Vitamins are organic compounds which are vital to life. Many of them function as coenzymes, supporting a multitude of biological functions. The fat-soluble vitamins include A, D, E, and K. These vitamins should be eaten with food that contains a small amount of fat to aid in their absorption. Once absorbed, these vitamins are delivered to target cells in the body, with any remainder being stored in the liver for future use. The rest of the vitamins are known as water-soluble. These include primarily Vitamin C, Biotin, and the B vitamins. Because they are water-soluble, many of these vitamins are more easily excreted from the body than the fat-soluble vitamins.
Vitamin B-complex refers to all of the known essential water-soluble vitamins except for vitamin C. These include thiamine (vitamin B1), riboflavin (vitamin B2), niacin (vitamin B3), pantothenic acid (vitamin B5), pyridoxine (vitamin B6), biotin, folic acid and the cobalamins (vitamin B12). Vitamin B was once thought to be a single nutrient that existed in extracts of rice, liver, or yeast. Researchers later discovered these extracts contained several vitamins, which were given distinguishing numbers. Unfortunately, this has led to an erroneous belief among non-scientists that these vitamins have a special relationship to each other. Further adding to confusion has been the unofficial designation of other substances as members of the B-complex, such as choline, inositol, and para-aminobenzoic acid ( PABA), even though they are not essential vitamins.
Each member of the B-complex has a unique structure and performs unique functions in the human body. Vitamins B1, B2, B3, and biotin participate in different aspects of energy production, vitamin B6 is essential for amino acid metabolism, and vitamin B12 and folic acid facilitate steps required for cell division. Each of these vitamins has many additional functions. However, contrary to popular belief, no functions require all B-complex vitamins simultaneously.
Human requirements for members of the B-complex vary considerablyfrom 3 mcg per day for vitamin B12 to 18 mg per day for vitamin B3 in adult males, for example. Therefore, taking equal amounts of each oneas provided in many B-complex supplementsmakes little sense. Furthermore, there is little evidence supporting the use of mega doses of B-complex vitamins to combat everyday stress, boost energy, or control food cravings, unless a person has a deficiency of one or more of them. Again, contrary to popular belief, there is no evidence indicating people should take all B vitamins to avoid an imbalance when one or more individual B vitamin is taken for a specific health condition.
Most multivitamin-mineral products contain the B-complex along with the rest of the essential vitamins and minerals. Since they are more complete than B-complex vitamins alone, multiple vitamin-mineral supplements are recommended to improve overall micronutrient intake and prevent deficiencies.
Vitamin B-complex includes several different components, each of which has the potential to interact with drugs. It is recommended that you discuss the use of vitamin B-complex and your current medication(s) with your doctor or pharmacist.
Vitamin A (Beta-carotene, Retinol)
Retinol is the pure form of Vitamin A, and comes from animal products. Beta-carotene is a provitamin A (which converts to Vitamin A in your body) which is found in plants. It converts to Vitamin A at about a rate of 50%.
Natural Sources: Cantaloupe, carrots, spinach, sweet potatoes, tuna, liver, milk, broccoli, asparagus, leaf lettuce, watermelon
RDI: 5000 IU (Retinol: 1 mcg = 1 RE = 3.3 IU; Beta-carotene: 6 mcg = 1 RE = 10 IU)
Function: Essential for night vision and proper function of the retina; supports mucus-forming cells which provide essential lubricants used throughout the body; promotes bone growth and maintenance; helps the body combat bacterial, parasitic, and viral infections. It can also be used as a topical treatment for acne.
Deficiency Symptoms: Most people get enough Vitamin A from their diet. Deficiencies can occur in people who have cancer, tuberculosis, pneumonia, urinary tract infections, prostate disease, digestive conditions that impair fat absorption. Early deficiency symptom include night blindness, dry or rough skin, lack of tear secretion, weight loss, poor bone growth, diarrhea, acne and fatigue.
Toxicity: For most people, up to 25,000 IU (7,500 mcg) of vitamin A per day is considered safe. However, people over age 65 and those with liver disease should probably not supplement with more than 15,000 IU per day, unless supervised by a doctor. In women who could become pregnant, the maximum safe intake is being re-evaluated. However, less than 10,000 IU (3,000 mcg) per day is generally accepted as safe. There is concern that larger intakes could cause birth defects. Excessive amounts can cause irritability, headaches, vomiting, bone pain, weakness, and blurred vision.
