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Lipids =Fats and Oils
Fats are made of fatty acids and are found in all plants and animals. Solid fats are found in animal products and are also produced by the hydrogenation of vegetable oils.
Dietary lipids are a heterogeneous mixture consisting of about 93% triglycerides, 6% phospholipids and lesser amounts of sphingomyelins, glycolipids, cholesterol, and phytosterols. Excess intake of animal fats has been associated with several major diseases: atherosclerosis, which leads to heart attacks and strokes, cancers of the colon and breast, and obesity. While many different lipids are ingested and metabolized, only two fatty acids are considered essential in the diet - linoleic acid and alpha-linolenic acid. All other fatty acids can be synthesized from these two basic molecules.
One idea of nutritional programming is that there must be an optimal nutrient set for each person. No one really knows how to select the best food to achieve a balanced intake of fatty acids. If we start with the two fatty acids, considered essential, linoleic acid and alpha-linolenic acid, we can begin to build a hypothetical best fatty acid mix.
Recall that linoleic acid gives rise to the omega 6 family of fatty acids and alpha-linolenic acid gives rise to the omega 3 group. Arachidonic acid is sometimes considered essential but may be produced internally by the conversion of linoleic acid. While all other fatty acids can be synthesized from the two basic molecules by normal people, there are persuasive arguments to include other fatty acids such as oleic acid in the diet. Oleic acid in olive oil may offer advantages in preventing atherosclerosis. Oleic acid is described as a "mono-unsaturate" to describe one -C=C- bond rather than two or more.
One of the most accepted ideas about healthy fat is that the fats found in plant oils are preferred over the saturated fats that are found in animal products. The use of vegetable oils, usually derived from plant seeds, is the most common and affordable method of adjusting fatty acid intake. The distribution of the two essential fatty acids is striking different in different vegetable oils. As a benchmark, the ratio of omega-6 and omega-3 FA should approach 1:1 much reduced from a more typical ratio of 10:1 in North American diets. In the USA, the omega-6 to omega-3 ratio fell from 12:1 in 1985 to 10:1 in 1994 associated with a 5-fold increase in the use of canola oil.
The human brain has special requirement for fatty acids; 60% of the brain's structural material is fat with high concentrations of two long-chain polyunsaturated fatty acids, docosahexaenoic acid (DHA), omega-3, and arachidonic acid (AA), omega-6 fatty acid. The requirement for these 2 FAs is highest during fetal growth and in early infancy when brain growth continues at a high rate.
A reasonable argument is that DHA and AA must be included in the diet in reasonable amounts to support brain structures; for any number of reasons, people who cannot synthesize sufficient amounts of these molecules from other fatty acids may suffer neurological dysfunction and or disease. The best source of DHA is shellfish and fish, particularly cold-water fish such as bluefish salmon and herring.
Canola and flax oils have the best distribution of the 3 fatty acids but flax oil is fragile oil that requires special handling to retain its desirable properties. Olive oil alone does not have the right balance to be considered as the primary oil. What about other fatty acids? If we consider the growing literature on the subject, there are many ideas, but conflicting evidence about what is best.
We have chosen two “best oils,” canola and olive oil. We suggest using these oils in combination to achieve a fatty acid balance. Canola oil is a Canadian product made from rapeseed that has been bred over decades to produce a high quality food oil, with little or no euracic acid, a non-essential fatty acid found in uncultivated rapeseed oil that was associated with heart abnormalities.Kris-Etherton PM et al. Polyunsaturated fatty acids in the food chain in the United States. Am J Nutr, 2000, 71, 179S-188S. Canola Oil Research Papers. See the bibliography at the Canola Oil Council of Canada Website. http://www.canola-council.org/
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