Vitamin D was discovered over 100 years ago, in 1922, and remains one of the most important vitamins for children's growth and development. Why is it especially crucial for children? Primarily, because it regulates calcium and phosphorus exchange, directly affecting bone growth. Vitamin D is a key factor in forming and maintaining healthy bone tissue.

In recent decades, our understanding of Vitamin D has expanded significantly. We now know that its physiological functions go far beyond bone health. Research has shown that Vitamin D also impacts the immune system, inflammatory responses, muscle function, mental health, metabolic processes, and more.

As awareness of Vitamin D's importance grows, so does the concern among parents about ensuring their children receive enough of this vital nutrient.

Sources of Vitamin D

There are two primary ways to obtain Vitamin D:

1. Sunlight: Vitamin D is synthesized in the skin when exposed to sunlight.
2. Diet: It can also be found in certain foods.

However, both methods have limitations:

• Sun exposure is hard to regulate safely. While the sun helps synthesize Vitamin D, modern medical advice strongly recommends protecting skin from UV radiation due to the risk of skin cancer.
• Dietary sources of Vitamin D are limited, mostly to animal-based products like fatty fish, egg yolks, meat, and milk. Even these contain relatively small amounts, and cooking can reduce Vitamin D content by 10-30%.

Because of these challenges, Vitamin D supplements are widely considered a safe and effective alternative to natural sources. These supplements are available for both direct consumption and as food fortifiers, enriching products like milk, cheese, infant formula, juices, cereals, and more.

Vitamin D For Kids: Common Questions + Concerns

Millions of parents give their children Vitamin D supplements based on medical advice. Here are answers to the most common questions about Vitamin D supplementation:

1. How are Vitamin D supplements measured?

On supplement packaging, Vitamin D is often listed in International Units (IU) or micrograms (mcg). It can also come in two forms: ergocalciferol (Vitamin D2) and cholecalciferol (Vitamin D3).

• 1 IU = 25 nanograms (ng) of either form of Vitamin D.
• One drop of a Vitamin D supplement solution typically contains 400 IU, following standard FDA guidelines.
• To convert IU to micrograms:
  400 IU = 10 mcg,
  800 IU = 20 mcg,
  1000 IU = 25 mcg,
  4000 IU = 100 mcg.

2. What is the recommended dosage of Vitamin D?

For healthy children, the recommended daily intake is between 400 and 800 IU of Vitamin D, depending on age. The optimal dosing is daily, particularly for children under two years old. After age two, periodic dosing is an option, with children receiving Vitamin D weekly, monthly, or even twice yearly (in fall and winter).

Key points to remember:

• The dosage for periodic intake should be prescribed by a doctor.
• Only Vitamin D3 should be used for periodic supplementation.
• For daily use, both Vitamin D2 and D3 are effective.

3. When should you increase Vitamin D intake?

Certain conditions may require increased Vitamin D intake, such as:

• Darker skin, which synthesizes less Vitamin D from sunlight.
• Lack of sun exposure, especially in colder climates.
• Obesity and certain medical conditions or medications (e.g., some anticonvulsants and hormonal drugs).
• Dietary limitations, such as vegan diets or eating disorders like anorexia nervosa, which reduce Vitamin D intake from food.

Importantly, any decision to increase Vitamin D dosage should be made by a healthcare professional.

4. When should you reduce or stop taking Vitamin D?

The recommended daily intake for healthy children remains 400-800 IU. However, certain medical conditions, such as kidney disease or high calcium levels, may require a child to stop taking Vitamin D altogether. In these cases, no reduced dose is necessary; the supplement should not be given at all. Parents should never reduce Vitamin D dosages without medical guidance.

Addressing Additional Questions

Although we've answered four major questions, it's natural for parents to have more concerns. Here’s a simple rule to remember:

For healthy children aged birth to 18 years, a daily intake of 400-800 IU of Vitamin D is recommended. If the child has specific health concerns, a doctor will provide tailored advice.

• Should you stop supplementing in summer when sunlight is plentiful?
  No, as long as the child is receiving the recommended daily dosage.
• Do healthy children need Vitamin D deficiency tests?
  No, tests are only necessary if prescribed by a doctor for specific health concerns.
• Which is better, Vitamin D2 or D3?
  For daily supplementation, either form works. However, if your child is unwell, consult a doctor about the best option.
• Is a water- or oil-based Vitamin D solution better?
  For healthy children, it doesn't matter. For those with medical conditions, a doctor will recommend the most appropriate form.

The most important takeaway: For healthy children, a daily dose of 400-800 IU of Vitamin D is safe and effective. If you have concerns or your child has health issues, always consult with a healthcare provider for guidance.

References: 

1. Ross AC, Manson JE, Abrams SA, et al. The 2011 Report on Dietary Reference Intakes for Calcium and Vitamin D from the Institute of Medicine: What Does It Mean for You? Harvard Health Publications. 2011. Available at: https://www.sciencedirect.com/science/article/pii/S0929693X22000732.
2. Houghton LA, Vieth R. Vitamin D: A Review of Its Role in Health and Disease. Nature Reviews Endocrinology. 2021;17(4):239-258. Available at: https://www.nature.com/articles/s41574-021-00593-z. 
3. Department of Health and Social Care. Vitamin D: Call for Evidence. UK Government. Available at: https://www.gov.uk/government/consultations/vitamin-d-call-for-evidence/vitamin-d-call-for-evidence. 
4. Office of Dietary Supplements. Vitamin D: Health Professional Fact Sheet. National Institutes of Health. Available at: https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/. 
5. Gineityte D, Gineitis A. Vitamin D Supplementation: Implications for Health. VU ePublications. Available at: https://epublications.vu.lt/object/elaba:114348688/114348688.pdf.