Researchers in Saudi Arabia studied 387 adults to see if drinking a lot of coffee affects vitamin D levels and how people feel. They found that people who drank more than 3 cups of coffee daily had lower vitamin D levels and higher body weight compared to those who drank less coffee. These heavy coffee drinkers also reported more sleep problems, sweating, and faster heartbeats. However, coffee drinking didn’t seem to affect mood issues like anxiety or depression. The study suggests that if you drink lots of coffee, you might want to check your vitamin D levels and pay attention to how much sleep you’re getting.

The Quick Take

  • What they studied: Whether drinking lots of coffee is connected to lower vitamin D levels, weight gain, and sleep or mood problems in adults living in Saudi Arabia.
  • Who participated: 387 adults between 20 and 60 years old living in Saudi Arabia. Researchers divided them into two groups: those who drank 3 cups of coffee or less per day, and those who drank more than 3 cups daily.
  • Key finding: Adults who drank more than 3 cups of coffee daily had noticeably lower vitamin D levels compared to those who drank less coffee. For every extra milligram of caffeine consumed daily, vitamin D levels dropped slightly but consistently.
  • What it means for you: If you’re a heavy coffee drinker (more than 3 cups daily), you might want to have your vitamin D levels checked by a doctor. You should also consider getting more sun exposure and eating foods rich in vitamin D. However, this study only shows a connection—it doesn’t prove that coffee causes low vitamin D. More research is needed before making major changes to your coffee habits.

The Research Details

This was a cross-sectional study, which means researchers collected information from all participants at one point in time (February-March 2024) rather than following them over months or years. Participants answered questions about how much coffee they drank, their physical activity, sun exposure, and any sleep or mood problems they experienced. Researchers also took blood samples to measure vitamin D levels and collected height and weight measurements.

The study divided people into two groups based on coffee consumption: normal drinkers (3 cups or less per day) and high drinkers (more than 3 cups daily). Researchers then compared the two groups to see if there were differences in vitamin D levels, body weight, and reported symptoms like sleep problems or mood changes.

Researchers used statistical methods to look for connections between caffeine intake and vitamin D levels while accounting for other factors that might affect vitamin D, such as sun exposure and diet. This helps isolate the effect of coffee from other influences.

This research approach is important because vitamin D deficiency is a common health problem in Saudi Arabia, even though it’s a sunny country. Understanding what factors might contribute to low vitamin D—like coffee consumption—could help doctors and public health officials give better advice to people. The study also looked at sleep and physical symptoms, which are important for overall quality of life. By examining these connections, researchers can identify groups of people who might need extra vitamin D monitoring.

This study has some strengths: it included a reasonable number of participants (387 people), measured actual vitamin D levels from blood samples rather than just asking people about it, and used proper statistical methods. However, there are important limitations to keep in mind. The study only looked at people in Saudi Arabia at one specific time, so results might not apply to other countries or populations. Because it’s cross-sectional, we can’t tell if coffee causes low vitamin D or if people with low vitamin D happen to drink more coffee. The study relied on people remembering and reporting their coffee consumption, which can be inaccurate. Additionally, researchers couldn’t control for all possible factors that affect vitamin D, such as specific dietary choices or exact sun exposure times.

What the Results Show

Heavy coffee drinkers (more than 3 cups daily) had lower vitamin D levels than normal coffee drinkers. The difference was small but statistically significant, meaning it’s unlikely to have happened by chance. For every additional milligram of caffeine someone consumed per day, their vitamin D level dropped slightly. Heavy coffee drinkers also had higher body weight on average compared to normal drinkers.

Interestingly, when researchers looked at vitamin D deficiency specifically (very low levels below 30 nmol/L), they found that higher caffeine intake was actually associated with lower odds of being deficient. This seems contradictory at first, but it likely reflects that the relationship between caffeine and vitamin D is more complex than a simple cause-and-effect.

The study found clear differences in sleep and physical symptoms between the two groups. Heavy coffee drinkers reported sleep problems or insomnia much more often (49.1% versus 34.2%), excessive sweating more frequently (20.8% versus 9.6%), and faster heartbeats more often (27.7% versus 17.2%). All of these differences were statistically significant.

Surprisingly, mood-related symptoms didn’t differ between heavy and normal coffee drinkers. Headaches, irritability, anxiety, and depression were reported at similar rates in both groups. This suggests that while coffee might affect sleep and physical arousal, it may not directly impact mood disorders in this population. The study also measured parathyroid hormone levels, which help regulate vitamin D, but the paper doesn’t detail specific findings about this hormone.

