5. DIETARY FIBRE
Lipids (fats, oils, sterols, prostaglandins), like carbohydrates, are composed of carbon, hydrogen and
oxygen. Lecithin (phosphatides), are lipids containing phosphorus. Lipids store energy in its most
concentrated form. Lipids carry the fat-soluble vitamins A, D, E and K and make their absorption into the body possible. A shortage of fats and oils in the diet prevents the absorption of fat-soluble vitamins, resulting in a deficiency of oil-soluble vitamins in the body and brings about health problems associated with deficiency of these essential nutrients. Dietary lipids also provide building blocks that the body requires to build membranes and other cell structures and to make hormone-like regulating substances known as prostaglandins.
Fats & Oils
Fats and oils are made from a glycerol molecules to which are attached three free-swinging fatty acids. The latter determine the properties of fats and oils. Fatty acid chains may be from 4 to 24 carbons long and may have zero (saturated), one (mono-unsaturated) or 2 to 6 (polyunsaturated) double bonds in the chain.
At room temperature, long-chained and/or saturated fatty acids are usually solid, while short-chained
and/or unsaturated fatty acids are liquid. Double bonds make fatty acids reactive, increasing metabolic rate as well as decreasing shelf stability. The more double bonds, the more active the fatty acid and the more powerful its effects in the body. Unfortunately, double bonds also make fatty acids more sensitive to destruction by light, oxygen and heat.
Essential Fatty Acids
Many fatty acids can be synthesized in the body from dietary lipids, excess carbohydrates or excess
proteins, but two fatty acids cannot be so produced. These are known as essential fatty acids: linoleic acid (omega-6; polyunsaturated) and alpha-linolenic acid (omega-3; super-unsaturated).
Note: Some manufacturers of nutritional supplements market essential fatty acid supplements as
containing omega 3 – 6 and 9 fatty acids. Omega-9 is oleic acid and is non-essential in humans. Virtually all animal fats and vegetable oils contain oleic acid in varying degrees and there is no known deficiency in humans. In fact, it has been shown that excessive oleic acid, along with increased copper to zinc ratio can inhibit linoleic acid and gamma linolenic acid metabolism with predictable long-term clinical consequences (1) There is also a strong correlation between the high intake of mono- unsaturated fat (oleic acid) and the incidence of early-stage macular degeneration (2). It is misleading to market essential fatty acid supplements that draw attention to omega-9 (oleic acid) as having nutritional significance and by inference, superior to those formulas that rightly do not show the oleic acid content.
1. Holman R.T. Essential Fatty Acids and Prostaglandins. Progress in Lipid Research, Volume 20, 1981, pp
601-603. Pergamon Press
2. Smith, Wayne, et al. Dietary fat and fish intake and age-related maculopathy. Archives of Ophthalmology, Vol. 118, March 2000, pp. 401-04
Like vitamins, essential fatty acids are required for normal health and must be provided by foods or by supplements. A deficiency of essential fatty acids leads to serious symptoms of degeneration in every cell, leading to premature death.
Essential fatty acids serve as starting material for derivatives that a healthy body can make from them.
These derivatives, in turn, are precursors of powerful hormone-like substances known as prostaglandins.
Minute quantities of these regulate the activities of most cells and tissues. Prostaglandins regulate platelet stickiness, blood pressure, tissue inflammation, kidney function, immune response and other vital functions. Essential fatty acid deficiency, excessive intake of sugar, non-essential fats, cholesterol, processed (hydrogenated) oils or a deficiency of mineral and vitamin co-factors can
interfere with prostaglandin production and function and can lead to impaired cardiovascular, immune, liver, kidney, gland, joint and brain function. The symptoms of defective prostaglandin function are far reaching.
Sterols, another class of lipids, are not essential in that the body can make them from other substances, but they are necessary for life due to their cell membrane and hormonal activities.
Cholesterol, the most important of the sterols, is present in foods derived from animals. Cholesterol has attracted more negative than positive press. Its contributions to health include its stabilization of the membranes that surround each cell and its functions in the production of stress (adrenal) hormones, male and female sex hormones, vitamin D and skin protection.
Excess dietary fats (especially saturated) and cholesterol can have negative effects on health,
cardiovascular disease being the most serious. Obesity, fatty degeneration of inner organs and breast,
stomach and colon cancer are also associated with high intake of dietary fats and cholesterol.