Are you getting enough vitamin D?

Vitamin D is special: it is the vitamin which (in contrast with others) rarely comes from food. It is called the “sunshine vitamin” for a reason: its primary source is sunlight exposure.

This makes a recent research initiative very relevant for all of us to consider how much vitamin D we may have.
In particular, the Cork Centre for Vitamin D and Nutrition Research has published a very interesting map of “Vitamin D deficiency” across some parts of Europe:

Copyright Cashman & Higgins 2016

Some highlights from the researchers' map:

Not surprisingly, inhabitants of countries further north are more likely to have higher vitamin D deficiency.
There appears to be discrepancy across measures of vitamin D even within the same country or area.
More than 1 in 5 people in the United Kingdom have vitamin D deficiency (based on a measurement in children and adults, and among children and teenagers).
Ireland is performing “low in vitamin D” as well, with 10-15% lacking this vitamin, based on this study.
Children and teenagers in Germany do not always have enough: 10-15% are deficient, while adults seem to have even less (15-20% deficiency rate)- at least based on these studies.
Although one would expect that people living in Iceland would have very low vitamin D levels, apparently only 5-10% of them are lacking enough vitamin D.
On the other extreme, even people in sun-kissed Greece are suffering from low vitamin D levels: 4.2% of children & 5.1% of children and teenagers.

What does this mean for breast cancer patients?

It is not easy to draw a singular conclusion from this map; however, it is clear that there are significant levels of vitamin D deficiency in many parts of the world. Therefore, while where you live would be a good indication about your personal vitamin D levels, it is not unlikely that you would have less than necessary.

Regardless of our health status, vitamin D is important because some studies indicate that it may:

help metabolise calcium and phosphorus
support bone and teeth health
help strengthen the immune system.

While vitamin D is important for everyone, those of us with a breast cancer diagnosis may need to be more diligent about its levels. This is because, beyond its positive impact on overall nutritional balance and our immune system, cancer and/or its treatments may affect our bone health.

Managing side effects on bone health

Some breast cancer treatments (like medications called “aromatase inhibitors”) may have an unintended impact on bone health. For instance, they can affect bone density which could even lead to fractures.

For breast cancer patients, medical teams would usually examine their bone health before treatment starts, and periodically afterwards. Depending on the outcome, patients may receive specific treatment, calcium, vitamin D supplements, or a combination of these, in order to help maintain or improve bone health.

Of course, if you are concerned about your bone health and cancer treatments, it is always a good idea to talk to your doctor and medical team.

Pain in the joints and muscles

While there is no such a thing as a “silver bullet” against these side-effects, researchers are always striving to understand how patients can cope with them. There are, therefore, many papers evaluating such impact. One of them is focusing on breast cancer patients taking a particular medication, and found that high levels of vitamin D can reduce joint and muscle pain. If interested, you can read the report from this 2011 study; you can also read the corresponding publication.

Main vitamin D sources

As mentioned, the sun is the primary source of vitamin D (although it is important to be aware of the risks of skin cancer and melanoma).

Beyond sunlight, however, vitamin D comes from the following foods:

Mushrooms (mainly vitamin D₂)
Beef liver (mainly vitamin D₃)
Fish liver oils (vitamin D₃)
Fatty fish, like salmon, mackerel, tune, sardines (vitamin D₃).

While vitamin D supplements do exist, it is generally better to get vitamins from natural sources.

Always speak to your medical team

Please make sure you keep your medical team informed about your concerns, other medications, supplements, and any issues throughout your care: they are the best equipped to provide you with the right advice based on your specific situation.

Further studies and references

In a study from 2012, researchers find that the current recommendations of 20ng/ml for vitamin D may be insufficient to ensure good bone health for breast cancer patients taking aromatase inhibitors.
A New Zealand study published in 2014 highlighted that the general population taking vitamin D supplements only reduces skeletal or non-skeletal outcomes by no more than 15%.
A 2013 study indicates that it is inappropriate to use vitamin D for osteoporosis prevention without specific risk factors for its deficiency.

For further information on breast cancer, read our articles on triple-negative breast cancer, diet and nutrition & Body Mass Index and breast cancer.