Essentiality to Humans

Plants, in contrast to animals, have the ability to convert carbon dioxide from the atmosphere and inorganic components of the earth direcdy into high energy carbohydrates (qv), fats, and proteins (qv). These plant materials are absolutely essential to human nutrition as well as to the nutrition of other animal species. Thus consumption of plant matter, either directly or through a food chain, is essential to animal life and humans are totally dependent on agricultural endeavors, ie, the culture and harvesting of plant matter. 

Chlorine. Chlorine, the material used to make PVC, is the 20th most common element on earth, found virtually everywhere, in rocks, oceans, plants, animals, and human bodies. It is also essential to human life. Eree chlorine is produced geothermally within the earth, and occasionally finds its way to the earth s surface in its elemental state. More usually, however, it reacts with water vapor to form hydrochloric acid. Hydrochloric acid reacts quickly with other elements and compounds, forming stable compounds (usually chloride) such as sodium chloride (common salt), magnesium chloride, and potassium chloride, all found in large quantities in seawater. 

Cobalt is one of twenty-seven known elements essential to humans (28) (see Mineral NUTRIENTS). It is an integral part of the cyanocobalamin [68-19-9] molecule, ie, vitamin B 2> only documented biochemically active cobalt component in humans (29,30) (see Vitamins, VITAMIN Vitamin B 2 is not synthesized by animals or higher plants, rather the primary source is bacterial flora in the digestive system of sheep and cattle (8). Except for humans, nonmminants do not appear to requite cobalt. Humans have between 2 and 5 mg of vitamin B22, and deficiency results in the development of pernicious anemia. The wasting disease in sheep and cattle is known as bush sickness in New Zealand, salt sickness in Florida, pine sickness in Scotland, and coast disease in AustraUa. These are essentially the same symptomatically, and are caused by cobalt deficiency. Symptoms include initial lack of appetite followed by scaliness of skin, lack of coordination, loss of flesh, pale mucous membranes, and retarded growth. The total laboratory synthesis of vitamin B 2 was completed in 65—70 steps over a period of eleven years (31). The complex stmcture was reported by Dorothy Crowfoot-Hodgkin in 1961 (32) for which she was awarded a Nobel prize in 1964. 

Copper is one of the twenty-seven elements known to be essential to humans (69—72) (see Mineral nutrients). The daily recommended requirement for humans is 2.5—5.0 mg (73). Copper is probably second only to iron as an oxidation catalyst and oxygen carrier in humans (74). It is present in many proteins, such as hemocyanin [9013-32-3] galactose oxidase [9028-79-9] ceruloplasmin [9031 -37-2] dopamine -hydroxylase, monoamine oxidase [9001-66-5] superoxide dismutase [9054-89-17, and phenolase (75,76). Copper aids in photosynthesis and other oxidative processes in plants. 

Figure 25.9 Structures of the eight monosaccharides essential to humans.

Of the ten trace elements known to be essential to human nutrition, seven are transition metals. For the most part, transition metals in biochemical compounds are present as complex ions, chelated by organic ligands. You will recall (Chapter 15) that hemoglobin has such a structure with Fe2+ as the central ion of the complex. The Co3+ ion... 

Although Zn2+ is essential to human nutrition, compounds of the two elements below zinc in the periodic table. Cd and Fig. are extremely toxic. This reflects the fact that Cd2+ and Flg2+, in contrast to Zn2+, form very stable complexes with ligands containing sulfur atoms. As a result, these two cations react with and thereby deactivate enzymes containing —SH groups. 

Essential AAs cannot be synthesized by the body. Therefore their isotopic composition is directly inherited from the ingested foods. Indeed, AAs which are essential to humans are generally also essential to the herbivores from... 

Oxygen A gaseous element essential to human life comprises about 20% of the air... 

The carotenoids are the most widely distributed group of pigments, occur naturally in large quantities, and are known for their structural diversity and various functions. The carotenoids constitnte a widespread class of natural pigments that occur in all three domains of life in the eubacteria, the archea, and the eucarya. Carotenoids are ubiquitous organic molecules, but they are not produced by the human body. They have been fonnd to be essential to human health based on the nutritional understanding of vitamin A (retinol) and (i-carotene. ... 

At least some of the antioxidant nutrients are essential to human health, and others (such as carotenoids) may be highly beneficial, particularly in preventing cancer (e.g. Block et /., 1992). However, we do not yet know what dietary intakes are optimal. In principle, this could be investigated by varying the dietary intake of antioxidants and measuring free-radical damage in the human body. This is one of our current research directions. 

In July, 1970, 14 trace elements were known to be essential to human health. One of these is cobalt. Yet at least one researcher suggests that the addition of small amounts of cobalt to stabilize beer foam may have resulted in the deaths of a number of people in Minneapolis and Omaha. He theorizes that cobalt was necessary to activate the toxicity of selenium, which is naturally present in those areas. This is another example of a synergistic affect. Separately neither would have been harmful, but together they could cause fatalities. 

Pain is a basic sensory, emotional, and cognitive phenomenon that signals some type of harm to the organism. It is practically universal to human experience, and although it is initially adaptive, it frequently outlives its usefulness and impedes one s ability to function. Accordingly, plants that alleviate pain have become essential to human civilization. 

O 4 A reliable supply of fresh, nutritious food is essential to human health. To this end, the food industry has developed different types of food additives to keep food fresh longer. Numerous reactions are responsible for food spoilage. For example, a food may become stale and rancid due to the oxidation of the molecules in the food by oxygen in the air. 

