How much vitamin D do we need?
The average Vitamin D intake according to the National Health and Nutrition Examination Survey (NHANES) was about 10.8 micrograms/day, but this varies based on age, sex, and season. Most people don't need much of it; an average adult should get a daily vitamin D requirement of around 600 IU from food sources alone.
Vitamin D is created when the skin is exposed to ultraviolet B rays (UVB) from sunlight. The body converts cholesterol to vitamin D 3 in skin cells through a process called "photolysis". The liver also produces approximately 25% of the body's vitamin D 2 by metabolizing 25-hydroxycholecalciferol (25-OH-D). Dietary sources of vitamin D include eggs, cod liver oil, fortified milk, some cereals and spreads, fatty fish such as tuna and salmon, and whole milk. Vitamin D 3 can be found in plants and mushrooms.
Vitamin D is good for bones and preventing cancer. General recommendations for Vitamin D are that the body gets at least 1,000 IU per day. For most people this will come from eating a combination of foods, however many people still are deficient in Vitamin D.
There are many skin problems that have been associated with too little Vitamin D and it should be taken to prevent rickets and other bone deformities.
Several countries are considering adding a dietary supplement for adolescents containing 10 micrograms of active form of vitamin D per day. A study found that many girls in the US are deficient in vitamin D. It is recommended that dietary intake increases and that supplements should be a part of the equation for all individuals (especially those at great risk of deficiency).
The two main forms of vitamin D are ergocalciferol (vitamin D 2 ) and cholecalciferol (vitamin D 3 ). Vitamin D 2 is produced from ergosterol, which is found in plants, whereas vitamin D 3 is produced when skin is exposed to sunlight. Both forms modify calcium absorption in the intestine. Vitamin D may also occur as calcitriol, which is activated to the hormone 1,25-dihydroxycholecalciferol. Vitamin D is a steroid hormone derived from cholesterol.
Vitamin D deficiency is an international public health problem. In North America, the United Kingdom, and other developed countries 7-44% of children ages 5–16 are vitamin D deficient according to NHANES data. Vitamin D deficiency has been reported in cases of congenital hypophosphatemia and systemic calcification including osteomalacia (Type I), due to a lack or insufficiency of calcium absorption from the intestines. The Institute of Medicine estimates that up to 80% of adults in some parts of the United States have inadequate intake levels.
Make sure you get plenty of sunshine and a good vitamin D supplement.
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