Abstract
The Biology of the Trace Elements –Their role in nutrition by Karl H. Schutte MSc PhD
Introduction: …trace-element nutrients play a most important part in many processes which they help to regulate, although they may only be present as one atom in ten million. The trace elements are anything but insignificant in their activities.
All living organisms require a regular supply of nutrients. If there is a deficiency or an excess, then normal development will cease, and abnormal development will result. Not all the elements present in plants or animals are essential for life. The fact that an element is present, or even that it exerts a beneficial influence upon development, does not (automatically) qualify it for the status of an essential element. Certain essential elements …exert their influence at very low concentrations. They are absolutely essential for proper development and growth, yet they are required in very small quantities, and if present in excess can be poisonous. The macro-elements or major elements, which are present in large quantities, are mainly constituents of proteins, cell walls, or mechanical structures…
The other essential elements which are present in minute quantities, the trace elements, or micro-nutrients, or minor elements (they have many names, but none of them is quite suitable for all purposes) cannot have important structural functions assigned to them. There is just too little of them to be present. Their role is primarily catalytic, although not necessarily exclusively so…catalytic systems…control the chemical processes of the organism. Their absence can prevent important reactions from taking place, and hence result in abnormal development and even in death… Unfortunately, the quantities of the trace elements which different organisms require for normal development varies so considerably that it is not possible to define trace elements in terms of the concentrations in which they occur. It is more enlightening to discuss mineral elements in terms of their functions…trace element (is) used (hereinafter) in a restricted sense to denote elements with a nutritional role whose functions are catalytic, even if they occur in fairly large quantities…
In order to discover if an element is really essential, it is necessary to study the growth and development of plants or animals, in the absence of the element being studied. As plants can be grown in water solutions made of pure chemicals, it is easier to study them than animals...As a consequence, more is known about the trace-element nutrition of plants…
Experimental difficulties
Trace elements are frequently required in such low concentrations that it is not always easy to prepare solutions lacking them. Even the purest of chemicals are not absolutely pure and always contain some traces of thee elements as impurities...trace-element deficiencies are not due to absolute shortages of elements but are induced deficiencies, brought about by altering the beneficial ratio of various nutrients to each other. This results in nutritional imbalance, with dire consequences,…
Catalysts and their characteristics
…very small amounts of catalyst can bring about very large changes. For example, one molecule of the enzyme catalase, the biological catalyst that decomposes hydrogen peroxide, can promote the decomposition of 40,000 molecules of hydrogen peroxide per second at the freezing point. Like most other materials, catalysts can wear out, and must be replaced…
It must be stressed that catalysts do not initiate chemical reactions that cannot occur in their absence. What they do is to speed up reactions that take place only very slowly without them...Catalysts promote many reactions by decreasing the activation energy required, and so promoting the chemical reaction, which takes place more readily.
The vast number of chemical reactions which take place in these microscopic cells are regulated by the 2000 or more different enzymes present in each of these cells... It must be stressed that trace-element deficiencies are widespread, and have been known from the earliest historic times. Their causes were not understood, but the conditions were recognized, and in some cases successfully treated. Just as these trace-element deficiencies and excesses are known in man and the animals, so they are well known in plants as well.
For normal development, balanced nutrition is essential. If there is too little or too much of any given nutrient, then this balance is upset, and either deficiency or toxicity symptoms of some sort will develop, for these symptoms clearly demonstrate the presence of disequilibrium, or imbalance, in the nutrition…the fact that the balance of nutrients is the important factor in normal development precludes absolute levels being established…trace elements are in fact the limiting factor in determining yield size in many places is quite clear…
The widespread distribution of trace-element deficiencies is not generally recognized, even by…investigators, because too much stress has been laid on visual clinical symptoms…These symptoms are of the greatest value in indicating the presence of nutritional deficiencies, but it must be appreciated that not all deficient plants show them. Deficiencies not acute enough to show visual signs may be severe enough to halve the potential yield.
What has been written about plants applies equally to animals…
Overliming is the commonest cause of the induced trace-element deficiency. The drop in pH caused by this practice results in all the trace elements except molybdenum being made less available to plants.
Another aspect of these micronutrient elements is the very considerable effect that they can exert upon quality…
Mineral content
As has been mentioned, the mineral content of plants and animals varies considerably. There are marked differences between species based upon genetically determined differences in requirements. Even within a species, the genetically determined differences can be very large…The fact that trace elements have a marked effect upon the vitamin content of vegetation is not as widely appreciated as it should be. (This) is of considerable practical importance, (since)…vitamin deficiencies are still widespread in both humans and animals.
Amino Acids
Another aspect of biological quality that is of very great importance is the amino-acid content of foods. Human beings, as well as animals, have a very definite amino-acid requirement. The body cannot synthesize certain of these amino acids from raw materials, and is thus dependent upon outside sources for these essential amino acids…It is also known that the trace elements do play an important part in determining the amino-acid composition in plant proteins…
Fat
…in pig breeding, while large and heavy animals are desirable, fat ones are not, as they give rise to …low-quality produce. It is of interest that manganese deficiency does, in fact, give rise to fat pigs.
Goitrogenic milk
…plants of the cabbage family contain goitrogenic substances which can induce goiter if the level of iodine in the diet is not fairly high.
