Vitamins are nutrients we get from the food we eat. They assist in the biochemical reactions related to the metabolic process. In this lesson we’ll look specifically at vitamins A, B, C, D, E, and K. When scientists were naming the vitamins, they didn’t realize that the vitamin they had named B was actually a group of vitamins. That’s why some of the B vitamins have a number and a name and some just have a name. For example, vitamin B1 is thiamin. The synthetic form of folate is folic acid, and this form of vitamin B is in nutrient supplements and in fortified foods. Because vitamin B is really a group of vitamins, it is referred to as the vitamin B complex.
Vitamins can be divided into two groups: those that are water soluble and those that are fat soluble. The following chart explains the groups and the vitamins that are included in each group.
| Group | Vitamins Included | In the Body |
|---|---|---|
| Fat Soluble | vitamin A vitamin D vitamin E vitamin K |
Fat soluble vitamins are transported through the body and are absorbed and stored in fat and in the liver. Excessive consumption of these vitamins can be harmful and can lead to toxicity. |
| Water Soluble | vitamin B complex thiamin riboflavin niacin folate vitamin C |
Water soluble vitamins are dissolved in water and transported through the body. They cannot be stored in the body and must be eaten daily. |
Vitamins help maintain healthy hair, skin, and nerves. Some vitamins function as antioxidants. Antioxidants are substances that react with oxygen to protect other substances in the body from the harmful effects of oxygen exposure. Vitamins A, C, and E are antioxidants.
Even though we do not need all vitamins in large amounts, we still need them, because they are essential to good health. Vitamins help keep body tissues healthy and body systems working properly. As you can see in the previous table, fat-soluble vitamins are stored in the body’s fat and liver, and if you eat more of these vitamins than you need, they are stored until they are needed. With water-soluble vitamins, your body takes what it needs, and the rest remain in the body for only a short time. It is necessary to eat foods rich in water-soluble vitamins on a daily basis. One important thing to remember about vitamins is that eating too few will keep our bodies from operating at full efficiency and eating too many can be damaging to health.
Let’s look in the following table at the individual vitamins to see their functions, good food sources, and deficiency diseases that they prevent. A deficiency disease occurs when the body has had a severe shortage of a nutrient and that shortage has caused an illness. The four fat-soluble vitamins will be listed first, followed by the water-soluble vitamins. Some of the vitamins in the vitamin B complex will be listed by number and name and some just by name.
| Vitamin | Function | Sources | Deficiency Disease |
|---|---|---|---|
| Vitamin A | Vitamin A is vital to good vision; it prevents night blindness; it promotes healthy skin, hair growth; it promotes the health of mucous membranes; and it is an antioxidant. | liver, oranges, pears, yellow fruits, and vegetables | night blindness, unhealthy skin and hair |
| Vitamin D “sunshine vitamin” |
Vitamin D works with minerals to help build healthy bones and teeth. | fortified milk and milk products, exposure to sunlight | rickets—a disease that causes bones to weaken |
| Vitamin E | Vitamin E helps break down polyunsaturated fats, and it protects membranes of white and red blood cells because it is an antioxidant. | green leafy vegetables, fruits, whole grains, liver, apples, fats | impaired fat absorption |
| Vitamin K | Vitamin K is essential for blood clotting. | dark-green vegetables, cabbage, cauliflower | liver hemorrhaging |
| Vitamin C | Vitamin C helps form collagen, which holds cells together; it helps the body heal itself; it helps in the growth and repair of body tissues and blood vessels; it is also an antioxidant. | citrus fruits, cantaloupe, strawberries, pineapple | scurvy—a disease of weakness, anemia, and spongy gums |
| Vitamin B1 Thiamine | Thiamine helps protect nerve tissue, and helps the digestive system and the appetite through energy metabolism. | milk, whole grains, poultry, fish, dried beans | beriberi—a disease that causes nerve disorders |
| Vitamin B2 Riboflavin | Riboflavin promotes growth, helps with nerves and digestion, and works with protein. | milk, whole grains, dark-green vegetables, fish, eggs | premature aging |
| Niacin | Niacin helps nerve tissues and the digestive system. | milk, whole grains, dates, peaches, fish, poultry, peanuts | pellagra—a disease that causes skin eruptions and mental disorders |
| Folate | Folate helps create new red blood cells. | oranges, dark-green vegetables, whole grains, meat, eggs | anemia, and some birth defects like neural tube damage |
| Vitamin B6 Pyridoxine | Vitamin B6 helps with hemoglobin and overall good health. | meat, vegetables, bananas | poor health |
| Vitamin B12 Cobalamin | Vitamin B12 helps with generation of DNA, and helps with cells, bone marrow, and red blood cells. | milk, eggs, meat, fruit, vegetables | anemia, damage to intestinal tract |
Just as the other vitamins, the vitamin B complex is very important. Vitamins B6 and B12 have a significant impact on the nervous system, and they release energy from fats, carbohydrates, and proteins. Folate, another B vitamin, is especially important for women of childbearing age. Those women who have an inadequate folate intake are more likely to give birth to babies with neural tube damage. Neural tube damage affects the brain and spinal cord and can cause mental retardation, paralysis, and premature death. Research confirms that folic acid from fortified foods and supplements reduces the risk of neural tube damage. Women of childbearing age should consume 400 micrograms of folic acid daily from supplements or fortified foods. Neural tube damage occurs during the first weeks of pregnancy before a woman may realize she is pregnant. It is essential for pregnant women to meet the requirement for folic acid so that this damage will not occur.
Because folate is such an important vitamin, I provided a copy of the Folate Fact Sheet from the National Institutes of Health (NIH). As you read over this fact sheet, notice which foods are the best sources of folate. Also, pay careful attention to the information about which groups of people are particularly susceptible to folate deficiency. Pay close attention to the information in this fact sheet, because it will be covered in your assignments and in the exam.