Principles of Biochemistry, Volume 3 - A. Lehninger 1985

Selected Aspects of Human Biochemistry
Human Nutrition
Human nutrition must include a wide range of chemical elements

In addition to the six "major" elements—carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus—which comprise CARBOHYDRATES, fats, Proteins, and Nucleic Acids, humans and experimental animals require numerous other chemical elements for proper Nutrition (Table 26-13). Trace element deficiency in humans is rare, most likely because these elements are abundantly present in most foods and drinking Water. There is every reason to believe that humans require the same elements whose essentiality has been demonstrated in rats and chicks. Furthermore, it is quite possible that The Development of new experimental Methods FOR STUDYING nutrient deficiencies, along with a broader understanding of active enzyme groups, will reveal additional essential elements for humans that are not yet listed in Table 26-13.

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Fig. 26-23. Vitamin K₁.

Table 26-13. Chemical elements required for normal Human nutrition

To determine whether a given element is essential to an Organism, one cannot rely solely on microanalysis of animal Tissues. The tissues of animals and humans may contain small amounts of elements that are not actually required for The formation of any biological Structure or the maintenance of any function, as these elements may have entered the body accidentally as food contaminants. A case in point is the accumulation of toxic levels of mercury in the tissues of tuna and other fish, typical of areas where the ocean is polluted with industrial waste.

Below we briefly discuss the elements whose dietary deficiency in humans is relatively frequent and can lead to significant health consequences. Chemical elements required for human nutrition can be divided into macroelements and trace elements (Table 26-13). Recall that the daily requirement for macroelements exceeds 100 mg/day, whereas the requirement for trace elements does not exceed a few milligrams. Only bioavailable chemical elements present in food as salts or other soluble chemical compounds possess nutritional value.