Why do we need fat?
Fats are a major source of energy, as they provide 9 kilocalories per gram (carbohydrates and proteins provide 4 kilocalories per gram), and represent the main energy stores in our body.
In healthy humans, ~95% of dietary fat is absorbed by the intestine into the blood for incorporation into body tissues where fatty acids can have three main roles:
- They provide energy.
- Monounsaturated fats (MUFA) s and polyunsaturated fats (PUFAs) are incorporated in cell membranes as structural elements and are thus important for body cellgrowth and repair. PUFAs contribute to the flexibility of biological membranes.
- PUFAs are precursors of hormone-like molecules (eicosaenoids) that are essential regulators of physiological functions (inflammation, immunity, neural transmission and regulation of blood flow and ionic transport).
Fats play also an important role in food as they provide desirable structure and taste as well as carrying fat-soluble vitamins and other nutrients.
How much do we need and what are the sources?
All fatty acids are natural constituents of animal and vegetable fats. More than half of the dietary fat is invisible, either natural or industrial. Only the marble in meat, the butter and oils we add ourselves are really visible.
It is recommended to eat at least 15-20% of our daily calories as fat to ensure adequate intake of energy, essential fatty acids and fat-soluble vitamins.
However, the tendency, even in developing countries, is to eat too much fat. The recommendations are to eat no more than 30 to 35% of the calories we take from food.
We should particularly limit the consumption of saturated fats to less than 10% of our daily calories. Most of the saturated fatty acids (SFAs) in our diet come from meat, dairy products and processed food, and often represent our major source of lipids. They are thought to be detrimental to cardiovascular health through an increase in blood cholesterol.
Did you know that 10 g of butter contain 8.3 g of fat, of which around 5g are saturated fat? It represents already a fourth of the recommendation.By comparison 10 g of canola (safflower) oil contain only 0.7 g of saturated fat.
We should try to increase our consumption of PUFAs to replace the SFAs and reduce the risk of cardiovascular diseases. Omega-6 PUFAs are found mainly in vegetable oils, so many people get plenty of them in the diet. On the other hand, omega-3 PUFA intake is generally low. The omega-3 essential fatty acid omega-3 alpha linolenic acid (ALA), is found in almonds, walnuts and some vegetable oils such as soybean or canola oils.
Oily fishes, such as mackerel, herring and salmon, and fish oil are the main dietary source of the omega-3 docosahexaenoic acid (DHA).
Fats and fatty acids in human nutrition, Report of an expert consultation, FAO, Rome, 2010
Essentials of Human Nutrition, J. Mann and A. S. Truswell Editors. Oxford University Press, 2012