Thiamin (Vitamin B1)
Natural Sources: Beans, beef, oatmeal, ham, oranges, pastas, wheat germ, pork, baked potato
RDI: 1.5 mg Safe Upper Limit: 50 mg
Function: Keeps mucus membranes healthy; maintains normal function of nervous system, muscles and heart; prevents beriberi; converts starches and sugars into energy for glucose formation which is needed by the brain for mental acuity
Deficiency Symptoms: Loss of appetite, fatigue, nausea, depression, pain or tingling in arms or legs, rapid heartbeat, irritability, headache
Toxicity: Surplus dietary thiamin is rapidly lost in the urine via the kidneys, so there is no danger from excessive intake
Riboflavin (Vitamin B2)
Natural Sources: Asparagus, broccoli, fortified cereals, cheese, fish, milk, poultry, spinach, yogurt, eggs
RDI: 1.7 mg Safe Upper Limit: 200 mg
Function: Aids in the release of energy from food; maintains healthy mucus membrane lining respiratory, digestive, circulatory and excretory tracts when used in conjunction with Vitamin A.; preserves integrity of the nervous system, skin, and eyes and activates Vitamin B6
Deficiency Symptoms: Cracks and sores in corners of mouth; inflammation of the tongue and lips; eyes that are overly sensitive to light and easily tired; itching and scaling of skin around nose, mouth, forehead, ear and scalp
Toxicity: There is no known toxicity as any excess is secreted in the urine
Niacin (Vitamin B3)
Natural Sources: Beef liver, fortified breads and cereals, chicken, tuna, veal, peanut butter, pork or ham, salmons, potatoes, soybeans
RDI: 20 mg Safe Upper Limit: 35 mg
Function: Prevents pellagra; acts as a coenzyme in 200 metabolic reactions; reduces cholesterol and triglycerides; treats vertigo and ringing in the ears.
Deficiency Symptoms: Delirium, fatigue, loss of appetite, headaches, skin lesions, indigestion
Toxicity: Because niacin is water-soluble, you would have to take exorbitant amounts to experience in toxicity. Some people take niacin in doses of 500 to 1000 mg daily to help reduce cholesterol. They experience common side effect of flushing and itching. Some doctors advise taking an aspirin to prevent these symptoms.
Pantothenic Acid (Vitamin B5)
Natural Sources: Fortified cereals, mushrooms, peanuts, salmon, whole grains, broccoli, chicken, milk, oranges
RDI: 10 mg Safe Upper Limit: 1000 mg
Function: Helps produce coenzyme A which the body uses to detoxify many harmful man-made compounds its exposed to in herbicides, insecticides and drugs; involved in the conversion of food to energy; essential for metabolism of carbohydrates, proteins, and fats.
Deficiency Symptoms: Sensation of burning feet, loss of appetite, depression, fatigue, insomnia, vomiting
Toxicity: There is no known toxicity
Pyridoxine (Vitamin B6)
Natural Sources: Avocados, bananas, beef, brown rice, chicken, eggs, oats, peanuts, soybeans, whole wheat
RDI: 2 mg Safe Upper Limit: 100 mg
Function: Helps in energy production; assists in fat and protein metabolism; helps to create neurotransmitters
Deficiency Symptoms: Reduced protein synthesis, weakness, confusion, irritability, insomnia,
Toxicity: Excess use has been linked to nerve disorders as well as to oversensitivity to sunlight, which can produce skin rashes and numbness.
Folate (Vitamin B9, Folic Acid)
Your best bet is to get folic acid from fresh, raw sources. In general, much of the folic acid is killed by heat and light.
Natural Sources: Asparagus, navy and pinto beans, broccoli, fortified cereals, spinach, citrus fruits and juices, sprouts, green leafy vegetables
RDI: 400 mcg Safe Upper Limit: 1000 mcg
Function: It works with approximately 20 different enzymes to build DNA; essential for normal nerve function, helps prevents heart disease, strokes, and cancers of the lungs, colon, and cervix; regulates embryonic and fetal development of nerve cells and prevents neural-tube defects.
Toxicity: Folic acid has virtually no side effects, even when taken in high amounts.
Vitamin B12 (Cyanocobalamin)
Vitamin B12 compounds are synthesized exclusively by bacteria, fungi and algae
Natural Sources: Beef, beef liver, clams, eggs, oysters, sardines, ham, crab, salmon, tuna
RDI: 6 mcg Safe Upper Limit: 3000 mcg
Function: Vital in the production of myelin, the fatty sheath that insulates nerve fibers, keeping electrical impulses moving through the body; aids in folate metabolism; treats some types of nerve damage and anemia
Deficiency Symptoms: Memory loss, confusion, delusion, fatigue, loss of appetite, loss of balance, decreased reflexes, impaired touch or pain perception, numbness and tingling in the arms and legs. Deficiencies have also been linked to multiple sclerosis and Alzheimers disease. Vegetarians are at risk of becoming deficient.
