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Fats

Fat. Feared for its connection with vascular diseases and cancer. Do we have so much to fear from fats, or are fats just a scapegoat? Let's take a closer look at the substance we are being told to avoid in favor of low-fat products.

Which kinds of fats exist?
Fats can be either solid or liquid. If they are usually liquid, they are called oils. We distinguish saturated, mono-unsaturated and poly-unsaturated fats. Generally speaking it does not matter if the consumed fats are saturated or unsaturated, because the body can convert both according to its needs. Only some specific unsaturated ([omega-3]) fatty acids need to be taken in directly. In a well-balanced diet both saturated and unsaturated fats are consumed.

What do we need fat for?
Our body uses fat for several purposes, two of which are energy and storage.
Skeletal muscles account for about 50% of the energy use in a resting person, and up to 90% during high physical activity. In resting and moderately active muscles the basic energy comes from fatty acids and ketone bodies (derived from fatty acids). The internal organs, for example the colon and the heart, need fats to function. Fat is essential to absorb vitamins and minerals (1) Fat also supplies us with energy most effectively - that is why it is the main ingredient and main source of energy in mother's milk. In nature, the availability of fat increases survival chances. We need fats for energy and to stabilize blood-glucose levels (to prevent diabetes). Sugars only supply short-term energy. Fats supply long-term energy, leveling the need for sugars.

Natural fats
There is nothing wrong with natural (raw) fats; they do not cause cancer. (2) Cold pressed olive oil, fats from avocado and Brazil nuts, for example, are clean and healthy natural fats. (3)

Harmful fats
Due to the influence of heat and/or hydrogenation, part of the unsaturated fatty acids is damaged, and transformed into so-called trans-fatty acids (also called trans-fats). Because of this damage, very often unsaturated fats become saturated (trans-fats are classified as saturated, though chemically speaking they are still unsaturated). Therefore 'bad food', like junk food, on average does contain more saturated fatty acids, and the ratio of essential unsaturated fatty acids to saturated fatty acids decreases due to food preparation. (4)
This does not implicate that saturated fatty acids are bad for one's health. Only the damaged fatty acids are bad; the ones in prepared food.
Along the same lines, not all unsaturated fats are good, as many damaged (due to heat) harmful fatty acids are unsaturated.

Examples of foods containing trans-fatty acids are french fries, margarine, meat, pastries and milk. Common diets usually incorporate enough foods containing trans-fatty acids for a regular daily intake. The average intake of trans-fatty acids (in Norway) is 8 to 15 grams a day. (12)

By consuming prepared food, trans-fatty acids are incorporated into fat deposits. Fat deposits in the average American already contain 4.7% trans-fatty acids. (13) In Europe, the Dutch absorb the most; their body fat contains 2.4% trans-fatty acids. (14) A study showed a correlation between margarine consumption and trans-fatty acid contents in adipose tissue. (15)

Because prepared food contains oxidized fats, requiring more vitamin E (16), one needs more vitamin E when eating prepared foods.

Oils can also be, to some extent, damaged by heat, which results in the formation of trans-fats and free radicals. The point where the damage becomes apparent is called "the smoking point". Predominantly unsaturated oils are more vulnerable than saturated ones.
Some oils are hydrogenated, so heated and treated with hydrogen. The optimum temperature for hydrogenation is 140-225°C. Heating non-hydrogenated oils also leads to the formation of trans-fats, though to a significantly lower extent than with hydrogenated oils. (17)

Unfortunately, even raw meat (and raw fish) can contain trans-fatty acids, because very often cattle (and fish) are fed processed foods. And part of these processed foods even contains animal residues, like dead cattle. Imagine: herbivores forced to be cannibals. 'Recycling' animal food like this causes disorder like 'mad cow's disease'.

Consequences
Our bodies cannot cope very well with artificial substances like trans-fatty acids. Consuming trans-fatty acids can cause vascular diseases (18), and increases the risk of breast cancer. (19) Logically, consuming margarine (20) also increases the risk of vascular diseases.

In pregnant women, consuming trans-fatty acids increases pre-eclampsia risk. (21) If the pregnant mother consumes trans-fatty acids, trans-fatty acid level in mother's milk increases. (22) For the child's sake, pregnant women should not consume dairy products, and as little prepared food as possible.

Conclusion
Natural (raw) fats are essential. For example, natural (raw) fats are required to successfully fight obesity, insomnia and depression.
Raw Brazil nuts, avocado, and salmon (that has only consumed its natural food) only contain healthy fatty acids. Similarly, cold-pressed olive oil (from a trustworthy brand) only contains clean and healthy fatty acids.
Like [protein] and [cholesterol], fatty acids can be damaged due to the heating of food. And like damaged protein and cholesterol, damaged (trans-) fatty acids are unhealthy.



