What are healthy fats?
Fats have always been a bit of a mysterious substance. Most people have heard of saturated and unsaturated fat, and know that one is ‘good’ and one is ‘bad’. But it can be a bit tricky to remember which is which and what it means for your health.
In reality, fat is an essential macronutrient. It provides energy, supports cell structure, helps to insulate the body and enables the absorption of certain vitamins.¹ The key is not to avoid fat altogether, but to understand the different types and how they can affect your wellbeing.
What is the difference between saturated and unsaturated fats?
All fats are made up of fatty acids, but their chemical structure differs. This structural difference affects how they behave in the body.
Saturated fats have no double bonds in their chemical structure and are typically solid at room temperature.¹ Common examples include butter, fatty cuts of meat and certain processed foods. Some tropical oils, such as coconut oil, are also high in saturated fat.²
Unsaturated fats contain one or more double bonds and are usually liquid at room temperature.¹ They are commonly found in plant-based foods such as olive oil, rapeseed oil, nuts and seeds. However, unsaturated fats are not exclusively plant-based. Oily fish such as salmon and mackerel contain important unsaturated fats, particularly omega-3 fatty acids.⁵
Most foods contain a mixture of fats rather than just one type. For example, olive oil is predominantly monounsaturated but still contains small amounts of saturated fat.³
Which is healthier: saturated or unsaturated fats?
Current nutritional guidance generally recommends replacing saturated fats with unsaturated fats where possible.²
Saturated fat has been shown to increase levels of low-density lipoprotein (LDL) cholesterol in the blood.² LDL cholesterol is often referred to as ‘bad’ cholesterol because elevated levels are associated with a greater risk of cardiovascular disease.³
Unsaturated fats – particularly polyunsaturated fats – can help to reduce LDL cholesterol when they replace saturated fat in the diet.² This substitution effect is key: the health benefit comes from replacing saturated fats rather than simply adding unsaturated fats on top of them.³
Omega-3 fatty acids, a type of polyunsaturated fat found in oily fish, are associated with supporting normal heart function.⁵
This doesn’t mean you should completely eliminate saturated fat from your food. Small amounts can form part of a balanced diet.¹ However, consistently high intakes – particularly from processed and fried foods – may increase long-term cardiovascular risk, so there are clear benefits to switching to unsaturated fats where you can.²
Is poly- or monounsaturated fat better?
Both monounsaturated and polyunsaturated fats are considered heart-healthy when consumed in appropriate amounts as part of a balanced diet.³
Monounsaturated fats, found in foods such as olive oil, avocados and certain nuts, have one double bond in their chemical structure. They are associated with improved cholesterol profiles when used instead of saturated fats, helping to support healthy heart function.³
Polyunsaturated fats, which include omega-3 and omega-6 fatty acids, have more than one double bond. Omega-3 fats, in particular, have been widely studied for their cardiovascular benefits and also play an important role in brain function and reducing inflammation.⁵
Because of these differences, neither type is inherently ‘better’ than the other. Both types play valuable and complementary roles in a healthy, balanced diet. Experts recommend including a variety of unsaturated fats from different sources wherever possible to maximise these benefits.¹
The role of fat in overall health
Beyond heart health, fats are essential for many bodily functions. They provide a concentrated source of energy and are necessary for the absorption of vitamin D, which contributes to the maintenance of normal bones and immune function.⁴
Ultimately, healthy eating is not about avoiding fat entirely, but about choosing the right types in balanced amounts. Replacing saturated fats with unsaturated fats, alongside an overall varied diet and healthy lifestyle, can support long-term wellbeing.¹,²,³
References
- National Health Service. (2023). Fat: the facts.
https://www.nhs.uk/live-well/eat-well/food-types/different-fats-nutrition/ - MedlinePlus. (2023). Dietary fats. https://medlineplus.gov/dietaryfats.html
- Harvard T.H. Chan School of Public Health. (n.d.). Fats and cholesterol.
https://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/fats-and-cholesterol/ - National Institutes of Health, Office of Dietary Supplements. (2023). Vitamin D – Fact sheet for health professionals.
https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/ - National Institutes of Health, Office of Dietary Supplements. (2023). Omega-3 fatty acids – Fact sheet for health professionals.
https://ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional/
