Fat from a biochemical point of view
Fats, or more specifically lipids, are water-repellent (=hydrophobic) molecules. This means that they are difficult to mix with water. You can observe this if you pour some oil into a glass of water and stir it; The oil quickly settles back on the surface of the water in large drops of fat.
There are different types of lipids; Fatty acids, phospholipids and steroids. The fatty acids are described in the next section.
Phospholipids are the main components of all cell membranes. The membrane of a cell consists of a double layer of phospholipids and thus forms an interface between the cell and its environment. It is therefore obvious that this layer must be intact for the existence of a living cell. Steroids are a group of lipids that include cholesterol and numerous hormones derived from it 2 . The function of cholesterol and steroids will be discussed in a later section.
Different fatty acids – the meaning of saturated and unsaturated
A fat molecule of a fatty acid consists of glycerin and fatty acids. Glycerin is a trihydric alcohol that should not be confused with ethanol in alcoholic beverages. A fatty acid is a long-chain carboxylic acid. This can be imagined as a framework of carbon atoms surrounded by hydrogen atoms and a carboxyl group (hydrogen, oxygen and carbon). The carboxyl group serves as a binding site to glycerin.
Basically, three fatty acid molecules are always connected to a glycerol molecule, creating a triglyceride; the chemical word for this form of fat. Depending on whether there are double bonds of carbon atoms in the structure of the fat molecule or not, these are so-called unsaturated or saturated fatty acids. If a double bond is present, the structure bends; because of these curvatures, the fat molecules cannot stack too closely together at room temperature.
The result is that a liquid oil is created, which belongs to the unsaturated fatty acids. An example of this is olive oil. If there is not a single double bond, it is a saturated fatty acid. This is the case with butter, for example. Without the double bonds, the fat particles can accumulate close together, creating a solid fatty acid 2 . However, there is another form; the polyunsaturated fatty acids, which still have at least two or more of the carbon double bonds. These include omega-6 and omega-3 fatty acids 6 . These will be described later in this article.
Artificially hydrogenated fats and the problem of trans fats
How is it possible that vegetable oils such as sunflower oil can be hardened to make them spreadable if their chemical structure would actually make them liquid? To do this, the actually unsaturated fatty acids have to be converted into saturated ones in a hydrogenation process. The carbon double bonds are reduced.
The best-known example of this is margarine, but peanut butter and inexpensive frying fats are also included. What is worrying is that this procedure produces free trans fats as by-products. These can also be found in low-quality fats such as deep-frying fat 2 .
According to the current state of science, these trans fatty acids contribute massively to atherosclerotic deposits, promote obesity and inflammation in the human organism. These factors, in turn, are directly linked to an increased risk of heart attack and stroke 4 .
How can you avoid harmful fats?
It is understandable that you should avoid this form of fat. Obvious trans fats such as margarine, palm oil, etc., as well as anything fried, should therefore be eliminated from your daily diet. However, the less obvious hydrogenated fats found in industrially processed foods are particularly problematic. You should always take a closer look at the ingredients in products. If the term hydrogenated vegetable fat or palm oil is mentioned, it can be assumed that trans fats are contained.
It should also be taken into account that if more sensitive oils are heated too much, oxidation can occur, which also creates trans fats because the natural chemical structure of the fats is destroyed. The heat resistance of the respective fat should therefore be taken into account.
Which fats are heat-resistant?
First and foremost, the fatty acid composition should be taken into account: Saturated fatty acids are more heat-resistant than unsaturated fatty acids, while polyunsaturated fatty acids are generally very sensitive to temperature. Another point is industrial fat processing; If the respective oil was cold-pressed, it is less thermostable compared to refined oils.
High-quality cold-pressed oils are called native oils. Native means that they should retain their typical taste and color, which means that valuable ingredients remain. The raw materials, such as olives, are placed in an oil press and mechanically processed at low temperatures so that the oil is filtered out at the end.
