Vitamin D

Answer 1

Vitamin D is an important vitamin that many people are not getting enough of. It is not easy to get sufficient amounts of vitamin D naturally in foods, but many foods are fortified with it. Vitamin D has numerous extremely important functions, although the most commonly thought of is for calcium absorption. Without vitamin D the body cannot properly absorb calcium to promote bone growth and density.

Populations the most at-risk for vitamin D deficiency are breast-fed infants, elderly, individuals with darker skin and others with limited UV ray absorption. If you live in a cold climate with excessive cloud-covering or that keeps you in doors often, you are not getting enough vitamin D from the sun.

To be sure you consume enough vitamin D turn to fish, fortified foods, supplements and sun. UV-B ray absorption from the sun for roughly 5 to 10 minutes a day will promote vitamin D synthesis, however the risks associated with UV ray absorption cause many professionals to recommend seeking your vitamin D from food or supplements. Additionally, if you have dark skin it is much harder for your skin to absorb and synthesize vitamin D, meaning you may need 10 times more sun exposure. Fish, such as salmon, tuna and sardines have high levels of naturally occurring vitamin D. Alternatively, you can purchase milk and Orange Juice fortified with vitamin D. If you are still lacking on vitamin D consumption consider taking a daily supplement.

The recommended daily intake is 200 international units (IU), more if you are over 50. You can be tested for your vitamin D level and make steps to improve it if you are low. Ideally your number should be between 40 and 50. If you find out your number is low you can easily bump it up through supplementation or sun exposure. Need more reason to have healthy vitamin D levels? It is extremely important to your immune system function, and is associated with a reduced risk of cancer and type 2 Diabetes.

Although exact healthy amounts are unclear and vary from person to person, toxicity may occur with levels greatly exceeding 1000 IU per day. However, vitamin D from the sun cannot cause toxicity.

Answer 2

Definition

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

Alternative Names

Cholecalciferol

Function

In addition to helping the body absorb calcium, vitamin D also helps the body keep the right amount of calcium and phosphorus in the blood.

Food Sources

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)
• Fish
• Oysters
• Fortified cereals
• Margarine

Side Effects

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

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. This can reduce their ability to function.

Kidney stones, vomiting, and muscle weakness may also occur if you have too much vitamin D.

Recommendations

Vitamin D is also known as the "sunshine vitamin" because the body manufactures the vitamin after being exposed to sunshine. Ten to 15 minutes of sunshine 3 times weekly is enough to produce the body's requirement of vitamin D. However, many people living in sunny climates still do not make enough vitamin D and need more from their diet or supplementation.

The Food and Nutrition Board at the Institute of Medicine recommends the following dietary intake for vitamin D as cholecalciferol. (One microgram of cholecalciferol is the same as 40 IU of vitamin D.)

Infants

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

Children

• 1 - 13 years: 5 mcg/day

Adolescents and Adults

• Males and Females age 14 to 50: 5 mcg/day
• Males and Females age 51 to 70: 10 mcg/day
• Males and Females age over 70: 15 mcg/day

Specific recommendations for each vitamin depend on age, gender, and other factors (such as pregnancy). In general, those over age 50 need higher amounts of vitamin D than younger persons. Ask your health care provider which amount is best for you.

References

Hamrick I, Counts SH. Vitamin and mineral supplements. Wellness and Prevention. December 2008:35(4);729-747.

Rakel D, ed. Integrative Medicine. 2nd ed. Philadelphia, Pa: Saunders Elsevier; 2007.

Mason JB. Vitamins, trace minerals, and other micronutrients. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 237.

Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Calcium, Phosphorous, Magnesium, Vitamin D, and Fluoride. National Academy Press, Washington, DC, 1997.

Answer 3

Definition

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

Alternative Names

Cholecalciferol; Vitamin D3; Ergocalciferol; Vitamin D2

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.

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.

References

Escott-Stump S, ed. Nutrition and Diagnosis-Related Care. 6th ed. Philadelphia, Pa: Lippincott, Williams & Wilkins; 2008.

Sarubin Fragaakis A, Thomson C. The Health Professional's Guide to Popular Dietary Supplements. 3rd ed. Chicago, IL: American Dietetic Association; 2007.

Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes: Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. National Academy Press, Washington, DC, 2010.

Reviewed By

Review Date: 02/08/2011

Alison Evert, MS, RD, CDE, Nutritionist, University of Washington Medical Center Diabetes Care Center, Seattle, Washington. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.