The assertions by some researchers are that vitamin D is immunosuppressive while others argue that the vitamin activates the immune system. Those who promote Vitamin D supplementation view base their case on the fact that almost all vitamins protect the body against a good number of the never-ending syndromes (Lappe, 2007). However, this claim has not been supported by any research findings. Even researchers who have hypothesised all-encompassing supplementation with the substance have not fully understood the metabolism of the vitamin. This study tends to examine whether vitamin D contributes to the activation of the immune system or is immunosuppressive. The study will provide explanations on how vitamin D benefits the immune system or whether these explanations do not exist. Statement of the problem The realisation that there is a lack of knowledge and explanations of vitamin D metabolism has led to the need for further study. Most recently, vitamin D is viewed as the most essential vitamin particularly to the enhancement of the immune system (Lappe, 2007). Explanations on how it provides these benefits are lacking. In addition, the available rationalisations on how these benefits accrue are simplistic and imprecise. Thus, it has been established that lack of sufficient and reliable information linking immune system and the vitamin is a major problem for most academic researchers and professional nutritionists. It is such attributive relations that will be explored in this study. Research questions This cross-sectional study will be assessing whether vitamin D increases the activities of immune systems. Therefore, the conclusion of this study tends to answer the following questions:   * Does intake of food rich in vitamin D increases the individual immune system?   * Is there any improvement in the symptoms of the related diseases such as autoimmune with the increase in Vitamin D intake?   * What are other factors that might explain the symptom improvement with the increased intake of Vitamin D? Hypothesis to be tested This study will test the following hypothesis:   * H1: Vitamin D contributes to the activation of the immune system.   * Ho: Vitamin D do not contributes to the activation of the immune system or suppresses the immune system. The above stated hypotheses will be tested based on the collected data. If the null hypothesis is correct, it will be accepted while the alternative hypothesis will be rejected. Conversely, in case null hypothesis is found to be incorrect, it will be cast off whereas alternative hypothesis will be suitable. Literature review Early studies indicate that various forms of vitamins including vitamin D may possibly be defensive against persistent maladies (Marshal, 2008). These findings have not been confirmed by long-term studies and systematic reviews. However, Arnson et al. (2007) assert that patients suffering from autoimmune indicate lack of 25-hydroxyvitamin-D. Arnson et al. (2007) further argue that the consumption of foods that will help elevates 25-D or rich in vitamin D alleviate the symptoms of the autoimmune disease. Molecular biologists, Autier & Gadini (2007) have associated secosteroids with 25-D.