Vitamin D Deficiency in Children. By Dr. Narmin Azizova, Dr. Ali Quliyev

Xəbərlər
17 Mart 2025

Despite the abundant sunlight in our country, vitamin D deficiency is common, especially among infants, children during adolescence, and pregnant women. In recent years, the prophylactic intake of vitamin D has become one of the key health measures in many countries.

Vitamin D deficiency and rickets have been long-standing health issues in developing countries. In the U.S. and European countries, the increasing incidence of rickets among children, particularly in certain ethnic groups, has brought this problem to the forefront again. Despite advancements in healthcare and doctors advising prophylactic vitamin D usage for children, rickets is still observed in about 6% of children aged 0–3 years. However, it’s important to note that even if a child does not exhibit active rickets, other harmful effects of vitamin D deficiency may still be observed.

What is the Role of Vitamin D?

In recent years, it has been discovered that vitamin D plays a critical role not only in bone development but also in various other organs and systems in the body. The main role of active vitamin D is to help absorb calcium (Ca) and phosphorus (P), and along with parathyroid hormone (PTH), it maintains the Ca/P balance in the body. Without vitamin D, calcium absorption is reduced to 10-15%, but with the presence of vitamin D, absorption increases to 30-80%.

Foods Rich in Vitamin D

The primary source of vitamin D is sunlight. Around 95% of vitamin D is synthesized in the skin under the influence of sunlight. Very few foods naturally contain vitamin D, but fatty fish such as salmon, sardines, mackerel, and tuna, as well as egg yolks, are particularly rich in vitamin D.

Causes of Vitamin D Deficiency

Vitamin D deficiency is most commonly observed in the breastfeeding period. Below is a summary of the causes of vitamin D deficiency:

  1. Reduced Vitamin D Synthesis
    • Skin pigmentation
    • Use of products that block sunlight (sunscreens, clothing)
    • Geographical factors (seasons, air pollution, humidity, altitude)
  2. Reduced Intake of Vitamin D
  3. Vitamin D Deficiency in the Mother
    • If the mother has vitamin D deficiency and the infant is only breastfed
  4. Malabsorption Disorders
    • Celiac disease, pancreatic insufficiency, cystic fibrosis, biliary obstruction, biliary atresia
  5. Reduced Synthesis or Accelerated Breakdown of Vitamin D
    • Chronic liver diseases, medications such as rifampicin, isoniazid, antiepileptics

More on the Causes of Vitamin D Deficiency:

  1. Reduced Vitamin D Synthesis
    Vitamin D synthesis is dependent on the amount of melanin in the skin. Dark-skinned individuals need more exposure to sunlight than lighter-skinned individuals to produce the same amount of vitamin D. For example, while a light-skinned child may need only 10-15 minutes of sunlight exposure during summer, a dark-skinned child may require 5-10 times more.
  2. Sunlight Blocking Factors
    The surface area of the skin exposed to sunlight is also important for vitamin D synthesis. At least 20% of the body surface must be exposed to sunlight for a significant increase in vitamin D levels. In Eastern countries, among teenage girls who wear coverings due to religious practices, vitamin D deficiency is more commonly observed. Similarly, in countries with abundant sunlight, rickets may still be present due to infants being overdressed or not exposed to the sun.

Another factor contributing to vitamin D deficiency, especially in adolescents, is the use of sunscreen, which blocks the penetration of sunlight into the skin, impairing vitamin D synthesis.

  1. Reduced Vitamin D Intake
    Inadequate socioeconomic conditions, improper diets, and poor eating habits in adolescents can contribute to vitamin D deficiency.
  2. Vitamin D Deficiency in the Mother
    If a mother has a deficiency, the infant will also be at risk for vitamin D deficiency. This is particularly true for women who cover their bodies according to religious customs or those who spend most of their time indoors. In these cases, there may also be a risk of delayed fetal development, premature birth, and low birth weight.

Even if the mother has sufficient vitamin D, breast milk alone cannot meet the infant’s needs for vitamin D, as it contains only 12-60 IU of vitamin D per liter, while the daily recommended dose for an infant is 400 IU. Therefore, infants need exposure to sunlight and vitamin D supplements. However, the American Academy of Pediatrics (AAP) recommends that infants under six months should not be directly exposed to sunlight due to the risk of skin cancer.

Why is Vitamin D Deficiency More Common in Winter?

During the winter months, the synthesis of active vitamin D decreases significantly. Studies show that in October, vitamin D synthesis drops by 4%, and between January and March, no vitamin D synthesis occurs at all.

Clinical Signs of Vitamin D Deficiency

In severe cases, vitamin D deficiency can lead to hypocalcemia, but typical rickets symptoms include:

  • General Condition
    • Developmental delay
    • Weakness
    • Swollen abdomen
    • Muscle weakness
    • Bone fractures
    • Growth retardation
    • Short stature
  • Head
    • Craniotabes (softening of skull bones)
    • Prominent forehead
    • Delayed closure of fontanelles
    • Delayed tooth eruption
    • Craniosynostosis
  • Chest
    • Rachitic rosary (bony enlargements at rib joints)
    • Harrison’s groove (bony thickening at the rib-cartilage junction)
    • Respiratory infections
  • Spine
    • Scoliosis, kyphosis, lordosis
  • Limbs
    • Wide wrists and ankles
    • Hip joint deformities
    • Bow legs or knock knees
    • Pain in the legs

Daily Vitamin D Requirements

According to the Food and Nutrition Board of the Commission on Life Sciences of the National Research Council, the daily recommended vitamin D intake is as follows:

  • For infants: 400 IU/day
  • For individuals up to 50 years old: 200 IU/day
  • For individuals aged 51-70 years: 400 IU/day
  • For individuals over 70 years old: 600 IU/day

Treatment of Vitamin D Deficiency

There are two main treatment methods for vitamin D deficiency:

  1. Long-Term Low-Dose Treatment
    The vitamin D dose and duration vary based on the child’s condition. For example, a dose of 2000-5000 IU/day for 4-6 weeks is commonly recommended. Calcium (Ca) and phosphorus (P) levels improve in 6-10 days, and PTH levels normalize within 1-2 months. Radiological signs of rickets improve in 3-6 months.

    • For infants under 1 month: 1000 IU/day for 6 weeks
    • For children 1-12 months: 2000 IU/day for 6 weeks
    • For children over 1 year: 2000-7500 IU/day for 6 weeks
  2. Stoss Therapy (High-Dose Vitamin D)
    In this method, vitamin D is administered in doses of 300,000-600,000 IU orally or intramuscularly in 2-4 doses, given every other day.

Overuse of Vitamin D

Excessive vitamin D supplementation can lead to serious health issues. In larger cities, some mothers administer excessive doses of vitamin D, leading to hypercalciuria (calcium in the urine) and kidney stones. This issue is often observed in pediatric hospitals, where children with vitamin D toxicity are admitted.

For further information on this topic, follow our upcoming articles at Pediatriya.az.