- Key People:
- Edmond Frémy
- Related Topics:
- fat and oil processing
- liquid fat
- animal fat
- marine oil
- suet
Fat
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What is fat?
Fats, of either plant or animal origin, are nonvolatile substances that don't dissolve in water and feel oily or greasy. Together with proteins and carbohydrates, fats form one of the three main food groups and act as a storehouse of energy.
Fats are chemically identical to animal and vegetable oils, and they consist mainly of glycerides. More than 90 percent of the world’s fat comes from about 20 plant and animal species.
Fats have several key functions in plants and animals. They serve as a food reserve, supply energy, and provide insulation against the cold.
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What are the main types of fats found in food?
Fats, a key class of nutrients, come in several main types: saturated, unsaturated, and trans fats.
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Saturated fats have hydrocarbon molecules with hydrogen atoms on every carbon. They are stable, solid at room temperature, and found in meat, dairy, and some plant-based oils.
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Unsaturated fats have hydrocarbon molecules with double or triple bonds, making them liquid at room temperature. They are categorized into monounsaturated and polyunsaturated fats.
- Monounsaturated fats like olive and canola oils have one double bond per molecule.
- Polyunsaturated fats have multiple double bonds and are found in fish, soybeans, and some oils.
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Trans fats can occur naturally in some animal products or are created during the hydrogenation of vegetable oils. They are found in fried and baked goods.
The American Heart Association recommends a moderate intake of all types of fats.
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Why does the human body need fat?
Fats, or lipids, are essential to the human body for storing energy, insulating organs, and facilitating the absorption of fat-soluble vitamins (A, D, E, and K). They also provide essential fatty acids, like omega-3 and omega-6, which the body can't produce on its own. These fatty acids are vital for forming cell membranes and synthesizing hormone-like compounds that regulate blood pressure, clotting, and immune responses. Furthermore, fat deposits in adipose tissue act as an energy reserve and help conserve body heat.
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How does fat help store energy in the body?
Fats, or triglycerides, are a major source of energy storage in animals and plants. In animals, triglycerides are stored in adipose tissue, with fat cells (adipocytes) specialized for synthesizing and holding large fat globules.
Excess dietary fat or carbohydrates are stored in adipose tissue as fat. When the body requires energy, hormones trigger the breakdown of triglycerides into fatty acids and glycerol through lipolysis. These fatty acids are then released into the circulation and metabolized to produce energy.
The energy available from the metabolism of a gram of triglyceride is more than twice that of a gram of carbohydrate.
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What health problems can too much or too little fat cause?
Both too much and too little fat intake can lead to health problems.
Too Much Fat
Excessive consumption of fats, especially saturated and trans fats, is a major cause of dyslipidemia and cardiovascular diseases like atherosclerosis. Trans fats raise levels of LDL ("bad") cholesterol and lower HDL ("good") cholesterol, increasing the risk of heart disease and type II diabetes. Obesity, resulting from excess body fat, elevates the risk of high blood pressure, blood lipid abnormalities, heart disease, stroke, type 2 diabetes, and certain cancers.
Too Little Fat
A deficiency in essential fatty acids can result in dry skin, hair loss, and impaired wound healing. Undernutrition, characterized by insufficient food intake, leads to weight loss, stunted growth, and wasting of body fat and muscle.
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How is fat broken down and used by the human body?
Dietary fats, mostly triglycerides, start breaking down in the small intestine with the help of lipases, enzymes that split fats into fatty acids and glycerol. Bile salts reduce fat droplet surface tension, allowing lipases to attack triglyceride molecules.
The resulting fatty acid and glycerol molecules are absorbed into the cells lining the intestinal wall, where they're reassembled into triglycerides. These are then transported to muscles and adipose tissues. Lipases in the bloodstream break down triglycerides, and the resulting fatty acids and glycerol are taken up by the cells of these tissues. In adipose tissues, triglycerides are re-formed for storage until the body requires more energy due to stress or exercise. Lipases in adipose tissue cells then break down triglycerides, so fatty acids can re-enter the bloodstream for transport to tissues.
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News •
Fat, any substance of plant or animal origin that is nonvolatile, insoluble in water, and oily or greasy to the touch. Together with animal and vegetable oils, fats comprise one of the three principal classes of foodstuffs, the others being proteins and carbohydrates. Nearly all cells contain these basic substances. Fat is a storehouse of energy—on a weight basis it contains more than twice as much energy as does carbohydrate or protein.
