Vitamin D May Impact Colorectal Cancer Outcomes

A recent analysis of 14 studies found that patients with colorectal cancer (CRC) who had a vitamin D deficiency tended to have poorer mortality outcomes than those who supplemented with vitamin D.

In an interview with CURE®, Laura A. Bolte, of the department of gastroenterology and hepatology at the University of Groningen and University Medical Center Groningen in the Netherlands, discussed these findings, and what patients need to know about vitamin D intake.

A recent study found that more than half of patients with cancer are deficient in vitamin D. Do you have a theory or are there hypotheses as to why this is so?

The major source of our vitamin D comes from our own production in the skin, which requires ultraviolet rays from sunlight to form vitamin D3. The liver and the kidneys are then needed to create the active form of vitamin D. As a consequence, higher sedentary time and less physical activity outdoors have been identified as risk factors for vitamin D insufficiency in general. Malabsorption could play a role in some cancer types as does chronic kidney or liver disease.

What effect can vitamin D have on cancer outcomes?

The authors performed a joint analysis of previous studies that investigated the relationship between vitamin D intake and mortality (overall risk of dying). The study showed that vitamin D intake is associated with a 12% lower mortality.

The study did not look at the effect of vitamin D on treatment outcomes, which is another really interesting area of research.

Are there any symptoms of vitamin D deficiency in people with cancer? Should patients be tested for it?

Vitamin D is essential for bone mineralization and to prevent osteoporosis. Medications such as corticosteroids (sometimes used in cancer patients, for example to treat side effects of immunotherapy) can increase the risk for osteoporosis; in these cases, vitamin D/calcium supplementation may be indicated.

(Being) underweight and malnourishment further increase the risk for osteoporosis. Moreover, vitamin D is important for the immune system!

Should patients take a vitamin D supplement, and if so, how can they know what kind and dosage to take?

A uniform dose is unlikely to fit all patients. The dose should be discussed with the treating physician based on each patient’s personal medical history, blood levels and age and body weight.

So far, studies do not show a clear dose-response relationship for cancer outcomes.

Moreover, depending on genetic factors, different doses may lead to the same serum level.

The study you mentioned suggests that keeping vitamin D levels at consistent levels is more beneficial in terms of survival than taking high dose vitamin D periodically.

Is there anything else you’d like patients to know?

The study you mentioned focused on mortality. It is important to also look into what drives cancer development and how we can prevent it. Why does the incidence of CRC increase in parts of the world where it has been low? Why do we see CRC at an earlier age then we used to? In this regard, studies of environmental factors including diet, also in relation with the gut microbiome, are important.

(For those diagnosed with cancer), now we’ve discussed a study looking at mortality, the next important question would be: is vitamin D implicated in a measurable decrease in tumor size? And, since it has an important role for the immune system, can it synergize with cancer immunotherapies? (I.e. the treatment of cancer through drugs that enhance an immune response against cancer)

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