Vitamin D Deficiency Causes

what causes vitamin d deficiency

Vitamin D deficiency has become a widespread concern in recent years as over 50% of US residents are estimated to be deficient in this essential nutrient. While most people associate Vitamin D with sunlight and bone health, few know its role in anti-aging and the many factors that can contribute to its deficiency.

This article will explore the primary reasons for Vitamin D deficiency, shedding light on the hidden culprits affecting your Vitamin D levels. So, let’s dive in and uncover the underlying causes of this prevalent issue. Understanding the potential causes of Vitamin D deficiency is crucial for maintaining optimal health and preventing the onset of various diseases.

There has yet to be an international consensus on the optimal level for Vitamin D supplementation, with recommendations varying across countries, ranging from 400 to 2000 IU daily. We recommend D3 and a daily intake of 1000-2000 IU. This may need to be increased for some individuals, especially during illness, to boost immunity. It’s essential to monitor levels through blood tests and adjust the dosage accordingly.1

The two primary forms of Vitamin D are D2 (ergocalciferol), which is mainly human-made and added to foods, and D3 (cholecalciferol), produced in the skin from 7-dehydrocholesterol and can also be obtained through the diet from animal-based foods, making it an essential component for maintaining optimal health. We recommend only supplementing with D3. A deficiency in Vitamin D is not something to take lightly, as it can significantly affect your overall well-being.

Key Takeaways:

  • Inadequate Vitamin D intake, limited sun exposure, malabsorption and health conditions, and medications that affect Vitamin D levels can contribute to Vitamin D deficiency.
  • At-risk groups for Vitamin D deficiency include older adults, individuals with darker skin pigmentation, those living in regions with limited sunlight, and individuals with obesity.
  • Consulting with healthcare professionals can help determine appropriate actions to address Vitamin D deficiency and support overall health.
  • Proactive measures like increasing Vitamin D-rich food intake and proper sun exposure can help prevent Vitamin D deficiency.
  • Supplementation may be necessary for individuals unable to meet their Vitamin D needs through diet and sunlight alone.

What Causes Vitamin D Deficiency

Vitamin D deficiency can be caused by factors such as inadequate intake, limited sun exposure, malabsorption and health conditions, and medications that affect Vitamin D levels. Understanding these causes is essential in addressing low Vitamin D levels and preventing further deficiency.

Inadequate Vitamin D Intake

One of the primary causes of Vitamin D deficiency is inadequate Vitamin D intake. Not consuming enough foods rich in Vitamin D, such as fatty fish (salmon, mackerel), fortified dairy products, and egg yolks, can contribute to low Vitamin D levels2. It is essential to include these food sources in your diet to ensure an adequate Vitamin D intake. Additionally, individuals following a vegan or vegetarian diet may have a higher risk of Vitamin D deficiency due to lacking these food sources.

Limited Sun Exposure

Another factor that can cause Vitamin D deficiency is limited sun exposure. Vitamin D is synthesized in the skin when it is exposed to sunlight. Therefore, individuals with limited sun exposure, such as those who spend most of their time indoors, consistently wear protective clothing, or live in areas with limited sunlight, are at a higher risk of developing low Vitamin D levels. Spending time outdoors and exposing your skin to sunlight is essential to ensure adequate Vitamin D synthesis.

Malabsorption and Health Conditions

Certain health conditions and malabsorption issues can also contribute to Vitamin D deficiency. These conditions may affect the body’s ability to absorb and utilize Vitamin D effectively, leading to low Vitamin D levels. Some examples of health conditions that can affect Vitamin D absorption include inflammatory bowel disease, celiac disease, and cystic fibrosis. If you have any underlying health conditions or malabsorption issues, working with your healthcare provider to manage and address them effectively to avoid Vitamin D deficiency is essential.

Medications That Affect Vitamin D Levels

Some medications can interfere with Vitamin D levels in the body. Certain medications, such as corticosteroids, anticonvulsants, and cholesterol-lowering drugs, affect Vitamin D metabolism or absorption. If you are taking any medications, it is essential to discuss their potential impact on your Vitamin D levels with your healthcare provider and explore ways to mitigate their effects, if necessary.

