In recent years there has been great talk about the value of fatty acids in the diet and their impact in overall health. But what is the truth about fat, how is it categorized and how can we distinguish "good" from "bad" fat?
Fat is one of the main macronutrients. One gram of fat has 9kcal, making it the most dense energy ingredient in our diet.
Categories of fatty acids
Fatty acids are categorized according to their chemical structure. The main categories of fat are unsaturated and saturated fatty acids. Normally, they all occur in nature and in a variety of foods, while each type of fat plays a different and important biological role.
Unsaturated fatty acids
Unsaturated fatty acids consists of mono-unsaturated and poly-unsaturated fatty acids. Some poly-unsaturated fatty acids are considered essential in the diet, as the human body is unable to compose them. The main ones are:
- ω3 fatty acids (linolenic - ALA, eicosapentaenoic - EPA, doxaenoic - DHA)
- ω6 fatty acids (linoleic - LA, arachidonic acid - ARA)
- ω9 fatty acids (oleic acid)
Natural sources of mono-unsaturated fats are olives and olive oil, nuts, avocados and certain vegetable oils such as rapeseed oil and peanut oil. Respectively, natural sources of ω3 and ω6 fatty acids are fatty fish (salmon, mackerel, herring, sardine), cod liver oil, seeds, nuts (almonds, walnuts, sesame seeds, sunflower seeds) and vegetable oils such as flaxseed, soybean oil and sunflower oil.
The biological roles of unsaturated fatty acids in the diet are:
- Reduction of cholesterol levels
- Reduction of serum triglycerides
- Prevention of cardiovascular disease
- Improvement of brain function
- Improved blood coagulation
- Anti-inflammatory action
Saturated and trans fatty acids
Saturated fats are mainly of animal origin, such as butter, meat, pastries (biscuits and cakes), dairy products, cream as well as herbal foods such as margarine and coconut oil. Correspondingly, trans fats are found in standard-packaged foods which have typically undergone some heat treatment or hydrogenation (industrial processing) such as potato chips, biscuits, junk food, french fries, margarine, etc.
Saturated fats are essential for the cellular health because it is the main structure of cell membranes. Despite that, overconsumption of saturated and mainly trans fatty acids leads to:
- Increase of blood cholesterol (total and bad cholesterol - LDL)
- Increase of triglycerides
- Weight gain
- Cardiovascular disease
- Increased mortality rates
Modern western diet is characterized by increased consumption of saturated fatty acids and this is why has been linked to obesity and cardiovascular problems.
The need of balanced healthy diet!
Since all kinds of fatty acids are essential to the body's health, what is necessary is to keep the correct fat ratio. According to global health organizations, dietary fat intake should range from 25-35% of total energy intake, while saturated and trans fats should be limited up to 10% of them.
Practically this means that standardized and processed products in our diet should be limited, red meat should be taken 1-2 times a week, and consumption of fish (small and large), seeds and vegetable oils should be increased.