The Benefits of Vitamin D

Vitamin D

Vitamin D is a steroid vitamin, a group of fat-soluble prohormones, which encourages the absorption and metabolism of calcium and phosphorous. People who are exposed to normal quantities of sunlight do not need vitamin D supplements because sunlight promotes sufficient vitamin D synthesis in the skin.

Five forms of vitamin D have been discovered, vitamin D₁, D₂, D₃, D₄, D₅. The two forms that seem to matter to humans the most are vitamins D₂ (ergocalciferol) and D₃ (cholecalciferol).

Researchers at the University of Minnesota found that Vitamin D levels in the body at the start of a low-calorie diet predict weight loss success, suggesting a possible role for vitamin D in weight loss.

Vitamin D for humans is obtained from sun exposure, food and supplements. It is biologically inert and has to undergo two hydroxylation reactions to become active in the body. The active form of vitamin D in the body is called Calcitriol (1,25-Dihydroxycholecalciferol).

Calcitriol promotes the absorption of calcium and phosphorus from food in the gut and reabsorption of calcium in the kidneys - this increases the flow of calcium in the bloodstream.

This is essential for the normal mineralization of bone and preventing hypocalcemic tetany. Hypocalcemic tetany is a low calcium condition in which the patient has overactive neurological reflexes, spasms of the hands and feet, cramps and spasms of the voice box (larynx). Calcitriol also plays a key role in the maintenance of many organ systems.

Function

Vitamin D helps the body absorb calcium. Calcium and phosphate are two minerals that are essential for normal bone formation.

Throughout childhood, your body uses these minerals to produce bones. If you do not get enough calcium, or if your body does not absorb enough calcium from your diet, bone production and bone tissues may suffer.

Vitamin D deficiency can lead to osteoporosis in adults or rickets in children.

 

What do we need vitamin D for?

1. It is crucial for the absorption and metabolism of calcium and phosphorous, which have various functions, especially the maintenance of healthy bones.
2. It is an immune system regulator.
3. It may be an important way to arm the immune system against disorders like the common cold, say scientists from the University of Colorado Denver School of Medicine, Massachusetts General Hospital and Children's Hospital Boston.
4. It may reduce the risk of developing multiple sclerosis. Multiple sclerosis is much less common the nearer you get to the tropics, where there is much more sunlight, according to Dennis Bourdette, chairman of the Department of Neurology and director of the Multiple Sclerosis and Neuroimmunology Center at Oregon Health and Science University, USA.
5. Vitamin D may have a key role in helping the brain to keep working well in later life, according to a study of 3000 European men between the ages of 40 and 79.
6. Vitamin D is probably linked to maintaining a healthy body weight, according to research carried out at the Medical College of Georgia, USA.
7. It can reduce the severity and frequency of asthma symptoms, and also the likelihood of hospitalizations due to asthma, researchers from Harvard Medical School found after monitoring 616 children in Costa Rica.
8. It has been shown to reduce the risk of developing rheumatoid arthritis in women.
9. A form of vitamin D could be one of our body's main protections against damage from low levels of radiation, say radiological experts from the New York City Department of Health and Mental Hygiene.
10. Various studies have shown that people with adequate levels of vitamin D have a significantly lower risk of developing cancer, compared to people with lower levels. Vitamin D deficiency was found to be prevalent in cancer patients regardless of nutritional status, in a study carried out by Cancer Treatment Centers of America

Food Sources

The body makes vitamin D when the skin is directly exposed to the sun. That is why it is often called the "sunshine" vitamin. Most people meet at least some of their vitamin D needs this way.

Very few foods naturally contain vitamin D. As a result, many foods are fortified with vitamin D. Fortified means that vitamins have been added to the food.
Vitamin D is found in the following foods:

• Dairy products
  • Cheese
  • Butter
  • Cream
  • Fortified milk (all milk in the U.S. is fortified with vitamin D)
• Fatty fish (such as tuna, salmon, and mackerel)
• Oysters
• Fortified breakfast cereals, margarine, and soy milk (check the Nutrition Fact Panel on the food label)

It can be very hard to get enough vitamin D from food sources alone. As a result, some people may need to take a vitamin D supplement. Vitamin D found in supplements and fortified foods comes in two different forms:

• D₂ (ergocalciferol)
• D₃ (cholecalciferol)

Side Effects

Too much vitamin D can make the intestines absorb too much calcium. This may cause high levels of calcium in the blood. High blood calcium can lead to:

• Calcium deposits in soft tissues such as the heart and lungs
• Confusion and disorientation
• Damage to the kidneys
• Kidney stones
• Nausea, vomiting, constipation, poor appetite, weakness, and weight loss

 

Recommendations

Ten to 15 minutes of sunshine three times weekly is enough to produce the body's requirement of vitamin D. The sun needs to shine on the skin of your face, arms, back, or legs (without sunscreen). Because exposure to sunlight is a risk for skin cancer, you should use sunscreen after a few minutes in the sun.

People who do not live in sunny places may not make enough vitamin D. Skin that is exposed to sunshine indoors through a window will not produce vitamin D. Cloudy days, shade, and having dark-colored skin also cut down on the amount of vitamin D the skin makes.
The Recommended Dietary Allowance (RDA) for vitamins reflects how much of each vitamin most people should get on a daily basis.

• The RDA for vitamins may be used as goals for each person.
• How much of each vitamin you need depends on your age and gender. Other factors, such as pregnancy and your health, are also important.

Infants (adequate intake of vitamin D)

• 0 - 6 months: 400 IU (10 micrograms (mcg) per day)
• 7 - 12 months: 400 IU (5 mcg/day)

Children

• 1 - 3 years: 600 IU (15 mcg/day)
• 4 - 8 years: 600 IU (15 mcg/day)

Older children and adults

• 9 - 70 years: 600 IU (15 mcg/day)
• Adults over 70 years: 800 IU (20 mcg/day)
• Pregnancy and breast-feeding: 600 IU (15 mcg/day)

In general, people over age 50 need higher amounts of vitamin D than younger people. Ask your health care provider which amount is best for you.
Vitamin D toxicity almost always occurs from using too many supplements.
The safe upper limit for vitamin D is:

• 1,000 to 1,500 IU/day for infants
• 2,500 to 3,000 IU/day for children 1 - 8 years
• 4,000 IU/day for children 9 years and older, adults, and pregnant and breast-feeding teens and women

One microgram of cholecalciferol (D₃) is the same as 40 IU of vitamin D.

Vutamin D TOP10  (Source: USDA National Nutrient data base)
순위	Fruits	함량/100g	RDA
1	Cod Liver Oil	10,000 IU	2,500%
2	Herring	1,628 IU	407%
3	Fortified Cereals	342 IU	85.5%
4	Oyster	320 IU	80%
5	Caviar	232 IU	58%
6	Tofu	157 IU	39%
7	Salami Sausage	62 IU	16%
8	Dairy Products	52 IU	13%
9	Eggs	37 IU	9%
10	Mushrooms	27 IU	7%