Vitamin D is a fat-soluble vitamin that our bodies can produce when our skin is exposed to the sunlight.   We can also get it from some foods such as fish, fish oil (especially cod liver oil), and eggs.  It is considered a hormonal vitamin because there are receptors for vitamin D in the body. In fact, every cell has vitamin D receptors on its surface.  When vitamin D binds to these receptors, various processes occur – and scientists are still trying to figure out what vitamin D does in some organs. The function that most of us have heard about is the role of vitamin D in bone health and absorption of calcium. Indeed, the daily recommended amount of vitamin D from the World Health organization is based on its bone health function, namely the level needed to prevent rickets. However, this vitamin has many other roles in the body including involvement in inflammation, immunity, hormonal balance, blood sugar regulation, the gut microbiome, and cancer. It appears that adequate functions of these systems require higher levels of vitamin D than are needed to prevent rickets.

Vitamin D deficiency is very common for reasons including living in northern latitudes when exposure to sunlight is limited particularly in winter; use of sunscreen; skin pigmentation; bodyweight/obesity; and gut disorders preventing absorption of dietary vitamin D.

The role of vitamin D in cancer prevention is emerging as a good reason for us to measure our vitamin D levels and supplement when necessary. In large studies, it has been shown that people with the lowest levels of vitamin D are at increased risk of developing colon, breast, prostate, pancreatic cancers, as well as non-Hodgkins lymphoma. The low levels are also seen to be linked to higher cancer deaths.

Vitamin D levels have also been recognized to be prognostic biomarkers in breast cancer.  This means that our vitamin D levels at diagnosis of cancer can predict the likely outcome of breast cancer.  So what exactly does the research show?

In a study [1] on 1800 early breast cancer patients, researchers found that:

  • Lower vitamin D levels (<20 ng/ml) significantly correlated with larger tumor size at diagnosis, but there was no correlation with lymph node invasion, receptor status (estrogen positive, HER2 positive, triple negative, etc.), or tumor grade.
  • Higher vitamin D levels (>30ng/ml) at the time of breast cancer diagnosis significantly correlated with improved overall survival.
  • In post-menopausal women, the relapse rate of patients (i.e. cancer returned) at roughly five years was 7.8% for those with low vitamin D levels compared to 5.6% for higher vitamin D levels. No correlation was seen in pre-menopausal women.
  • The risk of distant metastases in post-menopausal women decreased by 66% in those with vitamin D levels >30ng/ml, compared to those with less than 30ng/ml.

What comes out of these studies is that we should know what our vitamin D levels, and then, depending on the results, we can decide whether we need to increase our levels. Often increasing the levels is easiest using supplementation.

But it does get confusing as different organizations have different guidelines for the levels of vitamin D that are sufficient. Here are some of the guidelines:

  Vitamin D Council Endocrine Society Testing Laboratories
Deficiency 0-30 ng/ml 0-20 ng/ml 0-31 ng/ml
Insufficiency 31-39 ng/ml 21-29 ng/ml
Sufficiency 40-80 ng/ml 30-100 ng/ml 32-100 ng/ml
Toxicity >150 ng/ml    

The goal I generally use for anti-cancer effects is 45-65 ng/ml, based on studies of different types of cancer.

Image shows bright yellow sunflowers

You can ask your doctor to test your vitamin D level for you, or else you can get a home test kit, where you send off a finger prick blood sample to the laboratory. The Vitamin D Council has an in-home kit for $50 but also lists other testing labs on its site that can do the test.  The vitamin D council website has lots of great information too, so is worth exploring.

Your result will suggest whether you need supplementation and at what level. A supplement that I like is this liquid one by Biotics as it is formulated in an emulsion (i.e. already dissolved in fat) to help absorption, and is easy to take.  Each drop contains 2000 IU of vitamin D. I place the drop(s) on the back of my hand and then just lick it off. I find it easier than putting a drop directly on my tongue, as I can’t see how many drops are coming out.

As vitamin D is involved in many different aspects of health, I highly recommend you test your blood level and see whether you need supplementation. Then after supplementing, test again and see if your levels are adequate, and adjust if necessary. And of course, enjoying time outside in the sunshine is a great way to increase your levels too.  What will you do this Easter weekend to get outdoors? I’m going hiking tomorrow – will I see you on the trails?[1] Hatse S, Lambrechts D, Verstuyf A, Smeets A, Brouwers B, Vandorpe T, Brouckaert O, Peuteman G, Laenen A, Verlinden L, Kriebitzsch C, Dieudonné AS, Paridaens R, Neven P, Christiaens MR, Bouillon R, & Wildiers H (2012). Vitamin D status at breast cancer diagnosis: correlation with tumor characteristics, disease outcome, and genetic determinants of vitamin D insufficiency. Carcinogenesis, 33 (7), 1319-26 PMID: 22623648

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