Vitamin D

Vitamin D is a fat-soluble vitamin. Fat-soluble vitamins are stored in the body's fatty tissue.

Function

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

Calcium

Calcium is the most plentiful mineral found in the human body. The teeth and bones contain the most calcium. Nerve cells, body tissues, blood, and ...

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In 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.

Osteoporosis

Osteoporosis is a disease in which bones become fragile and more likely to break (fracture).

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Rickets

Rickets is a disorder caused by a lack of vitamin D, calcium, or phosphate. It leads to softening and weakening of the bones.

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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.

Fatty fish (such as tuna, salmon, and mackerel) are among the best sources of vitamin D.

Beef liver, cheese, and egg yolks provide small amounts.

Mushrooms provide some vitamin D. Some mushrooms you buy in the store have higher vitamin D content because they have been exposed to ultraviolet light.

Most milk in the United States is fortified with 400 IU vitamin D per quart. Most of the time, foods made from milk, such as cheese and ice cream, are not fortified.

Vitamin D is added to many breakfast cereals. It is also added to some brands of soy beverages, orange juice, yogurt, and margarine. Check the nutrition fact panel on the food label.

Supplements

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:

• D ₂ (ergocalciferol)
• D ₃ (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

  Kidney stones

  A kidney stone is a solid mass made up of tiny crystals. One or more stones can be in the kidney or ureter at the same time.

  

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• 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 best measure of your vitamin D status is to look at blood levels of a form known as 25-hydroxyvitamin D. Blood levels are described either as nanograms per milliliter (ng/mL) or nanomoles per liter (nmol/L), where 0.4 ng/mL = 1 nmol/L.

Levels below 30 nmol/L (12 ng/mL) are too low for bone or overall health, and levels above 125 nmol/L (50 ng/mL) are probably too high. Levels of 50 nmol/L or above (20 ng/mL or above) are enough for most people.

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

Children

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

Older children and adults

• 9 to 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 (25 mcg/day)
• 2,500 to 3,000 IU/day for children 1 to 8 years; ages 1 to 3 63 mcg/day; ages 4 to 8 75 mcg/day
• 4,000 IU/day for children 9 years and older, adults, and pregnant and breast-feeding teens and women (100 mcg/day)

One microgram of cholecalciferol (D ₃ ) is the same as 40 IU of vitamin D.