Vitamin D has been in the news a lot lately. Are we getting enough? Should we take supplements? What about people who can’t get enough sunshine to make vitamin D needed for bone health? And what about children? What are “normal” levels of vitamin D for them?
This study from the Shriners Hospital for Children in Texas addresses concerns about vitamin D levels in children having bone surgery. The goal was to find out how much vitamin D children had who were admitted for orthopedic surgery. Measurements were taken from blood samples of 70 children ages two to 19 years old before surgery.
Vitamin D helps regulate calcium absorption from the gut (gastrointestinal tract). Calcium is an essential ingredient in strong bones. The skin makes vitamin D but relies on sun exposure to do so. With so much time spent indoors and lower sunlight levels year round in the northern hemispheres, many children around the world have either vitamin insufficiency or deficiency.
The difference between insufficiency and deficiency is a matter of degree. Vitamin D insufficiency is defined as a blood level of 25-hydroxyvitamin-D (25 OHD) that falls below 32 ng/mL. 25 OHD is a chemical compound that must be present in the body in order for vitamin D to be made. It is called a precursor (comes before) chemical.
Vitamin D deficiency occurs when 25 OHD levels fall below 20 ng/mL. The levels for insufficiency and deficiency are actually determined by another factor — and that is the amount of 25 OHD needed to keep parathyroid levels in the normal range. Without going into the complex physiology of the body to explain the interactions between the hormonal systems, suffice it to say that vitamin D levels and parathyroid function are intimately linked together.
Other risk factors for decreased vitamin D include obesity, increased skin pigmentation (dark skin), older age, and not enough vitamin D in the diet. Children with metabolic bone disorders such as osteogenesis imperfecta (weak and brittle bones) and rickets are at a much greater risk for poor bone healing, which can be compounded by low vitamin D levels.
Finding out preoperative levels of vitamin D may be important because bone healing after fractures and surgical procedures depends on sufficient levels of vitamin D. In order to look for other factors that might affect vitamin D levels and/or bone healing, the researchers conducting this study also gathered additional information on each patient.
Age, sex (male or female), ethnicity, body mass index (BMI), diagnosis, and geographic location (where they normally lived: United States or Mexico) were included in the sampling. Vitamin D levels collected were also compared to the season.
They found that African American children were at greatest risk for vitamin D deficiency. As shown in other studies, vitamin D levels were at their lowest during the winter season.
Age and ethnicity combined was a major risk factor. For example, African Americans between the ages of 12 and 19 years old were 20 times more likely to be vitamin D deficient compared with Caucasians (whites). Seasonal levels of vitamin D did fluctuate with lower levels measured in the winter.
There was no obvious or statistically significant link between vitamin D levels and type of orthopedic diagnosis or body mass index (BMI). The kinds of orthopedic conditions children were treated for included scoliosis and other spine problems, cerebral palsy, hip dysplasia, leg length difference, and other (unspecified) orthopedic (bone) problems.
The authors did not examine complications or problems with bone healing after surgery compared with vitamin D levels. That will be the topic of the next study. The first step was just to see if vitamin D levels were normal or abnormal prior to surgery.
Future studies will be done to determine the implications of these findings. Clinical practice guidelines (what to do) will be developed after that. Routine monitoring of blood levels of vitamin D before and after pediatric orthopedic surgery may become necessary.
Ways to reduce risk factors and providing patient/family education are likely to be developed. These programs will be conducted as part of future preop programs for children undergoing orthopedic surgery involving bone. The protocol for all procedures requiring good bone healing for the best outcome will be reviewed as well.