Cheat Sheet

Vitamin D For Dummies

From Vitamin D For Dummies by Alan L. Rubin

Vitamin D is essential for good health; however, it is a required nutrient only when you don't get enough ultraviolet B (UVB) rays from the sun. Unfortunately, many people can't get enough sun exposure and need to get vitamin D from their diet or from supplements. When you have enough vitamin D in your body, you can protect the health of your bones and prevent osteoporosis. New evidence suggests vitamin D may also help prevent many other diseases.

Key Points You Need to Know about Vitamin D

Even as researchers continue to discover how vitamin D can protect your health, a lot of misinformation still surrounds this amazing vitamin. Here are some of the key points you need to know to understand the role of vitamin D in your health.

  • You can make vitamin D in your skin when you're exposed to UVB light from the sun.

  • People who don't get enough sun exposure need vitamin D in their diet.

  • Whether you get vitamin D from sun, diet, or supplements, your body turns vitamin D into a hormone called 1,25 dihydroxyvitamin D (or calcitriol). This is the form of vitamin D that directly affects your health.

  • Many people don't get enough UVB light to make vitamin D in their skin.

  • It's hard to get enough vitamin D from food alone.

  • You can find out if you have enough vitamin D in your system by getting a blood test for a form of vitamin D called 25-hydroxyvitamin D.

  • Vitamin D supplements are safer than people used to think.

  • The recommendations for vitamin D intake were set to help you protect your bones.

  • Breast milk generally doesn't provide enough vitamin D to babies.

  • Vitamin D may be important for more than just bone health. New evidence suggests it may strengthen your immune system, prevent cancer, and stop other chronic diseases.

  • The proposed new roles for vitamin D and health are still being tested.

What Are the Benefits of Vitamin D?

New information about vitamin D's role in health is being published almost daily. Here are the key functions of vitamin D, divided into those that are firmly established, those for which there is growing evidence, and those that are proposed but not yet confirmed.

It's firmly established that vitamin D

  • Facilitates absorption of calcium from your diet; essential for normal healthy bones

  • Prevents osteoporosis, osteomalacia, and rickets

There is growing evidence that vitamin D may

  • Contribute to a normal healthy immune system

  • Prevent autoimmune diseases

  • Protect the body from cancer, especially breast, colorectal, and prostate cancers

Vitamin D is showing promise that it may

  • Protect the heart from heart attacks and heart failure

  • Prevent both type 1 and type 2 diabetes

  • Prevent asthma

  • Prevent Alzheimer's disease

  • Prevent Parkinson's disease

Recommendations for Vitamin D Intake

New recommendations for vitamin D were released by an expert panel in 2010. These recommendations for daily intake of vitamin D are based on the current literature on vitamin D and are set to protect the health of your bones. They're based on the assumption that you get no vitamin D from sun exposure.

2010 Recommendations for Intake of Vitamin D
Age RDA or AI* UL**
Birth to 6 months 400 IU*** 1000 IU
7–12 months 400 IU 1500 IU
1–3 years 600 IU 2500 IU
4–8 years 600 IU 3000 IU
9–70 years 600 IU 4000 IU
More than 70 years 800 IU 4000 IU

*RDA = recommended daily allowance; AI = adequate intake
**UL = upper safe limit for daily intake
***IU = International Units

Some people believe that you may need even more vitamin D than these recommendations; however, the scientific evidence to support these claims is lacking. Still, as long as you stay under the recommended upper safe intake limit, you can choose to take more vitamin D.

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