percent drop in vitamin D levels per month.

“It is difficult for consumers to tell how much vitamin D is in non-cow's milk,” said Dr. Jonathon Maguire, a pediatrician and researcher with St. Michael's Hospital and lead author of the current study. “Caregivers need to be aware of the amount of vitamin D, calcium, and other nutrients in alternative milk beverages so they can make informed choices for their children.”

Source: Lee GJ, Birken CS, Parkin PC, et al. Non–cow’s milk consumption and serum vitamin D levels in early childhood. CMAJ. 2014.