Vitamin D: Benefits and Function
Vitamin D has two sub-forms that our body needs. Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol).
Vitamin D is primarily needed for the absorption of calcium and phosphorus. It is essential to bone and teeth growth as well as maintaining those throughout life. Vitamin D also plays an important role in the immune system of our body.
Vitamin D Dosage
The daily intake recommendations for vitamin D is 600 IU or 15µg (micrograms). Since skin synthesis of vitamin D varies so much, the latest dietary recommendations assume minimal sun exposure. There is recent research that shows that supplementing vitamin D might not be as commonly needed as suggested.
Vitamin D toxicity is very rare, but it can cause nausea, constipation, weakness, and kidney damage. The daily recommended upper limit of intake is 4,000 IU. You should never take that high dosage unless recommended by your doctor. Too much vitamin D can build up in your body and in the long run cause toxicity.
Sun exposure will not cause vitamin D toxicity.
See research articles below for recent studies of minimum and maximum levels of Vitamin D.
Vitamin D Foods
Vitamin D3 is only found in animals, while vitamin D2 comes from plant-sourced foods.
We get vitamin D from foods such as eggs, sardines, and salmon. It is also found in fortified drinks such as milk and orange juice.
Fortified breakfast cereals and bread supplement vitamin D as well.
When exposed to sunlight, our skin makes vitamin D, which is then activated in our body.
Most people get some vitamin D from sunlight. The amount of sunshine you get daily as well as the color of your skin can determine how much vitamin D your body produces.
People with darker skin produce less vitamin D with the same amount of sun exposure.
You can get vitamin D from supplements if you are worried that you don’t get enough from your diet or if you are part of groups with a higher risk of deficiency.
Vitamin D2 Food
- Mushrooms (grown in UV light)
- Fortified foods
- Dietary supplements
Vitamin D3 Food
- Oily fish and fish oil
- Egg yolk
- Dietary supplements
Vitamin D Deficiency
Lack of vitamin D affects bones and many other parts of the body.
Growing children who do not get enough vitamin D may have bones that are too soft and unable to support their weight (rickets).
Adults deficient in vitamin D can develop soft bones (osteomalacia). They can also lose bone mass, which leads to fragile bones that are at risk of fracturing (osteoporosis).
In general, the following groups of people may be at risk for vitamin D deficiency:
- People who do not get enough direct sun exposure
- Older people
- Persons with dark skin
- People who are obese or have kidney or liver disease