A Brief Introduction to Vitamins

Vitamins are a group of organic compounds only found in plants and animals. Vitamins were discovered by Dutch physician, Christiaan Eijkmann, who won the 1929 Nobel Prize in Physiology or Medicine. The term "vitamine" (which evolved to drop the "e") was first used in 1912 by Dr. Casimir Funk, a Polish biochemist, in reference to substances that were vital to life and contained an amine--a basic nitrogen compound.

Vitamins are divided into two groups based on their solubility: water-soluble and fat-soluble vitamins.

The water-soluble vitamins are B and C; the fat-soluble vitamins are A, D, E and K.

A key difference (particularly for consumers of nutritional supplements) is understanding that surplus amounts of fat-soluble vitamins will be stored by the body, whereas surplus amounts of water-soluble vitamins cannot be stored, and pass through the body's urinary system. This means that water-soluble vitamins must be consumed on a more regular basis to provide value to the body. But, it also means that there is general less concern about getting "too much" of these vitamins.

Vitamins are necessary in small amounts for good health. Vitamins and minerals are not an energy source, but assist in metabolizing nutrients in food to produce energy for the body, and are invaluable in keeping the body's systems functioning properly.

Vitamins make it possible for other nutrients to be digested, absorbed and metabolized by the body. They are required to do many things and their excess or deficiency can lead to acute and chronic disease.

The Fat Soluble Vitamins

Vitamin A - Vitamin A is the collective name for a group of fat-soluble vitamins. The most usable form of the vitamin is retinol. Vitamin A palmitate (retinyl palmitate) and vitamin A acetate (retinyl acetate) are the principal forms used as nutritional ingredients. The precursors of vitamin A (retinol) are the carotenoids (most commonly beta-carotene). Vitamin A is one of the most versatile vitamins, with roles in such diverse functions as vision, immune defenses, maintenance of body linings and skin, bone and body growth, normal cell development, and reproduction.

Vitamin D - Vitamin D actually refers to a group of steroid molecules. Vitamin D is called the sunlight vitamin because the body produces it when the sun's ultraviolet B (UVB) rays strike the skin. Vitamin D is important for the proper absorption of calcium from food. It is vital for the control of the levels of calcium in the blood and also controls the rate at which the body excretes calcium in the urine. Low levels of vitamin D and insufficient sunlight exposure are associated with osteoporosis. Maintaining sufficient vitamin D levels may help decrease the risk of several autoimmune diseases.

Vitamin E - Vitamin E is actually an umbrella term for a group of compounds called tocopherols and tocotrienols. Alpha-tocopherol is the name of the most active form of vitamin E in humans. Vitamin E is one of the many nutrients that have protective properties. The main function of vitamin E is to maintain the integrity of the body's intracellular membrane by protecting its physical stability and providing a defense line against tissue damage caused by oxidation. Vitamin E is an antioxidant that prevents free radical damage in biological membranes.

Vitamin K - Vitamin K is a group of 2-methilo-naphthoquinone derivatives. Vitamin K is involved in the carboxylation of certain glutamate residues in proteins to form gamma-carboxyglutamate residues. Vitamin K plays an important role in blood clotting and bone metabolism (carboxylation of osteocalcin). Vitamin K supplements may improve bone mass in postmenopausal women. Vitamin K is used to reduce risk of bleeding in liver disease, jaundice, malabsorption, or in association with long-term use of aspirin or antibiotics.

The Water Soluble Vitamins

Thiamine (vitamin B1) - Vitamin b1 is absolutely essential to several bodily functions. Thiamine is a coenzyme for the decarboxylation of pyruvate and the oxidation of alpha keto-glutamic acid. Thiamine aids the nervous system and is essential for the functioning of important enzymes. Vitamin B1 is essential for the body to be able to use carbohydrates as an energy source as well as for metabolizing amino acids . Thiamine is available in nutritional supplements in the form of thiamine hydrochloride and thiamine nitrate.

Riboflavin (vitamin B2) - Riboflavin or vitamin B2 is an essential nutrient in human nutrition and plays a key role in the production of energy. Vitamin B2 is an intermediary the transfer of electrons in the cellular oxidation-reduction reactions which generate energy from protein, carbohydrate and fat. Vitamin B2 helps prevent and is used to treat migraine headaches, cataracts, rheumatoid arthritis, and a number of skin disorders such as acne, dermatitis, and eczema.

Niacin (vitamin B3) - Vitamin B3 is also known as niacin, nicotinic acid, nicotinamide, niacinamide and antipellagra vitamin or PP factor. Vitamin B3 is essential in the metabolism of carbohydrates (to produce energy), fats, and proteins. It also aids in the production of hydrochloric acid, needed for proper digestion. Nicotinic acid, in pharmacological doses, is used as an antihyperlipidemic agent. Niacinamide is used to treat osteoarthritis, rheumatoid arthritis, insomnia, migraine headaches, and insulin-dependent diabetes.

