Sunlight is the most common source of vitamin D.
Serum 25(OH)D levels are lower in people who use sunscreens and in those with pigmented skin.
A practical and common recommendation for required vitamin D from sunlight is 5 to 15 minutes of sun exposure from the hours of 10 AM to 3 PM in the spring, summer, and autumn at least two times per week to the face, arms, hands, or back. This is usually enough for people with most skin types to maintain required vitamin D levels .
After this exposure,aplly sunscreen to limit solar skin damage. Therefore, it is important to remember that while harmful UV rays from sunlight can increase skin cancer risks, blocking these UV rays can predispose individuals to vitamin D deficiency.
If sufficient sunlight is not obtained, dietary sources of vitamin D can be utilized. Dietary sources of vitamin D include:
Fatty fish such as salmon, mackerel, and sardines which provide 300 to 600 units/3.5 ounces,
Egg yolks which provide 20 units/yolk, and cod liver oil which provides 400 units/teaspoonful.
The most common dietary source of vitamin D is found in fortified foods such as milk, orange juice, and some cereals which provide about 100 units per serving.
Due to the relative lack of vitamin D-containing foods, supplements of vitamin D are often necessary to achieve an adequate intake.
The National Osteoporosis Foundation (NOF) recommends an intake of 800 to 1000 international units (IU) of vitamin D3 per day for adults over age 50.
The safe upper limit for vitamin D intake for the general adult population was set at 2,000 IU per day in 1997 .
References:
Sunyecz JA. The use of calcium and vitamin D in the management of osteoporosis. Ther Clin Risk Manag. 2008;4(4):827-836. doi:10.2147/tcrm.s3552.