Previous research has suggested that caffeine might interfere with vitamin D absorption or metabolism, and this study provides some support for that idea. However, the relationship appears more complicated than previously thought. The finding that heavy coffee drinkers had higher body weight aligns with some previous studies suggesting caffeine might affect metabolism or appetite. The sleep disturbances reported by heavy coffee drinkers are well-established in caffeine research—caffeine blocks sleep-promoting chemicals in the brain. This study adds to existing knowledge by examining these connections specifically in a Saudi Arabian population, where both coffee consumption and vitamin D deficiency are common health concerns.

The biggest limitation is that this study only shows associations, not cause-and-effect relationships. We can’t determine whether coffee causes low vitamin D or whether people with low vitamin D tend to drink more coffee. The study only included people from Saudi Arabia during a specific two-month period, so findings might not apply to other countries or times of year. People self-reported their coffee consumption and symptoms, which can be inaccurate—people might not remember exactly how much coffee they drank or might underreport sleep problems. The study couldn’t account for all factors affecting vitamin D, such as specific foods eaten, exact duration of sun exposure, or use of sunscreen. Additionally, the study didn’t measure actual caffeine intake from all sources (tea, energy drinks, chocolate), only coffee consumption. Finally, the cross-sectional design means we’re looking at a snapshot in time rather than tracking people over months or years to see how coffee consumption changes vitamin D levels.

The Bottom Line

If you drink more than 3 cups of coffee daily, consider having your vitamin D levels checked by a doctor (moderate confidence). Increase your sun exposure when safe and practical, as this is the primary way your body makes vitamin D (high confidence). Eat more foods containing vitamin D, such as fatty fish, egg yolks, and fortified dairy products (high confidence). If you experience sleep problems and drink lots of coffee, try reducing your coffee intake, especially in the afternoon and evening (moderate confidence). Don’t make drastic changes to your diet or supplement routine based on this single study—discuss any concerns with your healthcare provider (high confidence).

This research is most relevant to people living in sunny climates like Saudi Arabia who drink large amounts of coffee and have vitamin D deficiency or symptoms like sleep problems. People with existing sleep disorders should pay special attention to their coffee consumption. Healthcare providers in regions with high coffee consumption and vitamin D deficiency should consider this information when counseling patients. However, if you live in a cloudy climate, drink moderate amounts of coffee, or have normal vitamin D levels, this study may be less directly applicable to you. People with caffeine sensitivity or anxiety disorders should already be limiting coffee intake regardless of vitamin D concerns.

If you reduce coffee consumption, you might notice improvements in sleep within 1-2 weeks, as caffeine leaves your system relatively quickly. However, vitamin D levels take much longer to change—typically 2-3 months of consistent sun exposure or dietary changes before you’d see meaningful improvements. If you start vitamin D supplementation based on a doctor’s recommendation, it could take 4-8 weeks to notice energy or mood improvements, though blood levels would improve sooner. Don’t expect overnight changes; focus on consistent habits over months rather than weeks.

Want to Apply This Research?

  • Track daily coffee consumption (number of cups and time of day consumed) alongside sleep quality ratings (1-10 scale) and energy levels. This allows users to see if reducing coffee, especially afternoon intake, correlates with better sleep. Include a reminder to note any sleep disturbances or daytime fatigue.
  • Set a daily coffee limit (e.g., maximum 2-3 cups) and establish a cutoff time (e.g., no coffee after 2 PM). Users can log each cup consumed and receive notifications when approaching their daily limit. The app could suggest alternatives like herbal tea for afternoon beverages and track how sleep quality changes as coffee intake decreases.
  • Create a weekly summary dashboard showing average daily coffee consumption, average sleep quality rating, and any reported symptoms (sleep disturbance, sweating, heart palpitations). Allow users to set reminders for vitamin D level check-ups every 3-6 months with their doctor. Include a section to log sun exposure time and vitamin D-rich foods consumed, helping users see the complete picture of factors affecting vitamin D status.

This study shows a connection between coffee consumption and vitamin D levels but does not prove that coffee causes low vitamin D. This research is observational and cannot establish cause-and-effect relationships. Individual responses to coffee vary greatly based on genetics, overall diet, sun exposure, and other health factors. Before making significant changes to your coffee consumption or starting vitamin D supplements, consult with your healthcare provider, especially if you have existing health conditions, take medications, or have symptoms like persistent sleep problems. This information is for educational purposes only and should not replace professional medical advice. If you suspect you have vitamin D deficiency, ask your doctor for a blood test rather than self-diagnosing based on this study.