Written by Ruairi Robertson, PhD,  Medically reviewed by Amy Richter, RD
Updated on October 22, 2020

Omega-3, omega-6, and omega-9 fatty acids are all important dietary fats.

They all have health benefits, but it’s important to get the right balance between them. An imbalance in your diet may contribute to a number of chronic diseases.

Here’s a guide to omega-3, -6 and -9 fatty acids, including:

  • what they are
  • why you need them
  • where you can get them

What are omega-3 fatty acids?

Omega-3 fatty acids are polyunsaturated fats, a type of fat your body can’t make.

The term “polyunsaturated” refers to their chemical structure, as “poly” means many and “unsaturated” refers to double bonds. Together they mean that omega-3 fatty acids have many double bonds.

“Omega-3” refers to the position of the final double bond in the chemical structure, which is three carbon atoms from the “omega,” or tail end of the molecular chain.

Since the human body can’t produce omega-3s, these fats are referred to as “essential fats,” meaning that you have to get them from your diet.

The American Heart Association (AHA) recommends eating at least two portions of fish per week, particularly oily fish, which is rich in omega-3 fatty acids (1).

There are many types of omega-3 fats, which differ based on their chemical shape and size. Here are the three most common:

- Eicosapentaenoic acid (EPA): This 20-carbon fatty acid’s main function is to produce chemicals called eicosanoids, which help reduce inflammation. EPA may also help reduce symptoms of depression.

- Docosahexaenoic acid (DHA): A 22-carbon fatty acid, DHA makes up about 8% of brain weight and contributes to brain development and function.

Alpha-linolenic acid (ALA): This 18-carbon fatty acid can be converted into EPA and DHA, although the process is not very efficient. ALA appears to benefit the heart, immune system, and nervous system.

Omega-3 fats are a crucial part of human cell membranes. They also have other important functions, including:

- Improving heart health. Omega-3 fatty acids may help manage cholesterol, triglyceride, and blood pressure levels.

- Supporting mental health. Omega-3 supplements may help manage or prevent depression, Parkinson’s disease, and psychosis in those at risk. However, more research is needed.

- Reducing weight and waist size. Omega-3 fats may help people manage their weight and waist circumference but more studies are needed.

- Decreasing liver fat. Initial research suggests that consuming omega-3s may help decrease the amount of fat in your liver.

- Supporting infant brain development. Omega-3s support brain development in a fetus.

- Fighting inflammation. Omega-3 fats may help manage inflammation that occurs with some chronic diseases.

- A low intake of omega-3 fatty acids compared with omega-6s may contribute to inflammation and chronic diseases, such as rheumatoid arthritis, diabetes, atherosclerosis, and heart failure.