What are dietary fats?
Dietary fat is a macronutrient, the other two being carbohydrate and protein, and it is the main energy source for our bodies. The fat we consume through foods is used to cover our body’s needs and whatever is left is then stored in specialised cells, called adipose cells, that form our body fat.
There are different types of fats, and these are found in different percentages in the foods with fat content. The two main fats are saturated and unsaturated fats, the former found mainly in foods from animal sources and the latter in some fish and products of plant origin. In general, saturated fats have been associated with adverse health effects and are often called harmful fats, while unsaturated fats are considered good healthy fats. Many government guidelines recommend cutting down on all fats and favouring unsaturated over saturated.
Leaving aside the debate of fat consumption and health, here I will focus on the impact of fats on the gut microbiota and what our gut microbes do with the fat we eat.
Foods high in saturated fats come mainly from animal sources and some from plants. Examples are:
- Meat (fatty cuts as oppose to lean cuts)
- Full fat dairy products (cheese, butter, milk…)
- Coconut oil
- Palm oil
Saturated fats are solid at room temperature.
Types of unsaturated fats are monounsaturated fatty acids and polyunsaturated fatty acids.
Monounsaturated fatty acids are found in some vegetable oils, like olive oil, and other foods like avocados, almonds or peanuts.
As for polyunsaturated fatty acids, aka PUFAs, there are two main types: omega-3 and omega-6. Omega-3 rich foods are mainly some types of fish and omega-6 is primarily found in many vegetable oils.
Unsaturated fats are liquid at room temperature.
Dietary fats and the gut microbiota
The first thing to take into account is that little is known about the relationship between dietary fat intake and gut microbiota. Current research has a few pieces of the puzzle and several studies seem to converge in some of their conclusions but many others seem to point in different directions.
The second thing to consider is that most of the fat we eat is absorbed in the small intestine. A small percentage, however, reaches the colon and it seems to have an effect in the microbial composition. Likewise, the microbiota living in the colon may use the fat to make other products.
The most studied type of fat in relation to the gut microbiota seems to be polyunsaturated fatty acids (PUFAs), omega-3 and omega-6. For more info on these two, check out the entries on “fish” (for their omega-3 content) and “vegetable oils” (for their omega-6 content).