Vitamin D is important for strong, healthy bones and good overall health throughout life. Calcium and phosphorous are essential for developing the structure and strength of bones, and our bodies need vitamin D to absorb these essential minerals. Furthermore researchers are now discovering that, in addition to maintaining strong bones, vitamin D may be also important in helping us to fight infection and in making sure that our muscles, heart, lungs and brain are healthy.
The main source of vitamin D for humans comes from the action of sunlight on the skin. A metabolite called cholecalciferol is produced under the skin on exposure to ultraviolet blue (UVB) sunlight. Cholecalciferol then undergoes a number of chemical changes in the body to produce the active form of vitamin D.
However, several environmental factors, such as latitude (distance north or south from the earth’s equator) or the weather influence whether sunlight of sufficient strength is available for the body to make vitamin D. Also, personal factors such as skin colour, age, clothing, use of sun screen, and time spent outdoors will all influence how much vitamin D the body can make.
Vitamin D can be obtained from foods in the diet. However, for most people, the amount of vitamin D provided in the diet is low. This is because very few foods contain high levels of vitamin D naturally. Oily fish such as salmon, tuna, and mackerel and fish liver oils are among the best sources of vitamin D but are not commonly eaten. Small amounts of vitamin D are found in meat, dairy foods and eggs. Some foods have vitamin D added, such as certain milks, margarine, breakfast cereals, breads and others, but the foods that are fortified with vitamin D differs by country.
Vitamin D supplements do help meet vitamin D needs in those who take them, however, supplement use is voluntary and tends to be highest amongst young children and older people and lowest amongst children, teenagers and young adults, who are also at risk of deficiency.
To read more about the research being carried out in the vitamin D-focused ODIN project, click here.