Vitamin D is a fat soluble vitamin, meaning it is stored and transported in fat and the body can store it. Vitamin D comes from two sources: food and sunlight. The skin can synthesize vitamin D from UVB rays from the sun (UVB rays are the ones responsible for sunburn). Food sources include salmon, sardines, mackerel, milk, fortified cereal, fortified orange juice, and eggs. Other fortified foods may also have smaller amounts of vitamin D.
Vitamin D has many functions in the body and may actually act more like a hormone than a vitamin. The most well-known function of vitamin D is to help the body use and absorb calcium for bone health. Vitamin D is also important for immunity, prevention of cancer, blood pressure regulation, and insulin secretion. There is some research out there about vitamin D's role in muscle strength, depression, heart disease, prevention of diabetes, and autoimmune disease prevention.
Vitamin D recommendations were changed in 2010. Some experts still argue that the recommendations are not high enough. Vitamin D recommendations are measured in IU, or International Units, which is just a unit of measure. Recommendations for vitamin D are:
- Infant up to 12 months - 400 IU
- Children and adults (age 1 to age 70) including pregnant and breastfeeding women - 600 IU
- Adults age 71 and up - 800 IU
It is tough to get the recommended amount of vitamin D from food alone. That's where the sun comes in handy. Although it is a good idea to wear sunscreen when in the sun, that prohibits the skin from receiving the UVB rays it needs to make vitamin D. Just 5-10 minutes in the sun (without sunscreen) three times a week will a fair skinned person all the vitamin D they need. If sunburn is a concern within that short amount of time, then sunscreen is necessary and a supplement may be useful. Here in Missouri, we cannot get vitamin D from the sun's UVB rays between November through March, so a supplement may be needed during that time.
Some groups are at risk for vitamin D insufficiency:
- Breast-fed infants - because breast milk does not have enough vitamin D, a supplement may be necessary, ask your physician.
- Individuals with dark skin - dark skin does not synthesize vitamin D as well, more sunlight or a supplement may be necessary.
- Older adults - older adults do not synthesize vitamin D in their skin as well and they may spend more time indoors (especially if in a care facility), a supplement may be necessary.
- Obesity - obesity increases the risk of vitamin D deficiency, because more body fat stores make stored vitamin D less available, a supplement may be necessary.
Vitamin D supplements are fairly inexpensive and have a range of amounts from 400 IU to 2,000 IU. The Linus Pauling Institute recommends the following supplement amounts:
- Infants - 400 to 1,000 IU daily
- Children - 600 to 1,000 IU daily
- Adults - 2,000 IU daily
The American Academy of Pediatrics recommends a supplement of 400 IU of vitamin D daily for infants, children, and adolescents. Of course, a supplement may not be needed in the months of April through October if they are getting a small amount of sunlight (without sunscreen for a short time). If sunburn is a concern within that short amount of time, then sunscreen is necessary and a supplement may be useful.
In healthy individuals, vitamin D toxicity is unlikely in amounts under 10,000 IU. This could only occur from a supplement, vitamin D from the sunlight will not cause toxicity. The upper level intakes are set conservatively for vitamin D, but they are:
Infants (0 to 6 months) - 1,000 IU
Infants (6 to 12 months) - 1,500 IU
Children (1 to 3 years) - 2,500 IU
Children (4 to 8 years) - 3,000 IU
Children (9 and up) and all adults - 4,000 IU
As with any supplement for adults or children, you should consult with your health care provider before beginning vitamin D supplementation.
Reference:Linus Pauling Institute, vitamin D