Which Groups Are at Risk for Vitamin D Deficiency?

October 18, 2025 •

4 min read

According to the National Health and Nutrition Examination Survey (NHANES) from 2011–2012, nearly 40% of the U.S. population has a vitamin D deficiency. This widespread issue means many people may not even realize they are part of a group at risk for vitamin D deficiency. Understanding your risk is the first step toward prevention and maintaining good health.

Quick Summary

Several populations face a higher risk of vitamin D deficiency, including older adults, breastfed infants, and individuals with darker skin pigmentation or limited sun exposure. Other risk factors include certain medical conditions, obesity, and gastric bypass surgery. Dietary intake alone is often insufficient, making supplementation crucial for high-risk individuals.

Key Points

Older Adults: The elderly are at increased risk due to decreased skin vitamin D production, reduced sun exposure, and potentially impaired kidney function.
Breastfed Infants: Exclusively breastfed infants are at risk because human milk contains very little vitamin D, and infants are advised to avoid direct sunlight.
Dark-Skinned Individuals: Higher melanin levels act as a natural sunscreen, inhibiting the skin's ability to produce vitamin D from UV rays.
Limited Sun Exposure: People who are housebound, wear extensive clothing, or live in northern latitudes receive less UV exposure and are therefore at risk.
Medical Conditions: Conditions such as malabsorption syndromes (e.g., celiac disease) and liver or kidney diseases impair the body's ability to absorb or activate vitamin D.
Obesity: Higher body fat can sequester vitamin D, preventing it from circulating freely in the bloodstream.
Certain Medications: Some medications, including steroids and anti-seizure drugs, can increase the breakdown of vitamin D in the liver.

Vitamin D is a crucial nutrient that aids in calcium absorption, bone health, and immune function. While most people can get some vitamin D from sun exposure, certain groups face significant barriers, putting them at a higher risk for deficiency. Awareness of these risk factors is key to effective prevention.

Older Adults

Age is one of the most significant risk factors for vitamin D deficiency. Several factors contribute to this increased vulnerability in the elderly:

Decreased skin synthesis: As we age, our skin's ability to produce vitamin D from sunlight becomes less efficient. An 80-year-old produces significantly less vitamin D in their skin than a 20-year-old under the same sun exposure.
Reduced sun exposure: Older adults, particularly those who are housebound or institutionalized in nursing homes, spend less time outdoors, limiting their exposure to the sun's ultraviolet-B (UVB) rays.
Insufficient dietary intake: Dietary intake of vitamin D can also decrease in older individuals.
Impaired kidney function: The kidneys play a vital role in converting vitamin D to its active form. Age-related decline in kidney function can hinder this conversion process.

Breastfed Infants

Breastfed babies are another high-risk population for vitamin D deficiency. Human breast milk, while excellent for an infant's overall health, contains very little vitamin D. This makes supplementation a crucial step for preventing conditions like rickets in infants.

Limited dietary source: The primary source of vitamin D for infants is the mother, either in utero or through milk. If the mother is vitamin D deficient, the infant will also be deficient.
Sun avoidance: Pediatric recommendations for sun safety advise keeping infants under 6 months out of direct sunlight to prevent skin damage. While this is vital for skin protection, it also eliminates sun exposure as a source of vitamin D for this age group.

Individuals with Dark Skin

Skin pigmentation is a major factor in vitamin D production. The higher the melanin content in the skin, the darker the skin tone. Melanin acts as a natural sunscreen, absorbing UV radiation to protect against damage. However, this also reduces the skin's ability to synthesize vitamin D from sunlight.

Melanin absorption: Dark-skinned individuals, such as those of African, African-Caribbean, and South Asian descent, need significantly more sun exposure than their lighter-skinned counterparts to produce the same amount of vitamin D.
Higher prevalence: Population studies, like NHANES, have consistently shown a higher prevalence of vitamin D deficiency among Black and Hispanic populations in the U.S..

People with Limited Sun Exposure

Beyond age and skin tone, lifestyle and geographic location can greatly impact vitamin D levels.

Northern latitudes: Those who live in northern latitudes (or southern latitudes in the southern hemisphere) receive less intense sunlight, especially during winter months, limiting the UV exposure needed for vitamin D synthesis.
Indoor lifestyle: People with jobs that require them to be indoors, homebound individuals, or those who cover most of their skin for religious or cultural reasons are at a higher risk.

