Causes and Risk Factors of Vitamin D Deficiency

Vitamin D is a nutrient necessary for immune and bone health, as well as overall well-being. You can get vitamin D through certain foods, supplements, and when the skin absorbs sunlight. Without enough vitamin D, you may experience fatigue (extreme tiredness), muscle cramps, and joint and back pain.

Vitamin D deficiency is common and can raise your risk of conditions like osteoporosis (a condition that causes weak bones) and depression. Many factors can affect your chances of being deficient in vitamin D. Understanding the potential causes and risk factors of vitamin D deficiency can help lower the odds of developing it.

There are many reasons why you might develop a vitamin D deficiency, such as having darker skin, not getting enough sunlight, having certain conditions, or taking certain medications.

1. Difficulty Absorbing or Digesting It

Your body absorbs vitamin D in the small intestine, and when you can’t absorb it properly, you may have a higher chance of developing a vitamin D deficiency.

People with medical conditions that affect the small intestine or pancreas, such as celiac disease, inflammatory bowel disease (IBD), cystic fibrosis, and exocrine pancreatic insufficiency, are at higher risk of vitamin D deficiency. These conditions prevent the body from properly absorbing fats, and vitamin D is fat-soluble, meaning it’s absorbed and broken down in the small intestine in the same way fats are.

People who don’t eat enough vitamin D-rich foods are more likely to develop low vitamin D levels, with older adults being particularly at risk.

2. Not Enough Sunlight 

When sunlight touches the skin, it turns a type of cholesterol found in the skin into vitamin D. Cholesterol is a fatty substance found in the blood and cells that helps produce hormones, vitamin D, and aids in digestion.

Your body’s ability to make vitamin D from sunlight can change if you:

• Have darker skin: People with darker skin need up to 15 times more sunlight to make the same amount of vitamin D as people with lighter skin. This is because people with darker skin have more melanin, a pigment that inhibits vitamin D production.
• Are older: As you age, your body’s ability to make vitamin D from sunlight becomes more difficult. People who are older are also less likely to go outside, which lowers their exposure to sunlight.
• Live in colder climates: Living in an area with colder temperatures and spending less time in the sun can make you more likely to develop low vitamin D levels. 

3. Chronic Diseases 

Certain chronic (long-term) health conditions can raise your risk of developing vitamin D deficiency. Some conditions include:

• Liver disease
• Hyperparathyroidism, a condition that causes high levels of calcium (a nutrient important for bone health) in your blood
• Renal (kidney) failure

These conditions may lead to a vitamin D deficiency because they can affect the liver enzyme 25-hydroxylation, a protein that converts vitamin D into its active form in the body after it is processed through the liver. Up to 93% of people with liver disease have some degree of low vitamin D levels. People with cirrhosis (liver scarring) are most likely to have a severe deficiency.

4. Medications

Certain medications may lead to a vitamin D deficiency. These medications may include:

• Antiseizure medications, like Luminal (phenobarbital) and Tegretol (carbamazepine)
• Anti-inflammatory drugs like Hemady (dexamethasone)
• Blood pressure medications like Procardia (nifedipine) and Aldactone (spironolactone)

These medications can affect vitamin D levels by preventing certain liver enzymes responsible for processing vitamin D from functioning properly.

Rarely, vitamin D deficiency can be hereditary, meaning it can be passed down through families.

Hereditary vitamin D-resistant rickets is a rare genetic condition that damages the vitamin D receptor (VDR) gene. This gene (trait) controls how the body processes vitamin D, leading to weak bones and skeletal changes.

Hereditary vitamin D-resistant rickets typically develop early in life. Treatment involves high doses of vitamin D and calcium supplements.

Some people are more likely to develop vitamin D deficiency than others:

• Age: Adults over 65 are more likely to develop vitamin D deficiency due to dietary challenges, lower sun exposure, and reduced ability to produce vitamin D from sunlight. 
• Ethnicity: People with darker skin are at a higher risk for vitamin D deficiency because they have more melanin, a pigment that reduces vitamin D production. 
• Medical conditions: Certain conditions can impact vitamin D absorption, such as celiac disease, IBD, and cystic fibrosis, as well as liver disease and kidney failure.
• People who live in colder climates: Less sun exposure means they are more at risk for vitamin D deficiency than people who live in warmer climates. 

Other groups at risk for vitamin D deficiency include individuals hospitalized in medical facilities and nursing home residents.

There are certain risk factors that make a person more susceptible to developing vitamin D deficiency, including:

• Vegan diets: Some of the main dietary sources of vitamin D are animal products, such as fatty fish and vitamin D-fortified milk. People who follow vegan diets are significantly more likely to be deficient in vitamin D. 
• Limited time spent outside: People who spend little time in the sunlight are more likely to be deficient in vitamin D.
• Darker skin tones: People with darker skin tones are more at risk for developing vitamin D deficiency than people with lighter skin tones.
• Medication use: Certain medications, such as antiseizure medications and blood pressure medications, may increase the risk for vitamin D deficiency.
• Medical conditions: Certain medical conditions, such as IBD and liver disease, can impact vitamin D absorption and breakdown.
• Heavy alcohol use: Drinking a lot can raise the risk of vitamin D deficiency by lowering dietary intake, impacting vitamin D absorption, and causing liver damage. 

If you have one or more risk factors for vitamin D deficiency, speak with your healthcare provider. They can test your vitamin D levels and help develop a treatment plan.

Vitamin D deficiency is a common condition that can impact physical and mental health. People at a higher risk include those 65 and older, those with certain medical conditions, and those who have less sun exposure.

If you’re at risk for developing vitamin D deficiency, speak with your healthcare provider. They can recommend appropriate testing and treatment to help you maintain healthy vitamin D levels.