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Vitamins: Functions & Food Sources

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Instructor: Sarah Lawson

Sarah has taught nursing courses and has a master's degree in nursing education.

Vitamins are organic compounds that aid in growth and nutrition. Explore an overview of vitamins, discover the functions and food sources of vitamins, and learn about water-soluble and fat-soluble vitamins. Updated: 11/03/2021

Vitamins Overview

A vitamin is an organic compound that is essential for normal growth and nutrition. Vitamins are required in small amounts in the daily diet because they cannot be synthesized, or made, by the body. Vitamins are found naturally in plants, such as fruits and vegetables, and also in animal sources.

Vitamins have a wide variety of importance and function in our bodies. Some examples of vitamin functions include helping to promote growth and repair of tissues and cells, acting as antioxidants, and improving metabolism. An antioxidant is a molecule that stops the action of free radicals. Free radicals occur naturally in the body and can cause damage to cells, which could lead to cancer. There are 13 vitamins presently that are universally recognized.

Vitamins are either water-soluble or fat-soluble. Water-soluble vitamins, B vitamins and vitamin C, dissolve in water and are excreted through the kidneys if excess amounts are taken. Fat-soluble vitamins, vitamins A, D, E, and K, dissolve in fat and are stored in the fat of the body. It is more difficult for the body to excrete excess fat-soluble vitamins, which makes it possible for toxic levels to accumulate if too many are taken.

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  • 0:01 Vitamins Overview
  • 1:23 Water-Soluble Vitamins
  • 4:44 Fat-Soluble Vitamins
  • 7:43 Lesson Summary
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Water-Soluble Vitamins

Water-soluble vitamins dissolve in water and cannot be stored for later use by the body. There are a total of nine water-soluble vitamins. They are the B vitamins: folate, thiamine, riboflavin, niacin, pantothenic acid, biotin, vitamin B6, vitamin B12, and vitamin C.

Folate is very important in the synthesis of DNA. For this reason, folate is vitally important during pregnancy in the prevention of birth defects. Folate is available in leafy green vegetables and legumes, seeds, orange juice, liver, and many enriched refined grains.

Thiamine plays a role in the transmission of nerve impulses by promoting nerve health. Thiamine is also needed for the metabolism of carbohydrates and amino acids. Thiamine is found in pork, whole-grain breads and cereals, and nuts and seeds.

Riboflavin helps with the metabolism of carbohydrates, proteins, and fats. It also helps to enhance the function of niacin and vitamin B12. Riboflavin is found in leafy greens, milk products, and enriched breads and cereals.

Niacin is necessary for skin tissue health and proper functioning of the digestive system. Niacin can also help lower triglycerides and LDL cholesterol, bad cholesterol, while raising HDL cholesterol, good cholesterol. Meat, poultry, fish, whole-grain and enriched breads and cereals, vegetables, and peanut butter are all sources of niacin.

Pantothenic acid and biotin help the body obtain energy from food ingested and are necessary for metabolism. Pantothenic acid also assists in the production of hormones and cholesterol. Biotin is produced in the gut by bacteria. Both pantothenic acid and biotin are available in a wide variety of foods.

Vitamin B6 plays a very important role in the production of nonessential amino acids and helps the body break down glycogen. Glycogen is the storage form of glucose; the body will break down glycogen when energy is needed. Vitamin B6 assists in the metabolism of nutrients and helps keep the immune and nervous systems healthy. Vitamin B6 is available in meat, poultry, fish, vegetables, and fruits.

Vitamin B12 is needed for metabolism of fatty acids and amino acids and is also necessary for DNA synthesis. It helps to keep the nervous system functioning appropriately and red blood cells healthy. Vitamin B12 is found in meat, poultry, fish, seafood, eggs, and milk products.

Vitamin C is needed to make collagen. Collagen is a structural protein; it is in the bones, skin, teeth, blood vessels, and other connective tissues throughout the body. Vitamin C is an antioxidant and helps to reduce the risk of developing some chronic diseases, such as heart disease and cancer. It also helps to support our immune system. Vitamin C is found only in fruits and vegetables; it is found in citrus fruits, vegetables in the cabbage family, cantaloupe, strawberries, peppers, tomatoes, potatoes, lettuce, papayas, mangoes, and kiwi.

Fat-Soluble Vitamins

Vitamins A, D, E, and K are the fat-soluble vitamins. They are called this because they are soluble in lipids, which are fat. After ingestion, they are absorbed into the blood circulation where they will then be stored into the body tissues. Once they are in the tissues, they tend to stay there. For this reason, if a person takes in too much of a fat-soluble vitamin, over time that vitamin can accumulate in their body. This is a potentially dangerous situation called hypervitaminosis and means that too much of a vitamin is present in the body.

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