Individuals with Medical Conditions

Several medical conditions can interfere with the body's ability to absorb or activate vitamin D, leading to a higher risk of deficiency.

Malabsorption syndromes: Conditions such as celiac disease, inflammatory bowel disease (Crohn's, ulcerative colitis), and cystic fibrosis can inhibit the absorption of dietary fat, and since vitamin D is a fat-soluble vitamin, this leads to malabsorption.
Obesity: People with a Body Mass Index (BMI) of 30 or higher often have lower blood vitamin D levels. The vitamin gets sequestered in fat cells, making it less available to the body.
Liver and kidney disease: These organs are essential for converting vitamin D into its active form. Chronic liver or kidney disease can impair this process, leading to low active vitamin D levels.
Gastric bypass surgery: This surgery bypasses a significant portion of the small intestine, where vitamin D is absorbed, creating a high risk of deficiency.

Comparison: At-Risk Groups and Their Primary Risk Factors


At-Risk Group	Primary Risk Factors	Mechanism
Older Adults	Age, reduced sun exposure, impaired organ function	Decreased skin synthesis and reduced kidney conversion with age; limited outdoor activity.
Breastfed Infants	Breast milk content, sun avoidance	Breast milk is a poor source of vitamin D, and infants are kept out of direct sun.
Dark-Skinned Individuals	Increased skin melanin	Melanin acts as a natural sunscreen, blocking UV rays needed for synthesis.
People with limited sun exposure	Geographical location, lifestyle, clothing choices	Lower UV availability in northern latitudes and limited exposure due to being housebound or wearing covering clothing.
Individuals with Malabsorption	Celiac disease, Crohn's, Cystic Fibrosis	Impaired intestinal absorption of fat, which is necessary for vitamin D absorption.
People with Obesity	Sequestration in fat cells	Fat tissue binds to and stores vitamin D, reducing its availability in the blood.
Individuals with Chronic Liver/Kidney Disease	Impaired conversion	Liver and kidneys cannot properly convert inactive vitamin D into its active form.

Conclusion

While many people associate vitamin D deficiency with a simple lack of sunlight, the reality is far more complex. Age, skin pigmentation, geographic location, and underlying health conditions all play a significant role in determining an individual's risk. For high-risk populations, including older adults, infants, those with dark skin, and people with conditions like malabsorption or obesity, relying solely on sun exposure or fortified foods is often not enough. In these cases, regular vitamin D supplementation is often necessary to prevent deficiency and maintain adequate levels for overall health. If you fall into one of these high-risk categories, speaking with a healthcare provider is the best way to determine your needs and ensure you're protecting your bone health and immune system. Learn more about the role of vitamin D in the body at the National Institutes of Health Office of Dietary Supplements.

Frequently Asked Questions

Older adults are more susceptible because their skin is less efficient at producing vitamin D from sunlight and they are more likely to spend limited time outdoors. Additionally, age-related changes can impair kidney and liver function, which are essential for converting vitamin D into its active form.

Individuals with darker skin have more melanin, a pigment that acts as a natural sunblock. This melanin reduces the skin's ability to synthesize vitamin D from ultraviolet B (UVB) rays, requiring significantly more sun exposure to produce adequate amounts.

Breastfed infants are at risk because breast milk is not a rich source of vitamin D. Additionally, infants are often protected from direct sunlight. Pediatricians typically recommend a daily vitamin D supplement for exclusively or partially breastfed babies to prevent deficiency.

People with a high body mass index (BMI) have lower circulating vitamin D levels because the vitamin is sequestered, or stored, in their excess body fat. This reduces its availability for the body to use, often requiring a higher dosage of supplementation to achieve adequate levels.

Yes, several medical conditions can lead to vitamin D deficiency. Malabsorption syndromes like celiac disease and cystic fibrosis hinder the absorption of fat-soluble vitamins. Liver and kidney diseases can also interfere with the conversion of vitamin D into its active hormonal form.

Yes, location is a significant factor. Those living at higher latitudes, where sunlight is weaker and scarcer during winter, are at a higher risk of deficiency. During these months, it may not be possible to synthesize enough vitamin D from sun exposure alone.

Some medications, including certain anti-seizure drugs, steroids, and cholesterol-lowering medicines, can interfere with the body's vitamin D metabolism. These can accelerate the breakdown of the vitamin, leading to lower levels.