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Abstracts of most sources can be found at the US National Library of Medicine

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(2) Gaard, M. et al, Risk of breast cancer in relation to blood lipids: a prospective study of 31209 Norwegian women. Cancer Causes Control 1994 / 5 (6) / 501-509. , Berg, J.P. et al, Long chain serum fatty acids and risk of thyroid cancer: a population-based case-control study in Norway. Cancer Causes Control 1994 / 5 (5) / 433-439.
(3) La Vecchia, C. et al, Olive oil, other dietary fats, and the risk of breast cancer (Italy). Cancer Causes Control 1995 / 6 (6) / 545-550.
(4) Ratnayake, W.M. et al, Trans, n-3, and n-6 fatty acids in Canadian human milk. Lipids 1996 / 1996 / 31 suppl./ S279--282. , Ulberth, F. et al, Quantitation of trans-fatty acids in milk fat using spectroscopic and chromatographic methods. J. Dairy Res. 1994 / 61 (4) / 517-527.
(5) Cuadrado, C. et al, Spanish contribution to the creation of a Euro-analytical database of trans-fatty acids. Nutr. Hosp. 1998 / 13 (1) / 21-27., Pedersen, J.I. et al, Trans-fatty acids and health. (Noors) Tidsskr. Nor. Laegeforen 1998 / 118 (22) / 3474-3480. , Molkentin, J. et al, Determination of trans octa-decanoic acids in German margarines, shortenings, cooking and dietary fats by Ag-TLC / GC. Z. Ernahrungswiss. 1995 / 34 (4) / 314-317. , Pfalzgraf, A. et al, Content of trans-fatty acids in food (Duits). Z. Ernahrungswiss. 1994 / 33 (1) / 24-43.
(6) Tholstrup, T. et al, Effect of modified dairy fat on postprandial and fasting plasma lipids and lipoproteins in health young men. Lipids 1998 / 33 (1) / 11-21. , Kramer, J.K. et al, Evaluating acid and base catalysts in the methylation of milk and rumen fatty acids with special emphasis on conjugated dienes and total trans-fatty acids. Lipids 1997 / 32 (11) / 1219-1228. , Nielsen, J.H. et al, Cholesterol oxidation in butter and dairy spread during storage. J. Dairy Res. 1996 / 63 (1) / 159-167. , Precht, D., Variation of trans fatty acids in milk fats. Z. Ernahrungswissenschaften 1995 / 34 (1) / 27-29.
(7) Zock, P. et al, Dietary trans-fatty acids: a risk factor for coronary disease (in Dutch) Ned. Tijdschrift Geneeskd. 1998 / 142 (30) / 1701-1704.
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(9) Ashes, J.R. et al, Potential to alter the content and composition of milk fat through nutrition. J. Dairy Sci. 1997 / 80 (9) / 2204-2212.
(10) Precht, D., Variation of trans-fatty acids in milk fats. Z. Ernahrungswiss. 1995 / 34 (1) / 27-29.
(11) Pfalzgraf, A. et al, Content of trans-fatty acids in food (Duits). Z. Ernahrungswiss. 1994 / 33 (1) / 24-43.
(12) Almendingen, K. et al, Effects of partially hydrogenated fish oil, partially hydrogenated soybean oil and butter on hemostatic variables in men. Arterioscler. Thromb. Vasc. Biol. 1996 / 16 (3) / 375-380.
(13) Lemaitre, R.N. et al, Assessment of trans-fatty acid intake with a food frequency questionnaire and validation with adipose tissue levels of trans-fatty acids. Am. J. Epidemiol. 1998 / 148 (11) / 1085-1093.
(14) Aro, A. et al, Adipose tissue isomeric trans fatty acids and risk of myocardial infarction in nine countries: the EURAMIC study, Lancet 1995 / 345 / 273-278.
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(16) Liu, J.F. et al, Dietary oxidized frying oil enhances tissue alpha-tocopherol depletion and radioisotope tracer excretion in vitamin-E-deficient rats. J. Nutr. 1996 / 126 (9) / 2227-2235.
(17) Daniel, D.R. et al, Nonhydrogenated cottonseed oil can be used as a deep fat frying medium to reduce trans-fatty acid content in french fries. J Am Diet Assoc. 2005 Dec; 105(12):1927-32.
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Saturated, mono-unsaturated and poly-unsaturated fats

Actually fats and oils together are called lipids.
They generally consist of a glycerol part and 3 fatty acids (RI, RII, RIII in the figure below). The kind of fatty acids determines if the fat is saturated or mono/poly-unsaturated, depending on the absence or occurrence of double bonds.
triglyceride
Fatty acids can have a number attached to their name, which indicates how many carbon atoms and how many double bonds it has. For example the omega-3 fatty acid eicosapentaenoic acid (EPA) has the number 20:5, which means it has 20 carbon atoms and 5 double bonds. This makes it a poly-unsaturated fatty acid (mono-unsaturated only has 1 double bond). Lauric acid, the main fatty acid in coconut oil, is 12:0, containing 12 carbon atoms and 0 double bonds, making it a saturated fatty acid.

Ketone bodies

One of the ways the liver distributes energy to the rest of the body is by the formation of ketone bodies (acetoacetate, beta-hydroxybutyrate, and acetone). These can be formed during the process of breaking down fatty acids. After being transported to where they are needed, they can be converted into energy.

Hydrogenation

(Partial) hydrogenation changes a fat's molecular structure. It raises its melting point and reduces rancidity, consequently increasing product shelf life and decreasing refrigeration requirements.

Examples of foods

Particularly french fries (non-home made), margarine, meat, pastries (5) and milk (6) contain trans-fatty acids. It is quite normal that fat used in bakeries contains an average of 30% trans-fatty acids. (7) An average portion of French fries contains 7 to 8 grams of trans-fatty acids. (8) Milk-trans fatty acids are extraordinarily susceptible to oxidation. (9) Fat in milk averagely contains an average of 3% trans-fatty acids. (10) Prepared meat-fat contains 2 to 10.6%, and hydrogenated products contain up to 34.9% trans-fatty acids. (11)