Researchers looked at vitamin D levels in 38 cancer patients, comparing those whose cancer had spread to the lungs with those whose hadn’t. They found that vitamin D levels naturally go up in summer and down in winter. Interestingly, patients who had multiple cancers in their history showed lower vitamin D levels during winter months compared to those with just one cancer. While the study is small, it suggests that cancer patients—especially those with multiple cancers—might benefit from vitamin D supplements during winter, but larger studies are needed to confirm this.

The Quick Take

  • What they studied: Whether vitamin D levels in the blood are different in cancer patients whose cancer has spread to the lungs compared to cancer patients whose cancer hasn’t spread to the lungs, and how seasons affect these levels.
  • Who participated: 38 cancer patients total: 28 patients whose cancer had spread to their lungs and 10 patients with cancer history but no lung spread. The study measured their blood vitamin D levels at different times of year.
  • Key finding: Vitamin D levels were significantly higher in summer (85 nmol/L) than winter (61 nmol/L). Patients with multiple cancers in their history had much lower vitamin D in winter (45 nmol/L) compared to those with one cancer (75 nmol/L).
  • What it means for you: If you’re a cancer patient, especially one who has had multiple cancers, you may want to discuss vitamin D supplementation with your doctor, particularly during winter months. However, this is a small study, so don’t make changes without talking to your healthcare provider first.

The Research Details

This was a small observational study where researchers measured vitamin D levels in blood samples from cancer patients. They used a precise laboratory method called high-performance liquid chromatography (HPLC) to measure two types of vitamin D: D2 and D3. The researchers then compared vitamin D levels between patients whose cancer had spread to the lungs and those whose hadn’t, and they looked at how seasons, number of previous cancers, and overall health status affected these levels.

The study included 38 patients total: 28 with confirmed lung metastases (cancer spread to lungs) and 10 without. The researchers collected blood samples at different times of year to see if seasons made a difference. They also looked at patient records to understand their cancer history and overall health status using a standard medical classification system.

Understanding vitamin D levels in cancer patients is important because some research suggests vitamin D may play a role in cancer development and survival. This study helps us see whether vitamin D levels are actually different in patients whose cancer has spread, and whether the time of year matters. This information could help doctors decide if vitamin D supplements might be helpful for certain cancer patients.

This is a small study with only 38 patients, which means the results should be viewed as preliminary. The researchers used accurate laboratory methods to measure vitamin D, which is a strength. However, because the group is small, the findings may not apply to all cancer patients. The authors themselves note that larger studies are needed before making firm recommendations. This study is observational, meaning it shows associations but cannot prove that vitamin D causes differences in cancer outcomes.

What the Results Show

The most important finding was that vitamin D levels naturally vary by season. In summer, patients had an average vitamin D level of 85 nmol/L, while in winter it dropped to 61 nmol/L—a statistically significant difference. This makes sense because sunlight helps our bodies make vitamin D.

When comparing patients with lung metastases to those without, there was no significant difference in vitamin D levels during either summer or winter. This was somewhat surprising and suggests that having cancer spread to the lungs alone doesn’t necessarily change vitamin D levels.

However, a more interesting pattern emerged when looking at patients’ cancer history. During winter months, patients who had experienced only one cancer in their lifetime had much higher vitamin D levels (average 75 nmol/L) compared to patients with two or more cancers in their history (average 45 nmol/L). This difference was statistically significant and suggests that patients with multiple cancer diagnoses may have lower vitamin D, especially in winter.

The study also examined whether overall health status (measured using a standard medical classification) affected vitamin D levels. Patients in different health categories showed no significant differences in vitamin D levels, suggesting that general health status alone doesn’t explain the vitamin D variations observed.

Previous research has shown that vitamin D deficiency is associated with increased cancer risk and worse outcomes in cancer patients. This study adds to that body of knowledge by showing that cancer patients with multiple malignancies may be at particular risk for low vitamin D, especially during winter months. However, this study doesn’t prove that low vitamin D causes worse outcomes—it only shows an association. The findings align with the known seasonal pattern of vitamin D (higher in summer due to sun exposure) but provide new information about cancer patients specifically.

This study has several important limitations. First, it’s very small with only 38 patients, which limits how much we can generalize the findings. Second, it’s observational, meaning researchers simply measured vitamin D levels rather than testing whether giving vitamin D supplements actually helps patients. Third, the study doesn’t tell us whether the vitamin D differences actually affect patient outcomes or survival. Fourth, the study doesn’t explain why patients with multiple cancers have lower vitamin D—it could be due to lifestyle factors, treatment effects, or other health issues. Finally, the study doesn’t include information about sun exposure, diet, or whether patients were already taking supplements, which could all affect vitamin D levels.

The Bottom Line

Based on this research, vitamin D supplementation may be worth discussing with your oncologist if you are a cancer patient, particularly if you have a history of multiple cancers and live in a climate with limited winter sunlight. However, this recommendation has low confidence because the study is small and doesn’t prove that supplements actually improve outcomes. Do not start supplements without consulting your doctor, as vitamin D can interact with some medications and too much can be harmful.

Cancer patients, especially those with a history of multiple cancers, should be aware of this research and discuss it with their oncology team. People living in northern climates with long winters may find this particularly relevant. However, people without cancer history or those in sunny climates year-round may not need to make changes based on this single study. Anyone considering vitamin D supplementation should consult their healthcare provider first.

If you and your doctor decide vitamin D supplementation is appropriate, it typically takes several weeks to months to see changes in blood vitamin D levels. Benefits to overall health or cancer outcomes would take even longer to assess and would require medical monitoring.

Want to Apply This Research?

  • Track your vitamin D supplementation (if recommended by your doctor) with the date, dose, and time of day. Also note seasonal changes and any sun exposure. If your doctor orders blood work, record your vitamin D levels and the date tested to see if supplementation is working.
  • If your doctor recommends it, set up a daily reminder to take your vitamin D supplement at the same time each day. During winter months, try to get outside during midday hours when sunlight is strongest, even for 10-15 minutes. Keep a simple log of sunny days versus cloudy days to correlate with how you’re feeling.
  • Work with your healthcare team to get vitamin D levels checked periodically (typically every 3-6 months) to see if supplementation is maintaining healthy levels. Track any changes in energy, mood, or overall wellbeing alongside your vitamin D levels. If you’re a cancer patient with multiple malignancies, discuss with your oncologist whether vitamin D monitoring should be part of your regular care plan.

This research is preliminary and based on a small study of only 38 patients. The findings suggest associations but do not prove that vitamin D supplementation will improve cancer outcomes. Do not start, stop, or change any vitamin D supplementation without consulting your oncologist or primary care physician. Vitamin D can interact with certain medications and excessive amounts can be harmful. This article is for educational purposes only and should not be considered medical advice. Always work with your healthcare team before making decisions about supplementation, especially if you have a cancer diagnosis.