By: Dr. Geoffrey Modest
No shocker here, but it turns out that non-vitamin D fortified non-cow’s milk (eg goat’s milk or plant-based milk such as soy, rice, almonds…) leads to lower 25-OH vit D levels in the blood. In this Canadian study, they looked at serum 25-OH in kids who were drinking non-cow’s milk (which is only voluntarily fortified with vit D and, if so, with no regulation of content) vs. those on fortified cow’s milk, by law required to have 40 IU vit D/100 ml (see DOI:10.1503/cmaj.140555). Note that this was an observational study, not RCT — so there might be other confounders (eg, those on non-cow’s milk are on it for specific reasons which could also affect their vitamin D levels, or have other dietary changes in addition to non-cow’s milk).
Results:
–2268 children aged 1-6 yo, coming in for routine well-child visits, had dietary history and blood tests. of these, 1950 drank only cow’s milk, 146 only non-cow’s milk, 88 both, 109 neither. Also, 50-60% of each group were on vit D supplementation
–Non-cow’s milk consumption was associated with a 4.2 nmol/L (1.7 ng/ml) decrease in 25-OH vit D per 250 ml milk consumed, vs. those on cow’s milk (p=0.008), and there was a linear gradient in those consuming both, reflecting the amount of non-cow’s milk drunk
–Those drinking exclusively non-cow’s milk were at higher risk of 25-OH vit D levels below 50 nmol/L (20 ng/ml), 11% vs. 4.7% with odds ratio of 2.7 (1.6-4.7)
–And (also not a shocker), there was variation in 25-OH vit D levels depending on whether there was either vit d supplementation (which, unfortunately, they did not quantify) and having darker skin pigmentation.
So, no big surprises. I bring this up because of the increasing understanding of the role of vitamin D in health in general and especially in kids. For example, the American Association of Pediatrics just released a clinical report for clinicians entitled “Optimizing Bone Health in Children and Adolescents” (see here), which suggests that “Adequate vitamin D intake for infants younger than 1 year is 400 IU/d. The RDA is 600 IU for children 1 year and older”. And, since fortified cow’s milk has been shown in several studies to be the main dietary source of vitamin D in early childhood, it may be very important for us clinicians to be particularly attentive to kids drinking non-cow’s milk (which anecdotally I have found occasionally but increasingly in our inner-city community) as well as the quantity of fortified dairy products consumed. Of course, one concern in a Canadian study is the remarkable lack of good sunlight in those northern climes, making the issue there (and a lot of northern US) even more important. Another perhaps significant issue is that an old study found a remarkable discordance between the advertised supplementation on fortified milk and the actual content (see DOI: 10.1056/NEJM199204303261802), with only 29% of 42 samples having between 80-120% of the advertise content.