Tuesday, 4 June 2013

Vitamin D facts

1. Why is Vitamin D important?
Vitamin D is essential for healthy growth and development, along with the formation of bones and teeth. It also regulates the production of phosphorus and calcium in the body.

2. When is it necessary to take vitamin D supplements?
 Your doctor will measure your blood vitamin D levels (25- hydroxyl vitamin D) and will prescribe the correct dose for you based on your results. Ideally, the 25-OH vitamin D level should be > 30 ng/ml.

3. What are the difference forms of vitamin D?
They are usually oral pills. The most commonly used is D3 tablets. The dosage ranges from 800 to 1000 IU per tablet.

4. How much Vitamin D is needed by the body?
The daily requirement is 400 IU a day. People older than 65 years may need up to 800 IU a day. Two whole large sardines can contain about 400 IU a day.

5. Is sun tanning alone sufficient to produce Vitamin D?
The skin makes vitamin D3 from exposure to the sun, but as one ages, the skin will be less efficient in making the vitamin. Sunscreen with SPF 15 can also reduce the manufacture of vitamin D by up to 99 percent.

6. What is the difference between Vitamin D2 and Vitamin D3?
Vitamin D3 is manufactured by plants or fungus and can be synthesized by exposing fat extract of yeast to ultraviolet light; Vitamin D3 is formed when skin is exposed to sunlight and is found in food. Supplements of vitamin D3 is from lamb’s wool extraction.

 7. Is Vitamin D2 or Vitamin D3 better?
Vitamin D2 is less effective than Vitamin D3 in humans. Most of the clinical trials employ Vitamin D3 and only few clinical trials examining the effectiveness of vitamin D2 preventing bone fractures in adults.

8. What foods contain Vitamin D?
Many types of fish such as salmon, mackerel, sardines and tuna are good sources of Vitamin D. Most dairy products and commercial bread are fortified with Vitamin D. Sundried shiitake mushrooms and egg yolks are good sources too.

9. What are the recommended dietary allowances for Vitamin D?
Age category
Vitamin D
10 to 18 years
400 IU
19 to 50 years
400 IU
51 to 70 years
400 IU
>70 years
800 IU

10. Is Vitamin D destroyed through cooking?
Vitamin D is stable and will not be destroyed through normal cooking.

11. Since I can get Vitamin D from sunlight, why do I still need Vitamin D supplement?
Although we may live in the tropics, we may not let our skin exposed long enough in the sun to get sufficient vitamin D because we may work indoors for long hours. Some of us use skin whitening cream too. As we age the skin becomes less efficient in making Vitamin D. there are very few food containing vitamin D.

12. What are vitamin D analogues?
The two available are calcitriol and alfacalcidol. They are drugs rather than vitamin supplements. For patients who have poorly functioning kidneys, this may be an option to treat osteoporosis. These tablets however, if taken in excess without indications, may lead to high blood-calcium levels and kidney stones.

Source: Osteoporosis: Your bones Matter by A/Prof Long Keng Hong and Louisa Zhang

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