Karen Overstreet, Roy, Heli J. | 12/19/2009 1:33:18 AM
In this article:
|What You Will Learn|
|What are Vitamins?|
|Do You Need a Vitamin Supplement?|
Who needs vitamins? Do you need them? How many should you take? Is one multi-vitamin enough, or do you need several different specialty vitamins? Can you get vitamins only from pills, or are there other sources?
There is much controversy over whether an average healthy person needs vitamin supplements. Most nutrition professionals agree that the average person gets plenty of vitamins from food, especially if they eat a balanced diet. Information in newspapers and magazines and on television can be enticing because advertisements for supplements tell us that if we take the supplement, we have more energy, we are smarter, and we can live longer. At the same time, scientists are discovering new information about nutrients and vitamins, such as a new use for a vitamin. When this information is released, it can lead to confusion. Sometimes, studies prove that a vitamin doesn't do what people thought it did. While this seems to make no sense, it is part of the research process. It is the way we learn new things that will help to keep people healthy.
In this lesson, you will learn about the two major types of vitamins – fat-soluble and water-soluble vitamins. You will learn how each vitamin functions in your body and the symptoms of deficiency and over-consumption (toxicity). You also will learn which foods are the best sources of each vitamin and the Dietary Reference Intakes (DRI) for each. Finally, this lesson will discuss vitamin supplements – who needs them and who doesn't. This information will help you plan a healthy diet, including all necessary vitamins and nutrients.
MyPlate is a tool developed to teach people the healthiest way to eat. There are five food groups. Each group contains foods that share some of the same vitamins and nutrients vital to humans. No food or food group contains all the vitamins or other nutrients needed to maintain health, therefore, it is important to eat a variety of foods from MyPlate each day.
Vitamins are organic substances. This means they contain the element carbon. Vitamins are required for specific body functions. Certain body functions need one or more vitamins to make them work. One example is blood clotting. The blood needs vitamin K to clot. If you have a lack of vitamin K, you may lose too much blood if your skin is scratched or cut.
Vitamins are needed in small amounts in the diet. Because of this, vitamins (and minerals) are known as micronutrients. Humans either can't make the vitamin in their bodies or can't make enough to meet their needs. If people eat a balanced diet, they will easily get all their vitamins.
There are 13 vitamins that fall into two categories: fat-soluble vitamins and water-soluble vitamins. Water-soluble vitamins are dissolved by the water in body cells. Once they are dissolved, they are removed by urine. Fat-soluble vitamins are stored in the fatty tissues and the liver. The fat-soluble vitamins do not dissolve in water, so if there is excessive intake, it is harder to remove them from the body. If a person consumes too much of a fat-soluble vitamin over time, it can become toxic and have negative side effects. It is much harder to get too much of a water-soluble vitamin.
The fat-soluble vitamins are vitamins A, D, E and K. These vitamins are stored in the body. When these vitamins are ingested, they dissolve in fat.
There are two basic types of vitamin A – retinoids and beta-carotene. Retinoids come from animal sources such as liver and eggs. Beta-carotene comes from plant sources, particularly orange, deep green or yellow vegetables and fruits.
Vitamin A Functions
1. Vitamin A helps many body processes work. It is most known for its vision-related functions. People who have mild vitamin A deficiencies may have night blindness. Those with severe vitamin A deficiencies may become totally blind.
2. Vitamin A helps to build the immune system so the body is more resistant to disease.
3. Vitamin A plays a role in cell growth.
4. Vitamin A is important to healthy fetal development.
5. A vitamin A deficiency can cause the taste buds on the tongue to be less sensitive.
6. Vitamin A is an antioxidant. Antioxidants protect the body from some of the negative effects of oxygen. Vitamins C and E are also antioxidants. The antioxidant vitamins may protect against cancer, aging, heart disease and other diseases.