Fatty acids, such as linoleic, hnolenic, and arachidonic acids, contain two or more cis carbon-carbon double bonds and are referred to as polyunsaturated fatty acids. Several of these fatty acids, including linoleic and linolenic acids, are required nutrients for humans and must be part of a healthy diet. They are termed essential fatty acids, of which there are eight. These fatty acids cannot be synthesized by human beings but are essential to human health. Therefore, they must be consumed in adequate amounts in a healthy diet, specifically in the form of ingested plant-derived foods. A diet devoid of the essential fatty acids eventually results in a fatal condition characterized by inflammation of the skin (dermatitis), failure of wounds to heal, and poor growth. The essential fatty acids serve as precursors for complex molecules termed eicosanoids, to which we return below. 

Chromium is commonly released to the environment from the electroplating industry and is extremely hazardous. Some studies suggest that in minute amounts, chromium may be essential to human beings, but this has not been proven. The standard for chromium is 0.05 mg/L of water [76]. 

Chromium Electroplating plants (as Cr +)( ), essential to human health in trace amounts 100 ppb... 

Enzymes found in both parasites and humans, but essential to parasite life while being nonessential or less essential to human life (e.g., purine nucleoside kinase, ornithine decarboxylase)... 

Water is an excellent solvator and dissolves many chemicals, particularly metal ions. Since some metal ions are essential to human health in the right dose, removing them completely to make demineralized water is not desirable. Hence metal ions will be part of the water used by humans, not just for drinking but also during domestic chemistry such as washing and cleaning, and for most industrial chemistry. However, metal ions can be undesirable for some domestic or industrial chemistry applications. 

Pantothenic acid is a vitamin, which is essential to human life. Its name is derived from a Greek root that reflects its universal occurrence in living things. The bacterium Lactobacillus bulgaricus, which converts milk... 

Yeast protein is easily digested (87%) and provides amino acids essential to human nutrition. Most commercial yeasts show the following pattern of amino acids, among others, as percent of protein 8.2% lysine 5.5% valine 7.9% leucine 2.5% methionine 4.5% phenylalanine 1.2% tryptophan 1.6% cystine 4% histidine 5% tyrosine and 5% arginine. The usual therapeutic dose of dried yeast is 40 grams/day, which supplies significant daily needs of thiamine, riboflavin, niacin, pyridoxine, and general protein. 

Sodium chromate and sodium dichromate are both starting points for the production of pigments, corrosion inhibitors, fungicides, and ceramic glazes. Chromium(III) is essential to human health and may play a role in the regulation of glucose metabolism. 

The trace minerals identified as essential to humans and for which deficiency states have been described are zinc, copper, manganese, selenium, chromium, iodine, molybdenum, and iron. 

Each of these minerals participate in a variety of biologic functions and is necessary for normal metabolism. Other trace minerals essential to humans but for which deficiency states have not been recognized include nickel, vanadium, cobalt, and silicon (Table 66.2). 

It is well known that the toxicity of many elements depends on the physicochemical forms they assume. So, for instance, determining the total content of a certain element in a sample is definitely not sufficient to measure its toxicity. Selenium is a case in point in small amounts this element is essential to human health. But the transition from the necessary amount (about 70pg of selenium per day for an adult) to a toxic dose (about 800 pg of selenium per day) is relatively easy. In rats, moreover, the fatal dose of Se(IV) compounds is 3.2 mg kg 1 of body mass, whereas for dimethyl selenide it is 1600 mg kg 1 of body mass. Nonorganic selenium compounds [Se(IV) and Se(VI)] are believed to be the most toxic ones, whereas in the environment selenium occurs most commonly bound to amino acids (selenomethionine and selenocysteine). The least toxic forms seem to be the volatile methyl compounds of selenium, which are metabolites of a detoxication process. 

Nickel, atomic number 28, is a transition metal with a variety of essential uses in alloys, catalysts, and other applications. It is strongly suspected of being an essential trace element for human nutrition, although definitive evidence has not yet established its essentiality to humans. A nickel-containing urease metalloenzyme has been found in the jack bean. 

Nicotinic acid (melting point 236°C, density 1.473) and nicotinamide (melting point 129°C, density 1.400) are known as niacin and niacinamide in the food industry. Niacin is the most stable of all vitamins and is essential to humans and animals for growth and health. Niacin and niacinamide are nutritionally equivalent, and compete with one another. 

We know it as Vitamin C, an anti-oxidant essential to human life. Photographers think of it as a secondary developing agent in superadditive pairs such as Metol-Ascorbate or Phenidone-Ascorbate. These have been known for years but recently made popular by Kodak XTOL film developer. 

Material Amino acid essential to human nutrition. 

Chromium speciation by using anion-exchange chromatography has also received much attention in recent years because the element is both essential to humans and toxic in large doses [62-66]. Cr (III) and Cr (VI) may be separated by... 

The earth is provided with two sources of energy, the capital resources deposited within the earth during its formation and the income resource continuously beamed onto the earth from the sun. Both are essential to human existence. 

Originally, nine of the trace elements were considered to be essential to humans cobalt, copper, fluorine, iodine, iron, manganese, molybdenum, selenium, and zinc. Recently, chromium, silicon, and nickel have been added to this list (Reilly 1996). These are mostly metals some are metalloids. In addition to essential trace elements, several trace elements have no known essentiality and... 

Here aura (as breath) is a component of a physiological process, essential to human life (if also increasingly redundant - or forced into crisis - for art in a technological age).36 The breathing in of aura , this exchange of air and... 

Twenty-one elements are essential to humans. An essential nntrient is one for which a deficiency results in an impairment in function that is relieved only by administration of that substance. Vitamins by definition and some minerals are essential. The significance of essentiality may be illustrated by burlesquing an old adage. 

---