What illness does lack of vitamin D cause?

January 9, 2026 •

3 min read

According to the National Institutes of Health, a significant portion of the global population has insufficient vitamin D levels. What illness does lack of vitamin D cause, and why is this 'sunshine vitamin' so crucial for overall health? This deficiency is particularly known for weakening bones, but its effects can also impact muscle function, mood, and immune response.

Quick Summary

A deficiency can lead to bone-softening disorders like rickets in children and osteomalacia in adults, causing bone pain, muscle weakness, and increased fracture risk. Long-term deficiency is also linked to osteoporosis, weakened immunity, fatigue, and potential mood changes.

Key Points

Rickets in Children: A lack of vitamin D can cause rickets, a condition leading to softened and weakened bones, often resulting in bowed legs and other deformities.
Osteomalacia in Adults: In adults, vitamin D deficiency causes osteomalacia, characterized by soft bones, persistent bone pain, muscle weakness, and an increased risk of fractures.
Fatigue and Depression: Common, non-specific symptoms of low vitamin D include fatigue, muscle weakness, and mood changes, which can sometimes be mistaken for other conditions.
Heightened Osteoporosis Risk: Long-term deficiency is a significant contributing factor to osteoporosis, a condition that makes bones brittle and prone to fractures.
Compromised Immune System: Adequate vitamin D is essential for a healthy immune system, and a deficiency can lead to an increased susceptibility to infections.
Sleep Disturbances: Research has indicated a link between low vitamin D levels and a higher risk of sleep disorders, including poor sleep quality and insomnia.

Bone-Related Illnesses Caused by Vitamin D Deficiency

Vitamin D's primary role is to regulate calcium and phosphorus absorption, vital for strong bones. Insufficient vitamin D prevents proper mineral absorption, severely impacting skeletal health. Rickets and osteomalacia are the most direct consequences.

Rickets in Children

Rickets softens and weakens children's bones due to severe vitamin D deficiency during development. This prevents proper bone mineralization, causing deformities.

Common signs of rickets include delayed growth, bone pain, muscle weakness, bowed legs, spinal curves, and joint deformities. Severe cases can cause muscle spasms. Nutritional rickets is rare in developed countries but affects some high-risk groups.

Osteomalacia in Adults

In adults, vitamin D deficiency causes osteomalacia, or 'soft bones'. Unlike rickets, adult bones don't grow, so bowing doesn't occur. Instead, it impairs bone mineralization during remodeling.

Symptoms often include bone pain, muscle weakness, stiffness, and increased fracture risk. Chronic osteomalacia raises osteoporosis risk.

The Link to Osteoporosis

Chronic vitamin D deficiency significantly increases the risk of osteoporosis. Poor vitamin D impairs calcium absorption. To maintain blood calcium, the body takes calcium from bones, accelerating demineralization. This makes bones porous and prone to fractures, especially in older adults.

Broader Health Consequences

Vitamin D deficiency affects various body systems. Chronic deficiency links to several health issues:

Fatigue and Depression: Many with deficiency report fatigue and depressed mood. Vitamin D receptors in mood-regulating brain areas may explain this.
Weakened Immune Function: Vitamin D modulates the immune system. Low levels link to increased susceptibility to infections and autoimmune disorders.
Cardiovascular Disease Risk: Observational studies show a link between poor vitamin D status and increased cardiovascular disease risk, though trials are mixed.
Sleep Disorders: Studies correlate deficiency with higher risk of sleep disorders like insomnia and poor sleep quality.

Comparison of Major Vitamin D Deficiency Illnesses


Feature	Rickets (Children)	Osteomalacia (Adults)	Osteoporosis (All Ages, Higher Risk in Older Adults)
Affected Population	Primarily infants and children whose bones are still growing.	Adults with fully grown bones.	Most common in older adults, especially post-menopausal women, but exacerbated by lifelong deficiency.
Core Problem	Failure of growing bones to mineralize properly.	Failure of existing bone to mineralize during remodeling.	Loss of bone mass and structural integrity, leading to fragility.
Primary Symptoms	Bowed legs, bone pain, muscle weakness, delayed growth, joint deformities.	Bone pain (especially in pelvis and legs), muscle weakness, increased fracture risk.	Fragile bones, increased risk of fractures from minor falls, stooped posture.
Treatment Focus	High-dose vitamin D and calcium supplements, exposure to sunlight, and sometimes orthopedic correction for severe deformities.	Vitamin D and calcium supplementation, addressing malabsorption issues, pain management.	Supplementation, lifestyle changes, and potentially medication to increase bone density.

Conclusion

Vitamin D is vital, and deficiency causes various illnesses, from rickets and osteomalacia to fatigue, depression, and weakened immunity. Prevention and treatment involve sun exposure, a balanced diet with vitamin D and calcium, and supplements if needed. Recognizing symptoms and consulting a doctor for diagnosis and treatment is crucial. Specialized treatment may be needed for underlying conditions like malabsorption. While non-skeletal effects are studied, its importance for bone health is clear.

What Illness Does Lack of Vitamin D Cause?

Bone-Softening Conditions: Lack of vitamin D causes rickets in children and osteomalacia in adults by preventing the proper mineralization of bone tissue. Increased Fracture Risk: Chronic deficiency is a major risk factor for osteoporosis, which leads to weak, brittle bones and a higher likelihood of fractures, especially in older adults. Non-Specific Symptoms: In adults, deficiency can manifest as fatigue, generalized tiredness, and muscle weakness or aches, often making it hard to identify the cause. Mood and Immunity: Low vitamin D has been correlated with a higher risk of depression, as well as reduced immune function, leading to frequent infections. Underlying Causes: Deficiency can stem from inadequate sun exposure, limited dietary intake, or malabsorption issues due to conditions like Crohn's disease or celiac disease.

Frequently Asked Questions

The primary diseases caused by vitamin D deficiency are rickets in children and osteomalacia in adults, both of which result in softened bones.

Yes, fatigue is a common and non-specific symptom of vitamin D deficiency. Many people with low levels of the vitamin report persistent feelings of tiredness and sluggishness.

There is an observed correlation between low vitamin D levels and a higher risk of depression and other mood changes. This is thought to be related to the presence of vitamin D receptors in parts of the brain that regulate mood.

In adults, low vitamin D leads to osteomalacia, where bones become soft, weak, and painful. This also increases the risk of developing osteoporosis and experiencing fractures.

The main difference is the age at which they occur. Rickets affects children whose bones are still developing, causing bowing and deformities. Osteomalacia affects adults with mature bones, causing them to soften and weaken but without the bowing.

While some foods like fatty fish, beef liver, and fortified products contain vitamin D, getting sufficient amounts from diet alone can be difficult. The body's natural production from sun exposure is the main source for most people.

You can increase your vitamin D levels through a combination of safe sun exposure (5-30 minutes of direct sunlight a few times a week), consuming vitamin D-rich and fortified foods, and taking supplements if recommended by a healthcare professional.