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Site author Richard Steane
The BioTopics website gives access to interactive resource material, developed to support the learning and teaching of Biology at a variety of levels.


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Vitamins and Minerals are categories of micronutrients, as opposed to macronutrients (carbohydrates, fats and proteins).

They are needed in smaller quantities - usually milligrams rather than grams.

Vitamins and minerals are very different sorts of substances. Vitamins are organic (moderately complex molecules based on covalent carbon-carbon bonds) whereas minerals are inorganic (simpler - often only one or two elements - usually in the form of ions).

Vitamins

Most vitamins are produced by plants and micro-organisms, but they may be concentrated in some animal tissues
A vitamin is a substance that is needed by the body, and which cannot be synthesised in necessary amounts, so it must be provided in the diet. It is therefore defined in the context of certain animal groups. The same substances may be produced in adequate amounts in other animal groups, or in plants, but they are not termed vitamins in this context. Vitamins perform a variety of functions in the body, mostly to do with transfer of energy. They can act as enzyme cofactors, as prosthetic groups attached to enzymes or as coenzymes, moving chemical groups or electrons from compound to compound within the cell.

The term vitamin was coined by Casimir Funk, from vital + amine. He was studying thiamine - lack of which causes beri-beri - but other vitamins were found not to have an amine (NH2) group, so the term was shortened.

Initially the chemical composition of vitamins were unknown until large enough amounts were prepared for analysis and identification methods were developed, so the system of describing them by letters was started. Then some, initially given the same letter, were found to be different, so groups like the B group were subdivided with numbers (B1, B2 etc.). Some were found to duplicate others, or not considered true vitamins, so there are gaps ; there is no vitamin B4, F , G, etc.

Some vitamins exist in several forms called vitamers. These are often variations on the same molecular theme, but sometimes they differ in activity compared with the basic version, and perhaps do not perform all the functions of the main vitamin.

Certain vitamins (B group, C) are water-soluble. This means they pass through the body in the blood system and are continuously excreted in urine. Consequently they need to be regularly obtained from the diet.

Others (A,D,E,K) are fat-soluble. These tend to be stored in the liver, and are not so quickly used up. This explains why liver is an important source of these vitamins.

It must be stated that most people consume adequate quantities of most vitamins if they have a balanced diet. In fact researchers originally had problems removing them from the main categories of food (carbohydrates, fats and proteins).

However people on restricted diets or with fairly serious metabolic problems may suffer from vitamin deficiency. Vitamin deficiency can be primary - poor vitamin sources in one's daily diet - or secondary, which may be a result of conditions that affect absorption in the intestine, the body not being able to use the vitamin, or an increase in the excretion of the vitamin from the body.

Some vitamins have been recommended at higher than usual amounts for treating metabolic disorders, and in cases where there may be interactions with drugs used to treat other conditions. Some health care and beauty products containing vitamins and associated compounds have been claimed to have a variety of advantages.

In the table below there are several links to interactive 3-D molecular models on this site which have been converted into a more user-friendly format (Jsmol).

DISCLAIMER: This material is provided in good faith, and for educational purposes. Do not rely on it in any way for medical purposes or as justification for outlandish dietary modification. However, I would be grateful to be informed of any major errors or omissions.
Vitamin
+ link to 3-D model
Role in body Deficiency causes Good sources Amount required
mg/day
[RDA]
A
Retinol
(+ others)
Converted into retinal which detects light in rod and cone cells of the retina (at the back of the eye) Night blindness Liver, many vegetables 0.6-0.7
B1
Thiamine
  • coenzyme in breakdown of glucose and amino acids (releasing energy)
  • involved in biosynthesis of the neurotransmitter acetylcholine and gamma-aminobutyric acid (GABA)
Beri-beri
symptoms include severe lethargy & fatigue, + complications affecting cardiovascular, nervous, muscular, and gastrointestinal systems
Yeast, cereal grains e.g. rice [but removed when processed into white rice], beans, nuts, and meat, esp. pork 1.4
B2
Riboflavin
Precursor to FAD and FMN (involved in a number of biochemical transformations to do with energy, as well as other B group vitamins).
Also acts as an antioxidant
Inflammation of the lips, lining of mouth and tongue, mouth ulcers, cracks at the corners of the mouth, and a sore throat or more general dry and scaling skin, fluid in the mucous membranes. Eyes may also be itchy/watery/bloodshot, and sensitive to bright light. Milk and dairy products, Lean meats, Eggs, Green leafy vegetables, Legumes, Nuts, Yeast
Flours and cereals are often fortified with riboflavin.

Riboflavin is destroyed as a result of exposure to light.
0.3-1.3
B3
Niacin, nicotinamide (niacinamide)
Precursor to NAD and NADP - hydrogen and electron acceptors in respiration and photosynthesis.
Niacin is involved in the production of various steroid hormones in the adrenal glands. It is also thought to help improve (blood) circulation and reduce atherosclerosis.

