What are the diseases associated with vitamin D deficiency?

October 28, 2025 •

5 min read

Globally, an estimated 1 billion people have vitamin D deficiency. Understanding what are the diseases associated with vitamin D deficiency is crucial, as this widespread issue impacts bone health, the immune system, and more, affecting individuals across all age groups and demographics.

Quick Summary

Chronic and severe vitamin D deficiency can cause bone disorders such as rickets in children and osteomalacia in adults. Inadequate levels are also linked to weakened immunity, certain autoimmune diseases, cardiovascular conditions, and depression.

Key Points

Bone Health: Severe vitamin D deficiency causes rickets in children and osteomalacia in adults, characterized by softened, weakened bones.
Osteoporosis Risk: In adults, low vitamin D levels contribute to osteoporosis and an increased risk of fractures by impairing calcium absorption and accelerating bone loss.
Immune System Modulation: Vitamin D is vital for immune function; deficiency is linked to frequent infections and a higher risk of developing certain autoimmune diseases like multiple sclerosis.
Cardiovascular Connections: Inadequate vitamin D levels are associated with increased risk factors for cardiovascular disease, including heart failure and hypertension.
Mental Well-being: Studies suggest a potential link between low vitamin D and mood disorders like depression and anxiety, influencing emotional processing and serotonin production.
Potential Cancer Link: Observational studies have linked lower vitamin D levels with an increased risk of certain cancers, though more research is ongoing.

The Importance of Vitamin D

Vitamin D is a fat-soluble vitamin that plays a vital role in calcium absorption, bone health, and immune system regulation. While the body produces vitamin D when skin is exposed to sunlight, it can also be obtained from a limited number of foods and supplements. A deficiency, often characterized by low serum 25-hydroxyvitamin D levels, is surprisingly common worldwide and is linked to a variety of serious health issues. Many tissues throughout the body, including those in the brain, heart, and immune system, have vitamin D receptors, which helps explain its wide-ranging impact on health.

Diseases of the Skeletal System

The most well-established consequences of vitamin D deficiency are bone-related diseases. When vitamin D levels are too low, the body's ability to absorb calcium and phosphorus from the intestines is impaired, leading to softened and weakened bones.

Rickets in Children

Rickets is a rare but serious bone-softening disease that affects infants and children. Because a child's bones are still growing, a severe deficiency can cause bowed or bent bones, bone pain, muscle weakness, and deformities in the joints. Breastfed infants are at a higher risk because human milk is a poor source of vitamin D, and supplementation is often recommended after consulting a healthcare professional. Early treatment is crucial to prevent long-term bone damage.

Osteomalacia in Adults

In adults, the equivalent of rickets is osteomalacia, which causes the bones to become weak and soft. Unlike osteoporosis, which involves a loss of bone mass, osteomalacia is a defect in the mineralization of new bone tissue. This can result in chronic muscle aches, bone pain, and an increased risk of fractures.

Osteoporosis

Vitamin D deficiency can exacerbate or contribute to osteoporosis, a condition characterized by low bone mineral density and increased risk of fractures, especially in older adults. Low vitamin D levels lead to elevated parathyroid hormone (PTH), which draws calcium from the bones to maintain blood calcium levels, causing bone loss. Multiple studies have shown that vitamin D supplementation, particularly when combined with calcium, can improve bone mineral density and reduce fracture incidence.

Links to Autoimmune and Neurological Disorders

Beyond its effect on bones, vitamin D plays a crucial immunomodulatory role, and its deficiency has been linked to several autoimmune diseases.

Multiple Sclerosis (MS): Research suggests a strong link between low vitamin D levels, especially during childhood, and an increased risk of developing MS. Many immune cells involved in the MS inflammatory process have vitamin D receptors, and optimal levels may help regulate the immune system to reduce disease activity.
Rheumatoid Arthritis (RA): Some studies have found a correlation between vitamin D deficiency and increased disease activity in RA, an inflammatory autoimmune disease.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause malabsorption of nutrients, including vitamin D, and lower levels are linked to more severe disease outcomes.

Cardiovascular Disease and Other Chronic Conditions

Vitamin D deficiency has been associated with a number of other serious chronic conditions, though causality is still under investigation.

