As it happens with carbohydrates now, fats used to be the enemy and cause of everything. Although the perspective towards fats has changed quite a bit, there's still some people afraid of fats. In this post, we go through the different types of fats in foods and how should the perfect fat intake be.
Are you ready?
Scroll down and learn with us!
What Are Fats?
Fats are one of the three macronutrients that make up most of our diet. Together with carbohydrates and protein, the macronutrients form ≈99% of our diet (without counting water).
Fats are biomolecules containing an ester fatty acid. In other words, a fatty acid attached to a glycerol (source). However, there are some exceptions to that rule. Molecules such as cholesterol contain an cyclic ring attached to the fatty acid. Thus, we can say that lipids must contain one or more fatty acid, but the structure is what differs between different types of fats.
Properties of Fats
To understand the importance of fats in our organism we first need to look at the properties of this molecule and how they behave inside us. For the sake of our understanding, we'll base these properties on triglycerides, the main form of dietary fats.
Fats contain a non-polar fatty acid (hydrophobic), and polar head (hydrophilic). Since water is a polar molecule, the fatty acid chain will do everything to avoid water interactions. On the other hand, the polar head will attract water. This is the principle of the cell membrane, one of the most important actions of fats in our metabolism (study)
Functions of Fat in Our Organism
Fats are important molecules in our organism. Although we can synthesize most of them, there are some fats called "essential fatty acids", and we'll need to take them through diet.
A correct fat dietary intake will make sure that all these functions are working perfectly, therefore optimizing your metabolism.
Constituents of the cell membrane
The cell membrane, as we have explained above, it's mainly formed by a lipid bilayer. The hydrophobic chain attract each other forming the inner core of the membrane. The polar head, on the other hand, will face the outer and inner environment, interacting with water.
Precursors of Steroid Hormones
Cholesterol, a type of fat, is the precursor of all steroid hormones. If there's not enough cholesterol in our organism, our hormonal environment will be deffective. But if we have too much cholesterol, the risk of cardiovascular disease explodes (study). In fact, for a 1% reduction of cholesterol, there's a 2% reduction in coronary heart diseases (study).
But that doesn't mean cholesterol is bad for us. We need to balance our diet to achieve the correct and healthy levels of cholesterol.
Fats, more in specific triglyerides, make up the main and largest energy storage in our body. When there's glucose available for energy production, triglycerides are stored in adipocytes, also called 'fat cells'.
Obese people with 15-20kg of adipose tissue could meet their energy needs for months just from the triglycerides stored in these fat cells. Glycogen stores, on the other hand, don't make up more than one day of energy needs (source).
When glucose and glycogen are not available, triglycerides are hydrolysed, transported, and oxidized to produce energy. This is the basic principle of fat loss.
Different Types Of Fats In Food
All dietary fats are no the same. Depending on the structure and nature of the fatty acids, we can talk about:
- Monounsaturated fatty acids
- Polyunsaturated fatty acids
- Saturated fatty acids
- Trans fats
These are fats containing one unsaturation on their fatty acid chain (source). Monounsaturated fats are olive oil, peanuts, avocado, nuts, and seeds.
Monounsaturated fats intake reduce the risk of cardiovascular diseases and all-cause mortality by 11% (systematic review). A higher ratio MUFA:SFA can help you reducing risk of cardiovascular disease (study).
Monounsaturated fats also play a role in carbohydrates metabolism. It reduces the requirement of insulin after acute glucose ingestion. It lowers plasma concentrations of glucose and insulin. This means an improvement on the development of diabates and other metabolic diseases (study)
Polyunsaturated fats (PUFAS), different from monounsaturated, present more than one unsaturation on their fatty acid chain (source)
There are three types of PUFAS: ω-3/6/9. The number here refers to the first unsaturation counting from the last carbon on the righ side of the structure (source). Out of these three classes of PUFAS, only the ω-3 and ω-6 are completely 'essential fatty acids', and we need to take them through diet.
These two series of PUFAs produce metabolites related to the inflammatory state. These are eicosanoides, prostaglandins, tromboxans,... While the metabolites derived from ω-6 are pro-inflammatory, the ones derived from ω-3 are less pro-inflammatory or anti-inflammatory.
Western Diets are generally high on ω-6 and low on ω-3. This promotes a chronic inflammatory state, related to higher risk of cardiovascular disease, diabetes, muscle dysfunction, allergies, and weaken inmune response (study).
Higher intakes of ω-3 and a lower ratio ω-6/3 can tremendously improve your health. It lower the risk cardiovascular disease (study), improves cognitive function and working memory (study), modulates the inmune system (study), and promote a better gut microbiome composition and richness (study)
Saturated fats don't contain any unsaturation on their fatty acid chain. All the carbons are "saturated" with four bonds, from there its name.
There's quite a lot of controversial scientific evidence regarding the effects of saturated fats in our health. While we thought they increased risk of cardiovascular disease and hyperlipidemia (study), there's now emerging evidence that saturated fatty acids may not increase CVD (study)
Intake of saturated fats do increase LDL, but the LDL formed is rather large than the small and light particles related to cardiovascular disease (study). Thus, controlled intake of saturated fats shouldn't be a problem for your health.
In all cases, U.S Guidelines recommend to limit the intake of saturated fats to ≤10% the total calorie intake, or ≤20% the total fat intake (study). Foods containing saturated fats are fatty meats, butter, bacon, whole milk, cheese,...
Trans fats are the execption to the rule. They are monounsaturated fats, but with a 'trans' double bond instead of the 'cis' double bond.
To improve the shelf-life and stability of unsaturated fats, they were partially hydrogenated in the industry. This converted most of 'cis' double bonds into single bonds, increasing the melting temperature and shelf-life. But it also converted some 'cis'-bonds into 'trans'-bonds (study)
There's high evidence of the health effects of trans-fats on our organism. It increases the risk of cardiovascular disease, increase LDL, and reduce HDL (study). But that's not all. Trans fats also promote inflammation on our body, another risk factor for heart disease (study).
Foods containing trans fats are baked goods, chips, microwave popcorn, fried food, margarine,...
Recommended Fat Intake
Now we have seen the different types of fats in food. Mono and polyunsaturated fats can contribute and improve our health and inflammation.
On the other hand, saturated fats show controversial evidence. They may not be as bad as we though, but there's not enough evidence yet to confirm anything. But they can help mantaining a good hormonal environment. Last, but not least, trans fats. Simple and clear... avoid them
Following the evidence known to date, you should base your fat intake on mono-/polyunsaturated fats, limit the saturated fats and totally remove trans fats.
Fats are one of the three macronutrients of our diet. In our organism, they play important roles forming the cell membrane, synthesizing and mantaining the hormonal environment, and being the largest long-term energy storage.
In this post we've seen the different types of fats and the benefits and/or adverse effects on our health. Base your fat intake on mono-/polyunsaturated fats, limit the saturated fats and totally remove trans fats.