It has been found that in higher doses, niacin (but not nicotinamide) blocks the breakdown of fats and increases the level of high-density lipoprotein (HDL) or "good" cholesterol and lowers low-density lipoprotein (LDL) in blood.
Pellagra
cracked, scaly skin, dementia, and diarrhea
Yeast and yeast products, most meats, many fruits and vegetables

Maize : (sweet)corn may prove to be deficient in niacin unless cooked in alkaline solution

In the liver, niacin can also be synthesized from tryptophan, an essential amino acid. This conversion requires riboflavin (vitamin B2), pyridoxine (vitamin B6) and iron.
14-18
B5
Pantothenic acid
Precursor to Coenzyme A which transfers smaller molecules in the process of respiration and in other processes

Many other possible functions have been suggested
Symptoms very rare but perhaps seen in extreme malnourishment (victims of famine and maltreated prisoners of war):
extreme tiredness due to reduced energy metabolism, neurological conditions e.g numbness due to reduced acetylcholine synthesis, perhaps increased sensitivity to insulin because receptors are not deactivated by acylation.
Pantothenic means everywhere, and this is found in nearly every food, especially whole-grain cereals, vegetables (legumes), fruit, eggs and meat 6
B6
Pyridoxine, pyridoxal, pyridoxamine,
Precursor to pyridoxal 5'-phosphate (PLP), which acts as coenzyme in the synthesis of amino acids and neurotransmitters, and other reactions Muscle weakness, nervous problems (irritability, depression, difficulty concentrating, and short-term memory loss) Meat, fish, dairy products, vegetables, cereals - especially wheat germ and whole-grain flour, and nuts. 5-25
B7
Biotin

(also sometimes known as vitamin H)
Essential cofactor of enzymes involved in carboxylation reactions, e.g. pyruvate carboxylase and acetyl-CoA carboxylase, which catalyze key reactions in gluconeogenesis, fatty acid metabolism, and amino acid catabolism. Main cause of deficiency: Raw egg white contains a protein avidin which absorbs biotin, making it unavailable. Cooking deactivates it, and does not damage biotin.
In various food sources, biotin is bound to a protein which must be broken down before it can be absorbed.

Symptoms of biotin deficiency: Hair loss , conjunctivitis, facial and other rash, various neurological symptoms.
Liver, green leafy vegetables, egg yolk.

Intestinal bacteria produce enough biotin for most people.
(uncertain)
B9
Folic acid
  • Involved in synthesis and repair of DNA, important in cell division, hence:
  • necessary for the formation of healthy red blood cells - in conjunction with vitamin B12 (and iron)
  • helps reduce the risk of central nervous system defects such as spina bifida in unborn babies
Macrocytic or megaloblastic anemia

Neural tube defects in developing embryos

plus other possible disorders, including cancer.
Many leafy vegetables: broccoli, brussels sprouts, spinach, and also legumes: peas, beans, lentils, chickpeas. In many countries different cereal products e.g. bread, flour, pasta and breakfast cereals are fortified with it. It is also available from animal sources: liver, kidney, egg yolk, and yeast and associated products. 0.2
(double this in pregnancy)
B12
(Cyano)cobalamin
Necessary for the formation of healthy red blood cells - in conjunction with vitamin B9 (and iron)

also involved on fatty acid synthesis and energy metabolism
Brain and nervous system damage: fatigue, depression, and poor memory.

Megaloblastic anemia

Vitamin B12 deficiency can be caused by the metabolic disorder pernicious anemia, which is an autoimmune disease which attacks certain cells of the stomach so that gastric intrinsic factor is not produced. This is necessary for the absorption of vitamin B12 in the small intestine; in its absence B12 in not absorbed from food that has been eaten.
Meat, especially liver, eggs, milk products, shellfish
Not produced in plant sources
0.002 - 0.003
(2-3g )
C
ascorbic acid
Needed for the formation of collagen in connective tissue and for healthy teeth, gums and blood vessels;
also as an antioxidant;
Scurvy
Gingivitis (inflammation of the gums) and bleeding gums; rough, dry, scaly skin; decreased wound-healing rate, easy bruising; nosebleeds; decreased ability to ward off infection
Fruit and vegetables:
citrus, capsicums (peppers), strawberries, blackcurrants,
potatoes (esp skins), broccoli, brussels sprouts
40-90
D
Cholecalciferol (D3) and Ergocalciferol(D2)
Converted into calcitriol which circulates in the blood and functions as a hormone which increases the uptake of calcium (Ca2+) from the gut into the blood Rickets (in children), osteomalacia (in adults) - bone deformities such as bowed legs caused by softening of the bone, possibly leading to curvature of the spine and thickening of the ankles, wrists and knees
- may also be caused by lack of the mineral calcium in the diet.
Liver, fish, cod liver oil
Vitamin D is also produced in the skin by the action of ultraviolet light on various lipid molecules such as cholesterol. The intensity of ultraviolet light varies in different areas of the world, and this production is also affected by skin colour and amount of skin covered by clothing.
As such it may be an issue with dark skinned people in certain latitudes, or those who do not go outside in the sun or expose themelves to it.
0.005 - 0.015
(5-15g)

