Fats represent another source of energy for your body. They are highly concentrated, and used primarily for muscular effort. They are also required for the production of various types of bodily tissue, and can be used as a replacement fuel when proteins or sugars are not available.
Fats also play an essential role in the make-up of cellular membranes, and are necessary for the production of hormones and substances called prostaglandines. They are indispensable for transporting liposoluble vitamins (vitamins that cannot be dissolved in water, but only in fat) to various parts of the body. They protect cells against certain types of cancer, and help protect your body against cold. And, as we mentioned earlier, fats are used to store energy in your body.
For your organism to function properly under normal conditions, your daily fat intake should be less than 40% of your total calorie intake. That means you should consume about 75 grams (about 3 ounces) of various kinds of fat per day:
– 25 grams (about 1 ounce) of saturated fat;
– 25 grams (about 1 ounce) of mono-unsaturated fat;
– 25 grams (about 1 ounce) of polyunsaturated fat.
To prevent your body from accumulating too much fat you have to eat a balanced diet, which means knowing what kinds of fats to ingest, in their proper proportions.
This is not as easy as it sounds. Why? Because, in addition to the fat contained in your food, the methods you use for cooking and seasoning, as well as hidden fats contained in processed foods, can drastically increase the amount of fat you absorb.
For example, 100 grams (4 ounces) of meat may contain between 5 and 25 grams (0.2 to 1 ounce) of fat, depending on whether it is lean or not. Processed meats contain huge amounts of fat, up to 50 grams per (about 2 ounces) 100 grams (4 ounces) of meat. An egg contains 10 grams of fat, but a fried egg contains about 25 grams!
Lipids are composed of three kinds of fatty acids:
– saturated fatty acids
– mono-unsaturated fatty acids
– polyunsaturated fatty acids
The last two types cannot be synthesized by your organism, and are needed to produce substances which compose your cells and tissues.
That’s why you should ingest more unsaturated rather than saturated fats. All types of oil are composed entirely of lipids. However, the difference in quality – and the reason you should use more of some oils and less of others – depends on what kind of fatty acids they contain.
Scientists have found that saturated fatty acids increase cholesterol levels in the blood and raise blood pressure, paving the way for heart disease.
Saturated fatty acids are found in:
– animal fat, including butter, fresh cream, lard
– peanut oil
– low-fat butter
– meat, processed meats and organs
– some seafood
– dairy products like yogurt and cheese
Mono-unsaturated fatty acids are found in:
– olive and colza oil
– oleaginous fruits like peanuts, almonds, olives and avocados
– duck and goose fat
Recent studies have shown that these kinds of fatty acids actually lower overall cholesterol levels. Olive oil not only lowers levels of harmful cholesterol, it raises levels of beneficial cholesterol at the same time!
Beneficial HDL (high density) cholesterol removes fatty deposits from arteries. Harmful LDL (low density) cholesterol is dangerous because it causes fatty deposits to accumulate along arterial walls, increasing the risk of cardiovascular disease.
The discovery that there are two kinds of cholesterol, one harmful and one beneficial, was made by comparing cholesterol levels and the incidence of heart disease in a number of diverse populations.
Inhabitants of the Greek island of Crete, for example, use olive almost exclusively, and have an extremely low incidence of death caused by heart disease. The same was found to be true of people living in a region of France, where large amounts of duck and goose fat are consumed.
The discovery was important because for years doctors had been telling patients with heart or circulation problems to stop eating fat altogether, unaware that certain types of fat are actually beneficial.
The best way to get your daily requirement of lipids is to use unsaturated, uncooked oils for seasoning salads, pasta, pizza, cooked vegetables, etc., and to mix them up (choose between olive, sunflower, colza and soybean oils). It would also be a good idea to use duck or goose fat instead of butter or margarine. Once again, however, there is no point going to extremes: your body needs both saturated and unsaturated fatty acids, in their right proportions.