Toxicity: Vitamin B12 supplements are considered extremely safe, even in larger doses. People suffering from folate deficiency, iron deficiency, Lebers disease, polycythemia vera or urema should consult with their doctor before use
Vitamin C (Ascorbic acid)
Natural Sources: Broccoli, grapefruit, lemons, orange juice, oranges, strawberries, spinach, tomatoes
RDI: 60 mg Safe Upper Limit: 2000 mg
Function: Promotes healthy capillaries, gums, and teeth; helps heel wounds, burns and broken bones; prevents and treats scurvy; enhances immune function; helps form collagen in connective tissue; increase calcium absorption; contributes to hemoglobin and red blood cell production in bone marrow; reduces free radical production
Deficiency Symptoms: Scurvy, muscle weakness, swollen gums, loss of teeth, lethargy, swollen or painful joints, slow wound healing, easing bruising
Toxicity: Overall, Vitamin C is really not toxic. However, excessive intake can cause diarrhea, frequent urination, and skin rashes
Vitamin D (Calcitriol)
Natural Sources: Vitamin D is synthesized by your skin when it is exposed to the sun. Food sources include egg yolks, liver, tuna, fortified milk and cereals
RDI: 400 IU Safe Upper Limit: 2000 IU
Function: Vitamin Ds most important role is maintaining blood levels of calcium, which it accomplishes by increasing absorption of calcium from food and reducing urinary calcium loss. Both effects keep calcium in the body and therefore spare the calcium that is stored in bones. When necessary, vitamin D transfers calcium from the bone into the bloodstream, which does not benefit bones.
Deficiency Symptoms: Elderly people and anyone who spends most of the day inside are at risk for deficiency. Symptoms include rickets, malformations of joints or bones, and late tooth development in children. Adults may experience a softening of the bones known as osteomalacia, and muscle weakness.
Toxicity: Excessive use can cause over-absorption of calcium and calcium deposits in kidneys, heart and blood vessels.
Vitamin E (Tocopherol)
The natural form of this vitamin is labeled d-alpha-tocopherol. The synthetic form is labeled dl-alpha-tocopherol. Theses two forms make more Vitamin E available to your body than other forms. Vitamin E loses its potency when exposed to air, heat and light, so make sure its stored in a cool dark place.
Natural Sources: Almonds, asparagus, avocados, broccoli, canola oil, fortified cereals, wheat germ, sunflower seeds, walnuts
RDI: 30 IU Safe Upper Limit: 1500 IU natural form, 1100 IU synthetic
Function: Acts as an anti-blood clotting agent; promotes normal red blood cell formation; protects against prostate cancer; improves immunity; serves as an antioxidant for cancer, heart disease, and free radicals in the body. Vitamin E helps neutralize free radical. Free radicals are naturally occurring unstable molecules that damage healthy molecules by stealing electrons for themselves.
Deficiency Symptoms: Lethargy, apathy, lack of concentration; nerve dysfunction
Toxicity: Appears to be relatively safe, even at higher doses. People who are taking anticoagulants (blood thinners or aspirin) should not supplement with Vitamin E. The nutrient may also interfere with the absorption and action of Vitamin K which is involved in blood clotting.
Biotin (Vitamin H)
Natural Sources: Egg yolks, walnuts, soybeans, yeast, corn, cauliflower, milk, peanuts, almonds, bananas
RDI: 300 mcg Safe Upper Limit: 2500 mcg
Function: Facilitates the metabolism of proteins and carbohydrates
Deficiency Symptoms: Deficiencies are rare, but symptoms include fatigue, depression, nausea, loss of appetite, hair loss, increased blood-cholesterol levels
Toxicity: There are no reports of toxicity, even when taken in doses far above the RDI of 300 mcg.
Supplements are available but doctors dont usually recommend them. Vitamin K can be synthesized by bacteria in the intestine. However, newborns are given a shot of this vitamin at birth because they lack the gastrointestinal bacteria that synthesize Vitamin K.
Natural Sources: Alfalfa, asparagus, broccoli, cheddar cheese, green leafy vegetables, liver
RDI: 80 mcg Safe Upper Limit: 30,000 mcg
Function: Essential for normal blood clotting
Deficiency Symptoms: Nosebleeds, blood in urine, bleeding from capillaries or skin