Researchers in Saudi Arabia tested vitamin D levels in 204 healthy adult men who weren’t taking vitamin D supplements. They found that 93% of these men had low vitamin D levels, even though Saudi Arabia gets plenty of sunshine year-round. The average vitamin D level was much lower than what doctors consider healthy. This surprising finding suggests that lifestyle and cultural factors—like spending less time in the sun—might be keeping vitamin D levels low in this population. The study helps doctors understand what normal vitamin D levels should be for people in this specific region.
The Quick Take
- What they studied: How much vitamin D is in the blood of healthy adult men in Alqurayyat, Saudi Arabia, and what the normal range should be for this population
- Who participated: 204 healthy Saudi men between ages 18-45 who were blood donors at a local hospital and were not taking vitamin D supplements
- Key finding: 93% of the men had vitamin D levels below what’s considered healthy (below 20 ng/mL), with an average level of 12.47 ng/mL. None of the men had adequate vitamin D levels, even though they live in a sunny climate
- What it means for you: If you live in a similar climate or have a similar lifestyle, you might also have low vitamin D even if you get sun exposure. This suggests that factors beyond just sunlight availability—like how much time people actually spend outdoors—affect vitamin D levels. Talk to your doctor about whether you should get your vitamin D checked and consider supplementation if needed
The Research Details
This was a cross-sectional study, which means researchers took a snapshot of vitamin D levels at one point in time rather than following people over months or years. Between December 2022 and August 2023, researchers collected blood samples from 204 healthy adult men at Alqurayyat General Hospital. They measured vitamin D using a precise laboratory test called chemiluminescence immunoprecipitation assay. To ensure accuracy, they removed extreme values that didn’t fit the normal pattern using a statistical method called the Tukey method. This helped them establish what a normal vitamin D level should be for this specific population.
Different populations around the world have different normal ranges for vitamin D based on their genetics, lifestyle, diet, and sun exposure patterns. By studying a local population without vitamin D supplements, researchers can establish what’s truly normal for that region rather than relying on international standards that might not apply. This helps doctors better understand whether their patients have a real vitamin D problem or if their levels are normal for their area.
The study used a reliable laboratory method to measure vitamin D and carefully selected healthy participants to establish a true reference range. The sample size of 204 people is reasonable for this type of study. However, the study only included men aged 18-45, so the results may not apply to women, older men, or younger people. The study was conducted at a hospital blood donor center, which might mean the participants were slightly healthier than the general population. The study is recent (2022-2023) and published in a peer-reviewed journal, which adds credibility.
What the Results Show
The researchers found that the average vitamin D level in this population was 12.47 ng/mL, which is quite low. When they calculated the normal range for this population (using the middle 95% of values), they found it to be 4.22-26.14 ng/mL. This range is significantly lower than international standards, which typically consider 30 ng/mL or higher as adequate. The most striking finding was that 93% of the men had vitamin D levels below 20 ng/mL, which is considered deficient by international standards. Only 7% had levels between 20-29 ng/mL (still below ideal), and not a single participant had adequate vitamin D levels above 30 ng/mL. This widespread deficiency was unexpected because Saudi Arabia receives abundant sunlight throughout the year.
The study didn’t report major secondary findings, but the data suggests that vitamin D deficiency is a widespread public health issue in this population. The fact that even healthy, young adult men—who theoretically should have better vitamin D levels—showed such low levels indicates that the problem likely affects the entire population, including women, children, and older adults.
International health organizations typically recommend vitamin D levels of at least 20 ng/mL as adequate and 30 ng/mL or higher as optimal. The reference range found in this study (4.22-26.14 ng/mL) is notably lower than what’s recommended internationally. This suggests that either the local population has adapted to lower vitamin D levels, or there’s a significant public health problem that needs attention. Previous research in other parts of Saudi Arabia has also shown high rates of vitamin D deficiency despite abundant sunshine, supporting the idea that lifestyle and cultural factors play a major role.
The study only included men aged 18-45, so results may not apply to women, children, or older adults. All participants were blood donors at a hospital, which might mean they were slightly healthier than the general population. The study was conducted in one specific city (Alqurayyat), so results might differ in other parts of Saudi Arabia. The researchers didn’t collect detailed information about participants’ sun exposure, clothing, diet, or other lifestyle factors that could explain the low vitamin D levels. The study is observational, meaning it can show what vitamin D levels are but can’t prove why they’re so low.
The Bottom Line
If you live in a sunny climate but have similar lifestyle patterns to this population, consider getting your vitamin D level checked by a doctor (moderate confidence). If your level is below 20 ng/mL, your doctor may recommend vitamin D supplements (moderate to high confidence). Even if you live in a sunny area, spending more time outdoors during peak sun hours may help improve vitamin D levels, though this should be balanced with skin cancer prevention (low to moderate confidence). These recommendations should be personalized based on your individual health situation and doctor’s advice.
Men in Saudi Arabia and similar climates should pay attention to this research, especially if they’re experiencing symptoms of vitamin D deficiency like fatigue or bone pain. Women, children, and older adults in these regions should also be concerned, as they may have even higher rates of deficiency. People who wear clothing that covers most of their skin for cultural or religious reasons should definitely discuss vitamin D screening with their doctor. Anyone living in a sunny climate but spending most of their time indoors should consider getting tested. People with certain medical conditions, darker skin tones, or those living far from the equator should also be aware of their vitamin D status.
If you start taking vitamin D supplements, it typically takes 2-3 months to see significant improvements in blood levels. Health benefits like improved bone strength or immune function may take several months to become noticeable. If you’re trying to increase vitamin D through increased sun exposure, allow at least 3-6 months to see meaningful changes in your vitamin D levels.
Want to Apply This Research?
- Track your vitamin D supplementation (if recommended by your doctor) by logging daily doses. Set a reminder to take supplements at the same time each day. Record any symptoms like fatigue or bone pain to discuss with your doctor at follow-up appointments.
- If your doctor recommends it, use the app to set a daily reminder to take a vitamin D supplement. Log outdoor time spent in direct sunlight (aiming for 10-30 minutes most days, depending on skin tone and location). Track any dietary sources of vitamin D like fatty fish, egg yolks, or fortified milk.
- Schedule reminders to get your vitamin D level retested every 3-6 months if you’re supplementing. Use the app to track trends over time and share results with your healthcare provider. Monitor for symptoms of deficiency (fatigue, muscle weakness, bone pain) and log any changes in how you feel.
This research describes vitamin D levels in a specific population in Saudi Arabia and should not be used for self-diagnosis. Vitamin D levels vary based on many factors including genetics, lifestyle, diet, skin tone, age, and location. If you’re concerned about your vitamin D level, consult with your healthcare provider who can order appropriate testing and recommend personalized treatment. This study is observational and cannot prove cause-and-effect relationships. Always discuss any supplements or major lifestyle changes with your doctor before starting, especially if you have existing health conditions or take medications.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.