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The Facts About Fats and Heart Health

The Facts About Fats and Heart Health

20 February 2019

For a long time a low fat diet has been proposed as a key to losing weight, managing cholesterol and preventing health problems. However, the types of fat we eat matter more than the amount of fat. In other words: not all fats are bad. In fact, fats are an essential part of a balanced diet. And whilst it is important to minimize the intake of unhealthy fats, it is equally as important to increase the intake of the healthier fats.

Why were we told to eat low fat?

The most discussed health topic when it comes to fats is 'heart health', and in particular, cholesterol. A diet high in saturated fat has been linked with an increased risk of heart disease and heart attacks, which is why the notion of a "low fat diet" became popular many years ago.

Saturated fats are said to increase cholesterol levels. And whilst this is technically correct, it is important to understand that there are two types of cholesterol: low density lipoproteins (LDL, or the 'bad cholesterol') and high density lipoproteins (HDL, or the 'good cholesterol').

LDL cholesterol indeed contributes to the build up of fatty material or plaque on the inside of blood vessels, narrowing of the arteries, and leading to heart disease and stroke.
HDL cholesterol however, carries cholesterol from the blood back to the liver to be broken down, thereby reducing the risk of chronic heart disease. And to increase HDL levels, we need to consume those beneficial fats that are considered to be heart-healthy.


Cutting fats out completely and replacing them with refined carbohydrates guarantees missing out on the benefits of healthy fats.


There are four major types of fats

  • monounsaturated fats, from plant sources
  • polyunsaturated fats (including omega-3 and omega-6), from mostly plant sources as well as fish
  • saturated fats, mostly from animal sources
  • trans-fats, formed during food processing (see table below)

Monounsaturated fats and polyunsaturated fats are beneficial and very important for overall health. Other than their role in HDL synthesis, these fats are required, amongst other things, for cell membrane health and the functioning of the immune and nervous systems. 

What exactly are trans-fats?

Trans-fats are quite possibly the worst of the lot. They are formed during food processing through partial hydrogenation of unsaturated fats. This process was initially created because plant fats were found to be a healthier option, however weren't stable and didn't have a shelf life. So, some clever chemists came up with the idea of adding an additional hydrogen molecule to the equation (aka hydrogenation), thereby stabilizing and solidifying the fat (think margarine), and literally changing the molecular structure of the fat. This new structure however is toxic to the human body, and yet is widely used in processed and packaged food.

How are they toxic?

Trans-fats increase LDL cholesterol and reduce HDL cholesterol which leads to increased risk of cardiovascular diseases.
Trans-fats calcify cells and cause inammation of the arteries, which are known risk factors in heart disease. Vegetable oils such as canola oil are subjected to high temperatures or chemicals and they are deodorised (removing a large proportion of the omega-3 fatty acids by turning them into trans-fatty acids). High levels of omega-3 fatty acids in canola oil become rancid and foul smelling when subjected to high temperatures and oxygen (like the smell of a fast food joint!).

So what are we meant to eat?

The advice from health experts is to eliminate trans-fats from the diet completely, limit intake of saturated fats and include monounsaturated and polyunsaturated fats in order to have a healthy balanced diet.


Types of fat and their sources
Type of Fat Source
Monounsaturated Fats Avocados, oils such as olive (75%), canola (61%) and peanut (48%).
Polyunsaturated Fats

Omega-3 oils:
Fish: Mackerel, tuna, salmon, herring, sea mullet, redfish, flounder, trevally, tailor, rainbow trout, whiting.

Vegetarian: Flaxseed oil (55%), hempseed oil (25%), canola oil (10%), soybean oil (8%), soybeans, walnuts.

Omega-6 oils:
Fish: Swordfish, Salmon, silver perch, mackerel, gemfish, herring, brown trout; also include omega-3 list from above.

Vegetarian: Safflower oil (75%), sunflower oil (71%), corn oil (57%), soybean oil (54%), sesame oil (33%), canola oil (22%), avocado, soybeans, pumpkin seeds, walnuts.

Saturated Fats

Full fat dairy, hard and soft cheeses cream, chicken skin, fat on meats, fatty and fried foods, butter.

Plant sources of saturated fats do not contain cholesterol (coconut oil, palm kernel oil, and palm oil).

Trans Fats

Hydrogenated or partially hydrogenated oils, vegetable fats such as deep fried and baked foods, French fries, donuts, crackers, margarines, shortening, pie crusts, pastries, pizza and biscuits.


About the Author: Dr Shala Rasouli

Shala is a Clinical Naturopath and highly accomplished senior researcher. She has a PhD in Cancer Immunology and completed her postdoctoral fellowship in Portland, USA. She sees patients with cancer, as well as complex general Naturopathy including autoimmune, thyroid and endocrine conditions.

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