[Some sources suggest wider range - possibly due to lifestyle differences]
E
Tocopherol
and others
Antioxidant: it acts as a peroxyl radical scavenger, in conjunction with vitamin C, and prevents the oxidation of polyunsaturated fatty acids

It also acts as an enzymatic activity regulator in smooth muscle growth and has an effect on gene expression, specifically those responsible for the repair of wounds and regeneration of the tissue damaged during atherosclerosis.
Neuromuscular problems due to poor nerve conduction

possibly heart disease and atherosclerosis

Vitamin E deficiency is quite rare, and more likely to be caused by problems in the absorption of fat than by inadequate diet.
Plant oils e.g. wheat germ, sunflower 3-4
K
Phylloquinone
Cofactor in the formation of coagulation factors II (prothrombin), VII, IX, and X by the liver.

Also required for bone protein formation and calcification.
Problems with blood clotting and loss: anaemia, bruising, bleeding from the nose or gums, and heavy menstrual bleeding in women. Greater chance of "all-cause mortality", coronary heart disease, arterial calcification and osteoporosis. Green leafy vegetables: broccoli and spinach
vegetable oils, cereals
meat and dairy foods (small amounts) - higher amounts in yoghurt and cheese
0.075
(75g)

Minerals

Minerals are fairly unreactive (chemically), which is surprising to some people. For example, calcium and phosphorus are thought of as reactive - even dangerous - in the context of these substances as elements. However as compounds these reactive properties are replaced - neutralised - so that calcium ions and phosphate ions are very different from the elements. Another good example would be sodium chloride, a compound of sodium and chlorine. This is in fact commonly known as table salt. In fact many minerals are known as mineral salts, or just as salts.

This transformation is explained by the fact that minerals are generally ions - atoms or groups of atoms of elements that have gained or lost electrons from their outer shell, which takes away the most obvious characteristics of the elements seen on their own, and gives these ions a charge. In terms of biological activity, most of the variation between ions of minerals/elements is explained by differences in charge and the size of the atomic nuclei involved.

There are two basic categories of ions, depending on the type or sign of charge they possess: positively charged ones are also called cations and negatively charged ones are called anions. Generally metals have positive ions, and non-metals have negative ions.

In normal circumstances (in living organisms), ions do not exist on their own. Each positively charged ion must be accompanied by a negatively charged ion, and some ions carry more than one charge so the number of positive and negative charges must balance each other. So in sodium chloride (NaCl) there are equal numbers of sodium ions Na+ and chloride ions Cl-, whereas in calcium chloride (CaCl2) there are twice as many Cl- ions as Ca2+ ions. This means that when we are talking about sodium ions Na+ or potassium ions K+ there must be an accompanying number or assortment of anions - possibly chloride ions Cl- or sulphate ions SO4- but in solution they are not partnered up in the way that sodium chloride and potassium sulphate might be in a jar in a chemistry lab or a drugstore.

This situation is slighty shifted when the pH of a solution is altered: increasing the pH from 7 to 8 (making it more alkaline) reduces the concentration of H+ ions to 1/10 of the previous value, whilst decreasing the pH from 7 to 6 (making it more acidic) raises the concentration of H+ ions to 10 x the previous value. Changing the pH of a solution can alter the solubility of other ions.

Minerals can be thought of as originating from the earth's crust (and the sea's water) in the form of salts which when purified are often seen as (usually white or colourless) crystals. But when absorbed into the body they are usually in the form of ions, dissolved in water. Some elements can interact with organic compounds and become absorbed in fatty tissue.

Different minerals perform different functions in animals and plants, a reflection of the different biochemical processes which are characteristics of each. There is some overlap with basic biological processes.

Minerals from a human/animal perpective

Some minerals are incorporated into major parts of the body such as the skeleton and teeth, and some form important parts of cells. Others are essential components of the blood and body fluids.

Certain minerals also participate in some of the same metabolic processes that vitamins are known for, so the distinction here is not so clear.

There is a subcategory of minerals that are needed in very small quantities: these are called trace elements.

Minerals and Green Plants

Green plants absorb mineral ions from the soil and incorporate them into their cells. The unique process of photosynthesis which relies on the green pigment chlorophyll produces carbohydrates which can then be converted into other classes of organic compound, notably proteins and nucleic acids. Consequently different mineral ions are needed by plants, and since there is a limited amount of these available in the soil they may act as limiting factors in plant growth. Put another way, several inorganic mineral salts usually improve plant growth.

Web links

Vitamin From Wikipedia, the free encyclopedia

Vitamins and minerals from NHS Choices

Other vitamins and minerals

List of micronutrients
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