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).