If your child is allergic to milk, can't tolerate lactose (the natural sugar in milk) or eats a vegetarian diet, non-dairy beverages are popular replacements for cow's milk.
But research from St. Michael's Hospital in Toronto suggests young kids who drink rice, almond, soy or goat's milk are at risk for vitamin D deficiency.
According to the study, published Oct. 20 in the Canadian Medical Association Journal, children who drank only non-dairy beverages were more than twice as likely to have vitamin D levels inadequate to build strong bones compared with milk-only drinkers. The research was funded by the Canadian Institutes of Health Research.
Vitamin D supports the normal development of bones and teeth by helping the body absorb calcium from foods and supplements. Too little vitamin D can lead to low calcium levels in the blood, causing the body to pull calcium from the bones to replace what's missing in the bloodstream. In young children, vitamin D deficiency can cause rickets, a condition causing the bones to become soft and weak and potentially leading to bone deformities. In older kids (as well as adolescents and adults), inadequate vitamin D can increase the risk of bone fractures. Vitamin D also helps muscles contract, supports the immune system, reduces inflammation and may be important for heart health and, possibly, cancer prevention.
For the study, researchers looked at differences in blood levels of vitamin D associated with drinking cow's milk and non-cow's milk among 2,831 healthy children, aged one to six, living in Toronto. Among children who drank only non-dairy beverages, 11 per cent had a vitamin D level below what's required for adequate bone health compared with 4.7 per cent of milk drinkers, even after accounting for factors that influence vitamin D levels, such as body weight, vitamin D supplementation, use of margarine, skin colour and outdoor playtime.
Vitamin D status is determined by measuring 25-hydroxyvitamin D in the bloodstream; 25-hydroxyvitamin D reflects vitamin D from food, supplements and sun exposure. The Institute of Medicine suggests that a target above 50 nmol/L is sufficient for healthy bone development.
Even milk drinkers in the study who also drank non-dairy beverages had lower levels of vitamin D than if they just stuck to drinking cow's milk.
These findings suggest that substituting cow's milk with milk alternatives that lack vitamin D, or are lower in vitamin D than milk, could put children at risk for complications of vitamin D deficiency.
In Canada and the United States, cow's milk is required by law to be fortified with 100 IU (international units) of vitamin D per 250 ml. (The only other food with mandatory vitamin D fortification is margarine, with 50 IU per two teaspoons.) Because milk fortification is legislated, vitamin D content is monitored by the government.
Fortification of plant-based beverages, such as soy, rice, almond, hemp and coconut as well as goat's milk, however, is voluntary. While many manufacturers do add vitamin D (100 IU per 250 ml) to their products – along with calcium, B12 and other nutrients – not all do.
Parents need to carefully read labels in order to ensure non-dairy beverages are vitamin D fortified. And you can't always rely on the front of the package to tell you. Check the Nutrition Facts box and look for a daily value (DV) for vitamin D of 45 per cent, which indicates 100 IU vitamin D per 250 ml.
Even if your child does drink cow's milk and/or fortified non-dairy beverages, there's a good chance he or she is not drinking enough of it to meet daily vitamin D requirements. Kids would have to drink six cups each day to get the 600 IU of vitamin D that children, aged one and older, need each day. Children who are obese may require two to four times more to achieve an adequate vitamin D level.
(Infants require 400 IU daily; breastfed babies should receive a daily supplement of 400 IU since human milk, unlike infant formula, is lacking adequate vitamin D.)
Very few foods have vitamin D naturally. Salmon (447 IU per 3 ounces) and tuna (154 IU per 3 ounces) are among the best sources. Eggs (41 IU per yolk) and cheese (14 IU per 2 ounces cheddar) provide a little. Besides fortified milk and non-dairy beverages, some brands of orange juice, yogurt and breakfast cereals may also have added vitamin D.
A major source of vitamin D is sunlight; your skin produces it when exposed to ultraviolet B rays. But in Canada, synthesis of vitamin D is minimal in the fall and winter months.
For children who don't get enough vitamin D from their diet, a vitamin D supplement is recommended in the fall and winter and for some, year-round. Children's multivitamins contain 400 IU; vitamin D is also available in capsules, tablets and drops for children.
Parents should also keep in mind the fact that taking more vitamin D than required is not better. Safe upper daily limits are 2,500 IU (aged 1-3), 3,000 (aged 4-8) and 4,000 IU (aged 9 and older). Excess vitamin D can cause nausea, vomiting, poor appetite, weakness, heart rhythm problems and kidney damage.
A parent's guide to non-dairy beverages:
For children aged two and younger, soy, rice, almond, coconut and other plant-based beverages – fortified or not – are not suitable alternatives to breast milk or whole cow's milk as they are generally lower in protein, fat and calories.
If parents choose a plant-based beverage or goat's milk as an alternative to cow's milk for children aged two and older, ensure it is labelled calcium and vitamin D fortified. Or, scan the nutrition facts table: Look for 45-per-cent daily value (DV) for vitamin D and 30-per-cent DV for calcium.
Kids who rely on fortified rice, almond, coconut and hemp beverages should eat a variety of protein-rich foods, such as lean meat, poultry, fish, eggs, beans, lentils and tofu, to ensure adequate protein intake (the protein content of soy beverages is similar to cow's milk).
Leslie Beck, a registered dietitian, is based at the Medisys clinic in Toronto. She is a regular contributor to CTV News Channel; lesliebeck.com.