Fats in Nutrition
Fats are an essential component of the diet, performing numerous functions in the body:
- Energy source – Fats provide a long-lasting energy reserve, supplying 9 kcal per gram, making them the most energy-dense macronutrient (European Food Information Council (EUFIC)).
- Hormone synthesis – They are involved in the production of hormones, including steroid hormones like testosterone and estrogen, which regulate metabolism and reproduction (National Institute of General Medical Sciences (NIGMS)).
- Vitamin absorption – Essential for absorbing fat-soluble vitamins (A, D, E, and K), which play critical roles in immune function, bone health, and cellular repair (National Institute of General Medical Sciences (NIGMS)).
- Cellular function – They are a major component of cell membranes, helping maintain fluidity and supporting key metabolic processes in the body (European Food Information Council (EUFIC)).
Different types of fats are found in food, differing in structure, properties, and their impact on metabolism. They can be broadly classified into four main groups.
Depending on their composition, fats can be classified into:
In this article, we will examine the different types of fats, their food sources, and how to incorporate them into a healthy diet.
Types of Fats and Their Characteristics
Strictly speaking, every oil contains several types of fatty acids in different proportions. However, oils are classified into a particular group based on the predominant type of fatty acids they contain, as most foods contain a mix of different fats, with some being richer in saturated fats and others in unsaturated fats (Mayo Clinic). Let’s examine each of these types in more detail.
1. Saturated Fats
What Are Saturated Fats?
Saturated fats are fatty acids in which there are no double bonds between carbon atoms. They have a solid consistency at room temperature and are resistant to oxidation (Mayo Clinic).
Where Are They Found?
- Animal-based products: fatty meat, lard, butter, cheese, cream. Animal-based fat consists almost entirely of saturated fats, although dairy fats (butter, cheese, cream), despite belonging to the saturated fats group, contain a significant amount of unsaturated fatty acids, making them similar to plant oils.
- Plant oils: coconut oil, palm oil, cocoa butter.
How They Are Used
- Saturated fats are resistant to high temperatures, making them suitable for frying.
- It is recommended to limit their consumption in favor of unsaturated fats, but they should not be completely excluded from the diet.
How Much Saturated Fat Should You Consume?
The World Health Organization (WHO) and the American Heart Association (AHA) recommend limiting saturated fat intake rather than eliminating it entirely. According to the WHO, saturated fats should make up less than 10% of total daily energy intake, with a preference for replacing them with unsaturated fats to reduce the risk of cardiovascular disease. Similarly, the AHA advises keeping saturated fats below 6% of total calories, as excessive consumption can raise LDL (“bad”) cholesterol levels and contribute to heart disease.
To maintain a balanced diet, experts suggest choosing healthy fat sources, such as olive oil, nuts, and fatty fish, while limiting foods high in saturated fats like butter, fatty meats, and full-fat dairy. Instead of complete avoidance, a well-structured diet should focus on moderation and substitution, prioritizing monounsaturated and polyunsaturated fats for better heart health.
Storage Guidelines for Saturated Fats
Saturated fats are resistant to oxidation and have a long shelf life. However, their quality can deteriorate under improper storage conditions.
Basic Storage Guidelines:
- Storage temperature: saturated fats, such as butter and lard, are best stored in the refrigerator, especially in warm weather. Coconut and palm oils can be stored at room temperature.
- Container: use airtight containers to prevent contact with air and avoid rancidity.
- Light and humidity: fats are sensitive to light exposure, so they are best kept in dark glass jars or opaque packaging.
- Shelf life: animal-based fats and butter can be stored in the freezer for several months without losing quality, while plant-based saturated oils typically remain fresh for up to a year.
2. Monounsaturated Fats
What Are Monounsaturated Fats?
Monounsaturated fats contain one double bond in the molecule, making them more flexible than saturated fats. They have high nutritional value and are an important part of a balanced diet, according to experts (Medical News Today).
Where Are They Found?
- Oils: olive oil, avocado oil, hazelnut oil.
- Foods: avocado, nuts (hazelnuts, almonds), olives.
How They Are Used
- Suitable for both cold dishes and moderate heat cooking.
- Olive oil and other cold-pressed oils retain the most benefits when used cold (in salads, cold appetizers, and sauces).
