Being a human being in general and a vegan in particular, the need for proper nutrition constantly asserts its boisterous presence. This is the sum total of my knowledge on the subject, assisted by some notes from a physical education class I was obliged to take some four or five years ago.
Vitamins are organic compounds required by the body for purposes of metabolism, health and especially for correct growth in children. They can also assist in forming hormones, blood cells, nervous system chemicals and genetic material. Vitamins usually act as catalysts in conjunction with proteins to produce these various reactions. The properties and actions of some vitamins are very intricate and so many functions are not entirely known. Thirteen vitamins have been well-identified.
Vitamin A is a pale yellow alcohol derived from carotene which is used in the formation and maintenance of bones, teeth, skin and mucous membranes as well as preventing the atrophy of vision and reproductive systems. Vitamin A can be derived from vegetables (carrots, broccoli, squash, spinach, kale and sweet potatoes) or animal sources (dairy products, egg yolk or liver). Deficiency in the vitamin can cause desiccation of the skin, eyes (tear ducts) and lack of mucous secretion (reducing anti-bacterial defences), as well as night blindness. Excess of this vitamin, however, can interfere with growth, disrupt or halt menstruation, damage red blood corpuscles, cause skin rashes, headaches, nausea and jaundice.
The B vitamins
B1 (thiamine) is colourless, crystalline and a catalyst in carbohydrate metabolism. It enables pyruvic acid to be absorbed and carbohydrates to release their energy. It also features in the synthesis of nerve-regulating substances. Thiamine deficiency can cause beriberi (characterised by muscle weakness, leg cramps and even heart failure) and is present in many foods, mostly the following: liver, heart, kidney, pork, brewer’s yeast, lean meats, green leafy vegetables, cereals (although milled cereal often lacks this vitamin), wheat germ, berries, nuts and legumes. Deficiency is rare due to this broad availability.
B2 (riboflavin) functions as a coenzyme (working with another to achieve its effect) in metabolising carbohydrates, fats and respiration-related proteins, as well as assisting to maintain mucous membranes. B2 is found in meats, dark green vegetables, cereals (whole or enriched), pasta and mushrooms. Oversensitivity to light and the outbreak of skin lesions can result from deficiency.
B3 (niacin) functions in the same manner as its predecessors (as a coenzyme) in the release of energy from nutrients. It can be gained from liver, meat, fish and poultry, cereals (whole and enriched), beans, peas and nuts. The body itself produces niacin from tryptophan. The first symptom of pellagra (which results from deficiency) is sunburn-like skin irritation which quickly forms upon exposure to sunlight, followed by reddening and swelling of the tongue, diarrhoea, disorientation (and accompanying irritability) and even depression and mental damage when the central nervous system is affected.
B6 (pyridoxine) is necessary for absorbing and metabolising amino acids, also playing a role in the use of fats in the body and the formation of red blood cells. It is found in whole grain, cereals, liver, avocadoes, spinach, green beans and bananas. Pyridoxine is needed only in proportion to the amount of protein consumed. Deficiency causes skin and mouth irritation/cracking, convulsions, dizziness, anaemia, nausea and kidney stones.
B12 (cobalamin) is one vitamin more recently identified. It is needed in miniscule quantities for the formation of nucleoproteins, proteins and blood cells and also in the function of the nervous system. Cobalamin can, to the best of my knowledge, be obtained in sufficient quantities only from animal sources such as meat (especially organ meats) and fish, eggs and dairy products. B12 can be produced synthetically, though, and is available in dietary supplements.
Other B vitamins are as yet unlabelled and may yet have unknown functions. Folic acid/folacin is needed far less than other vitamins (as a coenzyme in haemoglobin formation) and is found abundantly in vegetables, legumes, grains, yeast and nuts. Pantothenic acid plays a far-from-certain role in metabolising fats, proteins and carbohydrates. It is produced by intestinal bacteria, as well as being found in many foods.
Known as ascorbic acid, it is important in the formation of collagen, which supports body structures, helps in absorbing iron from vegetable sources and in forming bones and teeth. Ascorbic acid is present most potently in citrus fruits, but also in strawberries, cantaloupe, pineapple, brussel sprouts, guava, tomatoes, kale, green chilli, turnip, cabbage and broccoli. Now, we have all heard of scurvy, and this is what happens in cases of vitamin C deficiency. Scurvy is characterised by haemorrhages, loosening of teeth and harmful changes in the bones of children. There is evidence to suggest that large vitamin C doses can aid in preventing the formation of tumour-causing compounds, although prolonged excess can cause bladder and kidney stones, calcium depletion from bones, interference with blood-thinning chemicals and destruction of vitamin B12.
Required for normal bone formation, retention of calcium and phosphorus and the protection of teeth and bones thereby. When absorbed from foods such as egg yolk, liver, tuna and fortified milk (although available from non-animal sources as well), the sterols in those foods are irradiated (hence, the accurate reputation of this vitamin as being the product of exposure to sunlight). We are also familiar with rickets, I would hope. A common syndrome in cold climates where nutrition was inadequate, rickets causes bone deformities due to calcium and phosphorus loss. As vitamin D is fat-soluble, excess consumption can cause kidney damage, prolonged lethargy and appetite loss.
We don’t really know a great deal about this one, save that it plays some role in forming red blood cells, bodily tissues and in preventing vitamin A oxidation. Present in vegetable oils, wheat germ, liver and green leafy vegetables, it is thought (on little scientific basis) to have curative properties against a number of diseases.
Mainly used for blood coagulation. It aids in producing prothrombin (an enzyme) which in turn helps blood clotting. It occurs in leafy green vegetables, egg yolk, soy beans and fish liver. Digestive disturbances may lead to mild blood clotting disorders - a product of improper vitamin K absorption.
Edit: this writeup now feels less potent when contrasted with its company in the 'vitamin' node. It used to reside with 'vitamins