Refined oils, on the other hand, are pressed using heat and often further chemically processed. This includes, among other things, processing steps such as degumming, neutralization and deodorization. For example, this extends the shelf life and neutralizes odor and color. At the same time, valuable micronutrients are also destroyed 7 . Refined oils and hydrogenated fats are therefore very heat-stable, but are less recommended from a health perspective.
Grass-fed butter , ghee (clarified butter), cocoa butter or virgin coconut fat are well suited for frying and baking at high temperatures, as they belong to the saturated fatty acids and also have health benefits. The former also contains butyric acid, which promotes the microbiome in the intestine, i.e. the intestinal bacteria that help build the intestinal mucosa. It therefore supports intestinal health and helps maintain the barrier that prevents harmful substances from entering the bloodstream. (You can find out what other good properties grass-fed butter contains here read again.)
Cold-pressed olive oil, which contains unsaturated fatty acids, can be heated up to 180⁰C, so it can definitely be used to steam vegetables. However, linseed oil should not be heated at all because it consists of polyunsaturated fatty acids, which are sensitive to heat and oxidize immediately.
Omega-3 and Omega-6 fatty acids
As already mentioned above, these are polyunsaturated fatty acids, which are therefore heat-sensitive and should therefore not be processed under the influence of heat. Omega-3 and Omega-6 fatty acids are essential, so they must be supplied with food. They consist of a chain of at least 18 carbon atoms. The first double bond is located on the 3rd or 6th atom of the framework, from which their names were derived 14 .
Omega-3 can be found in tuna, salmon, sardines, linseed oil, hemp oil, chia seeds and walnuts, among other things. Omega-6 are found primarily in virgin olive oil, sunflower oil, safflower oil, grape seed oil and avocado.
Both fatty acids are of great health importance, but their ratio must be taken into account in the daily intake. An optimal ratio would be 5:1, so it is beneficial to consume five times as much omega-6 as omega-3 fatty acids.
The problem with today's diet is that this is not taken into account. The current ratio was 10:1 in the USA and 8:1 in Germany. This is probably due to the fact that the majority of the population eats a poor diet and consumes a lot of processed foods. These are mainly enriched with cheap vegetable fats consisting of omega-6 fatty acids. This imbalance is a risk factor for vasoconstriction, increased platelet aggregation and cardiac arrhythmias.
It is therefore advisable to consciously pay attention to a balanced ratio and avoid industrially processed foods 15 .
The reason for this is the inflammatory effect of omega-6 fatty acids. Omega-3 fatty acids, on the other hand, inhibit inflammation. Omega-3 fatty acids also have a positive effect on mood and memory performance. Fish oil has already been used successfully for dementia and AHDS 8 .
The digestive route
The digestion of nutrients begins in the mouth, where our teeth break down the food and enzymes become active, which partially break down more complex carbohydrates. Fats, on the other hand, first pass through the mouth, esophagus and stomach without being broken down into tiny particles.
The low pH value in the stomach and its digestive enzymes such as pepsin leave the fatty acids untouched. Nevertheless, gastric peristalsis – the contraction of the ring muscles in the stomach – already emulsifies 15% of the fats. However, proteins and carbohydrates are largely broken down up to this station 1 . Between the stomach and the small intestine is the pylorus, a sphincter that regulates the passage of food from the stomach into the intestines. The food pulp is released in small quantities into the small intestine 3 .
The fats that are now in the small intestine are emulsified by bile acids, which are produced by the liver. Emulsification means that the fats, which are actually water-insoluble, are distributed into smaller droplets. This process increases their surface area so that they can be optimally attacked by the lipases.
These are enzymes that break down free fatty acids - ultimately breaking them up so that they can then be absorbed by the intestinal mucosa and released into the blood. This produces the various lipids mentioned above: triglycerides from vegetable oils, cholesterol from eggs, meat, etc. and fatty acids 1 . They are then transported to the respective target organ or tissue via the blood.
Gut Health & Fat
The intestinal mucosa consists of a lipid layer that is nourished by probiotic intestinal bacteria. On the one hand, these microorganisms must receive enough fiber to stay alive. On the other hand, enough good fats are absolutely necessary in the diet so that the raw materials for the intestinal cell wall are available 8 .
