Vitamin D plays a key role in keeping your bones strong, keeping your immune system healthy, and keeping your overall body functioning properly. Your body can get this important nutrient from foods, supplements, or spending time in the sun. When levels are low, symptoms like fatigue, joint pain, and muscle cramps may occur.
What Happens Without Enough Vitamin D
Not having enough vitamin D can lead to serious health problems, such as osteoporosis (weakened bones) and even depression. Knowing what causes vitamin D deficiency—and who’s more at risk—can help you take steps to prevent it.
Common Causes of Vitamin D Deficiency
1. Trouble Absorbing Vitamin D
Vitamin D is absorbed in the small intestine along with fats. If you have conditions that affect fat absorption—like celiac disease, inflammatory bowel disease (IBD), cystic fibrosis, or pancreatic issues—your body may struggle to take in enough vitamin D from food or supplements, as highlighted by health.com.
Older adults are also more likely to have low levels if their diets don’t include enough vitamin D-rich foods.
2. Limited Sun Exposure
Your body makes vitamin D when sunlight hits your skin. However, your ability to produce it may decrease if you:
- Have darker skin (more melanin makes it harder to produce vitamin D).
- Are older (the body’s production slows with age).
- Live in colder climates or spend little time outdoors.
3. Long-Term Health Conditions
Certain chronic diseases can interfere with how your body processes vitamin D, including:
- Liver disease
- Kidney failure
- Hyperparathyroidism (causes too much calcium in the blood)
These conditions may prevent the liver from converting vitamin D into its active form. Up to 93% of people with liver disease may have some level of deficiency, especially those with cirrhosis (severe liver scarring).
4. Medications
Some drugs may reduce vitamin D levels in the body by affecting liver enzymes involved in processing it. These include:
- Anti-seizure drugs like phenobarbital and carbamazepine
- Steroids such as dexamethasone
- Certain blood pressure medications like nifedipine and spironolactone
Is Vitamin D Deficiency Genetic?
In rare cases, vitamin D deficiency can run in families. A genetic disorder called hereditary vitamin D-resistant rickets affects the body’s ability to process the vitamin. This leads to soft or misshapen bones and usually appears in early childhood. Treatment typically involves high doses of vitamin D and calcium, as per health.com.
Who’s Most at Risk?
Some groups of people are more likely to experience low vitamin D levels, including:
Older adults (65+): They often have less sun exposure and reduced ability to produce vitamin D.
People with darker skin: More melanin can block vitamin D production.
Those with digestive or liver conditions: Conditions like IBD, celiac disease, or liver/kidney disease can affect absorption.
Individuals living in colder or low-sunlight areas: Less sun equals less vitamin D.
Hospital or nursing home residents: Limited outdoor time may contribute to deficiency.
Additional Risk Factors
Vegan diets: Animal products are the main food sources of vitamin D, so vegans are more prone to deficiency.
Lack of sunlight: Staying indoors or living in low-sun areas increases your risk.
Certain medications: Drugs for seizures and blood pressure may lower vitamin D levels.
Chronic illnesses: Conditions that affect nutrient absorption or liver function can reduce vitamin D.
Heavy alcohol use: This can lower intake, harm the liver, and interfere with absorption.
What to Do If You’re at Risk
If you have any of these risk factors, talk to your doctor. They can test your vitamin D levels and recommend ways to boost them—whether through diet, supplements, or lifestyle changes.