Skin makes vitamin D when it is exposed to sunlight, therefore Vitamin D is commonly called “Sunshine vitamin.” Vitamin D deficiency is considered to be the most common nutritional deficiency and often one of the most commonly undiagnosed medical conditions in the world. The prevalence of vitamin D deficiency in young children is around 50–90% in the Indian subcontinent. In adults the deficiencies can be found in 70 out of 100 people.
The two main ways to ensure you are getting adequate amounts of vitamin D are by exposing your bare skin to sunlight and by taking vitamin D supplements. While eating the right foods can be helpful, it won’t necessarily give you the right amount of vitamin D that your body needs—there isn’t enough present in food to replenish deficiencies.
Vitamin D is primarily produced in the skin after exposure to ultraviolet radiation and less than 10% is derived from dietary sources. Vitamin D is a potent immune-modulator of adaptive and innate immune responses. In vitro studies have shown that 1,25-dihydroxyvitaminD3, the active metabolite of vitamin D, is important for promoting and regulating immune responses.
Vitamin D belongs to the family of fat-soluble vitamins, which include vitamins A, D, E and K. These vitamins are absorbed well with fat and are stored in the liver and fatty tissues.
There are two main forms of vitamin D in the diet:
- Vitamin D2 (ergocalciferol): Found in plant foods like mushrooms.
- Vitamin D3 (cholecalciferol): Found in animal foods like salmon, cod and egg yolks.
However, sunlight is the best natural source of vitamin D3. The UV rays from sunlight convert cholesterol in your skin into vitamin D3.
A low blood level of vitamin D is linked to a greater risk of fractures and falls, heart disease, multiple sclerosis, several cancers and even death.
Current US guidelines suggest that consuming 400–800 IU (10–20 mcg) of vitamin D should meet the needs of 97–98% of all healthy people. But many studies have shown that one needs to consume more vitamin D than the guidelines recommend.
According to the Institute of Medicine (IOM), the following values determine your vitamin D status :
- Deficient:Levels less than 12 ng/ml (30 nmol/l).
- Insufficient:Levels between 12–20 ng/ml (30–50 nmol/l).
- Sufficient:Levels between 20–50 ng/ml (50–125 nmol/l).
- High:Levels greater than 50 ng/ml (125 nmol/l).
The IOM also states that a blood value of over 20 ng/ml (50 nmol/l) should meet the vitamin D needs of 97–98% of healthy people Some studies suggest that a blood level over 30 ng/ml is better for preventing falls, fractures and some cancers.Whatever the amount you decide to take, you should always choose vitamin D3 as it is is twice as effective at raising blood levels of vitamin D as taking vitamin D2.
Vitamin D is unique among vitamins; you can synthesize it in your skin as well as absorb it from foods or supplements. To complicate things further, vitamin D also comes in two forms: D2 and D3. Getting either vitamin D2 and D3 from supplements, sunlight exposure or foods will raise your 25(OH)D level. Some researchers however believe that our body absorbs D3 more efficiently.
Spending time in sunlight is one of the most effective ways of raising D3 levels. Spending as little as 5 to 30 minutes in direct sunlight with our face, arms, legs or back exposed two times a week between 10 a.m. and 3 p.m. in the summer, fall and spring can synthesize enough vitamin D3 to supply our needs, the Office of Dietary Supplements reports. Our body can store excess vitamin D, a fat soluble vitamin, in our fat stores and liver, for use during the winter. How much is produced by sunlight depends on a range of factors, including:
■ Level of UV radiation: The amount of sun received at any location is dependent on the angle at which it strikes Earth. UVB rays are the primary source of vitamin D.
■ Time, year and location: The level of UV radiation varies with the time of day and year. It’s weakest when the sun slants, which is during the early and later parts of the day, and during most of the day in winters. So the closer to midday you expose your skin, the better it will be for vitamin D production.
Beef liver, cheese, Cod liver oil, egg yolks and fatty fish are the best dietary sources of D3
Over-the-counter and prescription supplements can increase your vitamin D3 intake. The Food and Nutrition Board’s adequate intake amount is 600 IUs per day between the ages of 1 and 70 and 800 IUs per day for adults over age 70. The Food and Nutrition Board’s adequate intake amount is 600 IUs per day between the ages of 1 and 70 and 800 IUs per day for adults over age 70.
Although it is possible to take too much vitamin D, toxicity is rare, even above the safe upper limit of 4,000 IU but consuming more than this amount may provide no extra benefit. There have been reports of people taking very large doses of vitamin D for months without symptoms, yet blood tests revealed severe hypercalcemia and symptoms of kidney failure .High doses of vitamin D can cause hypercalcemia without toxicity symptoms, but can also cause toxicity symptoms without hypercalcemia.