Pantothenic acid (vitamin B5) - Pantothenic acid is an antioxidant water-soluble vitamin needed to break down carbohydrates, proteins, and fats. Pantothenic acid comes in two forms: calcium pantothenate and pantethine. Vitamin B5 is essential for human growth, reproduction and many normal bodily processes. Vitamin B5 helps metabolize nutrients, manufacture antibodies and produce vitamin D. Pantothenic acid plays a role in the synthesis of hemoglobin, steroid hormones, neurotransmitters, and lipids.

Vitamin B6 (pyridoxine) - Vitamin B6 (pyridoxine) serves as coenzyme and is involved in the metabolism of protein and carbohydrates, the production of insulin and red and white blood cells, and the synthesis of neurotransmitters, enzymes , and prostaglandins. Vitamin B6 is a coenzyme for several enzyme systems. Vitamin B6, used mainly in the body for the processing of amino acids, performs this task along with certain enzymes. Vitamin B6 is required for the production of serotonin and helps to maintain healthy immune system functions.

Biotin (vitamin H, vitamin B7) - Biotin is of great importance for the biochemistry of the human organism. Biotin helps in the synthesis of fatty acids, in energy metabolism, and in the synthesis of amino acids and glucose. Biotin serves as an essential coenzyme for four carboxylase enzymes, each of which is important in metabolism. Biotin is an important vitamin for helping certain enzymes in the body. The primary role of biotin is in the metabolism of fats, proteins and carbohydrates.

Folic acid (folate, vitamin B9) - Folate and folic acid are forms of a water-soluble B vitamin. Folic acid is a synthetic folate form which is used for food fortification and nutritional supplements. Folic acid plays an essential role in human growth and development, in particular cell division and DNA synthesis. Folic acid is important for any stage of human life which involves growth such as pregnancy, lactation and early growth because of the role the folate plays in DNA, RNA and protein production.

Vitamin B12 - Humans cannot produce vitamin B12, it can only be synthesized by bacteria that possess the requisite enzymes. Therefore B12 must be obtained through the diet. Good food sources of B12 are red meat (especially liver), shellfish, and milk. Eggs are often listed as a food high in B12, however eggs also contain a compound that blocks the absorption of B12 in humans. Plants do not provide B12. This puts vegetarians and those on restrictive diets especially at risk for B12 deficiency. Deficiency in vitamin B12 can bring about low mood, megaloblastic anemia and can mask folic acid deficiency. In the most serious cases, low B12 can lead to neurological problems.

Vitamin C (ascorbic acid) - Vitamin C, also known as ascorbic acid is a water-soluble vitamin that is an essential part of life. Vitamin C is perhaps the most popular vitamin among the common nutrients and biochemicals. Ascorbic acid and its sodium, potassium, and calcium are commonly used as antioxidant food additives. The body requires vitamin C to form and maintain bones, blood vessels, and skin. Vitamin C is responsible for helping to build and maintain our tissues and strengthening our immune system.

Sources of Vitamins

Most of the vitamins can be found in plant and animal sources. They can also be chemically synthesized. Vitamin A occurs in nature in two forms: preformed vitamin A and provitamin A, or carotene. The vegetable sources of beta-carotene are fat and cholesterol free. Thiamine (vitamin B1) is found in fortified breads, cereals, pasta, whole grains, lean meats (especially pork), fish, dried beans, peas, and soybeans. Sources of riboflavin include organ meats (liver, kidney, and heart) and certain plants such as almonds, mushrooms, whole grain, soybeans, and green leafy vegetables. Niacin is found in dairy products, poultry, fish, lean meats, nuts, and eggs. Vitamin B4 (adenine) is found in brewer's yeast, whole grains, raw unadulterated honey, bee pollen, royal jelly, propolis, most fresh vegetables, most fresh fruits. Common sources of pantothenic acid are cheese, corn, eggs, liver, meats, peanuts, peas soybeans, brewer's yeast, and wheat germ. Foods rich in vitamin B6 include white meat (poultry and fish), bananas, liver, whole-grain breads and cereals, soyabeans and vegetables. Beans, leafy green vegetables, citrus fruits, beets, wheat germ, and meat are good sources of folic acid. Vitamin B12 is found naturally in food sources in protein-bound forms.

