VITAMIN D UPDATE: Low Vitamin D in Childhood Linked to Later Heart Risks. “A vitamin D level of between 30 to 50 is generally considered adequate. Children in the lowest one-quarter for vitamin D levels, about 15 nanograms per milliliter, were nearly twice as likely to have thickening of the carotid artery as those in the other three quarters. The association persisted after adjusting for age, sex and other cardiovascular risk factors.” Bad news given how many kids today are deficient.