Vitamin D is an important part of any diet since it helps strengthen the bones by assisting the body in absorbing calcium. Thus, a deficiency of this vitamin is harmful, but fortunately the causes can usually be pinpointed so that this condition can be treated. One of the most common causes of vitamin D deficiency is lack of exposure to sunlight, as the sun promotes the body to make this nutrient. Certain diseases that deal with the digestive tract can also lead to the body's inability to absorb this vitamin properly. Of course, simply not consuming this vitamin over a long period of time can lead to an inadequate supply, such as vegetarians and vegans who do not replace animal products with vitamin supplements.
It may seem surprising that the sun can help the body make a certain nutrient, but the fact is that avoiding the sun completely is one of the main causes of vitamin D deficiency. For this reason, people who constantly wear clothes that cover their entire body, live far from the equator, or just rarely go outside during the day are all likely missing out on this important vitamin. Another related risk is having dark skin, as a high amount of melanin can decrease the reaction of the skin to the sunlight, resulting in the body making less vitamin D after sun exposure.
Anyone avoiding animal products for a long period of time, such as vegetarians and vegans, should add a vitamin D supplement to their diet since they are particularly at risk for a deficiency of this nutrient. Cheese, egg yolk, fish, fish oil, and liver are some of the foods with a high amount of vitamin D, and avoiding these products is one of the causes of vitamin d deficiency since it makes it difficult to get enough of this vitamin. Of course, fruits and vegetables also contain vitamin D, but few vegetarians and vegans eat enough of these foods to make up for the lack of animal products in the diet.
Some people get plenty of sunlight and eat lots of foods full of vitamin D, but they still have a deficiency. This is because the causes of vitamin D deficiency include certain conditions that reduce the body's ability to absorb this nutrient properly. Celiac disease, Crohn's disease, cystic fibrosis, and colitis are all known for not allowing the body to properly absorb this and other vitamins. Additionally, kidneys that are not functioning at their best, perhaps due to old age, also slow the absorption of vitamin D, which means that old age is one of the many causes of vitamin D deficiency, as well.