Fats are basic source of energy and affect the cell structure in the human organism. A healthy adult should intake 20-35% of his or her total daily energy from fats and oils.


 

Chemical Structure and Classification of Fatty Acids

Fatty acids are the building blocks of fats. Simply defined, fat is a carbon chain with a carboxyl group (-COOH) at one end and a methyl group (-CH3) at the other. Fatty acid with any double bond on the carbon chain is called as saturated fatty acid. Fatty acid containing at least one double bond is called unsaturated fat. Fatty acids are classified as monounsaturated or polyunsaturated according to the number of double bonds they contain and short-chain (3-7 carbons), medium-chain (8-13 carbons) or long-chain (14-20 carbons) according to their chain lengths. For instance, oleic acid, predominantly found in olive oil, is a long-chain, monounsaturated fatty acid. Butyric acid, predominantly found in butter, is a short-chain, saturated fatty acid. Trans fats, on the other hand, can be formed when vegetable oils are processed at temperatures above 260 C°. In the past, trans fats could be formed during the production of margarine when vegetable oils are saturated with hydrogenation. With the transition to interesterification method in margarine production processes, trans fat levels have been reduced to a very low level. Today, even trans-fat free margarine is being produced. Turkey began labeling products with less than 1 gram of trans fat per 100 grams total "trans fat-free" as of August 2007.

Butyric acid – Short-chain, saturated fatty acid – C4:0 The dominant fatty acid in butter, milk and dairy products

Oleic acid – Long-chain, monounsaturated fatty acid – 18:1 n-9 – The dominant fatty acid in olive oil

Linoleic acid – Long-chain, polyunsaturated fatty acid – 18:2 n-6 – The dominant fatty acid in sunflower and corn oil.
 

Dietary Fats

Dietary fats are one of the three macro-nutrients, along with carbohydrates and proteins, found in foods and edible oils. Fat-containing foods include meat, fish, eggs, milk, and dairy products; seeds such as sunflower, soybean, and canola; nuts such as walnuts, hazelnuts, pistachios, and almonds; olives; and grains such as corn. Fats found in meat, eggs, butter, milk, and dairy products are defined as animal fats. Fats such as sunflower oil, corn oil, olive oil, and soy oil are defined as vegetable oils. Margarine is a solid vegetable oil, produced by the industrial saturation of oils such as sunflower, corn oil, and olive oil. It was first produced in 1869 in response to Napoleon III's challenge to create a butter substitute. Today, the fatty acid in most margarines is usually unsaturated, except in the case of classic margarines containing 65-70 % fat. Since margarines are derived from vegetable oils, they do not contain cholesterol, unlike butter. If you consume 100 grams of half-fat meat, you take 20 grams of fat (red meat contain relatively higher fats than white meat); 100 grams of walnuts or hazelnuts means 60 grams of fat; 100 grams of milk or yogurt means 3 grams of fat. If you consume 100 grams of butter, you take 80 grams of fat; 100 grams of olive or sunflower oil means approximately 95 grams of fat. Therefore, the fats we take in our diet consist of fats in the composition of foods, and the edible oils such as butter, sunflower oil, olive oil and margarines. Foods generally contain both saturated and unsaturated fatty acids. The predominant fatty acids in foods also affect the physical properties of it. For example, saturated fats are dominantly present in butter and butter is solid in room temperature whereas unsaturated fats are dominantly present in olive oil and sunflower oil and they are liquid.
 

What are the main types of fats and in which foods are they found?

There are various classifications of fats. Fats can be classified as vegetable fats/oils or animal fats/oils according to the foods they are present or obtained from. For example, fats found in butter or milk are animal oils whereas fats found in corn oil or olive oil are vegetable oils. Fats may also be classified as saturated, unsaturated, mono or polyunsaturated or trans fatty acids relative to fatty acids predominantly present in their composition. For example, olive oil can be defined as a vegetable oil rich in monounsaturated fatty acids, while margarine can be defined as a vegetable oil rich in saturated fatty acids. The structure of the fats found in milk, dairy products and meat is mostly composed of saturated fats. On the other hand, mono or polyunsaturated fatty acids are found in high concentrations in vegetable oils. Oily fish contain long-chain and polyunsaturated omega-3 fatty acids, which play an important role in cognitive functions.
 

Fatty acids found in high concentrations in foods and edible oils

Why we should consume fats?

The fats that we take in our diets play a role in many metabolic processes. Fats are a key part of every cell wall, provide energy and take part in heat insulation of the body. They contain omega-3 and omega-6 fatty acids, which cannot be produced by the body and must be taken in through food. In addition, they are also vital for the absorption of fat-soluble vitamins such as A, D, E, K.
 

How much fat should we eat?

It is recommended for adults to provide 20-30 percent of their total energy intake from fats, and if they are physically very active, this rate can reach up to 35 percent. That means that a moderately active woman, with a daily energy intake of 2,000 kcal, can consume 44-78 grams of fat per day. For men with a daily energy intake of 2,500 kcal, this amount is 55-97 grams of fat per day. In addition to total fat intake, it is also important to know how much of which fatty acid type is consumed. Saturated fat intake is recommended to be provided from saturated fats, and it should not exceed 10 percent of total energy intake. The rest should come from the monounsaturated and polyunsaturated fats. It is recommended that trans fats intake should not be more than 1 percent of total energy intake.
 

Does eating fat make us fat?

Body weight and its control cannot be linked to a single nutritional element. The balance between daily energy intake and expenditure is the main determinant of body weight. If energy intake exceeds energy expenditure, the body develops fatty tissue. While 1 gram of fat provides 9 kcal, 1 gram of protein and carbohydrates give 4 kcal of energy. Therefore, excessive consumption of fat-containing foods and edible oils may lead to an increase in total energy intake and consequently, an increase in the body weight.

As a result, if fats do not exceed 20-35 percent of your total energy intake, 10 percent of your saturated fats intake and 2 percent of trans fats intake, and with a diet in which you take omega-3 fatty acids by consuming fatty fish (300-450 grams) twice a week and consuming liquid vegetable oils as edible oils in your meals; you get both essential fatty acids and benefit from the health benefits of fats. In addition to total fat intake, the range of types and amounts of fatty acid intake should be appropriate for the desired fats quality in diet.

References:
1. EUFIC Review (2014). Facts on Fats - the Basics
2. EUFIC Review (2015). Facts on Fats - Dietary Fats and Health
3. Türk Gıda Kodeksi Etiketleme Yönetmeliği, Resmi Gazete, Thursday, December 29, 2011 Issue: 28157 http://www.resmigazete.gov.tr/eskiler/2011/12/20111229M3-7-1.pdf
4. FAO Food and Nutrition Paper 91 (2008) - Fats and fatty acids in human nutrition