MYTH: Polyunsaturated vegetable oils prevent heart disease.
TRUTH: Polyunsaturated oils may actually contribute to the incidence of heart disease.
Contrary to popular misconception, polyunsaturated oils do not prevent heart disease. On the contrary, they may contribute to it. As our national consumption of polyunsaturates (e.g. vegetable oils, margarines and other processed oils) has increased over the years, so too has the incidence of heart disease increased.
Polyunsaturated oils are chemically unstable. That is because they have a number of loose, double carbon bonds in their molecular structure. When subjected to heat or air, they oxidize rapidly to form harmful free radicals. The more unsaturated the oil, the more potentially hazardous it is. Examples of oils that are predominately polyunsaturated are safflower, sunflower, corn, soy, wheat germ, walnut, flax, pumpkin and cottonseed.
The most hazardous vegetable oils of all are the ones used in restaurants for deep frying. Those oils are heated and re-heated many times over. They are rancid, but you cannot taste or smell that rancidity because of deodorants that manufacturers purposefully add.
Other very hazardous vegetable oils are those which have been hydrogenated to form margarine, shortening and other manufactured or “tinkered” fats. These substances are not natural foods at all, but are rather in the category of food “artifacts”. They contain peroxidized fats, trans fatty acids and other modified fat molecules which can severely compromise immune processes in the body.
Even the highly promoted “cold pressed” oils can be harmful. For one thing, many of them are processed at a “cold” temperature of over 100 0C. For another, as soon as they are exposed to air they deteriorate rapidly – and if heated, their destruction is virtually guaranteed.
Healthy fatty acids are critical to our survival. They help to form the membranes that surround every cell in the body. They help to protect against degenerative diseases. They are precursors to hormone-like substances called “prostaglandins”, which help to regulate gastric secretions, pancreatic functions and the release of pituitary hormones. Fatty acids combine with glycerol to form triglycerides, which act as carriers for vitamins A, D and E and help to convert beta carotene into vitamin A.
Fatty acids are of three basic types: saturated (e.g., palmitic acid, stearic acid), mononunsaturated (e.g., oleic acid) and polyunsaturated (e.g., linoleic, linolenic, arachidonic). All of the fats and oils in our diet consist of various combinations and proportions of these three groups. If our diets provide an adequate supply of all the basic fatty acids, our bodies can pick and choose the best ones for the tasks that need to be accomplished on any given day. If the best ones are not available, then we force our bodies to make do with substitutes. Unfortunately, if only rancid or peroxidized fats or trans fatty acids are provided, then we end up with inferior or “leaky” cellular membranes, plus inadequate prostaglandins and an overloaded immune system which may struggle in vain to stave off free radical damage.
There are two fatty acids that are critical. They are deemed “essential” because we need them for our survival but our bodies cannot make them. We have to get them from food. They are linoleic acid (omega-6) and linolenic acid (omega-3). Without these essential fatty acids we perish. With enough of them (and in the presence of adequate vitamins and minerals), the body can manufacture all of the other fatty acids it needs.
The essential fatty acids we need are found in relatively high proportions in those oils that are predominately polyunsaturated. But these are the very oils that are most prone to deterioration and the production of excess free radicals. Therefore, balance is required. We need to do without overdoing. Fortunately, those fats and oils that are predominately saturated or monounsaturated also contain smaller but significant amounts of essential fatty acids.
Our primitive ancestors had an answer. They were unable to extract oils from plants. They got all of the essential fatty acids they needed from the natural whole foods that they ate – including poultry fat, animal fat, fish, avocado, egg yolk, olives, butter, nuts, and seeds and the like. There is wisdom in consuming our polyunsaturates as part of the whole nut or seed, where nature’s package protects them from deterioration. It is unwise to consume them as extracted and refined oils, in unnatural and potentially dangerous proportions.
Nuts and seeds that are heated or roasted lose their natural protection against the potentially harmful breakdown of the polyunsaturates they contain. Be especially wary of roasted nuts that are heavily salted. Their saltiness may hide the taste of rancid oils.
Monounsaturated fatty acids (omega-9) have only one loose double carbon bond in their molecular structure. That makes them much more resistant to deterioration from heat and light than the polyunsaturates. The monounsaturates contribute stability to cellular membranes in the plants in which they are found, and they do the same for our cells as well. Examples of oils high in monounsaturates are olive, almond, macadamia, avocado, hazelnut/filbert, pecan, and pistachio.
Fish body oils contain unique polyunsaturates. The principal one of these is EPA (eicosapentaenoic acid), an omega-3 fatty acid that has been demonstrated to improve the flow characteristics of blood. It prevents blood cells from sticking together to form clots that might otherwise prematurely plug up the arteries. EPA also tends (a) to reduce serum triglycerides and total serum cholesterol, and (b) to increase HDL cholesterol (the “good” kind). EPA is nature’s “anti-freeze”, to keep the fish’s body from stiffening up from cold temperatures. Therefore, the colder the water the fish lives in, the higher its EPA content. Almost any fish will do, but the best sources are salmon, mackerel, cod, herring, haddock, trout, whitefish, oysters and squid.
Organic flax oil provides approximately 57% linolenic acid, 16% linoleic acid and 18% oleic acid – and it is used therapeutically to treat a number of degenerative conditions. Raw flaxseed oil, however, is highly susceptible to deterioration that quickly transforms it into a source of free radicals. A healthier choice is flaxseed oil that has been specially processed at 40 0C in the total absence of oxygen. This oil is hermetically sealed into opaque capsules and bottled with nitrogen into light-resistant bottles, making it resistant to the destructive influences of oxygen, heat and light.
Both the quantity and quality of fats and oils we consume are critical to our health. If our total fat intake is too low, we will not be getting enough essential fatty acids to sustain life and we increase our risk for
cancer. If our total fat intake is too high, the body will use first the fatty acids it can most easily assimilate, leaving the less desirable ones to circulate throughout the lymphatic system where they can cause tissue damage and tumours.
The following are useful guidelines when considering the relationships of fats and oils to heart disease:
1. Saturated fats do not cause heart disease. If they did, the population of rural North America would have died off generations ago from its consumption of beef, pork, bacon, eggs, sausages, lard, etc. Natural fats that are predominately saturated are extremely stable and can still supply tiny amounts of essential fatty acids.
2. Polyunsaturated oils do not prevent heart disease. If they did, the incidence of heart attacks would not have increased as our national consumption of vegetable oils has increased. Polyunsaturated oils are very unstable and may actually contribute to the development of heart disease by increasing the body’s exposure to harmful free radicals.
3. Monounsaturated fats (e.g., olive, avocado and macadamia) protect cellular membranes from free radical damage. In Mediterranean countries that have a long history of use of olive oil, for example, the incidence of heart disease is significantly lower than it is elsewhere.
4. Hydrogenated and processed fats (e.g. margarine, shortening), deep fried fats, and rancid fats and oils of all kinds are very detrimental to arterial health.
5. Fish body oils are beneficial to arterial health, by helping to improve the flow characteristics of the blood and by reducing inflammation.
6. The most desirable source of fats in the diet include butter and olive oil – plus the naturally occurring fats in eggs, fish, poultry and unprocessed meats – plus the naturally occurring oils in avocado and fresh, raw nuts and seeds.
7. For optimal health, limit total intake of fats and oils to between 20 and 30 per cent of total daily caloric intake.
See also the chapter, “The Cholesterol Myth”, in NUTRITIONAL SOLUTIONS FOR 88 CONDITIONS (available at Amazon.com)