Fat-soluble vitamins & health risks with a fat-free diet
Vitamins A, D, E and K can only be absorbed with the help of fats in food. When the fats emulsify, they bind to the small fat globules and can thus be absorbed into the bloodstream and transported to the liver, for example.
For example, if carrots, which contain vitamin A, are consumed completely without fat, the vitamin cannot be absorbed and is excreted again 5 . If dietary fats are avoided on a low-fat diet, as was recommended until recently based on the misconception that they are linked to increased body fat, a vitamin deficiency is provoked.
Why you should cut out carbohydrates instead of fats on a radical diet:
In principle, radical diets should be viewed critically anyway. A diet that becomes routine and consists of as natural, unprocessed foods as possible that have no potential for intolerance, such as cow's milk, grains, etc., is much more sustainable than a short-term extreme diet.
However, if you want to avoid a macronutrient for a while, then the choice should be carbohydrates. They are not essential and can be produced by the human organism from fats or amino acids if too little of them is consumed in the diet.
Accordingly, on a low-carb diet, stored fats are transported from the cells to the liver and converted there into sugars. However, various fatty acids are essential, meaning they cannot be produced from other substances present in the body 1 . There is also the factor mentioned in the last section with vitamins that can only be absorbed with fat.
Steroids and cholesterol
The term steroid is quickly associated with doping and the bodybuilding scene. In fact, this is a chemical group of substances that belongs to the lipids and is of great importance for the human organism. Steroids are made of a carbon skeleton, but in the form of four rings. Functional groups of substances are attached to the rings, which specify their expression.
Cholesterol is a steroid that is found in the cell walls among the phospholipids described in the first section. Due to its structure, it ensures the mobility of the cell membrane and prevents it from solidifying when low temperatures occur. This would clarify an important function of this substance.
It plays another role in hormone metabolism: cholesterol serves as a starting substance for various hormones such as estrogen, testosterone, cortisol, calciferol (vitamin D) or progesterone. For this reason, this group is also known as steroid hormones. Cholesterol is the basis in hormone production. This is another reason why a completely fat-free diet - especially for sporting goals such as muscle building - does not make sense, because testosterone, for example, plays a central role here 2 .
Foods containing cholesterol that also have health benefits include butter, ghee, eggs, and calf liver ( 10 ) .
HDL and LDL cholesterol
Cholesterol gets a bad rap because it can actually promote clogging of blood vessels. However, a distinction must be made here and an understanding of the function in the vessels must first be gained: On the one hand, LDL cholesterol, the short form for low density lipoprotein, circulates in the human organism.
Strictly speaking, it only consists of 50% cholesterol lipids, the remaining components are proteins and phospholipids. Its job is to transport cholesterol stored in the liver to tissues 11 . Its counterpart, HDL cholesterol (high density protein), brings the cholesterol from the tissue back to the liver. The proteins essentially serve as a train that takes cholesterol from A to B. Depending on whether the proteins have a high or low density, the lipid is transported to or into the tissue 12 .
It is therefore obvious that the two must be in balance with each other. On the one hand, the tissue must be supplied with cholesterol, but on the other hand, an excess leads to fat deposits in the tissue, which ultimately counts as a risk factor for the development of arteriosclerosis 13 . A severely elevated LDL and a too low HDL value can be viewed as worrying, but a slightly elevated HDL value cannot.
Not long ago, doctors warned against eating saturated fatty acids and eggs containing cholesterol, under the mistaken belief that this would increase cholesterol levels so much that blood vessels would calcify. However, current evidence clearly shows that this is not the case 2 .
Why milk fat is not an optimal nutrient for the human organism
Cow's milk is a potential allergen, and not only the lactose it contains is important, but also other substances, including milk fat. In principle, a large part of it would not be absorbed by the human intestine because the elements cannot be broken down into small spheres with a larger attack surface.
