by Victoria Locke
If your parents directed you to “go play outside in the fresh air and sunshine, and soak up some vitamin D,” they were indeed giving you wise advice. We humans need ten to fifteen minutes of sun exposure (with a UV index of 3 or greater), at least twice a week (on the face, arms, hands, or back without sunscreen) to absorb enough vitamin D from the sun to adequately supply our bodies’ needs. If we live outside the tropics (and that’s all of us in Mississippi) where the UV index is lower part of the year, we need even more time in the sun for enough vitamin D to be synthesized through the skin.
Over the last few centuries, our lifestyles and livelihoods have changed dramatically as we turned from an agricultural society to an industrialized society. With this great societal change, we began spending less and less time outdoors receiving regular exposure to sunlight. To understand the significance of this cultural shift and how it potentially affects our overall health, we need to look at how vitamin D helps the body function.
Vitamin D is important because it is necessary for the absorption of calcium and phosphorus from food, nutrients essential for normal bone mineralization – in other words, to create strong, healthy bones.
Vitamin D is also crucial for a number of other biological functions or health concerns, including:
Some other potential benefits requiring further research:
It is a steroid vitamin that has five forms (discovered so far) – vitamin D1, D2, D3, D4 and D5. The two forms that are most important to humans are vitamin D2 (ergocalciferol) and D3 (cholecalciferol). These vitamins are obtained three ways, from sun exposure, food and supplements.
According to the most recent (2010) recommendations of the Food Nutrition Board at the Institute of Medicine (IOM), which created the Dietary Reference Intakes (DRIs), people who do not receive an adequate amount of regular exposure to the sun, should receive the following amounts of vitamin D:
The American Academy of Pediatrics recommends that breastfed babies (whether partially or exclusively breastfed, should receive vitamin D supplements. Once they are weaned, they should consume a minimum of 1,000 mL/day of vitamin D fortified formula or whole milk. Non- breastfed infants consuming less than 1,000 mL/day of vitamin D fortified formula or milk should receive a vitamin D supplement. Consult your pediatrician for recommended dosages.
While we think of milk as the most common source of vitamin D, that is because milk and other dairy products are fortified with it to help prevent the onset of diseases that can develop when vitamin D is deficient in our diets. Not that many foods naturally contain vitamin D. Some fish such as salmon, tuna and mackerel, as well as fish liver oils are considered to be the best sources. Some vitamin D is present in beef liver, cheese, egg yolks and some mushrooms. However, the majority of the vitamin D most Americans receive comes from fortified foods, such as milk and other dairy products, breakfast cereals, bread, pastries, oils, margarine and even orange juice.
Vitamin D is included in most multivitamins, usually in strengths from 50 IU to 1000 IU. According to the Mayo Clinic, since 2000 there have been disagreements between experts regarding the benefits of vitamin D and how much is sufficient. Safety research supports an upper limit (maximum) dose of no more than 10,000 IU daily for children and adults. For infants, aged 0 – 12 months, the upper limit for intake is 1,000 IU daily. Exceeding the upper limits of daily intake of vitamin D at any age can result in toxicity and may lead to serious side effects.