Research shows that 84% of people living at high altitude in Xining, China have vitamin D deficiency, and this deficiency is strongly linked to higher inflammation in the body. According to Gram Research analysis of 2,080 residents, those with the lowest vitamin D levels had significantly elevated inflammation markers including C-reactive protein, interleukin-6, and procalcitonin. Women were nearly four times more likely to have vitamin D deficiency than men, and vitamin D levels naturally peaked in summer and dropped in winter.
A new study of 2,080 people living in Xining, a high-altitude city in China, found that most residents have dangerously low vitamin D levels. According to Gram Research analysis, about 84% of people there don’t have enough vitamin D in their blood. The research shows that low vitamin D is connected to higher inflammation in the body—similar to how your body reacts when fighting an infection. Women were more likely to have low vitamin D than men, and vitamin D levels were highest in summer and lowest in winter. The findings suggest that people living at high altitudes may need special vitamin D supplementation, especially during winter months.
Key Statistics
A 2026 study of 2,080 high-altitude residents in Xining, China found that 84% had vitamin D deficiency, with average vitamin D levels of just 13.99 ng/mL compared to the recommended minimum of 30 ng/mL.
Research published in BMC Nutrition showed that people with vitamin D deficiency had inflammation markers 292-674% higher than those with adequate vitamin D, with the strongest correlation in procalcitonin levels (r=-0.674, P < 0.01).
A 2026 analysis of 2,080 high-altitude residents revealed that women had vitamin D deficiency rates of 88% compared to 77% in men, making female gender an independent risk factor for deficiency at high altitude.
The study found that vitamin D levels followed a clear seasonal pattern, peaking in summer and reaching lowest levels in winter, demonstrating that sunlight exposure remains the primary regulator of vitamin D even at 7,400-foot elevation.
The Quick Take
- What they studied: Whether people living at high altitudes have low vitamin D levels and whether low vitamin D is connected to body inflammation.
- Who participated: 2,080 people living in Xining, China, a city located 7,400 feet above sea level. The group included both men and women of various ages.
- Key finding: About 84% of residents had vitamin D deficiency, and those with the lowest vitamin D had significantly higher inflammation markers in their blood (P < 0.05).
- What it means for you: If you live at high altitude, you may need more vitamin D supplementation than people at sea level, especially in winter. Talk to your doctor about testing your vitamin D levels and whether supplements are right for you.
The Research Details
Researchers measured vitamin D levels in blood samples from 2,080 people living in Xining, a city in western China at 7,400 feet elevation. They divided people into three groups based on their vitamin D levels: those with enough vitamin D (above 30 ng/mL), those with slightly low levels (20-30 ng/mL), and those with deficiency (below 20 ng/mL). They also measured three markers of inflammation in the blood: procalcitonin (PCT), interleukin 6 (IL-6), and C-reactive protein (CRP). These inflammation markers are like warning signals your body sends when it’s fighting infection or stress.
The researchers then used statistical analysis to look for connections between vitamin D levels and inflammation. They checked whether the connection held true even after accounting for other factors like age and sex. They also used a special type of analysis called logistic regression to identify which factors independently increased the risk of vitamin D deficiency.
High-altitude locations receive less oxygen in the air, which may affect how the body produces and uses vitamin D. Understanding this connection helps doctors know who needs vitamin D supplementation and when. The seasonal pattern (higher in summer, lower in winter) suggests that sunlight exposure is the main factor controlling vitamin D levels, even at high altitude.
This study has a large sample size (2,080 people), which makes the findings more reliable. The researchers measured actual blood levels rather than relying on self-reported information. They used appropriate statistical methods and adjusted for confounding factors. However, this is a single study in one location, so results may not apply to all high-altitude populations worldwide.
What the Results Show
The average vitamin D level in the study population was 13.99 ng/mL, which is quite low. About 84% of people had vitamin D deficiency, 14% had insufficient levels, and only 3% had adequate vitamin D. This is much higher deficiency than typically seen in sea-level populations.
People with vitamin D deficiency had significantly higher inflammation markers compared to those with sufficient vitamin D. Specifically, procalcitonin was 674% higher, interleukin-6 was 533% higher, and C-reactive protein was 292% higher in the deficiency group. These differences were statistically significant (P < 0.05), meaning they’re unlikely to be due to chance.
Women had much higher rates of vitamin D deficiency (88%) compared to men (77%). Interestingly, age didn’t make a significant difference—both young and older adults had similar deficiency rates. Vitamin D levels followed a clear seasonal pattern, peaking in summer and dropping to their lowest in winter, suggesting that sunlight exposure is the main driver of vitamin D production even at high altitude.
