What depletes vitamin D in your body? Understanding the key factors

October 20, 2025 •

3 min read

According to the CDC, over 40% of US adults are vitamin D deficient, a condition linked to a variety of health issues. Understanding what depletes vitamin D in your body is crucial for maintaining proper bone density, immune function, and overall well-being.

Quick Summary

Several interconnected factors can cause vitamin D levels to drop, including limited sun exposure, inadequate dietary intake, various medical conditions, and certain medications. Genetics and lifestyle choices also play significant roles.

Key Points

Limited Sunlight Exposure: Factors like location, time of year, and sunscreen use can limit natural vitamin D production.
Poor Dietary Absorption: Conditions affecting fat absorption or past bariatric surgery can prevent vitamin D absorption.
Underlying Health Issues: Liver and kidney diseases hinder vitamin D conversion, and obesity can sequester it.
Medication Interference: Certain drugs can accelerate vitamin D breakdown or block absorption.
Lifestyle and Skin Pigmentation: Limited time outdoors, covering clothing, and darker skin tones can reduce sun-based vitamin D synthesis.
Air Pollution: High levels of air pollution can block UVB radiation needed for vitamin D production.

Vitamin D is an essential nutrient vital for regulating calcium and phosphate levels, which are critical for healthy bones, teeth, and muscles. However, a range of issues can reduce the body's ability to produce, absorb, or utilize this key vitamin, leading to a deficiency. Knowing these factors is the first step toward correcting a depletion and preventing long-term health complications.

Environmental and Lifestyle Influences on Vitamin D Levels

The primary source of vitamin D for most people is direct exposure to sunlight, but several environmental and lifestyle factors can hinder this process.

Sun Exposure and Geographic Location

Your geographic location significantly impacts your vitamin D synthesis from the sun. Individuals living at higher latitudes, far from the equator, receive weaker ultraviolet B (UVB) radiation, especially during winter months. For example, in Boston, vitamin D synthesis from sunlight is only possible for part of the year, from March to October. Consistent sunscreen use and spending most of the day indoors also limit sun exposure. Glass windows block UVB rays, preventing vitamin D production indoors. Air pollution can also block UVB radiation.

Skin Pigmentation and Clothing

Melanin, which gives skin its color, acts as a natural sunscreen and reduces vitamin D production. Wearing clothing that covers most of the skin can also prevent adequate sun exposure.

Medical Conditions Affecting Vitamin D

Several underlying medical conditions can interfere with the body's vitamin D metabolism and absorption.

Malabsorption Syndromes

Conditions that impair fat absorption, such as Celiac disease, Crohn's disease, and Cystic fibrosis, can lead to a deficiency since vitamin D is fat-soluble. Gastric bypass surgery can also impact absorption.

Liver and Kidney Disease

The liver and kidneys convert vitamin D into its active form. Chronic liver and kidney diseases can disrupt this process, leading to low active vitamin D levels.

Obesity

Individuals with a BMI of 30 or more often have lower vitamin D levels because body fat can sequester the vitamin. Higher supplementation doses may be needed in these cases.

Chronic Stress and Inflammation

Research suggests that chronic inflammation can deplete vitamin D.

Medications and Vitamin D Depletion

Certain medications can interfere with vitamin D metabolism or absorption, including antiseizure medications, corticosteroids, cholesterol-lowering drugs, weight-loss medications like Orlistat, and the antibiotic Rifampin. {Link: Drugs Causing Vitamin D Deficiency Consensus.app https://consensus.app/questions/drugs-causing-vitamin-d-deficiency/}

Comparison of Factors Affecting Vitamin D


Factor	Impact on Vitamin D	High-Risk Groups	Actionable Steps
Sun Exposure	Primary source, but limited by geography, season, and skin tone.	Higher latitudes, winter months, dark-skinned individuals, those wearing covering clothes.	Safe sun exposure (10-30 mins midday, arms/legs), supplements.
Dietary Intake	Limited natural sources; requires fortified foods or supplements.	Vegans, those avoiding fortified dairy products.	Consume fatty fish, egg yolks, fortified cereals/milk; consider supplements.
Malabsorption	Diseases like celiac, Crohn's, or past bariatric surgery limit absorption.	Individuals with gastrointestinal or post-surgical conditions.	Consult a doctor for diagnosis; require targeted high-dose supplements.
Organ Health	Liver and kidneys convert vitamin D to its active form.	People with chronic liver or kidney disease.	Regular monitoring and medical management of underlying condition.
Obesity	Excess body fat sequesters vitamin D, lowering circulating levels.	Individuals with a BMI of 30 or higher.	May require higher doses of supplementation as directed by a doctor.
Medications	Several common drugs increase vitamin D breakdown or block absorption.	Individuals on long-term steroids, anti-seizure, or cholesterol meds.	Discuss vitamin D monitoring and supplementation with a healthcare provider.

Conclusion

Numerous factors can lead to low vitamin D levels, including insufficient sun exposure, inadequate diet, medical conditions, and medications. Maintaining healthy vitamin D levels requires a combination of safe sun exposure, a healthy diet, and consulting a healthcare provider for testing and personalized treatment.

Frequently Asked Questions

Yes, correctly applied sunscreen with an SPF of 8 or higher can block over 90% of the UVB rays needed for vitamin D synthesis in the skin. This makes it crucial to get vitamin D from other sources, like diet or supplements, especially if you use sunscreen diligently.

Yes, several medications can interfere with vitamin D. Steroids, anti-seizure medications, some cholesterol drugs, and antibiotics like rifampin can all accelerate the breakdown of vitamin D or impair its absorption. {Link: Drugs Causing Vitamin D Deficiency Consensus.app https://consensus.app/questions/drugs-causing-vitamin-d-deficiency/}

Vitamin D is a fat-soluble vitamin that gets stored in the body's fat cells. In individuals with obesity, a greater amount of this vitamin is sequestered in excess body fat, making less of it available in the bloodstream for use.

The liver and kidneys are responsible for converting inactive vitamin D into its active form. When these organs are diseased or not functioning properly, this conversion process is impaired, leading to a deficiency of usable vitamin D.

Yes, for people living in higher latitudes, vitamin D synthesis from sunlight is greatly reduced during the winter months because the sun's UVB rays are weaker. This is why many health organizations recommend supplementation during autumn and winter.

It is difficult to get sufficient vitamin D from natural food sources alone. While some foods like fatty fish, egg yolks, and fortified cereals or milk contain it, most people in modern society rely on a combination of sun exposure, fortified foods, and supplements to meet their needs.

Yes, people with darker skin have more melanin, which provides natural protection from the sun's UV rays but also reduces the skin's ability to produce vitamin D. As a result, they may need more sun exposure or require supplementation to maintain adequate levels.