Vitamin

Fruits and vegetables are a source of vitamins

A vitamin is an organic compound that is essential for an organism's proper growth, development, and physiological function. Vitamins cannot be synthesized by the organism in sufficient amounts and must be obtained through the diet. In humans, there are 13 essential vitamins that are classified into two main categories: fat-soluble and water-soluble.

Various vitamin supplements

Fat-Soluble Vitamins

• Fat-soluble vitamins are absorbed in the presence of dietary fat and are stored in the body's fatty tissues and liver. The four fat-soluble vitamins are:
• Vitamin A (retinol): Essential for vision, immune function, and cellular growth and differentiation.
• Vitamin D: Important for calcium absorption and regulation, bone health, and immune function.
• Vitamin E (tocopherols and tocotrienols): Acts as an antioxidant, protecting cells from damage caused by free radicals.
• Vitamin K: Necessary for blood clotting and bone metabolism.

Water-Soluble Vitamins

• Water-soluble vitamins are readily absorbed and excreted by the body, requiring regular consumption through the diet. The nine water-soluble vitamins are:
• Vitamin B1 (thiamine): Crucial for energy production, nerve function, and carbohydrate metabolism.
• Vitamin B2 (riboflavin): Involved in energy production, cell growth, and antioxidant function.
• Vitamin B3 (niacin): Necessary for energy production, DNA repair, and the synthesis of fatty acids.
• Vitamin B5 (pantothenic acid): Required for the synthesis of coenzyme A, which is essential for various metabolic processes.
• Vitamin B6 (pyridoxine): Important for amino acid metabolism, neurotransmitter synthesis, and red blood cell formation.
• Vitamin B7 (biotin): Essential for fatty acid synthesis, amino acid metabolism, and the production of glucose.
• Vitamin B9 (folate): Crucial for DNA synthesis, amino acid metabolism, and red blood cell formation. Folate is particularly important during pregnancy to prevent neural tube defects.
• Vitamin B12 (cobalamin): Necessary for red blood cell formation, DNA synthesis, and maintaining nerve function.
• Vitamin C (ascorbic acid): Acts as an antioxidant, aids in collagen synthesis, and supports immune function.

Vitamin Deficiency

• Vitamin deficiency can occur when an individual's diet lacks the necessary vitamins or when the body cannot properly absorb or utilize them. Deficiencies can lead to various health issues, such as:
• Vitamin A:Night blindness, dry skin, and impaired immune function.
• Vitamin D:Rickets in children and osteomalacia in adults.
• Vitamin E:Peripheral neuropathy and hemolytic anemia.
• Vitamin K:Impaired blood clotting, leading to excessive bleeding.
• Vitamin B1:Beriberi, which can cause muscle weakness, nerve damage, and heart failure.
• Vitamin B2:Ariboflavinosis, characterized by cracked lips, inflammation of the mouth, and skin disorders.
• Vitamin B3:Pellagra, causing dermatitis, diarrhea, and dementia.
• Vitamin B6:Anemia, peripheral neuropathy, and impaired immune function.
• Vitamin B7:Hair loss, skin rashes, and neurological symptoms.
• Vitamin B9:Anemia, birth defects, and increased risk of cardiovascular disease.
• Vitamin B12:Pernicious anemia, nerve damage, and cognitive impairment.
• Vitamin C:Scurvy, which can result in fatigue, joint pain, and bleeding gums.

Vitamin Toxicity

Excessive intake of vitamins, particularly fat-soluble vitamins, can lead to toxicity and adverse health effects. Some symptoms of vitamin toxicity include:

• Vitamin A:Nausea, vomiting, blurred vision, and birth defects.
• Vitamin D:Hypercalcemia, which can cause kidney stones, bone pain, and cardiovascular issues.
• Vitamin E:Increased risk of hemorrhagic stroke.
• Vitamin K:Interference with blood-thinning medications.
• Water-soluble vitamins:Generally, toxicity is rare due to their rapid excretion from the body. However, excessive intake can still cause mild to moderate side effects, such as diarrhea, nausea, or flushing.

Dietary Sources

• Vitamins can be obtained through a balanced diet that includes a variety of foods. Some good sources of vitamins include:
• Vitamin A:Liver, dairy products, orange and dark green vegetables, and fruits.
• Vitamin D:Fatty fish, fortified dairy products, and sunlight exposure.
• Vitamin E:Vegetable oils, nuts, seeds, and green leafy vegetables.
• Vitamin K:Green leafy vegetables, vegetable oils, and fermented foods.
• B-complex vitamins:Whole grains, legumes, nuts, seeds, animal products, and fortified foods.
• Vitamin C:Citrus fruits, strawberries, kiwi, bell peppers, and broccoli.

Vitamin Supplements

• Vitamin supplements are available in various forms, such as tablets, capsules, and gummies. They may be recommended for individuals with specific dietary needs or restrictions, during pregnancy, or in cases of diagnosed deficiencies. However, it is generally advised to obtain vitamins through a balanced diet, as supplements may not provide the same health benefits as naturally occurring vitamins in food.

See also

• Mineral (nutrient)
• Dietary supplement
• Micronutrient
• Antioxidant

References

• Gropper, S. S., Smith, J. L., & Carr, T. P. (2017). Advanced Nutrition and Human Metabolism. Cengage Learning.
• Institute of Medicine. (2001). Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academies Press.
• Institute of Medicine. (2000). Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. National Academies Press.
• Institute of Medicine. (1998). Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. National Academies Press.

External Links

• Office of Dietary Supplements - Information on dietary supplements, including vitamins, from the National Institutes of Health
• Nutrition.gov - Information on vitamins and their functions from the U.S. Department of Agriculture

Related pages

• Dietary mineral
• Essential fatty acid
• Essential amino acid

Vitamin Resources
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Vitamins A Vitamin A B Biotin Vitamin B1 (see Thiamin) Vitamin B12 Vitamin B6 C Calcium Choline Chromium Copper Vitamin C D Vitamin D

E Energy Drinks Exercise and Athletic Performance Vitamin E F Fluoride Folate I Iodine Iron K Vitamin K

M Magnesium Multivitamin/mineral Supplements N Niacin P Pantothenic Acid Phosphorus Potassium Primary Mitochondrial Disorders R Riboflavin

S Selenium T Thiamin V Vitamin A Vitamin B1 (see Thiamin) Vitamin B12 Vitamin B6 Vitamin C Vitamin D Vitamin E Vitamin K Z Zinc