Vitamin D is an essential fat-soluble vitamin, a steroid derivative, mainly through sunlight irradiation by the transformation of 7-dehydrocholesterol in the skin, known as the “sunshine vitamin”, but also from milk, fish, lean meat, eggs, mushrooms, animal liver and other food intake. Vitamin D synthesis and metabolism are closely related to age, gender, race and skin color, seasons and dietary intake characteristics, etc. Its deficiency has now become a global public health problem. Studies have shown that vitamin D deficiency is not only associated with a variety of chronic metabolic diseases such as bone fractures, osteoporosis, autoimmune diseases, obesity, diabetes, and cardiovascular disease, but also with a variety of tumors, including colorectal, breast, prostate, pancreatic, and lung cancers. A number of clinical studies have shown a significant correlation between vitamin D levels and prognosis in cancer patients. Exposure to sunlight and increased intake of foods such as milk, fish, lean meat, eggs, mushrooms, and animal liver will help to increase the level of vitamin D in the body.