Fat is essential to the human being not only as an energy producing food representing nine calories per gram consumed but it plays a most important metabolic role. It serves as protection against heat and cold, injury from forceful bodily contact, affords the protection of the skeleton from bodily usage. It enters into complex metabolic processes in the formation of chemical entities that are essential for life. This is particularly true of the essential fatty acids. The lipoids are necessary to protect us from disease.

Lipid metabolism in its many complex ramifications is as important as protein metabolism, for no cell can live without it. The size of the individual lipid entity is usually within the molecular range of from 220 to 1800. Lipids are defined physically as substances of a waxy feel, soluble in alcohol, ether, and other hydrocarbon solvents, insoluble in water. This includes the fats, fatty oils, fatty acids, esters of fatty acids containing phosphoric acid, amino nitrogen, sulphur acid and carbohydrate groups, as well as the waxes and sterols. The discussion will be limited to the tryglycerides and other component parts which constitute the usual fats and oils of normal and medically controlled diets. They are divided into two major classifications: (1) those solid at 20° Centigrade, and (2) those which are liquid at 20° Centigrade. From a chemical standpoint, they are classified as glycerol esters, having the general formula

in which R-1, R-2, and R-3, may be the same or different hydrocarbon chains.

Whether a lipid is a solid or a liquid depends on the molecular weight of the fatty acid chain or whether or not the radicles are saturated or unsaturated hydrocarbon groupings. Saturated oils, liquid below 20° Centigrade are made up of fatty acid chains of less than 8 carbon atom linkages. The unsaturated fatty acids differ from the saturated acids by the formula:

Cn H2n O2 Saturated fatty acids

Cn H2n  –  2 x O2 Unsaturated

x – number of double unsaturated bonds

These unsaturated fatty acids have a much lower melting point as is shown. Specifically, olein and stearin have the same number of carbon atoms, namely, 17, in their side chains; but the oleic acid has two less hydrogens than the stearic acid. The former melts at minus 17° and the latter at plus 70° Centigrade.

Commercially, unsaturated fatty acids present difficulties in preserving and handling. They are for the most part obtained from vegetable sources and are frequently by-products. Although of greatest biological worth unsaturated, they are frequently changed into the saturated varieties by the process of hydrogenation to produce a stable product.

The Purpose of Fats–Protective Role in the Body

Fats are present in every living cell and are essential to its life. The human body varies in fat content, but as an average figure, the 150 pound standard man is estimated to be composed of:

Body weight	70 Kg.	100%
Fat	7 Kg.	10%
Protein	6.4 Kg.	9%
Carbohydrate	5.6 Kg.	8%
Mineral	2.0 Kg.	3%
Water	50.0 Kg.	70%

The intracellular fat is present in tissues such as muscle, brain, pancreas, and skin, as important constituent. It is stored in the subcutaneous tissues as so-called depot fat for metabolic purposes and bodily protection. The fat pads of the infant protect him from breaking his bones or impairing other parts of the body by acting as a cushion when he falls. Such pads are frequently lost as people grow older, either by design or altered metabolism, making them more susceptible to mechanical injury of broken blood vessels, bones; injuries to joints, etc. It serves as a cushion and a support for the viscera. Viceroptosis, so common in misguided young women, results from fat loss that, indeed, can become crippling. The pressure pads of the hands, especially over the metacarpal heads, are of utmost importance to comfort while working. A painful hand results from loss of these pads making any work requiring pressure of a tool or other object sometimes almost impossible to perform, such as the opening of a jar with a screw type cap. Similarly, the loss of the pads in the feet, especially those over the metatarsal heads and over the heels may almost preclude walking. Usually, everything but lack of fat in the diet is blamed first and sponge rubber pads and other types of crutches are sought to relieve it.

A well formed body is a pleasure to look upon and the loss of orbital fat and sucking pads do not enhance the beauty of modern women. Though the lack of fat may be the cause of such problems, pressure pads are only slowly replaced once lost. Many never return. Such is true of the ischial pads of the older person. A person may be obese and yet have poor fat that does not supply pressure pads. Age plays an important part in whether a realignment of pressure pads can be obtained. Apparent skinny persons, if muscular, may have excellent pressure fat pads regardless of their age while others with apparent extra-cellular pads cannot sit on a hard seat for any length of time in comfort.