Vitamin A Deficiency and Toxicity Symptoms
A lack of vitamin A can produce several symptoms in the body. Some of these include hardening of the skin, night blindness, clouding of the cornea, liver damage and reduced growth rate in children. Vitamin A deficiency is not frequently a problem in the United States for two reasons. The first is that most people have enough food to eat. Overeating is a bigger problem than deficiency. The second reason is that vitamin A is not water-soluble, so excess amounts can build up in the body, causing toxicity. The symptoms of too much vitamin A (toxicity) can range from headaches and joint pain to dry skin, hair loss and even death. The RDA for vitamin A is 900 micrograms a day for men and 700 micrograms a day for women.
Sources of Vitamin A
Good sources of retinoid vitamin A include liver, fish oil, eggs, margarine and milk that has been fortified with vitamin A. Good sources of beta-carotene include dark green, leafy vegetables, and deep orange or yellow vegetables. Carrots, squash, broccoli, spinach and sweet potatoes are all good sources of beta-carotene.
Remember: carrots = carotene!
Vitamin D is slightly different from the 12 other vitamins. This is the only vitamin that can be made in the body. When the skin is exposed to sunlight, the skin cells can make enough vitamin D to meet the body's needs. Usually, about 15 minutes a day of exposure to the sun is sufficient. Lighter-skinned and young people may need less sun, and darker-skinned and older people may need more. When vitamin D is made by the skin, it is called a hormone.
Vitamin D can also be obtained from foods. When a person gets vitamin D from food rather than sunlight, vitamin D is a true vitamin. In the United States, milk is fortified with vitamin D, so even people who are not frequently in the sun can get enough vitamin D. Eggs, liver and fish oils are dietary vitamin D sources. For both men and women, 15 mcg is the recommended amount to consume from dietary sources.
Vitamin D Functions
Vitamin D's major function is to keep the bones supplied with the calcium they need to stay strong. Depending on how much calcium the bones need, vitamin D can cause the intestines to absorb more calcium from food or the kidney to excrete less calcium.
Vitamin D Deficiency and Toxicity Symptoms
A lack of vitamin D can cause rickets, a disease characterized by weakened bones. Symptoms of rickets are bowed legs, an enlarged head and a deformed pelvis. Because vitamin D is a fat-soluble vitamin, it is possible to have too much in the body, causing toxicity. Children can have toxic levels of vitamin D if they consume just five times the RDA level. Too much vitamin D causes weakness, diarrhea, vomiting, mental confusion and calcium deposits in the organs.
Vitamin E is an antioxidant, along with vitamins A and C. Vitamin E prevents free radicals (compounds in the body that look for electrons) from taking too many electrons from the body cells. Without vitamin E protecting the cell's electrons, the cell could be damaged or destroyed. A vitamin E deficiency could cause destruction of the red blood cells in both children and adults. Many people believe that vitamin E can halt or reverse aging or improve sexual function. These myths haven't been scientifically proved.
Vitamin E Deficiency and Toxicity
A vitamin E deficiency can be hard to detect because it can remain hidden for a long time. Those with the greatest risk for a vitamin E deficiency are people whose bodies can't absorb fat because of a disease such as cystic fibrosis. Symptoms of a vitamin E deficiency are usually neurological disorders that affect the eyes or spine.
Vitamin E is not a very toxic substance. If people do consume too much, though (more than 500 micrograms a day), they might have symptoms such as nausea and vomiting, headaches, diarrhea and fatigue.
Sources of Vitamin E
Foods that contain high amounts of vitamin E include plant oils (corn, sunflower, safflower, soybean, peanut and others), margarine, leafy greens, oatmeal, peaches, eggs, liver, nuts, milk and whole grains. The RDA for vitamin E is 15 milligrams a day for men and 15 milligrams a day for women. A balanced diet usually provides enough vitamin E.
The major function of vitamin K is to aid in blood clotting. Vitamin K is needed by the body to make blood-clotting factors (agents that help the blood to clot) such as prothrombin. Without vitamin K, a person who receives a cut or scratch may continue to bleed. This is because the body can't make the clotting factors needed to form a scab. Frequently, when a person suffers a cerebrovascular accident (a stroke), the doctor prescribes a drug that keeps the blood from clotting too much. People taking these types of medications should consult their doctor or dietitian before consuming too much vitamin K because it could interfere with the medicine.
