Researchers followed college students for an entire year to see how their vitamin D levels changed with the seasons and how this affected their health. Vitamin D is a nutrient your body makes from sunlight and gets from food—it’s important for strong bones and a healthy immune system. The study tracked whether students’ vitamin D levels went up and down throughout the year, what they ate, and how they felt. Understanding these patterns could help students know when they might need to pay extra attention to getting enough vitamin D, especially during winter months when there’s less sunlight.

The Quick Take

  • What they studied: Whether college students’ vitamin D levels change throughout the year and how these changes affect their overall health and wellbeing
  • Who participated: University students followed over a full 12-month period to track their vitamin D status across all seasons
  • Key finding: Vitamin D levels in college students appear to fluctuate significantly throughout the year, likely following seasonal patterns related to sun exposure and dietary intake
  • What it means for you: If you’re a college student, your vitamin D levels probably change with the seasons. You may want to pay special attention to vitamin D intake during winter months when sunlight is limited. This could mean eating more vitamin D-rich foods or considering a supplement during darker months, but talk to your doctor first.

The Research Details

This was a prospective longitudinal study, which means researchers followed the same group of college students over an entire year and measured their vitamin D levels multiple times. The researchers collected information about what the students ate, how much sun exposure they got, and their overall health throughout all four seasons. By measuring the same people repeatedly over a full year, the researchers could see patterns in how vitamin D levels changed and what factors influenced those changes.

This type of study design is particularly useful for understanding how things change over time and how different seasons might affect nutrition and health. Unlike a one-time snapshot study, this approach captures the real-world variations that happen throughout the year.

Understanding how vitamin D levels naturally fluctuate throughout the year is important because vitamin D plays a crucial role in bone health, immune function, and mood. By tracking students over a full year, researchers can identify when people are most at risk for low vitamin D levels and provide better guidance about when to increase intake or sun exposure.

This study followed real people in their natural environment over a long period, which makes the findings more realistic than short-term lab studies. However, without seeing the full paper details, we can’t assess all aspects of study quality. The fact that it tracked the same individuals throughout all seasons strengthens the reliability of findings about seasonal patterns.

What the Results Show

The research suggests that college students’ vitamin D levels change noticeably throughout the year, following seasonal patterns. This makes sense because vitamin D production in your skin depends on sun exposure, which varies dramatically between summer and winter. Students likely had higher vitamin D levels during summer months when they spent more time outdoors and the sun was stronger, and lower levels during winter when days are shorter and colder.

These fluctuations weren’t just small variations—they appear to be significant enough to potentially affect health outcomes. The study also examined how much vitamin D students were eating through food and supplements, and how these dietary sources compared to what their bodies were naturally producing from sun exposure.

The research likely revealed connections between vitamin D levels and various health outcomes in college students, such as bone health, immune function, mood, and overall wellbeing. The study probably also identified which students were most at risk for vitamin D deficiency and during which times of year this risk was greatest. Information about dietary sources of vitamin D and their effectiveness compared to sun exposure would also be valuable secondary findings.

Previous research has shown that vitamin D levels follow seasonal patterns in the general population, with lower levels in winter. This study extends that knowledge specifically to college students, a population that may have unique patterns due to their lifestyle, living situations, and sun exposure habits. The findings likely confirm existing knowledge while providing new insights specific to this age group and their particular circumstances.

Without access to the complete paper, we cannot identify all limitations, but typical limitations for this type of study might include: the sample may not represent all college students (different regions have different sun exposure), students’ sun exposure and dietary habits may have changed during the study period, and the study only measured vitamin D and didn’t necessarily prove that changes in vitamin D directly caused health changes. Additionally, self-reported dietary information may not be completely accurate.

The Bottom Line

College students should be aware that their vitamin D levels likely drop during winter months. Consider these evidence-based approaches: (1) Eat more vitamin D-rich foods like fatty fish, egg yolks, and fortified milk year-round, especially in winter; (2) Get outside for sun exposure when possible, even in winter; (3) Talk to your doctor about whether a vitamin D supplement makes sense for you, particularly if you live in a northern climate or have limited sun exposure. Confidence level: Moderate—the seasonal pattern is well-established, though individual needs vary.

College students should definitely pay attention to this research, especially those who: live in northern climates with long, dark winters; spend most of their time indoors studying; have darker skin (which requires more sun exposure to produce vitamin D); follow a vegan diet; or have a family history of bone problems. If you’re generally healthy and get regular sun exposure and eat a balanced diet, you may need less concern, but it’s still worth being aware of seasonal patterns.

If you increase your vitamin D intake through food or supplements, it may take several weeks to notice changes in how you feel. Improvements in bone health and immune function happen gradually over months. If you’re trying to maintain adequate levels throughout the year, think of it as an ongoing practice rather than something with a quick fix.

Want to Apply This Research?

  • Track your vitamin D intake weekly by logging foods rich in vitamin D (salmon, fortified milk, egg yolks, mushrooms) and note your outdoor sun exposure time. Set a goal of 15-30 minutes of midday sun exposure at least 3-4 times per week, adjusting for your location and season.
  • Set seasonal reminders to increase vitamin D-rich foods during fall and winter months. Create a simple checklist: eat one vitamin D source daily, spend 20 minutes outside on sunny days, and note your mood and energy levels to see if there’s a connection to your vitamin D intake patterns.
  • Use the app to track vitamin D sources monthly and compare your intake across seasons. Note any changes in energy, mood, or how you feel physically. If you start a vitamin D supplement, track it consistently and monitor for any changes. Consider getting blood work done at the beginning of winter and spring to see if your levels are actually changing, then adjust your strategy based on results.

This research provides general information about vitamin D patterns in college students and should not replace professional medical advice. Vitamin D needs vary by individual based on age, skin tone, location, and health conditions. Before starting any supplement or making significant dietary changes, consult with your doctor or a registered dietitian, especially if you have existing health conditions, take medications, or have concerns about your vitamin D levels. If you suspect you have a vitamin D deficiency, ask your healthcare provider about blood testing to determine your actual levels.