Vitamins are organic molecules (or groups of related molecules, called vitamers) essential to an organism for normal metabolic functioning in small amounts, as dietary supplements or as part of a balanced diet.
Nutrition is necessary for living things to survive and flourish, and eating diets lacking sufficient amounts can result in health complications.
Vitamins A
Vitamin A (formerly beta-carotene) can be found in numerous food sources and plays many vital roles including supporting healthy eyes and skin, combatting infections and maintaining an efficient immune system.
Vitamins A, D, E and K are often referred to as fat-soluble vitamins as they can easily store within body fatty tissue after ingestion and are more readily absorbed with diet containing fat than without.
Folic acid, pantothenic acid, pyridoxine, biotin, folate and cobalamin were reclassified as part of the B-complex vitamins. Other chemicals once considered vitamins have either been renamed or decided not to count as vitamins (like laetrile which was once known as Vitamin B17); instead they now fall under micronutrient classification.
B
The water-soluble vitamin B complex includes thiamin, riboflavin, niacin (nicotinic acid), vitamin B6 (pyridoxine), pantothenic acid, biotin, folate and vitamin B12. They all play key roles in various biochemical reactions that convert food into energy production.
Water-soluble vitamins cannot be stored by our bodies, and must therefore be replenished daily via diet or supplementation. B vitamins play an essential role in turning carbohydrates, fats, and proteins into energy as well as producing red blood cells for blood flow and maintaining a healthy skin. They are found in foods like whole grains, nuts, seeds, dairy products, fresh fruits and leafy green vegetables.
C
Vitamin C (ascorbic acid) is a water-soluble vitamin found in food sources such as citrus fruits and can also be taken in supplement form. Since Vitamin C does not store in our bodies, people must consume it on an ongoing basis for best health results.
Linus Pauling, a double Nobel laureate, advocated daily dosages of vitamin C as an antidote or treatment for various illnesses such as colds and chronic disorders; however, evidence supporting his claims remains limited.
Vitamin C plays an essential role as both plasma and tissue antioxidant. It protects vital molecules from free radical damage while contributing to the redox cycling process of other important antioxidants such as Vitamin E.
D
Vitamin D, commonly referred to as the “sunshine vitamin,” promotes intestinal absorption of calcium and phosphorus and has an impact on bone mineralization. Produced endogenously as well as obtained through foods or supplements in form of D2 (ergocalciferol) or D3 (cholecalciferol), Vitamin D is converted by liver and kidney into 1,25-dihydroxycholecalciferol for active use in our bodies.
Low vitamin D levels can cause rickets in children and osteomalacia in adults. Low levels may also increase your risk for multiple sclerosis, type 1 diabetes and other so-called autoimmune diseases.
Food and Nutrition Board committee established DRIs for vitamin D, concluding that serum 25(OH)D levels below 30nmol/L (12ng/mL) indicate deficiency or inadequacy. Studies suggest higher 25OHD levels may also reduce cancer mortality risk.
E
Vitamin E is a fat-soluble antioxidant that protects cells by blocking free radicals. This may help protect against heart disease, cancer and eye disorders while aiding immunity and blood circulation. Vitamin E can be found both naturally in foods as well as added supplements that may contain it.
Alpha-tocopherol is the form of vitamin E most frequently seen in nutritional supplements and fortified food products, typically esterified to extend shelf life; however, our bodies still efficiently absorb its metabolites such as alpha-tocopheryl acetate and succinate just as efficiently [1].
Trials have demonstrated that regular consumption of vitamin E supplements does not prevent or diminish cardiovascular events in individuals at low risk for these conditions, though participants in such studies primarily consisted of middle-aged or elderly individuals with established heart disease or risk factors associated with it.
K
Vitamin K is an essential lipid-soluble vitamin required for blood clotting. It comes in two forms naturally found in nature – vitamin K1 (phylloquinone) and vitamin K2 (menaquinones).
Research has uncovered potential mechanisms by which vitamin K may combat mineralization of blood vessels – otherwise known as vascular calcification. One such protein, Matrix Gla Protein (MGP), secreted from smooth muscle cells in arterial vessel walls can act as an inhibitor.
MGP works to prevent calcium from binding with platelets and leading to blood clots; according to The Framingham Offspring Study, consumption of phylloquinone was found to be associated with knee osteoarthritis but not hip fracture (114). The US Dietary Reference Intake for vitamin K is 80 mg per day.