Egg quality
…The less (breakability of a hen’s egg) is determined, among other things, by the level of manganese in the diet…
The term trace element can be misleading, at times. It may give the impression that these elements are not as important as the major elements. Nowhere is the falsity of this impression more obviously evident than in the study of the anatomical implications of these minor elements. As they are essential, their absence or presence exert a tremendous influence; just as great as that of the major elements. It must be stressed that trace or minor only refers to the concentrations at which they are effective and not to their effect. This can be very clearly seen in the marked anatomical variations caused by or linked to pathological conditions associated with trace element imbalance. The microelements play a very important part in reproductive processes in all forms of life, and the consequences of imbalances are truly spectacular.
Seed and fruit production
The important part that micronutrients play in the reproduction of higher plants is often seen by the marked decrease in grain yields of cereals and fruit yields when deficiencies occur.
In animals, more information about the influence of trace elements on reproduction is available than in plants. (Several elemental) imbalances result in well-known reproductive failures.
Trace elements in reproduction
The general picture that emerges from an investigation of the part played by micronutrient in reproduction is that they are important in many phases of this process…The link between trace elements and normal reproduction is obviously a very strong one.
HEALTH AND DISEASE AS A FUNCTION OF TRACE ELEMENT LEVELS
The fact that disturbed trace-element nutrition can result in appreciable anatomical abnormalities…has already been discussed in Chapter VI. But other differences between healthy and diseased organisms, particularly biochemical ones, may be equally striking, and of great importance…
…Antagonisms among elements lead to an altered mineral requirement.
Chlorosis
Iron in mammals
Differences in iron requirements between sexes
Copper in mammals
Anemia and hemopoiesis
Goiter and upset iodine metabolism
Cancer and trace elements Trace elements appear to play some part in cancer. It is quite certain that in man the trace-element distribution is disturbed as a consequence of this disease.
Environmentally linked diseases
Diabetes and zinc
Phalaris staggers
Disturbances of trace-element metabolism in some diseases
Psychological phenomena and trace elements
Susceptibility to disease and trace elements
Animals cattle and sheep suffering from latent as well as visible cobalt deficiency are usually heavily infected with worms
Hookworm anemia in man
… Hookworm anemia is primarily an iron-deficiency disease
If imbalances of trace elements were rare in nature, and deficiencies or excess only occurred very infrequently, then they would still be of interest to scientists… Trace-element deficiencies are not confined to poorly developed areas.
Toxicities
No discussion concerning the distribution of deficiencies would be complete without reference to areas of excessive or toxic levels of these elements. These also occur, although on a very much more restricted scales.
Adaptation to special environments
Not all animals and plants have the same requirements, and some can survive, and even flourish, in habitats that are quite unsuitable for most organisms. These plants and animals that can survive in these regions are specially adapted to these conditions. The specific differences between plants are genetically determined, as is the ability to tolerate apparently toxic levels of certain elements, as in the case of mine-dump floras. In prospecting, this ability to concentrate elements which are present in very small quantities in the soil, and so make chemical analysis easier, is exploited.
The influence of the environment on trace-element requirement
Climatic conditions are of great importance in the development of deficiency diseases. In many parts of the world…the soil is now so impoverished that the indigenous flora is no longer adapted to these new conditions, and in some parts shows severe deficiencies of trace elements
Methods for determining deficiencies or excesses of trace elements in plants
(i) Visual symptoms.
(ii) Soil Analysis.
(iii) Leaf analysis.
Fertilizer trials
Perhaps the most informative method for studying plant nutrient requirements in the field is by means of fertilizer trials. Their great drawback is that they are difficult to lay out, and may take a number of years to complete. Hence they are very expensive.
The widespread existence of trace-element deficiencies calls for effective practical methods to overcome these imbalances. The fact that the modern agricultural techniques result in progressively heavier crops being removed from the soil means that the amount of trace-element material removed is greater than formerly.
Chelates
…the chelates, with their very special properties, are of particular interest.
Liver, blood, ovaries, and hair are the main tissues used in investigations of animals. From the analysis supplies, practical steps can be taken to remedy the imbalance. It must be stressed that it is frequently overlooked in practice that all nutrient elements interact and influence each other to a considerable extent…Mulder’s interaction chart shows how nutrient antagonizes or stimulate each other’s availability in the soil.
It must be stressed that over-liming is the bad agricultural practice, not liming.
…we must bear in mind not only the need for one or other essential element… but the importance of balanced nutrition. Otherwise, in our effort to solve one problem we may quite unwittingly and unnecessarily develop another. If production and quality are to be improved balanced nutrition must be maintained. All essential elements must be present and available in adequate amounts.
Nutrition is involved in virtually all living processes to some extent, and the contention that we are what we eat is not just a smart cliché, but a very profound concept. It cannot be over-emphasized that for proper development balanced nutrition is of the utmost importance…There is no balance of nutrients that is optimal for all species,…From a practical point of view, it is essential to grasp the fact that trace-element imbalances do exist on a very extensive scale, and that there are very real trace-element problems. It is only when this has been properly appreciated that really effective measures can be taken to remedy the ‘problems’, which are so widespread as to be a very normal part of our environment.…thousands of animals are below par because their mineral requirements have not been met. The fact that trace elements play a part in such conditions as cancer, atherosclerosis, and hypertensive states makes them particularly interesting… (they) play such an important part in the enzymatic activity of the cell, they might be expected to be seriously involved in such conditions…health of mind and body is dependent upon the food we eat and upon the trace elements which they contain.
For the full excerpts from Dr. Schutte's book go to www.montmorillonite.org