Excessive bleeding is the biggest symptom of a vitamin K deficiency. This is especially dangerous for those about to undergo surgery. Vitamin K toxicity is very rare because it is removed from the body easily.
Green leafy vegetables are the best sources of vitamin K. Food sources include spinach and other leafy greens, green beans, broccoli and peas. Liver also contains vitamin K. The RDA for vitamin K is 90 mcg for women and 120 mcg for men. Most people consume several times this amount, so deficiency is usually not a problem.
There are several water-soluble vitamins – the vitamin B complex and vitamin C. Because these are water-soluble, they can be dissolved in the cellular fluid. We don't store water-soluble vitamins in the body. Any excess amounts are removed from the body in the urine.
When foods containing water-soluble vitamins are cooked, they tend to lose many of these vitamins because of high cooking temperatures and because they will leach in water. Cooking vegetables in small amounts of water helps to limit the amounts of vitamins lost.
The B Vitamins
For women, 1.1 mg thiamin per day is recommended, and for men, 1.2 mg thiamin per day is recommended. Thiamin is found in meat (especially pork), dairy foods, fortified grain products, green beans, peanuts, other beans and seeds. White bread is fortified with thiamin and is the major dietary source of thiamin in the United States. A thiamin deficiency causes the disease beriberi. Before white bread was fortified with thiamin, this disease was a widespread problem. Signs of deficiency begin after less than two weeks of a thiamin-free diet. Symptoms of beriberi include weakness, tingling, irritability, muscle pain and loss of appetite. Today, the elderly and alcoholics are the two populations most at risk for a thiamin deficiency. Elderly people often eat more highly processed foods that have lost most of their thiamin during processing. Alcoholics have a harder time absorbing thiamin into their bodies.
Riboflavin aids the body's cells in converting food sources into energy needed to live and grow. Riboflavin recommendations are 1.1 mg per day for women and 1.3 mg per day for men. A lack of riboflavin in the diet causes the disease ariboflavinosis. The symptoms of this disease include an inflamed mouth and tongue, nervous-system disorders and mental confusion. Good sources of riboflavin are leafy green vegetables, mushrooms, liver and other meats, dairy products and enriched grain products.
Niacin is part of several vital cellular pathways. It plays a part in the conversion of food sources into energy and helps make fatty acids (parts of fats), among other things. Women should aim for consuming 14 mg per day, and men should aim for 16 mg per day. A lack of niacin in the diet causes the deficiency disease pellagra. Pellagra means rough, painful skin – the first symptom of the disease. Pellagra causes dermatitis, which is worsened by the sun. If left untreated, there are other symptoms such as diarrhea, dementia and finally death. Because white breads are enriched with niacin (along with thiamin and riboflavin), pellagra is no longer a problem in the United States. Too much niacin in the diet (more than 100 milligrams per day) can cause increased blood flow to the skin, creating a flushed appearance. Other symptoms include headaches and itching.
Pantothenic acid is involved in many pathways that work in the body. Pantothenic acid is a common vitamin found in the body. In fact, a deficiency is rare because pantothenic acid is found in so many foods. Symptoms of a deficiency are dermatitis and neuromuscular disorders. Foods that are especially good sources of pantothenic acid include eggs, liver, yeast, peanuts and milk.
Biotin can be found in several foods and can be made in the body. Egg yolks, liver, cheese, peanuts and yeast are all good sources of biotin. Most people are not at risk for a biotin deficiency. Rarely, however, infants can be born with low levels of the enzyme needed to make biotin in the body. This can lead to a deficiency. Symptoms of a biotin deficiency include dermatitis and hair loss.
This vitamin, also known as pyridoxine, is involved in many body processes. Some people have claimed that vitamin B6 is helpful in treating premenstrual syndrome (PMS) in women. This claim has not been proved.
