Adequate vitamin D levels in our blood are essential for maintaining balance for our body?s calcium metabolism and bone health. Severe deficiency results in rickets in children and osteomalacia and osteoporosis in adults.
Vitamin D deficiency is also a cause for depression, anxiety, fatigue and generalised musculoskeletal pain.
Low levels of vitamin D in our blood has been proposed as a risk factor for the development of many chronic diseases including Type 2 diabetes, cancer of the colon and prostate cancer. Studies looking into this area are however fraught with problems of interpretation. Therefore you can not be clear about any conclusions at the moment.
Many of the studies report observational data which examine a relationship between two variables. For example a relationship has been demonstrated between low levels of vitamin D and type 2 diabetes risk. Although interesting this does not prove cause and effect because there are many confounding factors that might influence that relationship.
It could be argued that because the diabetes population tend to be more overweight that it is the excess fat itself that is the cause of the low vitamin D levels rather than this low level causing the diabetes. Excess body fat could theoretically act as a sump or store for vitamin D thereby reducing the blood levels. Much work on these sort of variables is needed before we can draw conclusions.