Chemically, fats are identical to animal and vegetable oils, consisting primarily of glycerides, which are esters formed by the reaction of three molecules of fatty acids with one molecule of glycerol. Fats are usually solid at ordinary temperatures, such as 25 °C (77 °F), but they begin to liquefy at somewhat higher temperatures.
More than 90 percent of the fat recovered in the world is obtained from about 20 species of plants and animals. Fats appear in plant reproductive organs, such as pollen grains and seeds, probably as storehouses or depots of concentrated energy. Indeed, much dietary fat comes from natural foodstuffs without the need for extensive separation from other plant materials with which it occurs; examples include avocados, nuts, and seeds. The proportion of fat in these foodstuffs varies from 0.1 percent in white potatoes to 70 percent in some nut kernels.
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Most of the fat separated from plant tissues is used eventually as human food. Consequently, fat technology deals largely with the separation and processing of fats into forms acceptable to the various dietary customs in the countries in which they are to be used. (For further information on the subject, see food processing.)
Uses of fats
Humans have used many natural fats for both food and nonfood purposes since prehistoric times. The Egyptians, for example, used olive oil as a lubricant in moving heavy building materials. They also made axle greases from fat and lime, mixed with other materials, as early as 1400 bce. Homer mentions oil as an aid to weaving, and Pliny talks about hard and soft soaps. Candles and lamps using oil or tallow have been used for thousands of years.
The commercial uses of fats have increased in number as the understanding of the chemical nature of fats has expanded. German-Swedish chemist Carl Wilhelm Scheele discovered in 1779 that glycerol could be obtained from olive oil by heating it with litharge (lead monoxide), but it was not until about 1815 that French chemist Michel-Eugène Chevreul (1786–1889) demonstrated the chemical nature of fats and oils. A few years later the separation of liquid acids from solid acids was accomplished. Margarine was invented by the French chemist Hippolyte Mège-Mouriès, who in 1869 won a prize offered by Napoleon III for a satisfactory butter substitute. The modern hydrogenation process had its origin in research in the late 19th century that led to the establishment of the vegetable-oil-shortening industry and a variety of industrial applications.
After World War I, organic chemists gained extensive knowledge first of fatty-acid compositions and then of glyceride compositions. Growth of the chemical industry stimulated a simultaneous expansion of the use of fats as raw materials and as intermediates for scores of new chemicals. The modern application of many organic chemical reactions to fats and fatty acids formed the foundation of a new and rapidly growing fatty-chemicals industry.
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Functions in plants and animals
The universal distribution of fats in plant and animal tissues suggests physiological roles that go beyond their function as a fuel supply for cells. In animals the most evident function of fats is that of a food reserve to supply energy (through subsequent enzymatic oxidation—that is, combination with oxygen catalyzed by enzymes). The storage of fat in vegetable seeds can be explained similarly on the basis that it is a food reserve for the embryo. It is not so easy, however, to account for the presence of large quantities of fat in such fruits as olives, avocados, and palms; much of this fat is probably lost or destroyed before the seed germinates. Fats fulfill other valuable functions in plants and animals. Subcutaneous deposits of fat insulate animals against cold because of the low rate of heat transfer in fat, a property especially important for animals living in cold waters or climates—for example, whales, walruses, and bears.
Fats that have been separated from tissues always contain small quantities of closely associated nonglyceride lipids, such as phospholipids, sterols, vitamins A, D, and E, and various carotenoid pigments. Many of these substances are vital emulsifying agents or growth factors. Others function as agents that prevent deterioration of fats in plant tissues and seeds caused by destructive combination with oxygen. These minor constituents probably are present in the fats as a result of their physical solubility, and thus fats serve as carriers for these substances in animal diets.
Many animals require some fat containing one or more of the essential fatty acids—omega-6 linoleic acid and omega-3 linolenic acid. These fatty acids are described as essential because they cannot be synthesized in the body and therefore must be supplied in the diet since. Moreover, without them, physical symptoms of essential-fatty-acid deficiency manifest, typically in the form of skin lesions, scaliness, poor hair growth, and low growth rate.
The prostaglandins, discovered by Swedish physiologist Ulf von Euler, are hormonelike compounds derived from arachidonic acid. These biologically active fatty acids, which are present in very minute quantities in animal tissues, apparently are involved in contraction of smooth muscles, enzyme activity in lipid metabolism, function of the central nervous system, regulation of pulse and blood pressure, function of steroid hormones, fat mobilization in adipose tissue, and a number of other vital functions.