Good sources of orotic acid are root vegetables and whey. Pangamic acid is found in whole grains such as brown rice, brewer's yeast, pumpkin and sunflower seeds, and beef blood. Vitamin B17 is found in most all fruit seeds such as the apple, peach, cherry, orange, plums, nectarine and apricot. Inositol is available from both plant and animal sources. Dietary sources of carnitine include foods of animal origin. Natural sources of PABA include bran, eggs, kidney, liver, molasses, wheat germ, brewer's yeast, and yogurt. Good dietary sources of biotin include organ meats, oatmeal, egg yolk, soy, mushrooms , bananas, peanuts, and brewer's yeast. Cabbage and many dark green leafy vegetables are all good sources of vitamin C. Exposure to sunlight is an important source of vitamin D. Good food sources of vitamin D include milk, fatty fish. Vitamin E is found in the germ of a seed or grain. Alpha-lipoic acid is mainly derived from dietary sources. Rich sources of vitamin K include broccoli, Brussels sprouts, cabbage, cauliflower, kale, spinach and soybeans. Bioflavonoids are abundant in the pulp and rinds of citrus fruits and other foods containing vitamin C. Coenzyme Q10 is found in the membranes of endoplasmic reticulum, peroxisomes, lysosomes, vesicles and notably the inner membrane of the mitochondrion.

Vitamin Deficiencies and Health

Vitamins are of vital importance in maintaining human health. Deficiencies of most of the vitamins will result in corresponding diseases.

A deficiency of vitamin A can cause slow skeletal growth, lead to night blindness, and cause various abnormalities of the skin and lining of the gastrointestinal tract.

In children, the disease rickets results from a vitamin D deficiency.

Vitamin E deficiency affects the central nervous system and causes muscle weakness, loss of muscle mass, abnormal eye movements, impaired vision, and unsteady gait.

Symptoms of vitamin K deficiency include easy bruisability, epistaxis, gastrointestinal bleeding, menorrhagia and hematuria.

Among the B vitamins, thiamine deficiency can lead to muscular weakness, leg cramps, slow heartbeat, irritability, defective hydrochloric acid production in the stomach and consequent digestive disorders. Riboflavin deficiency can cause inflamed tongue, inflammation and ulcers in the mouth, dandruff, weakness, and low blood counts. A niacin deficiency often leads to a chronic illness called pellagra. Vitamin B5 deficiency causes depression, personality changes, and heart problems. Vitamin B6 deficiency can cause impaired immunity, skin lesions, and mental confusion. Biotin deficiency results in fatigue, depression, nausea, muscle pains, hair loss, and anemia. Folic acid deficiency during pregnancy increases the risk for neural tube defects. A deficiency of vitamin B12 (cobalamin) deficiency can cause pernicious anemia. An inositol deficiency could be a contributing cause of abnormal platelet aggregation, and alcoholism. Patients with systemic carnitine deficiency have a progressive neuromuscular disorder with nausea and vomiting. A deficiency in PABA may cause fatigue, irritability, depression, nervousness, headache, constipation and other digestive disorders.

A lack of vitamin C eventually leads to scurvy. There is significant evidence that prior to advance to the visible symptoms of scurvy, a vitamin C deficiency can lead to a myriad of invisible health problems.

Vitamin Side Effects and Toxicity

Too much of certain vitamins may causes some side effects. Therefore, the supplementation of vitamins should done within the guides of a reliable medical instruction.

Excessive intake of vitamin A can be harmful to bones and skin, causing weakness and brittleness. Thus it is recommended to supplement with beta carotene instead of vitamin A, as the former is freely converted by the body into vitamin A as needed.

Even the water-soluble vitamins can be problematic at high doses, because the body needs to process them in order to discharge the surplus as waste. For example, large doses of niacin can cause liver damage, peptic ulcers, and skin rashes. Vitamin B6 toxicity can damage sensory nerves. High doses of PABA can cause blood sugar to drop.

Recommended Vitamin Intakes

Insufficient vitamin intake will lead to a number of vitamin deficiency diseases. However, high doses of vitamins may cause potential health problems. To keep people informed of the correct nutrition intake, the Food and Nutrition Board of the National Academy of Sciences/National Research Council publishes the Recommended Daily Allowances (RDA) for vitamins and minerals based on scientific researches and clinical findings. The amounts of nutrients and calories an individual is recommended to consume daily to maintain good health for the majority of populations.

Recommended Dietary Allowance (RDA) is the average daily dietary nutrient intake level sufficient to meet the nutrient requirement of nearly all (97 to 98 percent) healthy individuals in a particular life stage and gender group.

Adequate Intake (AI) is the recommended average daily intake level based on observed or experimentally determined approximations or estimates of nutrient intake by a group (or groups) of apparently healthy people that are assumed to be adequate - used when an RDA cannot be determined.

Tolerable Upper Intake Level (UL) is the highest average daily intake level that is likely to pose no risk of adverse health effects to almost all individuals in the general population. As intake increases above the UL, the potential risk of adverse effects may increase.