The subcutaneous fat of an individual aids him to resist excessive environmental temperature changes. Fats form an excellent thermal barrier and prevent the body from losing heat when exposed to cold or from too much heat when the weather is hot. In case of accident from excess thermal exposure, a reasonably distributed subcutaneous adipose tissue may save a life or protect a vital structure less well prepared to withstand heat than the subcutaneous fat. A person’s physical beauty depends upon the texture of his skin. Proper dietary fats are essential to this bodily function. Not only does insufficient intake of the right kind of fat produce an unsightly, unlovely skin but it can produce a skin that is no longer resistant to mechanical abrasions. It fractures, fissures, becomes painful as well as unsightly.

The skin is protected on its surface by a very fine fatty secretion, an important part of which is the unsaturated fatty acid fraction of this sebaceous secretion. This is in combination with other lipoid materials, hormones, proteins, and the like. However, the ability of the unsaturated fatty acids to polymerize and to form plastic surfaces, flexible in character, constitutes a large part of the protective covering of our skin surface. The basic reaction is no different from the effect of oxygen of the air in polymerizing linseed oil to make a fine plastic surface for our furniture. Adequate fat intake of the proper kind not only provides the elastic surface covering for skin, but it provides it with bactericidal properties that prevent us from infection with the myriad of pathological organisms we daily contact. Likewise, this plastic layer prevents dirt and grime from penetrating the layers of our skin such as occurs to one who continually handles dirty materials in fat solvents or to one whose fat metabolism is incorrect.

Diseases that interfere with fat metabolism are usually associated with nervous irritability, either central or local. Similar effects are noted when improper consumption of quality and quantity of fats is habitually practiced by the individual. Our nerves are surrounded by a myelin sheath largely composed of fats. The leukocytes are composed in a great measure of fats which are essential to these life-protecting scavengers of our body.

Chemical Usage of Fats

Fat is the energy fuel of the body. Like an olefine, the potential rate of heat production is proportional to the degree of saturation of the fat. The unsaturated bonds provide a breakdown point of the fat into fragments of different lengths from the usual C-2 fragments that are considered the end products of fat and carbohydrates metabolism, and was long considered the only way the fat was utilized in the body. However, odd number C fragments have been (1) isolated from animal fats and where once it was thought that only the even carbon fragments were present in biologically active fat, it has been shown in recent years that tissues contain C-5’s, 7’s, 9’s, 11’s and 13’s, and others: (2) Bentley³ has suggested that in the cow, at least, n-Caprylic and n-Valeric may have a vitamin-like action in the animal. Some of the unsaturated fatty acids may be so fragmented. A group of the so-called diethenoid and polyethenoid acids most commonly found in natural fats are listed with reference to the number of double bonds and the possibility of positional breakdown. (Fig.)

C7—possibility Elaeostearic Indirect Elaeostearic 7 Morocitic 1, Parinaric 1, Arachidonic 2nd 1, Clupanodonic 3, Nisinic 1.

C5—possibility, direct, 2 Elaeostearic, 1 Arachidonic indirect, 1 Parinaric. Caprylic Acid CH3 (CH2) 5 COOH 7C. Valeric Acid CH3 (CH2) 3 COOH 5C.

The commercial producer of solid fats from vegetable oils, saturates the unsaturated fatty acids by hydrogenization at the double bonds. The chemist tests the degree of the unsaturation by the addition of iodine, so does the bodily economy possess the ability to substitute metal and other metabolic substances at the double bond of these fatty acid chains. It is at the double bonds that processes of polymerization can and do take place, making it possible for our body to elaborate ring compounds not only from the C-2 fragments but from the larger fragments.

Though some of the fats we consume are immediately brought into new chemical relationships, much of it is stored in the fat depots. The nature of this fat is dependent, in part, on the ingested fat. It is simple to change the character of the bodily fat of a human being from a soft to a hard fat according to the food intake, as it is with any other animal.⁴ The high melting point fat when stored depends on the synthesis of carbohydrate or the transport of high melting point fat producing a hard fat in the subcutaneous tissue of the fat depot.

Essential Fatty Acids

Burr and Burr⁵ first showed that there was a marked difference in the requirement of animals for different fats. They showed that a definite deficiency state develops in animals deprived of the so-called essential fatty acids. These fatty acids.are those with two or more double bonds. Without these fatty acids in the diet, animals did not thrive, they failed to reproduce and died. Hansen⁶ showed further that these were essential in human nutrition.

