What Are Vitamins?

There are 13 essential vitamins that your body needs to function properly.

Vitamins are nutrients that your body needs for normal cell function, growth, and development.

They can be grouped into two main categories based on how they act in your body.

Fat-soluble vitamins, such as vitamins A, D, E, and K, are stored in your body's fatty tissue, where they are absorbed easily.

Water-soluble vitamins, such as vitamins B and C, are used immediately after entering the body.

Unneeded water-soluble vitamins are excreted from the body in your urine. The only exception is vitamin B12, which can be stored in your liver for years.

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Essential Vitamins

The following vitamins are considered essential, meaning your body can't produce them but needs them to function properly:

• Vitamin A, which helps form and maintain teeth, bones, soft tissue, mucous membranes, and skin
• Vitamin C (ascorbic acid), which promotes healthy teeth and gums, healing of wounds, and absorption of iron by the body
• Vitamin D, which helps absorb and maintain proper blood levels of phosphorus and calcium, minerals needed for development and healthy teeth and bones
• Vitamin E, which helps red blood cells form and use vitamin K
• Vitamin B1 (thiamine), which helps convert carbohydrates into energy and is important for the heart and nerve cells
• Vitamin B2 (riboflavin), which promotes body growth and the production of red blood cells
• Vitamin B3 (niacin), which helps maintain healthy skin and nerves and can lower blood cholesterol levels
• Pantothenic acid, which is needed to metabolize food and helps produce hormones and cholesterol
• Biotin (B7), which is needed to metabolize proteins and carbohydrates, and to produce hormones and cholesterol
• Vitamin B6, which helps red blood cells form, helps maintain brain function, and supports protein synthesis
• Vitamin B12 (cyanocobalamin), which helps with metabolism, red blood production, and maintaining the central nervous system
• Folate (folic acid and B9), which helps red blood cells form and is needed to produce DNA, which controls tissue growth and cell function
• Vitamin K, which is necessary for blood clotting

Getting the Right Amount of Vitamins

Eating a balanced diet that includes a variety of fruits, vegetables, fortified dairy foods, legumes (beans, lentils, and peas), and whole grains is the best way to get adequate vitamins.

In some cases, though, you may need to take supplements if your diet isn't providing enough vitamins.

Talk with your doctor about what's best for you. Keep in mind that taking too much of certain vitamins, without medical supervision, can cause serious health problems.

The Recommended Dietary Allowance (RDA), set by the Institute of Medicine, is a guideline for how much of each vitamin most people should get daily.

Vitamin Deficiencies and Malnutrition

Less than 10 percent of the U.S. population had nutrition deficiencies in selected categories, according to a 2012 report by the Centers for Disease Control and Prevention (CDC).

Based on results from the National Health and Nutrition Examination Survey, conducted by the CDC between 2003 and 2006, the report provides data on fat- and water-soluble vitamins, iron, iodine, and other nutrients that are important to health.

The largest number of people had vitamin B6, iron, and vitamin D deficiencies, and the smallest number of people had vitamin A, vitamin E, and folate deficiencies.

Black and Hispanic people, though, were more likely to have a vitamin D deficiency than non-Hispanic white people.

Worldwide, the World Health Organization (WHO) reports that iron deficiency is the most common nutritional disorder, affecting 2 billion people in both developing and industrialized countries.