The statistical analysis revealed that the connection between low vitamin D and high inflammation remained strong even after adjusting for other factors like age and sex. Female gender was identified as an independent risk factor for vitamin D deficiency (4 times more likely than males). Among the inflammation markers, procalcitonin showed the strongest connection to vitamin D deficiency, followed by interleukin-6 and C-reactive protein.
Previous research has shown vitamin D deficiency is common in high-altitude populations, but this study provides more detailed data on the inflammation connection. The seasonal pattern matches findings from other high-altitude studies. The stronger deficiency in women aligns with research from sea-level populations, though the overall deficiency rate in Xining is much higher than typical sea-level communities.
This study was conducted in one specific city in China, so results may not apply to other high-altitude regions with different climates or populations. The study measured vitamin D at one point in time for most participants, so we can’t determine cause-and-effect—we only know that low vitamin D and high inflammation occur together. The study didn’t measure sun exposure directly, so we can’t be certain sunlight is the only factor affecting vitamin D levels. Additionally, other factors affecting inflammation (like diet, exercise, and infections) weren’t fully controlled for.
The Bottom Line
People living at high altitudes (especially above 6,500 feet) should consider vitamin D testing, particularly if they experience fatigue or joint pain. Based on this research, vitamin D supplementation appears beneficial, especially for women and during winter months. Consult your doctor about appropriate dosing—typical recommendations range from 1,000-4,000 IU daily for adults, but your needs may be higher at altitude. Confidence level: Moderate (based on observational data showing strong associations).
This research is most relevant to people living at high altitudes, particularly women and those in regions with limited winter sunlight. Healthcare providers in mountainous regions should consider routine vitamin D screening. People with chronic inflammation or autoimmune conditions at high altitude may benefit especially from vitamin D assessment. This may be less relevant to sea-level residents unless they have limited sun exposure.
Vitamin D supplementation typically takes 4-8 weeks to raise blood levels meaningfully. Inflammation markers may begin improving within 8-12 weeks of adequate vitamin D levels, though individual responses vary. Seasonal improvements in vitamin D naturally occur in summer months due to increased sunlight exposure.
Frequently Asked Questions
Why do people living at high altitude have low vitamin D?
High-altitude locations have thinner air with less oxygen, which may reduce vitamin D production. Additionally, winter sunlight is weaker at high altitudes, and people may spend more time indoors. This study found that 84% of high-altitude residents had vitamin D deficiency compared to much lower rates at sea level.
Does low vitamin D cause inflammation or does inflammation cause low vitamin D?
This study shows they’re connected but doesn’t prove which causes which. The strong correlation (r=-0.674) suggests low vitamin D and high inflammation occur together. Likely, low vitamin D contributes to inflammation, but other factors may also play a role. More research is needed to establish definitive cause-and-effect.
How much vitamin D should I take if I live at high altitude?
Standard recommendations are 1,000-4,000 IU daily for adults, but high-altitude residents may need more. This study suggests women especially may benefit from supplementation. Get your vitamin D level tested to determine your specific needs, then work with your doctor to establish an appropriate dose for your situation.
Can I get enough vitamin D from sunlight at high altitude?
This study found that vitamin D levels naturally peaked in summer and dropped in winter, showing sunlight does help at high altitude. However, 84% of residents still had deficiency even during sunny seasons, suggesting sunlight alone isn’t sufficient. Supplementation appears necessary, especially in winter months.
Why do women have more vitamin D deficiency than men at high altitude?
This study found women had 88% deficiency versus 77% in men, but the exact reason isn’t clear. Possible factors include different sun exposure patterns, clothing choices, or biological differences in vitamin D metabolism. The research identifies female gender as a risk factor but doesn’t explain the underlying cause.
Want to Apply This Research?
- Log vitamin D supplementation daily (dose and type) and track seasonal patterns. Set reminders for vitamin D testing twice yearly (winter and summer) to monitor levels and adjust supplementation accordingly.
- Users living at high altitude should set a daily vitamin D supplement reminder, especially from October through March. Track outdoor sun exposure time daily and aim for 15-30 minutes of midday sun when possible, noting that high altitude may require less time for adequate vitamin D synthesis.
- Create a seasonal tracking system that increases vitamin D supplementation in fall/winter and decreases in spring/summer. Monitor energy levels and joint pain as indirect indicators of inflammation. Schedule annual blood tests to measure actual vitamin D levels and adjust supplementation based on results.
This research describes associations between vitamin D deficiency and inflammation in a high-altitude population but does not establish definitive cause-and-effect relationships. Individual vitamin D needs vary based on age, sex, skin tone, sun exposure, and health conditions. Before starting vitamin D supplementation, consult with your healthcare provider, especially if you take medications or have existing health conditions. This article is for educational purposes and should not replace professional medical advice. Blood testing is recommended to determine your actual vitamin D status before beginning supplementation.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.