What are the common causes of vitamin D deficiency?

Common Causes of Vitamin D Deficiency

The most common causes of vitamin D deficiency include decreased dietary intake, impaired absorption, and limited sun exposure, which can significantly impact bone health and potentially increase risk for various chronic diseases. 1

Primary Risk Factors

• Inadequate sun exposure - Limited UVB exposure due to:

  • Living at high latitudes 1
  • Winter season (reduced UVB radiation) 1, 2
  • Physical sun avoidance or excessive sunscreen use 1, 2
  • Routinely wearing clothing that prevents sun exposure on most of the skin 1
  • Being homebound or institutionalized 1, 3

• Decreased dietary vitamin D intake - Few foods naturally contain significant vitamin D 4, 5:

  • Limited consumption of vitamin D-rich foods (fatty fish, cod liver oil, fortified dairy products) 1, 5
  • Inadequate supplementation in high-risk individuals 6

• Impaired vitamin D absorption - Medical conditions affecting absorption:

  • Inflammatory bowel disease 1, 3
  • Malabsorptive conditions 1
  • History of gastric bypass surgery 1

Demographic and Physiological Risk Factors

• Skin pigmentation - Darker skin reduces vitamin D synthesis:

  • African Americans have 2-9 times higher prevalence of low vitamin D levels than white persons 1
  • Hispanics have 2-3 times higher prevalence than white persons 1
  • Increased melanin reduces the skin's ability to produce vitamin D in response to UVB exposure 1

• Age-related factors:

  • Older age (decreased skin synthesis capacity) 1, 3
  • Decreased outdoor activity in elderly populations 3

• Body composition:

  • Obesity - allows for greater sequestration of vitamin D into adipose tissue 1
  • Higher body fat mass increases risk of deficiency 7

Medical and Environmental Considerations

• Medication interactions:

  • Some medications can interfere with vitamin D metabolism 4

• Geographic and seasonal factors:

  • Living at high latitudes significantly reduces UVB exposure 1, 2
  • Winter months in temperate regions reduce vitamin D synthesis 2

• Lifestyle factors:

  • Indoor occupation with limited daytime sun exposure 2
  • Cultural practices involving covered clothing 3

Clinical Implications

• Severe vitamin D deficiency can lead to bone mineralization diseases:

  • Rickets in children 1
  • Osteomalacia in adults 1
  • Osteoporosis and increased fracture risk 1, 7

• Moderate deficiency may be associated with:

  • Muscle fatigue and weakness 3
  • Increased risk for falls, especially in elderly 3
  • Potential links to cardiovascular disease, certain cancers, and autoimmune conditions 2, 7

Prevalence and Measurement

• Approximately 33% of the U.S. population had 25-(OH)D levels ≤ 20 ng/mL (2001-2006) 1, 3
• 77% had levels < 30 ng/mL (2001-2004) 1, 3
• Vitamin D status is determined by measuring serum 25-hydroxyvitamin D 4
• Cut points for defining deficiency remain debated, with various thresholds used (20-30 ng/mL) 1, 6

Understanding these risk factors can help identify individuals who may benefit from targeted assessment and intervention to prevent the consequences of vitamin D deficiency.