Vitamin Compendium

The Physiological Importance
of the Vitamins in Man and Animals

Essential dietary components
Human and animal organisms require, for the proper operation of all of their physiological functions, a regular intake of some forty different dietary components. If only one of these is missing or its supply is in adequate, deficiency symptoms appear which if prolonged, can be fatal. All these components of the dietare therefore indispensable for life ("essential" ); they comprise the actual energy-yielding and body-building substances (proteins, fats, carbohydrates, amino-acids, mineral salts) and also the "micro"-nutrients (vitamins, trace elements).

Vitamins: essential dietary components
The vitamins are therefore active substances essential for life. As a group, they are recognised by two characteristic properties:

1. The daily requirement for each vitamin for an individual is very small, usually measured in microgrammes or milligrammes; in this respect they differ from the "macro"-nutrients which are required in at least 1000 times larger amounts. Vitamins, on the other hand, are mediators of synthetic and degradative processes without serving as building substances themselves.

2. Vitamins are organic compounds, differing in this respect from the trace elements such as iron, iodine, manganese and zinc which, however, are also essential compounds.

To-day, 13 vitamins are known, each of which represents a group of related compounds with the same qualitative activity. The provitamin A group is also of great practical importance; this comprises compounds which are partly transformed into vitamin A in the organism. The Table (p. 8/9) surveys the compounds with vitamin properties.

In addition to these 13 vitamins, there are other substances which have been classed with the vitamins although their vitamin character has not yet been established. Examples are: orotic acid (vitamin BI3); inositol or Bios I; lipoic acid or thioctic acid; rutin (vitamin P); xanthopterin (vitamin BI4); carnitine (vitamin BT); pangamic acid (vitamin BI5); and ubiquinone (coenzyme Q).

Unidentified growth factors
In this connection, the so-called "unidentified growth factors" (U.G.F.) growth factors which, under certain conditions, can favourably affect the growth and productivity of livestock, should be mentioned. They are present, for example, in residues of alcohol fermentation, in fish-solubles, grass sap, whey and egg-yolk. Nothing is yet known of the chemical nature of these unidentified growth factors. They may perhaps not be single entities but mixtures of known essential nutritional factors with mutually potentiating effects (synergism).


Vitamins in metabolism
Unlike the nutrients which serve as building materials and storage substances in the growth of an organism, the vitamins exercise catalytic functions. They facilitate the synthesis and degradation of the principle nutrients, thereby controlling metabolism. Research into these biochemical processes is still active. The key functions of the vitamins of the B-complex in particular, have been extensively clarified. Vitamins B15 B2, B6, Niacin, B12, pantothenic acid, folic acid and biotin, and also, in part, their metabolites are incorporated into enzymes which are indispensable for normal metabolism of carbohydrate, lipid and protein. In these processes the vitamins play no part as building substances and this also explains why the daily requirement is small, compared with that of the main nutrients.

Vitamin deficiency: avitaminoses, hypovitaminoses
If one or more vitamins are either not available at all to an organism, or only in inadequate amounts, certain metabolic processes are impaired, leading to disturbances of productivity, growth inhibition and disease. Vitamin deficiency also causes disorders of fertility in male and female animals as well as increased liability to infectious and parasitic disease. The functions of the individual vitamins in metabolism are very specific, so that, in deficiency, one or more defined biochemical reactions in certain organs can be adversely affected. These disturbances of metabolism can therefore give rise to very characteristic deficiency symptoms; frequently, however, the pattern of disturbed health is confused, for example, when the vitamin is required for several metabolic reactions, or when other nutrients or active substances are lacking simultaneously.

In countries where diets are unbalanced and inadequate, or where there are particular dietary customs, certain commonly observed typical disease patterns have been shown to be due to vitamin deficiency. Knowledge of the cause has led to the remedy, so that these avitaminoses, which also occurred quite frequently in Europe even during the last century, are now no longer of importance. In the developing countries, however, they are still significant to-day.

Examples of the most common avitaminoses are:
Xerophthalmia, Keratomalacia (Vitamin A-deficiency)
Beri-beri (Vitamin B1-deficiency)
Pellagra (Niacin-deficiency)
Scurvy (Vitamin C-deficiency)
Rickets (Vitamin D-deficiency)

In addition to the avitaminoses which are characterised by clearly defined symptoms, there are also hypovitaminoses - unspecific states - which are brought about by the inadequate provision of one, or more frequently several, vitamins. They appear in the form of ill-defined symptoms such as skin changes, reduced vitality, lowered resistance to infections, etc.

Finally, latent hypovitaminoses are also known; these are states which, under normal environmental conditions, are not recognisable through deficiency symptoms, but which can immediately induce symptoms under sudden stress. The relationship between stress and vitamin requirements in animal maintenance is discussed in detail in the section on "Vitamins and Carotenoids in Animal Nutrition."

