Vitamin D is a fat-soluble vitamin and is sometimes called the sunshine vitamin because your body can typically produce vitamin D from exposure to UV rays. However, if you do not spend enough time outdoors, you may not get the recommended amount of vitamin D. In order for your body to use the vitamin D from your foods, you need to absorb it through your digestive system.
Absorption of Vitamin D
Dietary vitamin D is absorbed in the small intestine through the small hairlike projections called villi. It is a fat-soluble vitamin, so it is absorbed along with fat from your diet. Patients who are not able to absorb fat, such as cystic fibrosis patients, will have difficulty absorbing vitamin D. Also, patients who have had small bowel surgery may not be able to absorb vitamin D from dietary sources.
Functions of Vitamin D
Absorption of adequate vitamin D is important because it plays many roles in your body. One function of vitamin D is that is helps absorb calcium in the digestive system. It also helps maintain the proper levels of calcium and phosphorus in the blood. Vitamin D is also needed for proper bone growth and for bone remodeling.
Deficiency of Vitamin D
A deficiency of vitamin D can occur if you are not exposed to enough UV light or if you do not absorb enough vitamin D from your diet. Vitamin D deficiency in children can lead to a condition called rickets. Children with rickets have soft and weakened bones. Adults who do not have enough vitamin D may develop osteoporosis. This condition is characterized by thinning of the bones that become prone to fracturing.
Recommended Intake
The Institute of Medicine recently revised the recommended intake for vitamin D. The vitamin D recommendation for adults ages 19 to 70 is 600 IU per day. For adults ages 71 and older, 800 IU of vitamin D is recommended. The recommendation for pregnant and lactating women is 600 IU per day.
Sources of Vitamin D
Your body can make all the vitamin D it needs when you are exposed to UV light. The UV rays start a chemical transformation in your skin that eventually produces active vitamin D. Vitamin D is found naturally in very few foods. It is found in fatty fish such as mackerel, sardines and tuna and is also found in egg yolks. Vitamin D has also been added, or fortified, to many different food products, such as milk, orange juice and cereal.
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