Polyunsaturated fatty acids are found in:
– sunflower seed, corn and grape seed oil
– margarine made from sunflower seeds or corn, and light margarine
– fish, shellfish, fish oil.
There are two kinds of polyunsaturated fatty acids:
– Those of vegetal origin contain two essential fatty acids (linoleic and alpha-linoleic acid). They are used to regenerate cells, reduce overall cholesterol levels, and are necessary for the production of various hormones. They are also rich in Vitamins
A, D and E, making them extremely beneficial for the human organism.
Linoleic acid is found primarily in sunflower seed, corn, soybean and peanut oil, while alpha-linoleic acid is found in walnut, soybean and colza oil.
– Those of animal origin are primarily found in fish and contain
EPA (eicosapentanoic) and DHA (docosahexanoic) acids.
These fatty acids lower triglyceride levels and make the blood more fluid.
What happens when you ingest too much fat?
In addition to obesity, ingesting too much fat raises cholesterol levels and causes heart disease. Fatty deposits in arteries (atheroma) and thicker blood result in the formation of clots. Excess fat can also increase your risk of developing certain types of cancer. Research conducted by Lea and Ward showed a significant correlation between excess fat and breast cancer, as well as cancer of the colon and rectum. ‘The rate of death due to cancer is significantly higher among persons whose weight is 40% or more above their ideal weight.’ (Results published in the medical journal The Lancet).
What happens when you lack certain lipids?
Mono-unsaturated fatty acids decrease levels of harmful cholesterol and blood sugar, and lower blood pressure. A deficiency will deprive you of these beneficial effects.
A linoleic acid deficiency can also cause:
– growth problems
– cellular anomalies affecting the skin, mucous membranes and endocrine glands
– lesions associated with atheroma, and increased risk of cardiovascular disease.
An alpha-linolenic deficiency can have very serious consequences:
– brain cell alteration
– problems with the retinas of the eyes
– lowered resistance to toxins, notably alcohol.
Elderly persons: a case apart
Epidemiological studies have revealed a significant correlation between high levels of serous cholesterol and the risk of coronary problems. Doctors naturally recommended that persons at risk lower their intake of saturated fats and foods containing cholesterol. Preventing high cholesterol is certainly a good thing, inasmuch as cholesterol is one of the main factors causing heart disease, along with tobacco addiction, stress and a lack of exercise.
However, for this kind of prevention to be effective, three important factors should be taken into account:
– Only a small part of the population (10% to 15%) have trouble metabolizing lipids.
– What may be true for serous cholesterol is not necessarily the case for cholesterol obtained from food.
In fact, the metabolism of cholesterol is remarkable in that fully two thirds is of endogenic origin (I.e. produced inside the body). When examined in this light, there seems to be no correlation between the consumption of animal fat or cholesterol and death from heart disease among different populations.
– There is great variability among individuals in the way serous cholesterol levels respond to dietary changes: in some there is a significant reduction, while in others there is hardly any change at all. This is true for diets that contain very little cholesterol, and slightly less so for diets that partially replace saturated fats with unsaturated fats.
As a general rule, a diet containing little or no cholesterol lowers overall cholesterol levels only by about 10%.
In the case of elderly persons you should also be aware that:
– Cholesterol levels in the blood become less and less of a clear risk factor as you age. Past the age of 60 it is not a risk factor at all. In addition, there is no proof that dietary measures can reduce the risk of coronary problems in elderly persons.
– Aging is accompanied by modifications in the metabolism of essential fatty acids . To prevent deficiencies, diets should be varied, containing not only linoleic acid (sunflower seed, corn and peanut oil) but linolenic acid (Canola and soybean oil, and butter), arachidonic acid (red meat, liver, eggs) and eicosapentanoic acid (fish) as well.
For these reasons we may ask if it is reasonable to recommend that persons over the age of 60 (except those at high risk) restrict themselves to a diet that is low in saturated fats and cholesterol. Eliminating eggs, dairy products and butter also means depriving these people of important nutrients like protein and calcium, as well as linolenic and arachidonic fatty acids.