Vitamin D Deficiency

At-Risk Groups for Vitamin D Deficiency

Several population groups are at higher risk for Vitamin D deficiency. These include:

Age-Related Risk Factors

Older adults are more susceptible to Vitamin D deficiency due to age-related changes in the body. As individuals age, their skin’s ability to produce Vitamin D decreases. Additionally, there can be age-related declines in the kidney’s ability to convert Vitamin D into its active form, resulting in lower Vitamin D levels. Older adults must be mindful of their Vitamin D intake and consider supplementation if necessary.3

Skin Pigmentation and Vitamin D Synthesis

Skin pigmentation plays a role in Vitamin D synthesis. Individuals with darker skin pigmentation have higher amounts of melanin, which can impact the body’s ability to produce Vitamin D from sun exposure. The higher melanin content reduces UVB ray absorption, leading to less Vitamin D synthesis4. Individuals with darker skin tones must be mindful of their Vitamin D levels and consider alternative sources such as dietary supplements or fortified foods.

Geographic and Seasonal Influences

Geographic location and seasonal variations in sunlight exposure can affect Vitamin D synthesis. Individuals living in regions with limited sunlight, such as northern latitudes, are at a higher risk of Vitamin D deficiency5. During winter, reduced sunlight exposure and shorter days can lower Vitamin D levels. Individuals living in regions with limited sunlight must pay attention to their Vitamin D status and consult with healthcare professionals if necessary.

Obesity and Vitamin D Utilization

Obesity can also impact Vitamin D utilization in the body. Adipose tissue, commonly found in higher amounts in individuals with obesity, can sequester Vitamin D and make it less bioavailable6. This means that individuals with obesity may require higher Vitamin D intake to maintain adequate levels. It is recommended that individuals with obesity monitor their Vitamin D levels and consider supplementation under healthcare professionals’ guidance.

Understanding these at-risk groups and their specific risk factors can help identify individuals requiring extra attention to ensure optimal Vitamin D levels. It is important to remember that Vitamin D deficiency can have significant implications for overall health, and appropriate measures should be taken to prevent and mitigate poverty in these vulnerable populations.

at-risk groups for vitamin d deficiency


In conclusion, Vitamin D deficiency remains a widespread concern with numerous contributing factors that can significantly impact an individual’s health. From inadequate dietary intake and limited sun exposure to malabsorption issues, health conditions, and the use of certain medications, understanding these causes is crucial for addressing and preventing Vitamin D deficiency. Moreover, recognizing the specific risk factors that place certain groups, such as older adults, individuals with darker skin pigmentation, those living in areas with limited sunlight, and individuals with obesity, at higher risk is vital for targeted prevention and treatment strategies.

To combat Vitamin D deficiency, a multifaceted approach is necessary. This includes ensuring adequate intake of Vitamin D-rich foods, optimizing sun exposure while balancing skin cancer risks, managing health conditions that may affect absorption, and carefully considering the impact of medications on Vitamin D levels. Supplementation, particularly Vitamin D3, may be necessary for many individuals, especially those at higher risk, with dosages tailored to individual needs determined through regular blood tests and healthcare consultations.

Proactive measures and awareness are vital in preventing Vitamin D deficiency and supporting overall health and well-being. By addressing the underlying causes and risk factors, individuals can take significant steps towards maintaining optimal Vitamin D levels, thus reducing the risk of bone health issues and certain diseases and potentially aiding in the anti-aging process.


  1. Vitamin D deficiency 2.0: an update on the current status worldwide ↩︎
  2. Vitamin D in foods and as supplements. ↩︎
  3. Vitamin D3 and calcium to prevent hip fractures in elderly women ↩︎
  4. Increased skin pigment reduces the capacity of skin to synthesise vitamin D3 ↩︎
  5. Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin. ↩︎
  6. Decreased bioavailability of vitamin D in obesity. ↩︎

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