Storage Guidelines for Monounsaturated Fats
Monounsaturated fats have good resistance to oxidation, but prolonged storage can reduce some of their beneficial properties. To preserve their quality:
- Store in dark bottles – especially relevant for olive and nut oils.
- Avoid high temperatures – store oils in a cool place, but refrigeration is not necessary.
- Keep the lid tightly closed – exposure to air accelerates oxidation.
3. Polyunsaturated Fats
What Are Polyunsaturated Fats?
Polyunsaturated fats contain two or more double bonds between carbon atoms, making them liquid at room temperature (Linus Pauling Institute, Oregon State University).
Important: Only Omega-6 and Omega-3 fatty acids are essential (i.e., they cannot be synthesized in the body and must be obtained from food). Omega-9 can be synthesized by the body but is also obtained from food sources.
Key Types of Polyunsaturated Fatty Acids (PUFAs):
- Omega-3 (alpha-linolenic acid, ALA) – essential for brain function, heart health, and inflammation regulation.
- Omega-6 (linoleic acid, LA) – needed for cell function and metabolism.
- Omega-9 (oleic acid, OA) – classified as a monounsaturated fat but often considered in this category due to its similar properties. The body can synthesize Omega-9 on its own.
Omega-3 and Omega-6 Balance
The optimal linoleic acid (Omega-6) to linolenic acid (Omega-3) ratio is between 2:1 and 4:1. However, modern diets often contain an excess of Omega-6, sometimes exceeding 10:1, which may contribute to inflammation and cardiovascular risks (Harvard T.H. Chan School of Public Health, National Institutes of Health).
Omega-3 fatty acids are essential for brain function, heart health, and inflammation regulation, helping to counterbalance excess Omega-6 intake.
Sources of Polyunsaturated Fats
Omega-3 (ALA, DHA, EPA)
- Flaxseed oil
- Chia seeds, walnuts
- Fish oil, fatty fish (salmon, mackerel, sardines)
- Krill oil
Omega-6 (LA, GLA, AA)
- Sunflower, corn, soybean, safflower oil
- Nuts (walnuts, almonds, peanuts)
- Seeds (sesame, sunflower)
Omega-9 (OA)
- Olive oil
- Avocado
- Almonds, hazelnuts, peanuts
Storage and Usage Tips for Polyunsaturated Fats
Polyunsaturated fats are highly biologically active but easily oxidized by exposure to oxygen, light, and high temperatures. Oxidation leads to the formation of free radicals, which can negatively affect oil quality and its properties.
According to a study published in the Journal of Biological Chemistry, unsaturated organic molecules with weak C-H bonds are particularly prone to autoxidation, a process that proceeds by a free radical chain mechanism. This autoxidation of polyunsaturated fatty acid esters and sterols, known as lipid peroxidation, has attracted increased research attention due to the unique role that lipid-derived peroxides play in biology.
To prevent this:
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- Store oils in dark bottles and in a cool place.
- Avoid prolonged heating of oils, as it accelerates oxidation processes.
- Prefer fresh, unrefined cold-pressed oils.
4. Trans Fats
What Are Trans Fats?
Trans fats are artificially modified fatty acids obtained through the hydrogenation of vegetable oils. They have a long shelf life, but their effects on health are controversial and widely considered harmful.
According to the World Health Organization (WHO), high intake of trans fats increases the risk of coronary heart disease and mortality. The American Heart Association (AHA) also warns that trans fats raise LDL (“bad”) cholesterol while lowering HDL (“good”) cholesterol, contributing to heart disease and stroke.
Where Are They Found?
- Margarine, cooking fats.
- Baked goods, fast food, processed foods.
How They Are Used
- Trans fats are widely used in industrial baking due to their resistance to spoilage.
- Their consumption should be minimized whenever possible. The World Health Organization (WHO) recommends reducing trans fat intake to less than 1% of daily calories.
Conclusion
Fats are an essential part of the diet and play a crucial role in human health. However, it is important to balance the types and sources of fats:
- Prioritize unsaturated fats, especially those rich in Omega-3.
- Limit saturated fats, but do not eliminate them entirely.
- Trans fats should be minimized.
Key fat sources for a healthy diet:
- Healthy oils (olive, flaxseed, avocado).
- Whole foods (nuts, seeds, avocados).
- Fatty fish for Omega-3.
By following these principles, you can maintain a healthy fat balance and provide the body with essential nutrients.