A Definition and Examples of Vitamins

Why these nutrients are key to survuval

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Approximately half of all Americans take vitamins every day, but the popularity of these nutrients doesn't mean that most people know what they are or what their role is in the body. So, what exactly are vitamins?

Clinical Definition of Vitamins

Also known as macro or micro nutrients, vitamins are essential organic compounds that people, animals and organisms require in small doses for survival and for the body to function properly.

People naturally obtain vitamins when they consume plant- and animal-based foods.

Fat-Soluble or Water-Soluble Vitamins

The 13 classified vitamins fall into two categories: water-soluble or fat-soluble.

Fat-soluble vitamins include vitamins A, D, E and K. They dissolve in fat and are stored in the body, so you don’t need to consume them daily. Water-soluble vitamins, which include vitamin C and the family of B vitamins (biotin, folate, niacin, pantothenic acid, riboflavin, thiamin, B6 and B12), are removed from the body daily and need to be replaced. Although all vitamins are essential, several can be toxic in very high doses. This is known as hypervitaminosis.

Fat-soluble vitamins, in particular, are more likely to be toxic in high doses. That's because the body typically excretes water-soluble vitamins in the urine. But even some water-soluble vitamins can be toxic if taken in excessive amounts.

Vitamins that contain iron are the most likely to be toxic, especially if taken by children. Because the body only eliminates iron through blood loss, it can quickly rise to toxic levels in the body if over ingested. That said, women with heavy menstrual periods may be advised to take iron to prevent developing anemia.

To minimize your risk, consult your doctor before taking a vitamin that contains iron.

The B vitamins (water soluble), as well as vitamins A, E and D (fat soluble), may be toxic to the body if taken in large amounts as well.

Vitamin Deficiencies

While large doses of vitamins can lead to hypervitaminosis, an insufficient amount of certain vitamins can lead to adverse health effects as well. People commonly have deficiencies in the amount of calcium, vitamin D, potassium, iron, vitamin B12, folate and magnesium in their bodies.

A folate deficiency can be dangerous in pregnant women, leading to neural tube defects in unborn children. Moreover, many women of child-bearing age suffer from iron deficiency, which can cause anemia and symptoms such as fatigue. This symptom is also found in individuals who lack vitamin D. In addition, vitamin D deficiency causes muscle aches and can result in bone softness if left untreated for a long period of time.

The Origin of the Name "Vitamins"

Vitamins got their name back in the beginning of the 20th century when a scientist named Casmir Funk hypothesized that not enough “vital amines” (an amine is a kind of biologic molecule) in the diet could result in illness.

Wrapping Up

If you suspect you're lacking certain nutrients or want to take vitamins to treat a health problem, mood disorder or other condition, speak with a health care professional to determine which vitamins to take and in what quantities. Blood tests can reveal which nutrients you're missing.


Harvard School of Public Health. Nutrition and vitamins. Accessed July 2013.

Lonn E, Bosch J, Yusuf S, et al. Effects of long-term vitamin E supplementation on cardiovascular events and cancer: a randomized controlled trial. Journal of the American Medical Association 2005; 293: pages 1338-47. Accessed July 2013.

Vitamins and minerals. Accessed July 2013.

American Heart Association. Nutrition Center. Accessed July 2013.

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