Minerals and Vitamins

The materials that an animal's cells require but cannot synthesize are called essential nutrients. Obtained from dietary sources, these nutrients include both minerals and preassembled organic molecules. Some nutrients are essential for all animals, whereas others are needed only by certain species. For instance, ascorbic acid (vitamin C) is an essential nutrient for humans and other primates, guinea pigs, and some birds and snakes, but not for most other animals. There are four classes of essential nutrients: essential amino acids, essential fatty acids, vitamins, and minerals. Let’s focus on two latter groups.

Vitamins are organic molecules with diverse functions that are required in the diet in very small amounts. Vitamin B₂, for example, is converted in the body to FAD, a coenzyme used in many metabolic processes, including cellular respiration. Scientists have identified 13 essential vitamins for humans. Vitamins are classified as water-soluble or fat-soluble. The water-soluble vitamins include the B-complex, which are compounds that generally function as coenzymes, and vitamin C which is required to produce connective tissue. Among the fat-soluble vitamins there are vitamin A, which is incorporated into visual pigments of the eye, and vitamin K, which functions in blood clotting. Another one is vitamin D, which aids in calcium absorption and bone formation. Our dietary requirement for vitamin D is variable because we synthesize this vitamin from other molecules when the skin is exposed to sunlight. For people with poorly balanced diets, taking vitamin supplements that provide recommended daily levels is certainly reasonable. It is much less clear whether massive doses of vitamins confer any health benefits or are, in fact, safe.

Dietary minerals are inorganic nutrients that are usually required in small amounts. Mineral requirements vary among animal species. For example, humans and other vertebrates require relatively large quantities of calcium and phosphorus for building and maintaining bone. In addition, calcium is necessary for the functioning of nerves and muscles, and phosphorus is an ingredient of ATP and nucleic acids. Iron is a component of the cytochromes that function in cellular respiration and of hemoglobin, the oxygen-binding protein of red blood cells. Many minerals are cofactors built into the structure of enzymes.

Determining the ideal diet for the human population is an important but difficult problem for scientists. As objects of study, people present many challenges. Unlike laboratory animals, humans are genetically diverse. They also live in settings far more varied than the stable and uniform environment that scientists use to facilitate comparisons in laboratory experiments. Ethical concerns present an additional barrier. For example, it is not acceptable to investigate the nutritional needs of children in a way that might harm a child's growth or development.

The methods used to study human nutrition have changed dramatically over time. To avoid harming others, several of the researchers who discovered vitamins a century ago used themselves as subject animals. Today, an important approach is the study of genetic defects that disrupt food uptake, storage, or use. For example, a genetic disorder called hemochromatosis causes iron buildup in the absence of any abnormal iron consumption or exposure. Fortunately, this common disorder is remarkably easy to treat. By studying the defective genes that can cause the disease, scientists have learnt a great deal about the regulation of iron absorption.

Many insights into human nutrition have come from epidemiology, the study of human health and disease at the population level. By tracking the causes and distribution of a disease among many individuals, epidemiologists can identify potential nutritional strategies for preventing and controlling diseases and disorders.

Notes to the texts:

nutrient – поживна речовина

primate – примат

blood clotting – згущення крові

is exposed to sunlight – піддається дії сонця

to confer – надавати

vertebrates – хребетні

cytochrome – цитохром

challenge – виклик

IX. Look through the text and decide whether the following sentences are true or false:

1. Essential nutrients include either minerals or preassembled organic molecules.

2. Vitamin C is a vital nutrient for all humans and animals.

3. Both vitamins and dietary minerals are required in the diet in tiny amounts.

4. There are thirty essential vitamins for humans.

5. Our dietary requirement for vitamin D is inconstant.

6. The problem of determining the ideal diet for the human population is quite sophisticated for scientists.

7. People are genetically different as laboratory animals.

8. A genetic disorder called hemochromatosis is not difficult to treat.

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