Importance of Vitamin D

Vitamin D
Vitamin D plays a crucial role in the human body's use of calcium and phosphorous. Vitamin D works to increase the amount of calcium that is absorbed from the small intestine, which helps to form and maintain human bones. Vitamin D also benefits one's body by playing a role in cellular immunity and modulating cellular growth. Children are in need of adequate amounts of vitamin D in order to develop stronger bones as well as healthier teeth.

Dietary Sources of Vitamin D
The primary dietary sources of vitamin D are milk and dairy products that are fortified with vitamin D. Vitamin D can also be found in oily fish (for example herring, sardines, and salmon) as well as in the liver oil from cod. In addition to the vitamin D that is provided by food, one can obtain vitamin D through one's skin, which may produce vitamin D in response to exposure to sunlight.

How much Vitamin D is recommended daily?
The Recommended Dietary Allowance (RDA) for vitamin D intake is reported as micrograms (mcg) of cholecalciferol (a.k.a. vitamin D3). From age twelve months to age fifty, the RDA is set at 15 mcg per day. Twenty mcg of cholecalciferol is equal to 800 International Units (IU), which is the daily recommendation for maintenance of healthy bone in adults over fifty. Exposure to UV light is needed for the body to produce the active form of vitamin D. Ten to fifteen minutes of daily sunlight without sunscreen on your hands, arms and your face, twice or more per week is sufficient to synthesize enough vitamin D. This can easily be achieved during the time spent riding a bike to the gym or taking a walk. In order to reduce your risk for skin cancer, one may apply sunscreen with an SPF of 15 or more, if one's time spent in the sun exceeds 10 to 15 minutes.

Vitamin D Deficiency
The symptoms of vitamin D deficiency in children include rickets (long bowed legs) and a flattening of the back of their skulls. Vitamin D deficiency in adults can result in osteomalacia (muscle and/or bone weakness), as well as osteoporosis ( loss of bone mass). Clinical data introduces a concern that some adults and children might be more susceptible to developing a vitamin D deficiency due to increased use of sunscreen. Additionally, those that live in cities, wear clothing that covers most of their skin, or live in the northern climates where little sun is seen in the winter are also prone to vitamin D deficiency. Since most foods contain very low vitamin D levels (unless they are enriched) a deficiency might be more likely to develop without an adequate exposure to sunlight. Adding fortified foods to your diet, such as milk, or a supplement for adults, are proven effective at ensuring adequate daily vitamin D intake as well as preventing low vitamin D levels. Vitamin D deficiency has also been associated with increased risk of common cancers, some autoimmune diseases, primary hypertension, and several infectious diseases. In the absence of adequate daily sun exposure, at least 800 to 1,000 IU of vitamin D3 is likely needed to reach the circulating level needed to maximize vitamin D's benefits to you.

Who is at Risk for Vitamin D Deficiency?
Infants that are exclusively breast-fed: human milk provides only 25 IU of vitamin D per liter. Infants that are breast-fed or partially breast-fed should be given a vitamin D supplement of at least 400 IU/day People with darker skin: those with darker skin pigmentation synthesize less vitamin D when they receive exposure to sunlight compared to those who have lighter pigmented skin. Elderly: this population has a much reduced ability to synthesize vitamin D upon their exposure to sunlight, and this group is also more likely to stay indoors and wear sunscreen, which may also block vitamin D synthesis. Covered / protected skin: people who cover up all of their skin with clothing while they are outside, and those that wear sunscreen with an SPF factor of 8 or more, are likely to block the majority of the synthesis of vitamin D from sunlight. Persons with Disease: Lipid malabsorption syndrome, inflammatory bowel diseases (IBDs), and obesity are all known to result in an attenuated ability to absorb and/or utilize vitamin D in their fat stores.

What happens if one ingests high levels of Vitamin D?
The Tolerable Upper Intake Level (TUIL) for vitamin D is 100 micrograms for people nine years of age and older. Higher doses of vitamin D supplements coupled with larger amounts of fortified foods might cause accumulations in the liver that produce signs of poisoning. Signs of vitamin D toxicity include, but are not limited to excess calcium present in the bloodstream, slowed mental and physical growth, a decrease in appetite, nausea and subsequent vomiting. It is especially important for infants and young children not to consume excess amounts of vitamin D regularly, because of their smaller body sizes.