However, commercially available milk is homogenized; in this process, the fat molecules are already broken down so that their surface allows absorption in the intestine. This is touted as an advantage by producers, but it is actually a disadvantage: especially in conventional milk from factory farming, increased levels of pollutants can be found, especially in the milk fat content. Toxins, drugs such as antibiotics and hormones accumulate in the lipid molecules.
These would be excreted again if milk was not homogenized, but through this industrial process they are reabsorbed with the small fat globules by the intestine, whereby they enter the bloodstream and ultimately into the tissue. There they promote inflammatory processes and additional storage of fat in the cells 9 .
Fat and energy density vs. how it is metabolized / fat as an energy supplier
No major attention has been paid to the high calorie content of dietary fats in this article, as all the relationships described above are considered to be more relevant. In fact, one gram of fat contains 9.3 calories, proteins and carbohydrates only contain 4.1 calories per gram. This means that the energy density of dietary fat is more than twice as high as the other two macronutrients 2 .
However, on the one hand, it should be borne in mind that the amount of foods consumed with a high fat content is generally smaller, as they are also more filling. On the other hand, the timing, the combination, the bioavailability of the respective fat and the associated biochemical processes in the body must be taken into account. (Especially a balanced breakfast should consist of at least one good source of fat - here go to the post.)
As described in detail, not every calorie is metabolized in the same way; our organism functions in a much more complex way. Nevertheless, it should be noted that obesity and health problems can of course also occur if too many energy-rich foods are consumed - be it fats, proteins or carbohydrates. As Paracelsus said in the 15th century: “The dose makes the poison.”
Literature & Sources:
1 Bütikofer, Markus; Hopf, Zensi; Rutz, Guido; Stach, Silke and Grigoleit, Andrea (2015): Human Biology 1: Basics, Metabolism and Defense Systems. Zurich: Compendio Educational Media. pp. 43-66.
2 Campbell, Neil A. and Reece, Jane B. (2015): Biology. Munich: Pearson. 8th updated edition. pp. 103-107.
3 Doccheck Flexikon: Pylorus.[ https://flexikon.doccheck.com/de/Pylorus?utm_source=www.doccheck.flexikon&utm_medium=web&utm_campaign=DC%2BSearch ; 03/29/19]
4 Holzapfel, Christina (2015): Extremely bad testimony for trans fats. In: Urban & Vogel (eds.): Advances in medicine. Heidelberg: Springer-Verlag GmbH.
5 Doccheck Flexikon: Phylloquinone. [https://flexikon.doccheck.com/de/Vitamin_K; 04/03/19]
6 Horlemann, Gisela (2017): Fats and oils. Munich: Bavarian State Ministry for the Environment and Consumer Protection.
7 Kießling, Tina (2016): Native, refined, cold pressed - what now? [https://www.deutschlandfunknova.de/teil/oele-raffiniert-kalt-PRESSED-nativ-was-heisst-das; 04/05/19]
8 Axt-Gadermann, Dr. Prof. Michaela (2015): Slim with your intestines – achieve your desired weight with the right intestinal flora. Munich: Südwest Verlag.
9 Warrior, Dr. Elena (2015): The milk lie: The milk does it - unfortunately not. Munich: CBX Verlag.
10 SGE (2015): Swiss nutritional table. Bern: Swiss Society for Nutrition SGE. pp. 60-83.
11 Doccheck Flexikon: LDL cholesterol. [https://flexikon.doccheck.com/de/LDL cholesterol;10.04.19]
12 Doccheck Flexikon: HDL cholesterol. [https://flexikon.doccheck.com/de/HDL cholesterol; 04/10/19]
13 Paolo Zanoni et al. (2016): Rare variant in scavenger receptor BI increases HDL cholesterol and increases risk of coronary heart disease. Science 11 Mar 2016: Vol. 351, Issue 6278, pp. 1166-1171 DOI: 10.1126/science.aad3517
14 Alimenta (2008): A closer look at omega-3 fatty acids.
15 Singer, Priv.-Doz. Dr. med. Peter (2010): Practical aspects of omega-3 fatty acid intake. Stuttgart: Hippokrates Verlag in MVS Medizinverlage.
