Vitamins are a group of substances essential to normal metabolism, growth and development, and regulation of cell function; vitamins work together with enzymes, co-factors, and other substances.They are obtained exclusively from food, except for vitamin D and vitamin K, which the body can synthesize. There are 13 vitamins needed by the body: Vitamins A, C, D, E, K, and the B vitamins (thiamine, riboflavin, niacin, pantothenic acid and biotin, vitamin B6, vitamin B12, and folacin). In addition, vitamin A, which comes from animal sources such as eggs and meat, is present in the form of a precursor, beta carotene, when manufactured by plants.
Each vitamin has specific functions. If a certain vitamin is deficient, a deficiency disease results.
Recommended daily allowances (RDAs), are defined as the levels of intake of essential nutrients that, on the basis of scientific knowledge, the Food and Nutrition Board judges to be adequate to meet the known nutrient needs of practically all healthy people.
The best way to get the daily requirement of essential vitamins is to eat a balanced diet that contains a variety of foods from the food guide pyramid.
The term "balanced" simply means that a diet adequately meets your nutritional needs while not providing any nutrients in excess. A balanced diet provides optimal protein and complex carbohydrate while containing only moderate amounts of sodium, fats, and simple sugars. To achieve a balanced diet, you must consume a variety of foods from each of the food groups.
- milk, cheese, yogurt
- meat: chicken, fish, beef, pork, lamb
- legumes: beans and peas
- nuts and seeds
- whole grain breads
- enriched breads
An unbalanced diet can cause problems with maintenance of body tissues, growth and development, brain and nervous system function, as well as problems with bone and muscle systems.
Here are the vitamins that your body requires, their functions, and sources:
- Vitamin A
This fat-soluble vitamin helps in the formation and maintenance of healthy teeth, skeletal and soft tissue, mucous membranes, and skin. It is also known as retinol, as it generates the pigments that are necessary for the working of the retina. It promotes good vision, especially in dim light. It may also be required for reproduction and lactation. Beta carotene is a precursor to vitamin A; it has antioxidant properties.
Vitamin A is found in milk, cheese, cream, liver, kidney, and cod and halibut fish oil. All of these sources, except for skim milk that has been fortified with vitamin A, are high in saturated fat and cholesterol. The vegetable sources of beta carotene are fat and cholesterol free. The body regulates the conversion of beta carotene to vitamin A based on the body's needs. Sources of beta carotene are carrots, pumpkin, sweet potatoes, winter squashes, cantaloupe, pink grapefruit, apricots, broccoli, spinach and most dark green leafy vegetables. The more intense the color of a fruit or vegetable, the higher the beta carotene content.
- Vitamin B1
Thiamine (vitamin B1) helps the body cells convert carbohydrates into energy. It is also essential for the functioning of the heart and for healthy nerve cells and the brain.
Thiamine is found in fortified breads, cereals, pasta, whole grains (especially wheat germ), lean meats (especially pork), fish, dried beans, peas, and soybeans. Dairy products and milk, fruits, and vegetables are not very high in thiamine, but when consumed in a large amounts they become a significant source.
- Vitamin B2
Riboflavin (vitamin B2) works with the other B vitamins and is important for body growth and red cell production. Similar to thiamine, it helps in releasing energy from carbohydrates.
Lean meats, eggs, legumes, nuts, green leafy vegetables, dairy products, and milk provide riboflavin in the diet. Breads and cereals are often fortified with riboflavin. Because riboflavin is destroyed by exposure to light, foods with riboflavin should not be stored in glass containers that are exposed to light.
- Vitamin B3
Niacin (vitamin B3) assists in the functioning of the digestive system, skin, and nerves. It is also important for the conversion of food to energy.
Niacin is found in dairy products, poultry, fish, lean meats, nuts, and eggs. Legumes and enriched breads and cereals also supply some niacin.
- Vitamin B6
Vitamin B6 is also known as pyridoxine. The more protein a person eats the more B6 is required to use the protein. It helps in the formation of red blood cells and in the maintenance of normal brain function. It also assists in the synthesizing of antibodies in the immune system.
Vitamin B6 is found in beans, nuts, legumes, eggs, meats, fish, whole grains, and fortified breads and cereals.
- Vitamin B9
Folacin (vitamin B9) acts as a coenzyme (with vitamin B-12 and vitamin C) in the breakdown (metabolism) of proteins and in the synthesis of new proteins. It is necessary for the production of red blood cells and the synthesis of DNA (which controls heredity), as well as tissue growth and cell function. It also increases the appetite and stimulates the formation of digestive acids. Synthetic folacin supplements may be used in the treatment of disorders associated with folacin deficiency and may also be part of the recommended treatment for certain menstrual problems and leg ulcers.
Sources of folacin include: beans and legumes, citrus fruits and juices, wheat bran and other whole grains, dark green leafy vegetables, poultry, pork, shellfish and liver.
- Vitamin B12
Vitamin B12, like the other B vitamins, is important for metabolism. It helps in the formation of red blood cells and in the maintenance of the central nervous system.
Vitamin B12 is found in eggs, meat, poultry, shellfish, and milk and milk products.
- Pantothenic Acid and Biotin
Pantothenic acid is essential for the metabolism of food. It is also essential in the synthesis of hormones and cholesterol. Biotin is essential for the metabolism of proteins and carbohydrates like the other B vitamins, and in the synthesis of hormones and cholesterol.
Pantothenic acid and biotin are found in eggs, fish, milk and milk products, whole-grain cereals, legumes, yeast, broccoli and other vegetables in the cabbage family, white and sweet potatoes, lean beef, and other foods.
- Vitamin C
Vitamin C is also known as ascorbic acid. It promotes healthy teeth and gums, helps in the absorption of iron, and in the maintenance of normal connective tissue. It also promotes wound healing.
Vitamin C is found in citrus fruits, strawberries, tomatoes, broccoli, turnip greens and other greens, sweet and white potatoes, and cantaloupe. Most other fruits and vegetables contain some vitamin C; fish and milk contain small amounts.
- Vitamin D
Vitamin D promotes the body's absorption of calcium, which is essential for the normal development of healthy teeth and bones. It also helps maintain adequate blood levels of the minerals calcium and phosphorus.
Vitamin D is found in cheese, butter, margarine, cream, fortified milk (all milk in the United States is fortified with Vitamin D), fish, oysters, and fortified cereals. The body can synthesize vitamin D when the skin is exposed to sunshine.
- Vitamin E
Vitamin E is also known as tocopherol; it is an antioxidant. It is also important in the formation of red blood cells and the use of vitamin K.
Vitamin E is found in wheat germ, corn, nuts, seeds, olives, spinach, asparagus, and other green leafy vegetables, vegetable oils (corn, sunflower, soybean, and cottonseed) and products made from them such as margarine.
- Vitamin K
Vitamin K is known as the clotting vitamin, because without it blood would not coagulate. Some studies indicate that it helps in maintaining strong bones in the elderly.
Vitamin K is found in cabbage, cauliflower, spinach, and other green leafy vegetables, cereals, soybeans, and other vegetables. Bacteria in the intestines normally also produce vitamin K.
For more information about vitamins and their functions, visit any of the websites listed below: