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Health Impacts of Vitamin D Deficiency

author avatar Dr. Eric Berg 03/08/2024

Various factors, such as a lack of sunshine, skin color, and genetic variances, can contribute to a vitamin D deficiency.

This essential nutrient is needed to maintain optimal health, and understanding the underlying reasons behind vitamin D deficiency is crucial in addressing potential health risks and supporting healthy vitamin D levels.

Learn about some sources of vitamin D - diet and sun exposure - and how age and skin color affect vitamin D absorption rates, and explore obesity's role in vitamin D deficiency. 

Also, discover various health issues related to vitamin D deficiency, such as rickets and osteoporosis, that are linked to low vitamin D status. 

Causes of Vitamin D Deficiency

Vitamin D deficiency is a common health issue that affects millions of people worldwide. A range of factors, such as diet, sun exposure, age, skin color, obesity, metabolic health, and inflammation, can lead to vitamin D deficiency. In addition, polymorphism - a mutation in the genes that control the vitamin D receptor - is another potential cause for impaired vitamin D absorption. 

Primary Vitamin D Sources 

Your body primarily obtains vitamin D through two sources: your diet and sunlight exposure.

Foods rich in vitamin D include fatty fish like salmon or mackerel, fortified dairy products such as milk or yogurt, egg yolks, beef liver, mushrooms exposed to UV light (like shiitake), and supplements.

However, even with a well-balanced diet, it may still be difficult for some individuals to maintain adequate vitamin D levels due to limited sun exposure or other factors.

Sunlight is essential in helping our bodies produce the active form of vitamin D by converting cholesterol present within our skin cells into cholecalciferol (vitamin-D precursor).

This process occurs when ultraviolet B (UVB) rays from sunlight interact with your skin's surface layers during outdoor activities like walking, jogging, swimming, and gardening, especially between late spring and early fall, when more direct solar radiation is available at higher latitudes closer towards equator regions around the world.

The Impact of Age and Skin Color on Absorption Rates

Age and skin tone can significantly affect how much vitamin D is produced. As you age, the efficiency of your skin's conversion process declines, making it more challenging for older adults to maintain adequate vitamin D levels.

Additionally, darker skin tones have higher amounts of melanin, which reduces their capacity to produce vitamin D from sunlight exposure compared with lighter complexions due to reduced penetration depth by UVB rays within epidermal layers, where vitamin D synthesis occurs. 

Obesity's Role in Vitamin D Deficiency 

Another factor that contributes to vitamin D deficiency is obesity.

Research has shown that obese individuals tend to have lower circulating levels of this essential nutrient because fat cells sequester (store) it away from other tissues like bones, muscles, or the liver, thereby limiting its availability for use throughout the body as needed.

This means people carrying excess weight may require additional supplementation or increased sun exposure to overcome potential deficiencies.

Vitamin D deficiency can have a major effect on our well-being, and it is critical to understand potential causes. 

Polymorphism as a Cause of Vitamin D Deficiency

Polymorphism refers to a genetic mutation affecting the vitamin D receptor (VDR) gene.

This can cause resistance within receptors responsible for receiving communication from circulating blood vitamin D levels, causing impaired vitamin D synthesis and metabolism. As most body tissues have these receptors, including immune cells, liver cells, and brain cells, a VDR polymorphism can result in various health issues. 

Definition and explanation of polymorphism

In genetics, polymorphism refers to the occurrence of two or more distinct forms, known as alleles, at a specific location within the DNA sequence.

In the context of vitamin D deficiency, it specifically relates to mutations in the genes that control the vitamin D receptor (VDR). These mutations can alter how well our bodies absorb this essential nutrient and impact if and how cells can utilize vitamin D.  

Vitamin D is vital for keeping bones strong, managing immune system performance, and sustaining general health. A mutation in the VDR gene can lead to impaired absorption and utilization of vitamin D by various tissues throughout our body.

Consequently, individuals with these polymorphic mutations may struggle with obtaining adequate amounts of vitamin D through primary sources like diet and sun exposure. 

