Which Population Group Is at Greatest Risk of Having Insufficient Vitamin D?

December 9, 2025 •

3 min read

According to the National Institutes of Health, a significant portion of the U.S. population is at risk of vitamin D inadequacy, with certain groups facing higher risks. This highlights a crucial question: which population group is at greatest risk of having insufficient vitamin D?

Quick Summary

Several factors increase the risk of low vitamin D levels, including skin pigmentation, age, sun exposure, and various medical conditions. Identifying these risk factors is essential for proper supplementation and maintaining healthy bone, immune, and overall bodily function.

Key Points

Dark Skin Pigmentation: The melanin in darker skin acts as a natural sunscreen, significantly reducing the skin's ability to produce vitamin D from sunlight.
Older Age: Individuals over 65 have less efficient vitamin D production in their skin and often experience reduced sun exposure due to mobility issues or institutional living.
Obesity: A high body mass index can lead to lower circulating vitamin D levels, as fat cells sequester the vitamin, making it less available for use.
Malabsorption Conditions: Disorders such as celiac disease and Crohn's disease interfere with the absorption of fat-soluble vitamins, including vitamin D, in the intestines.
Limited Sun Exposure: Individuals who are homebound, live in northern climates, or cover their skin for cultural or religious reasons are at a high risk for deficiency.
Kidney and Liver Disease: These chronic illnesses impair the body's ability to convert vitamin D into its active, usable form.

Vitamin D is an essential fat-soluble vitamin that plays a vital role in bone development, immune function, and overall health. While the body can produce vitamin D naturally from sun exposure, many factors can inhibit this process, leading to a deficiency. While anyone can develop low vitamin D, certain groups are disproportionately affected due to physiological, environmental, or lifestyle factors.

The Role of Melanin and Skin Pigmentation

One of the most significant risk factors for vitamin D deficiency is skin pigmentation. Melanin, the pigment responsible for darker skin tones, acts as a natural sunscreen, protecting the skin from UV radiation. However, this protective mechanism also reduces the skin's ability to produce vitamin D from sunlight.

Less efficient production: Individuals with darker skin require significantly more sun exposure to produce the same amount of vitamin D as those with lighter skin tones.
High prevalence in studies: Studies have shown a high prevalence of vitamin D deficiency in Black and Hispanic populations, even when compared to white populations with similar sun exposure.

The Impact of Age on Vitamin D Production

As we age, our bodies become less efficient at synthesizing vitamin D. Older adults, particularly those over 65, face a higher risk of deficiency for several reasons.

Decreased synthesis: The skin's ability to convert sunlight into vitamin D declines with age.
Reduced sun exposure: Elderly individuals, especially those who are homebound, institutionalized, or live in care facilities, often have limited opportunities for sun exposure.
Dietary challenges: Older adults may also have inadequate dietary intake of vitamin D.

Medical Conditions and Absorption Issues

Certain medical conditions can severely impact the body's ability to absorb or utilize vitamin D, regardless of sun exposure or diet. These conditions often affect the digestive system, where fat-soluble vitamins are absorbed.

Malabsorption disorders: Conditions such as cystic fibrosis, Crohn's disease, and celiac disease can prevent the intestines from properly absorbing fat and, by extension, fat-soluble vitamin D.
Kidney and liver disease: The kidneys and liver play crucial roles in converting vitamin D into its active form. Chronic liver or kidney disease can impair this process, leading to low vitamin D levels.
Obesity: Individuals with a Body Mass Index (BMI) of 30 or higher are at a greater risk of deficiency. Fat cells sequester vitamin D, preventing it from circulating in the blood. As a result, obese individuals may require higher doses of supplementation to achieve healthy vitamin D levels.

Comparison of Risk Factors for Vitamin D Insufficiency


Risk Factor	Mechanism of Increased Risk	Example Population	How to Mitigate Risk
Dark Skin	Increased melanin blocks UV absorption necessary for vitamin D synthesis.	People of African, Hispanic, or South Asian descent.	Safe sun exposure, dietary intake, and supplementation.
Older Age	Decreased skin efficiency and reduced sun exposure due to mobility issues.	Individuals over 65, nursing home residents.	Supplementation, increased outdoor time, dietary intake.
Obesity	Fat cells store vitamin D, reducing its availability in the bloodstream.	Adults with a BMI over 30.	Higher doses of vitamin D supplementation often required.
Malabsorption	Diseases like Crohn's or celiac inhibit intestinal fat and vitamin D absorption.	Patients with GI disorders or post-gastric bypass surgery.	Specialized vitamin D supplementation (oral or injected).
Limited Sun Exposure	Insufficient UVB radiation to trigger cutaneous vitamin D production.	Office workers, northern climate residents, individuals covering skin.	Safe, moderate sun exposure, fortified foods, and supplements.

Conclusion: A Multifactorial Risk Landscape

While a variety of factors contribute to vitamin D deficiency, the single most prominent risk factor is having darker skin pigmentation, due to the inhibitory effect of melanin on cutaneous synthesis. This is exacerbated by other risk factors, such as limited sun exposure, making individuals with dark skin living in higher latitudes especially vulnerable. Other high-risk groups include older adults, obese individuals, and those with certain gastrointestinal, kidney, or liver conditions. Proper management of vitamin D insufficiency involves identifying these specific risk factors and implementing tailored strategies, which may include increased dietary intake, safe sun exposure, or supplementation.

For more information on vitamin D metabolism, consult the authoritative fact sheet from the National Institutes of Health. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/

Frequently Asked Questions

No, living in a sunny climate does not guarantee sufficient vitamin D. Factors such as skin pigmentation, age, time spent indoors, and consistent use of sunscreen can still lead to a deficiency, even with ample sunlight.

Yes, breastfed infants are at risk because human breast milk contains very little vitamin D. Pediatricians often recommend daily vitamin D supplementation for breastfed babies until they begin eating a more varied diet.

Fat cells in obese individuals store vitamin D, effectively trapping it away from the bloodstream. This means less vitamin D is available for the body's use, necessitating higher intake to reach adequate levels.

Yes, some medications, including certain anti-seizure drugs, steroids, and cholesterol-lowering medicines, can interfere with vitamin D metabolism and increase the risk of deficiency.

Older adults are more susceptible because their skin produces vitamin D less efficiently with age. Additionally, they often spend less time outdoors and may have a reduced dietary intake of the vitamin.

Signs of vitamin D insufficiency can be subtle and include fatigue, muscle cramps, bone and joint pain, and muscle weakness. Severe, long-term deficiency can lead to bone-related disorders like osteoporosis or osteomalacia.

Yes, people with darker skin require more sun exposure because melanin, the pigment that causes darker skin tones, absorbs UVB radiation. This means they need more time in the sun to produce the same amount of vitamin D as individuals with lighter skin.