Vibrant Lives Podcast - Dietary Fat Overview

In this, the first episode of my 4 part series about dietary fats, I will describe to you what fat is, the different types of dietary fats, a brief overview of fat digestion, and why our bodies need fat. When you've listened to this episode you'll know the difference between saturated fat, monounsaturated fat, and polyunsaturated fat. Tune in and join me to sort out fa(c)t from fiction.

Transcript

Hello and welcome to Vibrant Lives podcast five minute food facts series where I bring you short podcast episodes about nutrition related topics.

I'm Amanda Hayes,

Your host,

A lawyer turned nutritionist with a passion for learning about how to live a vibrant life through practicing mindfulness and meditation,

Eating a nourishing and healthy diet and moving my body and sharing what I learn with you here on this podcast.

Please note that any information or advice provided in Vibrant Lives podcast is not intended to be used to treat,

Cure or prevent injuries,

Disease or medical conditions and is not a substitute for advice from your own health professionals.

This will be the first of a four part series about dietary fat.

The four topics will be a dietary fat overview,

What it is and that's today's episode and then I'll follow up with a look at unsaturated fats including essential fatty acids like omega-3s.

The third episode will be all about saturated fats and I'll delve into why it is that nutrition advice can be so confusing because one moment we hear that saturated fat is the enemy and the next minute it's not and in the final and fourth episode I will look at cholesterol.

In this first episode I'll describe to you what fat is,

The different types of dietary fats and a brief overview of fat digestion.

I think it's really helpful to understand what fat is from a scientific point of view because there is so much in the media about fat,

You know,

Eat it,

Don't eat it,

Eat this fat,

Not that fat etc.

Is confusing.

So starting from a solid knowledge base is always helpful.

In the following episodes I'll delve more deeply into the characteristics of the different types of fats including their health pros and cons,

Where they are found in our diets and general advice on how much we should aim to consume.

So to start with what is dietary fat?

In nutrition fats are part of a family of nutrients called lipids.

Within this family there are triglycerides which are fats and oils,

Phospholipids and sterols.

Today I'll mainly focus on triglycerides as these make up the majority of lipids we consume and store in our bodies,

About 95% in fact.

So time for some basic chemistry,

No more complex than the chemistry for dummies level.

Like carbohydrates fats are made up of carbon,

Hydrogen and oxygen.

A triglyceride is formed by a glycerol molecule which is a three carbon alcohol with three fatty acids attached to it.

So fatty acids are even numbered chains of carbon atoms with hydrogen atoms attached.

Fatty acids can have from four to twenty four carbons in their carbon chain.

Fatty acids can be saturated or unsaturated and I expect most of you can probably name some saturated fats such as butter and lard and unsaturated fats like olive oil and nut oils.

But it might interest you to understand why they are described that way and it comes down to their different chemical structures.

Let's start with saturated fatty acids.

Each carbon molecule in the fatty acid chain,

Except for the carbon molecules at either end,

Have two hydrogen atoms attached to them plus they are attached to the carbon molecule before and after them in the chain.

Carbon atoms need to have four bonds or attachments each.

So in this case each carbon is attached to four other molecules,

That is two carbons and two hydrogens.

Two hydrogens is the maximum number of hydrogens a carbon can have in this chain configuration and therefore that's why we say it is saturated with hydrogen.

And then for unsaturated fatty acids,

This describes a carbon chain where some of the hydrogen atoms are missing and at those points in the chain the carbon molecule,

Which needs a total of four bonds as I mentioned,

Will form a double bond with the carbon next to it in the chain.

These fatty acids are described as unsaturated because they are not saturated with hydrogen molecules.

I hope that makes sense.

The number of double bonded carbons,

The location of those double bonds in the chain and the length of the chain all affect the chemical and therefore health properties of the fatty acids.

Fatty acids with one double bond are called mono unsaturated fatty acids and those with two or more double bonds are called polyunsaturated fatty acids.

Common mono unsaturated fatty acids you'd be familiar with are olive oil and canola oil.

Well known polyunsaturated fatty acids include nut oils and fish oils.

You've probably also heard of omega-3 and omega-6 fatty acids which are unsaturated.

Some omega-3 fatty acids are essential and I'll delve into why this is the case and the health benefits of those particular unsaturated fatty acids in episode two of this series.

Most fats are actually a mixture of saturated,

Mono unsaturated and polyunsaturated fat and it is the dominant type of fat that gives it the overall classification.

So for example coconut oil is described as a saturated fat.

It is about 80 to 90 percent saturated fat with the remaining 10 to 20 a mix of mono and polyunsaturated fats.

