Vitamin D is a key ingredient in the recipe for pediatric bone health

Managing bone health can be confusing and time-consuming for orthopaedic surgeons. This article offers a simplified, evidence-based approach, highlighting areas that should be emphasized for pediatric patients.

In any “recipe” to achieve optimal bone health, the first ingredient to consider is vitamin D. To date, the best studies on vitamin D supplementation have been conducted in adult populations. For example, the VITAL trial suggested that routine supplementation is not helpful for patients with adequate levels. Studies have been mixed about whether supplementation reduces falls and fractures in adults with deficient levels. Meanwhile, other research has shown that vitamin D supplementation is valuable during fracture healing with reduced rates of nonunion. A newer, exciting area of investigation has suggested that vitamin D deficiency is associated with sarcopenia and that supplementation may boost muscle strength. In general though, the best evidence does not currently support vitamin D supplementation in adults.

Unlike adult populations, empiric vitamin D supplementation is recommended for all children (1-18 years of age) to avoid rickets among other issues, according to a recent multi-endocrine society panel. Researchers have linked low vitamin D levels to fracture severity (especially in children with higher BMI), curve progression in adolescent idiopathic scoliosis, and slipped capital femoral epiphysis. Meanwhile, peak bone mass is achieved by the end of the second decade, making childhood and adolescence a crucial window for bone health intervention. Moreover, vitamin D deficiency is common in this age group, particularly for the overweight.

Dosing and testing
However, practical treatment guidelines for vitamin D supplementation in children do not yet exist. The Institute of Medicine and the Endocrine Society have made age-based recommendations, but treatment must be weight-based given size variability among pediatric patients. Additionally, the lipophilic property of vitamin D causes it to be sequestered in adipose tissue, reducing its bioavailability. Until guidelines catch up with clinical nuance, orthopaedic surgeons must use physiology, emerging data, and clinical reasoning to guide supplementation decisions.

Vitamin D₃ supplementation increases serum levels of vitamin D over time, typically reaching a steady state after six to eight weeks of dosing. With a half-life of two to three weeks, daily or weekly dosing is advisable, and monthly dosing is too infrequent. Moreover, supplementation should not be stopped because the patient will experience a precipitous drop in serum levels. Proposed supplementation regimens vary widely, but based on a synthesis of available literature, the authors recommend the following (dosed in international units [IU]):

• 0-90 lbs: 1,000 IU
• 90+ lbs: 2,000 IU
• 150-199 lbs: 5,000 IU
• 200+ lbs: start with 5,000 and increase to 10,000 IU

These values provide a place to empirically start supplementing children, adolescents, and young adults. These dosing ranges adhere to the ranges and upper limits of dosing described by the Endocrine Society and have not been associated with toxicity.

Although the various pediatric and endocrine societies do not recommend routine laboratory screening for healthy children before beginning empiric treatment, serum 25(OH)D testing can be considered after eight weeks of empiric treatment to assess effectiveness and make appropriate dosing adjustments. For example, patients who weigh 200 lbs or more may need 10,000 to 15,000 IU daily to achieve a level of 40 ng/mL. A 25(OH) D blood test can be ordered (current procedural terminology code 82306) with E55.9 ICD-10 code (vitamin D deficiency); this is widely covered by insurance. Screening should be considered in high-risk populations such as children with chronic pain, malabsorption syndromes, obesity, fatigue, liver or kidney disease, depression, etc. ICD-10 codes for these conditions will typically successfully facilitate insurance approval of laboratory testing. However, the test may only be approved a certain number of times per year depending on insurance type.

When checking vitamin D 25 level, consider including a complete blood count and comprehensive metabolic panel (CMP) with the initial blood draw to check liver and kidney function. Calcium and alkaline phosphatase are tested as part of CMP, but calcium levels are typically homeostatic, even in the face of essentially no dietary calcium intake. So, these levels are not particularly helpful in determining bone health status. If there is a specific concern regarding metabolic bone disease, then phosphorus and intact parathyroid hormone should also be checked.

Beyond vitamin D
Vitamin D’s main job is to move calcium into and around the body. It does not act alone, so expecting good bone health based solely on vitamin D levels is unrealistic. Healthy bone development requires several key nutrients and lifestyle factors, which can be explained to families as a bone health “recipe”:

• Calcium provides the structural matrix of bone. It is readily available in dairy products, but many people have milk-avoidant diets and require fortified alternatives or chewable calcium supplements, such as calcium carbonate antacids. The daily minimum target is 700-1,300 mg, dependent on age and weight. To simplify counseling, the authors recommend using the round number 1,000 mg per day, which is approximately three cups of calcium-rich foods (e.g., milk, yogurt, calcium orange juice). These levels far exceed the calcium in typical multivitamins, so when providing supplementation, calcium-specific options are needed.
• Vitamin C is important for collagen crosslinking, which helps frame out the bone to then be mineralized. Young children tend to get sufficient vitamin C from fruit-rich diets. In older children and adolescents, a daily supplement of 500 mg is recommended. Like calcium, this level far exceeds the amount in typical multivitamins.
• Vitamin K helps regulate bone turnover and calcium deposition. Leafy greens are a primary source. If they are omitted from the diet, then the vitamin D₃ supplement should contain vitamin K₂. The recommended daily intake is approximately 55-75 mcg in children and 90-120 mcg in adults.
• Exercise is indispensable. Mechanical stress stimulates bone remodeling; just three days of bed rest can result in measurable bone loss. A reasonable recommendation is 30 minutes of weight-bearing exercise (e.g., dancing or running rather than biking or swimming) five times per week. Resistance training also builds bone and muscle.

Clinical pearls
To summarize, in adults, routine vitamin D supplementation is not recommended by endocrine societies except in deficient patients. Supplementation can reduce muscle weakness (sarcopenia) and fracture nonunion when paired with calcium. In pediatrics, vitamin D deficiency has been associated with several conditions other than rickets, including fractures, adolescent idiopathic scoliosis, and slipped capital femoral epiphysis. In this population, empiric vitamin D supplementation is recommended with weight-based dosing.

Routine vitamin D 25 laboratory screening is not recommended but can be considered after eight weeks of treatment to monitor progress. Limited testing is usually covered by insurance with accepted coding, potentially in collaboration with endocrinology. And, of course, the full bone health “recipe” should always include calcium, vitamin C, vitamin K, and exercise.

Barbara Minkowitz, MD, is a pediatric orthopaedic surgeon at Morristown Medical Center in Morristown, New Jersey. She is a member of AAOS and the Pediatric Orthopaedic Society of North America, where she serves on the Advocacy Committee.

Carter Clement, MD, MBA, is a pediatric orthopaedic surgeon at Manning Family Children’s and the Louisiana State University Health Sciences Center New Orleans. He serves on the AAOS Health Care Systems Committee and the Pediatric Orthopaedic Society of North America Advocacy Committee.

References 

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