It is these essential fatty acids that are both dangerous and beneficial. Their breakdown in foods can cause death. It is their spontaneous change into odoriferous aldehydes, ketones and esters that is responsible for much destruction of food. Their instability is responsible for salad oils becoming gummy and unusable. For such oils are intended to provide us with a protective surface that preserves our lives. The factor of rancidity is one of pre-eminent interest to the food industry. Its control is essential for our industrial age. The result is that many of our finest fats are being rendered biologically useless for important chemical processes other than the production of heat. It is this fact that makes many Americans fat deficient in a food economy that provides us with an overabundance of fat calories.

Even the heat processing of some of our fats, like milk fats⁷ seems to render them less valuable when they are so treated and may be one of the factors in producing aging.

Clinical Studies

Dry skin is a very common complaint today. It ranges from the complaint of the woman that her skin and hair is unsightly to the severe breakdown that one finds in some of the most stubborn dermatological conditions. Some skins are painful, some ache, some itch, some burn. Others cannot be cleaned. Yet many of these people are eating adequate amounts of fats in the form of saturated fats obtained from oleo, cooking fats, and others, yet they are not getting the right kind of unsaturated fatty acids. We⁸ studied the problem of simple dry skin and reported that in women, dry skin was a far more serious complaint than in men; while in children, dry skin in boys was a far more common complaint than in girls. Not only do many people have dry skin, but because of the same lack of unsaturated fatty acids, lack sex drive; they cannot conceive; the sexual act is distasteful to them; they are nervous; they do not sleep; awake from sound sleep; they are apprehensive, irritable, hard to get along with; their energy is low and their resistance to allergies is lacking. Many have nose and chest complaints and poor appetites. Frequently, they may be oversize or even obese, suffer from gastric complaints, headache, and a whole gamut of other complaints. Many of these individuals are consuming adequate calories of fat, but are consuming insufficient essential fatty acids. They can be aided by placing them upon a dietary of good fats.

Conclusion

What is the solution? It is not just giving unsaturated fatty acids in the dietary, because some individuals may no longer be able to tolerate them alone. It is a problem of rehabilitation. Some of the processes may have gone too far for return, but it takes patience and courage on the part of not only the patient but his guiding physician. There is no quick surgical cure. Many attempt it. There is no miracle drug. Most have tried it. It is not psychiatric, though proper counseling may help. By and large, the cure is a well rounded medical approach with a good dietary utilizing an adequate intake of biologically active non-rancid unsaturated fatty acid as a part of a whole organized program of rehabilitation.

References Cited:

1. Hansen, R. P., and McInnes, A. G., Nature, 173, 1093 (1954).
2. Deuel, Harry J., Jr., The Lipids, Vol. 1, 1951, p. 9-11.
3. Bentley, O. G.; Lehmkuhl, Alfred; Johnson, Ronald R.; Hershberger, T. V.; Moxon, A. L., J. Am. Chemical Soc. 76, 5000 (1954).
4. Maynard, Leonard A., Animal Nutrition, McGraw-Hill, 1947, Second Edition, pp. 70-75.
5. Burr, G. O., and Burr, M. M., (1930), J. Biol. Chem., 86, 587.
6. Hansen, A. E., (1933) Proc. Soc. Exper. Biol. & Med., 30, 1198.
7. van Wagtendonk, W. J., and Wulzen, R., Arch. Biochem., 1:373, (Feb) 1943.
8. Pottenger, F. M., Jr., J. Southern Med. Assoc., Vol. 43, No. 2, Feb. 1950, pp. 165-168.

Summary

Fats have been defined and the purpose of fats in protecting the body from mechanical and chemical injury and microbial damage has been discussed. The important biochemical factors have been briefly sketched. Particular reference has been made to the essential fatty acids. A simple essential fatty acid deficiency has been reviewed as seen by a clinician in his practice.

Francis M. Pottenger, Jr., MD / Autumn, 1956

Presented before the 20th Annual National Convention of the American Academy of Nutrition, Los Angeles, 1956. Reprinted from The Journal of Applied Nutrition, Vol. IX, No. 2, pp. 394-397, Autumn 1956.

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