The role of fats in our diet
Dietary fats are important for optimal functioning of the human body, and they have different responsibilities such as provision of energy (they provide 9 kcal per gram consumed, while protein and carbohydrates provide 4 kcal per 1 g consumed), they function as structural building blocks of the body and they carry fat-soluble vitamins such as vitamin A, D, E, K.
All fat molecules are made of chain fatty acids, which are either held together with single bonds (saturated fats) or double bonds (unsaturated fats). There are three types of fatty acids: short, medium and long chains. Short and medium fatty acids are absorbed directly into the bloodstream and used for energy, but long chain fatty acids are transported to the liver, which raises blood cholesterol level (LDL cholesterol).
The two types of fats
We can distinguish two types of dietary fats: saturated and unsaturated.
Saturated fats are also known as “bad fats” as they accumulate in the liver, and they increase the risk of cardiovascular disease and liver disease. They are primarily found in animal products such as beef, pork, dairy, margarine, cream and butter.
One type of unsaturated fatty acids are trans fats. They are formed through an industrial process that adds hydrogen to vegetable oil which causes the oil to become solid at room temperature. The manufactured form of trans fat known as partially hydrogenated oil, is found in products such as cakes, cookies, microwave popcorn, fried foods or frozen pizza. However, since trans fats represent a public health risk more than other saturated fats (they increase heart disease risk by 21% and death by 28%), from 2021 all manufacturers are required to reduce the amount of them in processed foods to 2 g per 100 g.
On the other hand, unsaturated fats are known as “healthy” fats, as they raise the good cholesterol (HDL), and they break down and discard the bad cholesterol (LDL). Therefore, they reduce the risk of cardiovascular disease, stroke and liver disease.
Unsaturated fats can be monounsaturated and polyunsaturated. Monounsaturated fats are found in avocado, nuts, seeds and oils such as olive oil and rapeseed oil. Polyunsaturated fats include omega-3 and omega-6 fatty acids which are found in soybeans, nuts and oily fish including salmon, mackerel, tuna and trout.
Current recommendations for dietary fat intake
Dietary guidelines from the World Health Organisation (WHO) recommend a total fat intake between 20% to 35% of total calories, of which saturated <10% and trans fats <1%.
One of the main consequences of consuming too many fats and particularly unhealthy fats, is to develop cardiovascular disease. Several studies have examined the potential benefits of incorporating specific foods and oils on cardiometabolic risk factors. For example, the PREDIMED study demonstrated that it’s possible to reduce cardiovascular disease events with either the intake of mixed nuts or extra virgin olive oil in place of butter and coconut oil.
Olive oil is the main fat source of the Mediterranean diet, and it is high in polyphenols, antioxidant and anti-inflammatory factors. Guash-Ferre et al., 2020 at Harvard University, analysed the diet of more than 100.000 people over 24 years and made the conclusion that those with higher intake of olive oil had a 15% lower risk of heart disease. She claimed that olive oil is renewed for being the healthiest of plant oils. Olive oil displays cardioprotective properties, has beneficial effects on the gut microbiota and prevents cancer and type-2 diabetes.
What about coconut oil?
There is increasing popularity for coconut oil, due to perceived health benefits as well as its rich flavour and mild coconut aroma. However, coconut oil is not as healthy as we may think. It is composed of 80-90% of saturated fats and 10% of unsaturated fats. The predominant type of saturated fat is lauric acid which raises LDL cholesterol. Clinical trials have shown that people consuming high amounts of coconut oil had increased HDL cholesterol (the good cholesterol) but also increased LDL cholesterol (the bad cholesterol). In another study, rapeseed oil and olive oil were compared with coconut oil. Results showed that coconut oil raises total cholesterol to a similar degree as other saturated fats like goose fat or palm oil. We should therefore limit coconut oil in our diet and replace saturated fats with unsaturated fats.
Another consequence of eating too many saturated fats is the risk of developing non-alcoholic fatty liver disease (NAFLD). For instance, a diet based on high consumption of dairy products like cheese, butter and cream, increases visceral fat and the risk of NAFLD. Cheese is a great source of protein, but it is also high in saturated fats and salt. We should not consume more than 30 g of cheese a day and try to opt for more lower-fat cheeses such as mozzarella, feta or cottage cheese.
Essential tips to replace saturated fats with unsaturated fats
- Replace coconut oil with olive oil or rapeseed oil
- Grill, bake or steam food rather than frying
- Choose lower-fat or reduced-fat dairy products or swap for alternatives. You can try to make your own cheese by using tofu, nutritional yeast and cashews. This way, you will replace the saturated fats found in the cheese with the unsaturated fats found in the cashews and still keep a high protein content, due to the use of tofu (high in protein) and achieve a very similar taste and texture to the cheese. Example of recipe: https://okonomikitchen.com/best-vegan-cream-cheese/
- Create your own vegan butter with the use of almond milk instead of heavy cream to reduce the saturated fats. Example: https://eatplant-based.com/vegan-butter/
- You can use aquafaba in place of egg whites. Eggs are a very good source of protein, and they are recommended as part of a healthy and balanced diet. However, as they contain a small amount of saturated fats and cholesterol, you can try substituting egg whites with aquafaba which is the liquid from tins of beans and chickpeas, and it is very low in calories and fat.