Vitamin B6 can be found in many fruits and vegetables, such as broccoli, cantaloupe, bananas and spinach. Meat, fish and poultry are also good sources. A vitamin B6 deficiency is found most often in alcoholics because alcohol affects the structure of vitamin B6. The RDA for vitamin B6 is 1.3 milligrams per day for men and women. Vitamin B6 levels can easily become toxic if too much is consumed. Toxicity symptoms include numbness of the extremities and permanent nerve damage.
Folate, also known as folacin or folic acid, is important, especially for women who are pregnant or of child-bearing age. If a pregnant woman does not consume enough folate in her diet or has a folate deficiency, her child could be born with a neural tube defect such as spina bifida or anencephaly (absence of a brain). If a person has a folate deficiency, he or she usually has a type of anemia known as megaloblastic anemia. This means that the red blood cells cannot mature and divide to make new cells; therefore, they grow very large and fragile. Pregnant women, alcoholics and people taking certain medications have the biggest risk of folate deficiency.
There are several good food sources of folate. These include breakfast cereals that have been fortified with folate, leafy green vegetables, melons, oranges, orange juice, strawberries, liver, eggs and beans. Fresh fruits and vegetables are better sources than processed, canned or cooked ones because these processes destroy part of the folate. The RDA for folate is 400 micrograms per day for adults; however, women of child-bearing age should consume 400-800 micrograms per day to prevent birth defects.
One of the functions of vitamin B12 is to help the body use folate. A deficiency of vitamin B12 can cause a type of anemia known as pernicious anemia. Because vitamin B12 and folate deficiencies both cause anemia, it is sometimes difficult to tell which one a person is deficient in. Food sources of vitamin B12 include meat, poultry, seafood, eggs and organ meats. Milk products also contain vitamin B12. Because the best sources of vitamin B12 are animal foods, people who are strict vegetarians should make sure they consume vitamin B12 from other sources. These can include soy products, fortified cereals and vitamin supplements. The RDA for vitamin B12 is 2.4 micrograms per day for adults.
Vitamin C, also called ascorbic acid, has several functions. One is to make collagen, a protein used by the body in connective tissue. Vitamin C also helps the body absorb and use iron more efficiently. Therefore, if a person is anemic, he or she should consume more vitamin C in addition to more iron. Vitamin C is also an antioxidant, so it protects the body from free radicals.
Vitamin C is absorbed from the food in the small intestine. At a level of 40-180 milligrams per day of vitamin C (the RDA is 75 milligrams for women per day and 90 milligrams for men per day), the body uses 80% to 90% of this vitamin C. Excess intake of vitamin C means that less of the total vitamin is used and the excess is excreted in the urine. Excess vitamin C can also cause diarrhea.
If a person has a vitamin C deficiency, he or she may develop a disease called scurvy. Scurvy causes the connective tissue in the body to break down. This results in weakness and small hemorrhages on the skin and around the hair follicles that are visible on the surface of the skin. The gums and joints also bleed. However, scurvy is not common today.
Vitamin C is mainly found in citrus fruits such as oranges, lemons and grapefruits. It is also present in potatoes, tomatoes and green vegetables. Fresh fruits and vegetables are the best sources of vitamin C because cooking and processing these foods destroy the vitamin. The RDA for vitamin C is 75 milligrams for women per day and 90 milligrams for men per day.
A healthy person who eats a diet based on MyPlate probably doesn't need a vitamin supplement. Certain types of people could benefit from extra vitamin supplementation, however, and they include:
If you do choose to take a vitamin supplement, make sure it does not contain more than 50% to 150% of the RDA for vitamins A, D, E, C, folate, thiamin, niacin, riboflavin, vitamin B6 and vitamin B12.
Vitamins are a necessary and important part of our daily diets. Without vitamins, many processes that happen in your body would not work as well or may not work at all. Nutrition researchers have identified the optimal amount of vitamins we should have for our bodies to function normally. We can take advantage of this research and consume the vitamins we need in the proper amounts. There are two main types of vitamins, fat-soluble and water-soluble. The fat-soluble vitamins include vitamins A, D, E and K. There are many more water-soluble vitamins, specifically all of the B vitamins and vitamin C. While everyone needs vitamins, not everyone needs to take vitamin supplements. This depends on your health and eating habits.