Researchers studied over 1,200 cancer patients in China to measure their vitamin levels using advanced lab tests. They found that most cancer patients were missing important vitamins, especially vitamin D and B vitamins. The most important discovery: patients who didn’t have enough vitamin C had worse survival rates than those with normal vitamin C levels. This suggests that checking vitamin levels in cancer patients might be an important part of their care, and vitamin C deficiency could be a warning sign that doctors should pay attention to.

The Quick Take

  • What they studied: Whether cancer patients have lower vitamin levels than healthy people, and if low vitamins are connected to how well cancer patients survive
  • Who participated: 1,257 cancer patients at a major cancer hospital in China. For the survival analysis, 510 patients with advanced cancer (stage IV) were followed
  • Key finding: About 9 out of 10 cancer patients didn’t have enough vitamin D, and about 4 out of 10 didn’t have enough vitamin C. Patients lacking vitamin C had a 41% higher risk of dying compared to those with normal vitamin C levels
  • What it means for you: If you have cancer or know someone who does, vitamin C levels might be worth checking. Low vitamin C appears to be linked to worse outcomes, though more research is needed to prove that taking vitamin C supplements will actually help

The Research Details

This was a prospective cohort study, which means researchers followed cancer patients forward in time and collected information about them as they progressed through treatment. When patients entered the cancer center, doctors took blood samples and measured their vitamin levels using a special lab technique called liquid chromatography-tandem mass spectrometry (LC-MS/MS). This is a very accurate way to measure vitamins—much better than older methods. The researchers also recorded information about the patients’ cancer stage, nutritional status, and how long they survived. They followed patients with advanced cancer (stage IV) to see how their vitamin levels connected to their survival rates.

The special lab test used in this study is important because it can measure vitamins more accurately than traditional methods. This means the researchers could trust their vitamin measurements. By following patients over time and measuring their vitamins at the start, the researchers could see whether low vitamins were connected to worse outcomes. This type of study is stronger than just comparing sick and healthy people at one point in time.

This study has several strengths: it included over 1,200 patients, used highly accurate lab testing, and followed patients to track real health outcomes like survival. However, the study was done in one hospital in China, so results might be different in other countries. The researchers adjusted their analysis for other factors that could affect survival, which makes the results more reliable. The main limitation is that this study shows a connection between low vitamin C and worse outcomes, but doesn’t prove that vitamin C deficiency actually causes the problem—it could be that sicker patients naturally have lower vitamin C

What the Results Show

Vitamin deficiencies were extremely common in cancer patients. About 89% didn’t have enough vitamin D, 81% were low in vitamin B1, 54% lacked folic acid, and 41% had low vitamin C. These deficiencies were much more common in cancer patients than in healthy people used for comparison. Interestingly, the level of vitamins didn’t seem to be directly connected to how advanced the cancer was or how malnourished the patient appeared to be. The most important finding was about vitamin C: patients with low vitamin C had significantly shorter survival times. Specifically, patients with vitamin C deficiency had a 41% higher risk of death compared to those with normal vitamin C levels. This connection remained strong even after researchers adjusted for other factors that could affect survival, like age and cancer stage.

The researchers measured other vitamins including vitamin D, vitamin B1, and folic acid, but these didn’t show the same strong connection to survival outcomes. This suggests that vitamin C deficiency may be uniquely important as a warning sign in advanced cancer patients. The fact that vitamin deficiencies weren’t directly related to cancer stage or visible malnutrition suggests that vitamin levels provide additional information that doctors might not pick up from standard assessments.

Previous research has suggested that vitamins play a role in cancer development and survival, but this study provides clearer evidence using better measurement methods. The finding that vitamin C specifically matters for survival is new and important. The high rates of vitamin deficiency in cancer patients match what other studies have found, confirming that this is a real and widespread problem in cancer care.

The study was conducted at one hospital in China, so results might not apply to all cancer patients worldwide. The study shows that low vitamin C is connected to worse outcomes, but it doesn’t prove that vitamin C deficiency causes the problem—it’s possible that very sick patients naturally have lower vitamin C. The study didn’t test whether giving vitamin C supplements would actually improve survival. The researchers only measured vitamins at one point in time, so they couldn’t see how vitamin levels changed during treatment

The Bottom Line

For cancer patients, especially those with advanced disease: Ask your doctor to check your vitamin levels, particularly vitamin C (moderate confidence). If you’re deficient, discuss with your healthcare team whether supplementation might help (low confidence—more research needed). For the general population: This study doesn’t provide guidance for cancer prevention through vitamins, as it only studied patients who already had cancer

Cancer patients should care about this research, especially those with advanced cancer. Oncologists and nutritionists treating cancer patients should consider adding vitamin screening to their standard care. Healthy people shouldn’t use this as a reason to take high-dose vitamin supplements, as the study doesn’t address cancer prevention. People with other serious illnesses might also benefit from vitamin screening, though this study only looked at cancer

If vitamin C deficiency is corrected, benefits wouldn’t be immediate. Survival improvements, if they occur, would likely take weeks to months to become apparent. This is why ongoing monitoring and follow-up care are important

Want to Apply This Research?

  • If you have cancer and your doctor has checked your vitamin levels, track your vitamin C status monthly and note any changes in energy levels, appetite, or how you feel during treatment. Record the date of vitamin level checks and the results
  • Work with your healthcare team to develop a vitamin supplementation plan if deficiencies are found. Use the app to set reminders for taking supplements and to log when you take them. Track any dietary changes recommended by your nutritionist to increase vitamin C intake through foods like citrus fruits, berries, and vegetables
  • Set quarterly reminders to discuss vitamin status with your oncology team. Track trends in your vitamin levels over time if repeat testing is done. Monitor how you feel and any changes in treatment tolerance, which might be connected to nutritional status. Keep a record of all supplements and medications to share with your healthcare providers

This research shows a connection between vitamin C deficiency and worse outcomes in advanced cancer patients, but does not prove that vitamin C supplements will improve survival. Cancer patients should not start, stop, or change any supplements without discussing it with their oncologist first. Vitamin supplementation decisions should be made in consultation with your healthcare team, as some supplements may interact with cancer treatments. This study was conducted in one hospital in China and results may not apply to all populations. Anyone with cancer should work with their medical team on all nutritional decisions.