Vitamin D Insufficiency Across US Demographics

Most Americans have adequate vitamin D, but the risk of true deficiency is concentrated sharply by race, age, body weight, and supplement use. According to the CDC's National Health and Nutrition Examination Survey (NHANES) for 2011–2014, about 5.0% of people aged 1 and older were at risk of vitamin D deficiency and another 18.3% were at risk of inadequacy — meaning roughly 1 in 4 Americans fell below recommended blood levels, while about three-quarters were in the sufficient range.

The gap between groups is the real story. Non-Hispanic Black Americans were at risk of deficiency at a rate of 17.5%, compared with just 2.1% of non-Hispanic white Americans — a more than eightfold difference. (These are population risk categories from a single blood draw, not individual diagnoses.)

This article is informational and educational. It describes population-level patterns in public-health data; it does not diagnose any condition or provide medical advice. Decisions about vitamin D testing or supplementation should be made with a qualified clinician.

How vitamin D status is defined

Vitamin D status is measured by serum 25-hydroxyvitamin D [25(OH)D], the standard blood marker. The CDC's National Center for Health Statistics classifies status using these cut points:

• At risk of deficiency: below 30 nmol/L (under 12 ng/mL)
• At risk of inadequacy: 30–49 nmol/L (12–19 ng/mL)
• Sufficient: 50–125 nmol/L (20–50 ng/mL)

These thresholds matter because prevalence figures swing widely depending on which one a study uses. Under a looser definition — counting everyone below 50 nmol/L — a pooled NHANES analysis covering 2001–2018 found about 2.6% with severe deficiency (<25 nmol/L) and 22.0% with moderate deficiency (25–50 nmol/L). So context determines whether the 'deficient' share looks closer to 5% or closer to 25%.

Race and ethnicity show the widest gap

The disparity by race and ethnicity is the most consistent finding across decades of NHANES data. In 2011–2014, the share at risk of deficiency was:

• Non-Hispanic Black: 17.5%
• Non-Hispanic Asian: 7.6%
• Hispanic: 5.9%
• Non-Hispanic white: 2.1%

The same ordering holds for the broader 'at risk of inadequacy' category, where 35.8% of non-Hispanic Black Americans fell short versus 11.8% of non-Hispanic white Americans.

The pooled 2001–2018 analysis, using a stricter severe-deficiency threshold (<25 nmol/L), found an even starker gap: 11.9% of non-Hispanic Black Americans versus 0.9% of non-Hispanic white Americans.

What it means: Higher skin melanin reduces the skin's vitamin D synthesis from sunlight, which is one biological driver of this pattern. Behavior compounds biology — supplement use is far lower in the groups with the highest deficiency risk. In 2011–2014, 43.7% of non-Hispanic white adults reported vitamin D supplement use, versus 24.8% of non-Hispanic Black and 22.0% of Hispanic adults. NHANES is observational, so these are associations, not proof of cause.

Young adults, not the elderly, carry the highest deficiency risk

Contrary to the common assumption that older people are most vulnerable, NHANES shows the risk of deficiency peaks in young adulthood. In 2011–2014, the share at risk of deficiency by age was:

• 1–5 years: 0.5%
• 6–11 years: 1.4%
• 12–19 years: 4.8%
• 20–39 years: 7.6% (the peak)
• 40–59 years: 5.7%
• 60+ years: 2.9%

The 2001–2018 pooled data agree, locating peak deficiency in the 20–29 age band. Lower deficiency among older adults likely reflects higher supplement and fortified-food use rather than better sun-driven synthesis, which actually declines with age.

Sex, season, and body weight each shift the risk

Sex: Women carry a modestly higher burden. In 2011–2014, 5.7% of females were at risk of deficiency versus 4.4% of males. The longer 2001–2018 series shows the same pattern for severe deficiency (3.1% of women vs. 2.1% of men).

Season: Sunlight exposure drives a large seasonal swing. In the 2001–2018 data, severe deficiency was 4.1% in winter versus 1.6% in summer, and moderate deficiency was 28.9% in winter versus 17.0% in summer.

Body weight: Obesity is associated with low vitamin D. In NHANES 2011–2012, 42.5% of vitamin D–deficient adults were obese (BMI ≥30) versus 31.1% of sufficient adults (adjusted odds ratio 1.31; 95% CI 1.15–1.49). Vitamin D is fat-soluble and is thought to be sequestered in adipose tissue, which can lower circulating levels.

Supplement use tracks with much lower deficiency risk

The clearest behavioral signal in the data is supplementation. Among people reporting vitamin D supplement use in 2011–2014, only 1.1% were at risk of deficiency — versus 6.9% among non-users. Because the survey is observational, this reflects a strong association rather than a guaranteed cause-and-effect. The NIH Office of Dietary Supplements sets the Recommended Dietary Allowance at 600 IU (15 mcg) daily for most people aged 1–70 and 800 IU (20 mcg) for adults over 70, with an Adequate Intake of 400 IU (10 mcg) for infants. Individual needs vary, and high-dose supplementation should be guided by a clinician.

The longer-term trend is slowly improving

The longer-term picture is cautiously encouraging. After deficiency risk rose between NHANES III (1988–1994) and the early 2000s — the age- and season-adjusted share at risk of deficiency climbed from 3% to 7% in males and from 7% to 11% in females, per CDC — the 2001–2018 series shows moderate deficiency edging down and sufficiency edging up. The reported changes are statistically significant but small, and severe deficiency showed no significant change.

Limitations

NHANES is cross-sectional, so it shows associations, not causation. A single blood draw captures a moment in time and cannot reflect an individual's seasonal variation. Comparing studies is tricky because deficiency thresholds differ, and assay methods have been recalibrated over time, complicating long-run trends. Self-reported supplement use and diet are subject to recall error. The 'at risk' categories are population classifications, not clinical diagnoses. None of these figures should be read as medical advice; testing and treatment decisions belong with a healthcare provider.

Sources

• Herrick KA, et al. "Vitamin D status in the United States, 2011–2014." *American Journal of Clinical Nutrition*, 2019. pmc.ncbi.nlm.nih.gov/articles/PMC7263437
• Cui A, et al. "Prevalence, trend, and predictor analyses of vitamin D deficiency in the US population, 2001–2018." *Frontiers in Nutrition*, 2022. pmc.ncbi.nlm.nih.gov/articles/PMC9573946
• CDC National Center for Health Statistics. "Vitamin D Status: United States, 2001–2006." NCHS Data Brief No. 59. www.cdc.gov/nchs/products/databriefs/db59.htm
• "Prevalence of Vitamin D Deficiency and Associated Risk Factors in the US Population (2011–2012)." pmc.ncbi.nlm.nih.gov/articles/PMC6075634
• NIH Office of Dietary Supplements. "Vitamin D — Health Professional Fact Sheet." ods.od.nih.gov/factsheets/VitaminD-HealthProfessional