Typically, vitamin D has different variations. Some of them are active in nature, whereas some are not. For example, calciferol is the most active variation of vitamin D. Our liver and kidney help in converting vitamin D to its most essential hormone variety. When we consume vitamin D from our diet or we produce it in our skin, vitamin D needs to be converted into 1, 25 dihydroxyvitamin D, which is the most active physiological variety of vitamin D. The activated vitamin D functions like a hormone by sending neural messages to the intestine in order to boost up the assimilation of phosphorous and calcium.

Vitamin D functions by maintaining a balance of calcium and phosphorous in the blood level. By enhancing calcium absorption, vitamin D aids in developing and preserving bone strength. Vitamin D functions in addition to other helpful nutrients to enhance bone mineralization. To keep the bone structure firm and strong, vitamin D is a must need nutrient. Without the presence of vitamin D, our bones become thin and fragile. A deficiency in vitamin D may cause rickets in children and osteomalacia in adults. These are two types of bone disorder in which bones become weaker.

Long term restricted breast feeding practice without proper vitamin D supplementation may lead in developing reemergence of rickets. A decrease in outdoor activity and insufficient sun exposure may also trigger in developing rickets in infants.

Vitamin D functions at cellular level as well. It manages cell development and differentiation. It also aids in maintaining healthy immune system.

Some scientific studies also suggest that potential vitamin D functions like a protective shield against various forms of cancer, however, more clinical trials are needed to determine its actual relevance.

Vitamin D functions as an integral supplement in treating Alzheimer's patients. It is due to the fact that these patients lack outdoor activities, so their natural level vitamin D synthesis may get hampered.

Fortified foods can be considered as one of the wise vitamin D natural source. During 1930s, rickets was a primary health complication in US and it turned out as an epidemic. By that time, a milk fortification program was implemented to fight against rickets. This implementation was a success and it nearly eradicated this complication in the US . Nearly 98-99% milk is fortified with vitamin D supplements in the US . However, milk derivatives such as cheese and ice creams are not fortified as it is with milk. So these products contain only a small amount of vitamin D in it.

Our mother nature is generous in vitamin D natural source. There are wide varieties of natural foods that contain vitamin D in it. These are cod liver oil, salmon, mackerel, tuna fish, sardines, egg, beef liver, and many others. We can easily avail vitamin D from cheese and pudding prepared from fortified milk.

Sun exposure can be considered as the most important vitamin D natural source. It offers us plenty amount of vitamin D that we actually need for our body. Ultraviolet rays from the sun activate the synthesis of vitamin D in our skin area. The intensity of sunlight, humidity, season, smog, cloud and geographical latitude affect vitamin D synthesis in our body. We all need to expose ourselves to the sunlight in order to receive benefits from vitamin D synthesis.

There is potential health risk associated with the excessive usage of vitamin D supplements. The adverse effects may include poor appetite, nausea, constipation, vomiting, weakness and weight loss. It can also boost up calcium levels in the blood stream causing various psychological complications such as confusion, depression and irritation.