Cancer:
Many epidemiological studies showed higher prevalence of some type of
cancers in those geographical locations which observe less sun exposure
throughout the year (80). The 50 ng/mL and 30 ng/mL of vitamin D were
found to be associated with 60% and 33% decreased risk of colorectal
cancer, respectively, and more than 50 ng/mL of vitamin D was found to
have preventive role (81). Other studies also showed that the UVB
exposure and vitamin D are associated with lower cancer risk and higher
survival from cancer (82).
In Pakistani population, several studies have been conducted to probe
the link between vitamin D deficiencies with incidence of some cancers.
Breast cancer is a common cancer type in the women of this country (83,
84). Studies conducted in different parts of this country showed
negative association of vitamin D levels with breast cancer incidences.
In one of the study, 42 newly diagnosed breast cancer subjects were
found vitamin D deficient (85). In Lahore, 300 newly diagnosed pre and
post-menopausal women belonging to different parts of the Punjab
province showed positive association with vitamin D deficiency and the
tumor size in breast cancer (86). However, tumor grade and stage were
not associated with vitamin D levels in this study. A study conducted in
90 newly diagnosed breast cancer patients in Lahore showed association
of breast cancer with low vitamin D levels (87). Another study to
understand the onset of breast cancer in women with the relevance of
dietary habits, dress style and sun exposure showed that vitamin D
deficiency was more prevalent in breast cancer patients (88).
A study to assess the effect of vitamin D supplementation in breast
cancer risk showed that the odds of breast cancer were more significant
in the subjects which were not taking vitamin D supplement (89). A cross
sectional study to evaluate BMI, bone markers and vitamin D status in
the newly diagnosed breast cancer patients showed low levels of vitamin
D in the subjects (90). Another study conducted in Multan, South Punjab
also showed that 90% breast cancer patients had vitamin D deficiency
(91).
Instead of breast cancer, vitamin D deficiency has been studied in
leukemic patients. One study showed vitamin D deficiency was prevalent
in patients of B-chronic lymphoid leukemia (92). Another study showed
that after remission-induction chemotherapy, this deficiency was
increased as compared with subjects with no chemotherapy (93).