Vitamin D is a fat-soluble vitamin. These types of vitamins are stored in the body's liver and fatty tissues.

Vitamin D acts as both a vitamin and a hormone. It is found in some foods, but the main sources are vitamin D-fortified milk and sunlight.

Functions

Vitamin D plays a role in the growth and maintenance of strong, healthy bones. It also helps to maintain normal blood levels of calcium and phosphorus.

As a supplement, it may help treat osteoporosis and high blood pressure.

Recommended Intake

Here are the guidelines for vitamin D intake:

Vitamin D Deficiency

Symptoms of severe vitamin D deficiency are rare today, but can lead to:

• Rickets—a disease in children in which the bones become soft and weak
• Osteomalacia—a disease in adults in which the bones become soft and weak
• Muscle weakness

Mild deficiency is common, especially in places that have less sunlight.

Vitamin D Toxicity

Vitamin D is stored in the body and does not pass out through urine. It can build up and reach toxic levels. Here are safe upper level intakes for vitamin D:

IU: international units

Symptoms of toxicity are:

• Nausea
• Vomiting
• Constipation
• Weakness
• Weight loss
• Heart rhythm problems
• Deposits of calcium in soft tissues from raised levels of calcium in the blood

Sunlight and diet are not likely to cause vitamin D toxicity.

Major Food Sources

Fortified foods have the most vitamin D. Examples of foods that may be fortified with vitamin D are:

• Milk
• Cereal
• Orange juice
• Yogurt
• Margarine
• Soy drinks

There are not many foods that are natural sources of vitamin D. They are:

• Fatty fish, such as salmon, tuna, and mackerel
• Beef liver
• Cheese
• Egg yolks
• Mushrooms

Health Implications

Tips to Raise Your Vitamin D Intake

Here are tips to help raise your intake:

• Make sure your multivitamin contains vitamin D.
• Drink vitamin D-fortified milk.
• Spend time in the sun. You should still use sunscreen with an SPF of 30 or higher.