Anti-vitamin, vitamin antagonists
In addition to the hypovitaminoses and avitaminoses, which are due to Anti-vitamins, inadequate provision of vitamins, deficiency states occur occasionally vitamin when the function of a vitamin is disturbed or inhibited. This can occur antagonists in the presence of specific substances which are designated as antivitamins or vitamin antagonists. They reach the digestive tract as natural dietary constituents or as additives (medicaments), either immediately inhibiting resorption of the vitamin or disturbing its specific biochemical action. Thus, in raw and dried egg-white, for example, the substance avidin occurs which forms a complex with biotin in the gastro-intestinal tract, thereby preventing resorption of this vitamin. Raw fish, especially fresh-water fish, and various bacteria contain thiaminase, an enzyme that destroys vitamin B1. Avidin and thiaminase are destroyed by cooking.

Vitamin antagonists also occur in bracken, various foodplants and in certain varieties of vegetables. Thus, lucerne contains one or more substances which markedly reduce the efficacy of the vitamin E present in lucerne, and significantly increase its faecal excretion. Antagonists of vitamin E have also been demonstrated in beans. Linatin - a substance identified in linseed has been shown to be an antagonist of vitamin B6.

Nutrient constituents that raise vitamin requirements
The mechanism of action of typical antivitamins is based on the similar chemical structures of the vitamin and antivitamin which enables the latter to displace the vitamin from its site of action. The antagonistic activity of certain medicaments may also be explained in this way.
bacteriostatics (sulphonamides, and coccidiostats) and antibiotics which, on prolonged administration in high dosage, destroy intestinal flora and so eliminate a source of vitamins for a host organism.

Disease, parasites, bodily stress
When the defence mechanisms of the body are mobilised and demands made on reserve substances there is an associated increase in the activity of enzyme systems. Thus, every increase in metabolic activity leads unavoidably to an increased usage of anabolic and catabolic enzymes and increased vitamin requirement. This is true not only in illness but also for physical exertion and increased production.

In addition infective organisms and parasites themselves require vitamins; they compete with their host organism. Intestinal parasites attack. the mucous membranes and interfere with vitamin resorption. Viruses and bacteria leave toxins in the body, the degradation and excretion of which require greater enzyme activity.

Vitamin requirements
Every individual is constantly exposed to changing influences and environmental pressures. Therefore the metabolic rate must be adapted to the immediate necessity, so that vitamin requirements are also subject to continuous variation between certain limits. It follows that only approximate quantitative estimates of vitamin requirements can be expressed. Even in extended animal studies the results are only valid under the special circumstances of a particular experiment. For example, in studying vitamin requirements, different results may be expected when different criteria are followed - e.g. the maintenance of body weight in indoor rearing, or intensive fattening, work output, milk yield or egg production.

Numerous studies have been made of the vitamin requirements of livestock under different conditions, leading to an approximate estimate of vitamin requirement of the various animal species. It is also known under what conditions increases in requirements can be expected.

In man, however, figures for vitamin requirements cannot be given with the same reliability as for animals. It is of course possible to determine minimum amounts which must be supplied daily to avoid severe deficiency diseases. But observations made on domestic animals show that the vitamin requirements for maximum production are many times greater than such minimum amounts.

The daily supply of vitamins can only be estimated within certain limits from the contents of a diet. In addition to the external influences already mentioned, which affect the utilisation of the vitamins supplied, other factors play a part; the analytical determination of the vitamin contents of foods is costly and time-consuming, and may be subject to errors of 10% or more, according to the concentrations of the vitamins. Some vitamins can only be assayed by biological or microbiological methods, which are also subject to systematic errors.

A further problem in the calculation of the vitamin supply is the degree of utilisation of the vitamins from different foods and animal feeds. Thus, for example, -carotene and vitamin B2, as components of food of vegetable origin, are only incompletely utilised. It is assumed that these compounds are bound very firmly to certain parts of the plant-cells and that the enzymes of the gastric juice are incapable of liberating them completely in the gastrointestinal tract. Accurate data on the degree of utilisation of naturally occurring vitamins are available in only a few cases.

Consideration of all the factors influencing vitamin requirements leads to the following conclusions relating to practical human and animal nutrition:

Data on the minimum vitamin requirements are available, based on numerous experimental results; in view of biological variations and experimental errors these can, however, only be regarded as approximate values. In particular cases account must be taken of appreciable variations since, on the one hand the utilisation of administered vitamins is impaired by many factors and, on the other, vitamin requirements under conditions of physical stress or increased production can rise to a degree that is difficult to estimate.

To cover vitamin requirements fully it is therefore necessary to add a supplement to the diet so that even in unfavourable cases adequate supplies are assured.

Contrary to other active substances, such as the hormones, vitamins can be absorbed in large quantities without ill-effects. Only when the supply exceeds a certain upper limit (more than a hundred times the requirement for most vitamins) and, for a prolonged period, can symptoms of so-called hypervitaminoses develop. So far, hypervitaminosis in man has only been observed in the case of excessive administration of vitamin D.


Vitamin Compendium. The Properties of the Vitamins and their Importance in Human and Animal Nutrition. Vitamin and Chemicals Department. F. Hoffmann-La Roche & Co. Ltd, Basle. Switzerland