  • Foods rich in vitamin D include fatty fish such as salmon and mackerel, fortified dairy products like milk and cheese, eggs, beef liver, and mushrooms exposed to UV light. However, most of these food sources contain only small amounts of vitamin D, and obtaining adequate vitamin D through diet alone can be challenging. 

  • Sun exposure is another way to intake vitamin D. Skin naturally produces vitamin D when exposed directly to the sun. However, factors including living in higher latitudes or spending more time indoors can limit the amount synthesized.

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Health Issues Related Vitamin-D Receptor Mutations

Individuals with polymorphic mutations in their vitamin D receptor (VDR) gene may experience various health problems due to the impaired ability of their receptors to receive necessary communications effectively.

Some common health issues associated with these mutations include rickets and osteoporosis.

Rickets and Osteoporosis 

Rickets is a condition characterized by bone deformities, primarily affecting children who have insufficient levels of vitamin D. This can lead to softening and weakening of bones, resulting in pain, delayed growth, and skeletal abnormalities such as bowed legs or knock knees.

This study published in the journal of Inflammation Research has shown that VDR polymorphism plays a significant role in determining susceptibility to rickets.

Vitamin D plays a crucial role in regulating intestinal calcium absorption, and low vitamin D status significantly increases the risk of calcium deficiency. Bones become more fragile and prone to fractures when bone density is reduced, as seen in osteoporosis and osteopenia.

Research suggests that individuals with VDR polymorphisms are at an increased risk for osteoporosis or osteopenia due to decreased calcium absorption caused by inadequate activation of the mutated receptors.

Autoimmune Disorders 

A malfunctioning VDR gene can also contribute significantly to autoimmune disorders since most body tissues, including immune cells, have VDR receptors.

Autoimmune diseases arise when the body's natural defense mechanisms mistakenly target healthy cells and tissue instead of invading pathogens such as viruses or bacteria.

  • Multiple Sclerosis: A study published in Aerosol Science and Technology has found a correlation between VDR gene polymorphism and an increased risk of developing multiple sclerosis, a neurological disorder that affects the central nervous system.

  • Lupus: Systemic lupus erythematosus (SLE) is another autoimmune disease that can be influenced by VDR polymorphism. Research indicates that certain variations in the VDR gene may contribute to susceptibility to SLE.

  • Type 1 Diabetes and Rheumatoid Arthritis: Both type 1 diabetes and rheumatoid arthritis have been linked with specific VDR gene mutations, suggesting a potential role of vitamin D receptor dysfunction in these conditions.

In addition to these health issues, individuals with defective VDR genes may also experience hair loss (alopecia), increased susceptibility to viruses, and liver inflammation resulting in autoimmune conditions like Hashimoto's thyroiditis.


Various factors can cause vitamin D deficiency, such as dietary habits, lack of sun exposure, age, skin tone, and obesity. Additionally, polymorphic vitamin-D receptor mutations can also hinder our ability to absorb essential nutrients like vitamin D.

These deficiencies can lead to health issues such as rickets, osteoporosis, and autoimmune disorders. To prevent vitamin D deficiency, it’s essential to ensure you are getting enough sunlight or taking a vitamin D supplement.



1. What causes a person to be vitamin D deficient?

Vitamin D deficiency can result from inadequate sun exposure, poor diet, certain medical conditions affecting absorption, and genetic factors such as polymorphism. Age and skin color can also play a role in the body's ability to produce vitamin D.

2. What health issues are caused by vitamin D deficiency?

Vitamin D deficiency can lead to rickets in children and osteoporosis in adults due to impaired calcium metabolism. It is also associated with autoimmune disorders linked to defective VDR genes, muscle weakness, depression, and an increased risk of infections.

3. How does polymorphism contribute to vitamin D deficiency?

Polymorphism contributes to vitamin D deficiency by causing mutations in the vitamin D receptor (VDR) gene, hindering the effective reception of communication from circulating blood vitamin D levels. This impairment in VDR functionality results in compromised vitamin D synthesis and metabolism, impacting the body's ability to absorb and utilize this essential nutrient.

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