Cardiovascular Diseases

Low vitamin D status has been correlated with a higher risk of several cardiovascular problems, including hypertension, heart failure, and ischemic heart disease. Proposed mechanisms suggest vitamin D may help regulate blood pressure by influencing the renin-angiotensin system and may improve vascular compliance. Individuals with both low vitamin D and elevated C-reactive protein (an inflammatory marker) are at a significantly higher risk of cardiovascular mortality.

Mental Health Conditions

Low vitamin D levels have been associated with mood changes, such as depression and anxiety. While the exact link is still being researched, vitamin D influences brain receptors and serotonin production, which are involved in mood regulation. People with severe depression may also have lower vitamin D levels due to social withdrawal and reduced sun exposure, creating a complex relationship between the two conditions.

Cancer

Many observational studies and experimental research have explored a link between vitamin D and cancer risk or prognosis. The active form of vitamin D has been shown to induce cell differentiation and apoptosis in cancer cells in laboratory settings. Low vitamin D levels have been associated with a higher risk of certain cancers, such as breast, colorectal, and prostate cancer, although the evidence remains complex and requires further research.

Comparison of Rickets and Osteomalacia


Feature	Rickets	Osteomalacia
Affected Population	Infants and children, whose bones are still growing.	Adults, after skeletal growth is complete.
Primary Cause	Impaired mineralization of the growth plates in a child's bones.	Impaired mineralization of existing bone tissue.
Key Symptoms	Bowed legs, swollen wrists, joint deformities, muscle weakness, and bone pain.	Muscle aches, chronic bone pain, and an increased risk of fractures.
Skeletal Impact	Leads to incorrect growth patterns and skeletal deformities.	Weakens existing bones, making them more susceptible to breaks.

Symptoms of Vitamin D Deficiency

While severe deficiency is linked to specific diseases, a general lack of vitamin D can cause a variety of non-specific symptoms that may serve as warning signs.

Fatigue and tiredness
Bone and back pain
Muscle weakness, aches, or cramps
Mood changes, including depression and anxiety
Impaired wound healing
Frequent infections
Bone loss and increased risk of fractures
Hair loss

Conclusion

Vitamin D is a crucial nutrient that extends far beyond its well-known role in bone health. Deficiency can lead to serious skeletal diseases like rickets and osteomalacia, but emerging research consistently points to wider implications for overall health, including an increased risk of cardiovascular disease, certain cancers, and autoimmune disorders. While more research is needed to fully understand some of these complex relationships, maintaining adequate vitamin D levels through sunlight, diet, and supplementation after consulting a healthcare provider is a prudent strategy for disease prevention and overall well-being. Regular monitoring by a healthcare professional can help ensure proper levels are achieved and maintained, especially for those in high-risk categories such as older adults, individuals with darker skin, and those with malabsorption issues. Addressing a vitamin D deficiency is a straightforward step towards better health.

For more information on the function and requirements of vitamin D, visit the NIH Fact Sheet on Vitamin D.

Frequently Asked Questions

The most common cause of vitamin D deficiency is a lack of sun exposure. Other causes include limited dietary intake, certain medical conditions like malabsorption disorders, and kidney or liver diseases that affect vitamin D metabolism.

Addressing severe vitamin D deficiency typically involves intervention guided by a healthcare provider. This may include supplementation to help restore levels, followed by maintaining appropriate intake as recommended by a medical professional.

Rickets affects children whose bones are still growing, causing deformities due to a failure of proper mineralization at the growth plates. Osteomalacia affects adults after their bones have matured, resulting in weakened and painful bone tissue.

While studies show a link between low vitamin D and depression symptoms, they do not prove that deficiency directly causes the illness. However, vitamin D does play a role in brain function and mood regulation, and deficiency is common among those with depression.

Links have been found between low vitamin D levels and autoimmune conditions such as multiple sclerosis (MS), rheumatoid arthritis (RA), and inflammatory bowel disease (IBD).

Few foods are naturally high in vitamin D. Good sources include fatty fish (salmon, mackerel, sardines), fish liver oils, egg yolks, beef liver, and fortified foods like milk, cereals, and orange juice.

While specific recommendations can vary, a serum 25-hydroxyvitamin D level of 30 ng/mL or higher is generally considered sufficient for bone and overall health. Levels below 20 ng/mL are often considered deficient.