If you are a patient of mine, you’ve had your vitamin D tested. In my practice, it is mandatory, and I would like to share why I feel this way. I’m almost crazy about it. If you have cancer, or have a history of cancer, you should have your vitamin D levels tested at least once per year, and I’ll help you correct any deficiency you may have.
Humans obtain vitamin D from the sun through their skin. Depending on cultural habits, skin colour and altitude, different regions of the world have higher rates of vitamin D deficiency, like here in Canada. We can also get vitamin D through liquid or gel cap supplements.
The role that vitamin D plays in cancer was first discovered in 1981. As you will read about below, vitamin D has a major role in the immune system. Vitamin D has been linked to having a better response to chemotherapy and radiation therapy, lower recurrence rates, and even lower mortality rates. This has been found in many different cancers, including breast, pancreatic, colon, melanoma, esophageal, gastric, lymphoma and glioblastoma.
WHAT DOES VITAMIN D DO IN THE BODY?
Generally, vitamin D is important for regulating the immune system. It is classically known for increasing calcium absorption and having positive effects on bone structure. It has antiviral activity and helps fight infections, and decreases inflammation. It has been found in clinical trials to be beneficial for the treatment of psoriasis, type I diabetes, MS, inflammatory bowel disease, rheumatoid arthritis and even COVID.
With respect to cancer, it regulates the cell cycle causing cellular arrest and decreases growth of rapidly dividing cells (which happens in cancer!) and is involved in cell death, called apoptosis. It also decreases signalling in cancer cells that are involved in invasion and migration of cells, leading to decreased metastasis. Let’s look at some of the research below.
VITAMIN D DECREASES MORTALITY IN AGGRESSIVE CANCERS
The following recent studies have looked at the link between vitamin D levels and survival:
- a shorter overall survival was found in patients with non-small cell lung cancer who had vitamin D deficiency (1);
- a meta-analysis of 7718 patients with colorectal cancer showed a 33% decreased risk of mortality with vitamin D was high (2);
- in mantle cell lymphoma, vitamin D deficiency was associated with worse progression free survival and overall survival (3);
- deficiencies in vitamin D linked to increased progression and mortality in melanoma (4);
- a review of 303 women with breast cancer found increased mortality when the women were vitamin D deficient, regardless of lymph node status, stage or subtype (5);
- 5 year survival was significantly longer in stage I-III GI cancers (esophageal, gastric, colorectal) when vitamin D was optimal (6);
- statistically significant longer survival found in pancreatic cancer (7) and glioblastoma (8) with higher vitamin D levels;
- the VITAL trial followed 25,871 people with cancer over 5 years, and found that people who supplemented with vitamin D on a daily basis had decreased cancer specific mortality. The authors think this is due to vitamin D decreasing the risk of metastasis. When we decrease the risk of metastasis, we decrease the risk of recurrence (9).
VITAMIN D DECREASES SIDE EFFECTS AND INCREASES RESPONSE TO CHEMOTHERAPY
The following studies have looked at how vitamin D interacts with chemotherapy:
- having sufficient vitamin D levels correlates to a higher likelihood of having a pathologic complete response to chemotherapy in locally advanced breast cancer (10);
- vitamin D deficiency correlates with increased risk of radiation induced proctitis (11);
- low vitamin D is associated with chemotherapy induced peripheral neuropathy (12);
HOW TO TEST YOUR VITAMIN D LEVELS
You can ask your family doctor, or I can give you a requisition.
As stated previously, optimizing vitamin D levels is critically important and one of the easiest factors to test and correct if needed. If you have cancer or have a history of cancer, I recommend getting your vitamin D tested at least once yearly. Please contact me if you are overdue for your vitamin D screening test.
(1) Mak et al. Cancer Biomark, 2017;18(3):297-303.
(2) Maalmi et al. Nutrients, 2018;10(7):896.
(3) Xu et al. J Cancer Res Clin Oncol, 2020;146(4):1003.
(4) Slominski et al. Lab Invest, 2017;97(6):706.
(5) Thanasitthichai et al. Asian Pac J Cancer Prevention, 2019;20(10):3101.
(6) Yonaga et al. Nutrients 2019;11(10):2547.
(7) Yuan et al. J Clin Oncol, 2016;34(24):2899.
(8) Elmaci et al. Metab Brain Dis, 2019;34(3):687-704.
(9) Br J Cancer, 2020; 123(8): 1205.
(10) Viala et al. BMC Cancer, 2018;18:770.
(11) Int Radiat Oncol Biol Phys, 2015;92(3):613.
(12) J Clin Med, 2022;11(2): 355.