And just so your knowledge is complete but without going into much detail I'm trying to keep this science lesson short.

You may also be familiar with the descriptors short chain,

Medium chain and long chain fatty acids.

This refers to how many carbons are in the chain.

So just briefly long chain fatty acids have between 12 and 24 carbons and they are abundant in our food supply.

Medium chain fatty acids have between 6 and 10 carbons.

They're also found in our diet mainly in dairy products and short chain fatty acids have less than 6.

They are produced by bacteria in our gut when it ferments dietary fibre in our colon.

Short chain fatty acids have an important role to play in our health including keeping the cells of our colons healthy.

So eat your dietary fibre.

And now for a quick look at the characteristics of fats.

As most of you know fats and oils are insoluble in water.

Polyunsaturated fats are usually liquid at room temperature that's about 25 degrees Celsius because the double bond reduces the melting point whereas saturated fats are generally solid at room temperature.

When fats are exposed to oxygen this causes them to spoil.

The double bonds between the carbons in unsaturated fats are unstable and therefore more susceptible to spoilage.

Saturated fats with no carbon double bonds are therefore more stable.

And now to complete the family tree of the lipid family we also have phospholipids and sterols.

Together these make up only about 5% of the lipids in our diet.

Very briefly because of the chemical structure of phospholipids they are soluble in both fat and in water and they are important components of cell membranes because they allow fat soluble substances like fat soluble vitamins to pass in and out of our cells.

Sterols are compounds with multiple ring structures as opposed to a chain structure.

The most well known one is cholesterol and that's found only in animal foods such as eggs,

Meat and dairy products.

As there's a lot of information and misinformation I might add about cholesterol this little lipid will get an episode of its own in episode four of this series.

And there is one more type of fat that you would have heard of and that is trans fat.

So trans fat occurs in tiny amounts in nature but the trans fat I'll mention here are industrial trans fats.

Trans fats are fats and oils that have been altered by an industrial process known as hydrogenation and that is when hydrogenate atoms are added to the double bonds of mono and polyunsaturated fatty acids to increase the degree of saturation and also increase the melting point.

Essentially what this does is convert a liquid oil to a solid oil at room temperature and these oils are used by food manufacturers as cooking fats for deep frying and shortening for baking so are found in highly processed foods like baked goods,

Pies and pastries.

Hydrogenated fats are cheap to produce and also make the fat more stable and therefore increase the shelf life of a product.

Hydrogenation also changes the shape of the carbon chain from a cis shape to a trans shape hence the name and that has negative health impacts.

In my opinion there's really nothing good to say about industrial trans fats.

The National Heart Foundation has found that trans fats are linked to an increased risk of heart disease.

However the good news is that Australians generally have a low intake of trans fats but given that food manufacturers are not required to declare trans fats on their labels the best way to minimise intake is to avoid highly processed foods and deep fried foods.

So just a quick note on digestion.

Lipid digestion begins in the mouth and stomach but only a very small amount is digested here and most of it takes place in our small intestines.

The gallbladder excretes bile into the small intestine.

This helps emulsify the fat so that the enzymes excreted from the pancreas can break down the fat into molecules small enough to be absorbed into the intestinal cells where they're packaged up and then transported around the body by the lymph fluid and the blood where they can be either used or stored in the body's adipose tissue,

That is fat cells.

Lipids are transported in the blood by lipoproteins and you'll most likely be familiar with two of these low density lipoprotein,

LDL,

And high density lipoprotein,

HDL,

Which contain different amounts of protein,

Cholesterol,

Phospholipids and triglycerides with LDL composed mostly of cholesterol but more about that in episode 4.

And to wrap up,

What do fats actually do in our bodies?

Well the most obvious role of fat is to provide us with energy from food or from the body's stores,

That is the adipose tissue.

Fat provides us with 37 kilojoules of energy per gram compared with carbohydrate and protein which provide us with 17 kilojoules per gram.

So fat is a really dense source of energy.

Fat has other important roles including maintaining the structure and functional integrity of cell membranes,

Insulating our bodies and keeping us warm and protecting or cushioning our bones and organs against shock.

In addition some fats,

Like omega 3s which I'll discuss in more detail in episode 2,

Are essential and this is because the body cannot produce them or produce enough of them so we need to obtain them from our diet.

And that's a wrap for fat today.

I'll build on this basic knowledge in the next three episodes where I'll go into more detail about unsaturated fats,

Saturated fats and cholesterol and especially the health impacts of those fats.

Thank you so much for listening today and I hope that science lesson wasn't too boring but it's good foundational knowledge to have.

Eat well,

Move well,

Think well.