Vitamin D may have a protective association against chronic lymphocytic leukemia –but not lymphoma cancers on the whole — according to a new study published in the American Journal of Clinical Nutrition.
Lymphoma cancers make up about 3-4% of total cancers worldwide. In Europe, where this study took place, they are in the top 10 most frequent malignancies.
There are many types of lymphomas and thus “lymphoma” describes a group of cancers that predominately arise from B-cell lymphocytes (cells involved in your immune system). How lymphoma cancers arise is not well understood to date, but it is speculated that lymphoma arises when the immune system is disrupted from its regular functioning somehow.
Like many cancers, some studies have shown that sun exposure has a protective association against lymphomas, though research is mixed. If there is a protective effect of sun exposure, it could be by way of vitamin D. Vitamin D may help lymphocytes differentiate and avoid harmful proliferation, crucial processes in making sure cells function properly.
However, to date, the protective association of sun exposure has not been replicated for vitamin D levels. Only two studies have looked at vitamin D levels and lymphoma risk and neither found an association, protective or otherwise.
In this present study, researchers led by Dr Anna Luczynska of the University of Freiburg in Germany wanted to see if they could find a relationship between vitamin D and lymphoma.
They took a look at data from the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. This cohort consists of over a half million participants from 23 centers in 9 countries. Participants of this cohort enrolled between the years 1992-2000 and had blood samples drawn at baseline. Researchers are still following this cohort, sending out regular questionnaires about lifestyle habits and any conditions and diseases they have developed.
In this EPIC cohort, 1127 people have or have had lymphoma since baseline. Of the 1127 lymphoma cases, the more subtypes of lymphomas were as follows: Hodgkin lymphoma (n = 52); B-cell lymphoma (n = 949), a category that includes B-cell NHL (n = 699) and multiple myeloma (n = 250); T-cell non-Hodgkin lymphoma (n = 39); and lymphoma not otherwise speciﬁed (n = 87).
They matched these 1127 cases with healthy controls from within the same EPIC cohort. They wanted to know, if we pool controls and lymphoma cases together, do baseline vitamin D levels correlate at all with risk of getting lymphoma later in life?
Here is what they found:
- There were no differences between the mean vitamin D levels of people with lymphoma (23.6 ng/ml) and controls (24 ng/ml).
- When broken into quartiles of vitamin D levels, there was no protective association at having higher vitamin D levels compared to lower levels. In general, the risk of getting lymphoma was about the same in every quartile and not statistically significant.
- When the researchers looked at specific lymphoma types, they did find an association between chronic lymphocytic leukemia and vitamin D levels, however. When they looked at those who were diagnosed with chronic lymphocytic leukemia more than two years post-baseline, in those in the highest quartile of vitamin D, they had a 60% reduced risk of getting chronic lymphocytic leukemia compared to those in the lowest quartile of vitamin D levels (incidence rate ratio 0.40; 95% CI: 0.18, 0.90; p-trend = 0.05).
The researchers concluded,
“In conclusion, ﬁndings from the current investigation together with the results from previous prospective studies do not provide support for an inverse relation between plasma 25(OH)D and lymphoma risk. However, our data suggest that higher concentrations of 25(OH)D are associated with a reduced risk of chronic lymphocytic leukemia.”
They call for further research examining the relationship of vitamin D on specific lymphoma subtypes. It’s plausible, as seen in this study, that vitamin D plays a role in some subtypes, but not in others. We have discussed this before. One issue in studying vitamin D and specific subtypes is how rare each subtype is, which makes gathering enough data a difficult task.
For now, it looks like good vitamin D status may have a protective association against chronic lymphocytic leukemia, but not against lymphoma when subtypes are lumped together.