Dietary fats: are they really the bad guys?

Okay, it’s a long post today but hear me out on this!  There are thousands of articles out there describing how we should cut fats out of our diet and choose low-fat options of products where possible.  I don’t necessarily disagree with all of them, but I’d like to plead the case for the defence.  Let’s start at the beginning…

First, the science bit!

On a molecular level, 90% of fats are triglycerides - they’re composed of one glycerol molecule and three fatty acids.  As they consist mostly of carbon and hydrogen atoms, they are naturally hydrophobic.  Obviously, this causes a bit of a problem in our digestive tract because fat then tends to clump together to form large droplets.

I present to you the superhero of the story – bile!  As you know, bile is produced in the liver and stored in the gall bladder.  When the time is right it mixes with the fat droplets in the small intestine and acts as an emulsifier – hurrah! The bile salts in bile break the larger fat droplets up and coat them to form much finer droplets.  This of course gives them a larger surface area which allows pancreatic lipase (the fat-digesting enzyme) to act on them more efficiently.

Pretty cool, right?  It’s crazy to think that all of these chemical reactions are going on in our bodies without us having to lift a finger!

So what happens next?

Well, I’m glad you asked!  Once the lipase has done its work, we’re left with glycerol and fatty acids (remember that they’re the components of fat that we talked about earlier?  All the lipase has done is break the dietary fat down into its basic parts so that it can be used by the body).  The monoglycerides and fatty acids are resynthesized into triglycerides in the epithelial cells within the small intestine.  These new triglycerides are then diffused into the lacteals, or lymphatic capillaries, and from there into the bloodstream.

Once they are in the bloodstream, these triglycerides are once again broken down into fatty acids and glycerol by lipoprotein lipases.  And then, quite randomly (well, not that randomly, I guess!) insulin gets involved.

Isn’t insulin associated with blood sugar and diabetes?

Yes, the function of insulin relates to the storage of glucose as glycogen.  After I’ve eaten my lunch, for example, the pancreas secretes insulin which, long story short, causes the ingested fats and glucose to be stored as fat for future use.  It stimulates the creation of glycogen from glucose – the glycogen is then stored in my liver and muscle tissue until it’s needed.

However, if my insulin levels are too high then too much glycogen is produced for the liver to store.  Instead, insulin instructs my fat cells to take up the excess glucose and store it as saturated body fat (yep, those triglycerides again!).  And that’s how insulin plays a part in how fats are stored in the body.

That’s quite a journey!

I’ve simplified the process quite a lot, but it’s obvious that the fat we eat goes through a lot of different stages before it finally gets used up by our bodies as energy, or gets stored for later as body fat.

So after all that, what do we actually need it for?

We literally can’t survive without dietary fat

I die a little bit inside when someone tells me that they are cutting fat out of their diet completely.  I mean, I can completely understand the sentiment but cutting a whole macro-nutrient out of your diet is a little bit extreme and can actually do more harm than good.

Did you know that fatty acids are vital for regulating hormone production?  Fat is stored in our bodies as adipose tissue (which sounds so much nicer than just saying “body fat”!), and it has been found that this tissue is responsible for releasing a number of different essential hormones with the following functions:

• Blood pressure control

• Clotting of blood

• Sending messages between cells

• Storage and metabolism of fat to release energy

As I’m sure you know, there are water-soluble vitamins and fat-soluble vitamins. Without fat in our diet we can’t metabolise and use the fat-soluble variety – vitamins A, D, E and K (more about them in another post, just know for now that these all have vital functions that we really can’t remain healthy without).

Fat also insulates our bodies and helps to regulate our temperature, as well as keeping our skin and hair healthy.  And, while carbohydrates are our main energy source (I've written a bit about this in a previous article), our bodies can easily use fats to serve this purpose should carbohydrate-based energy not be available.

What do we mean when we talk about dietary fats?

It’s almost impossible to get through an advert break on TV without hearing about how a particular brand of butter or spread contains mono-unsaturated or poly-unsaturated fats.  But what does this actually mean and which fats should we be looking for?

I’ll spill the tea for you!  Firstly, we have saturated and unsaturated fats.

Animal fats are mostly saturated (i.e. all of the carbon molecules we mentioned earlier are completely saturated with hydrogen bonds) and so are solid at room temperature, while plant and fish fats are generally unsaturated (and are usually liquid at room temperature as a result).  It's important to remember that foods like coconut, dark chocolate, eggs and unprocessed meat are all considered saturated fats, and all have health benefits if consumed in moderation. Saturated fat is not the villain here!

Unsaturated fat can then be split into mono-unsaturated and poly-unsaturated fats.  Mono-unsaturated fats can be found in red meat, whole milk products, olives, and avocados.  Poly-unsaturated fats can be found in walnut oil, sunflower seeds, peanut butter, and salmon.

We also have trans fats, which I’m sure you’ve heard of.  These fats are found naturally in animal products such as milk, cheese, beef, and lamb.  Research has found that these are not harmful as long as the daily intake is moderate.  Artificially produced trans fats are a by-product of the hydrogenation process and should be avoided at all costs!

Hydrogenation?  What’s that all about?

So here’s the thing – in an effort to make fat that’s cheaper than animal fats but has the same properties, manufacturers use hydrogen to convert liquid vegetable oils into semi-solid and solid fats.  These hydrogenated fats are usually more heat stable and have an increased shelf life.

How do they do this?  The unsaturated vegetable oil is heated, then hydrogen gas is pushed into the oil in the presence of a catalyst such as nickel.  This changes the molecular structure of the oil so that it forms into a more solid fat.  The level of saturation can be managed so that the end result is either fully or partially hydrogenated.  Check the ingredient labels on the food in your fridge and pantry – you’ll be surprised how often this is included in everyday items.

Artificial, or industrial, trans fats are a by-product of this process and it has been found in clinical studies that consuming these trans fats can increase LDL cholesterol without also raising the HDL cholesterol levels.  Not exactly ideal.  Trans fats have also been linked to an increased risk of heart disease.

Omega oils

There’s been a real trend over the last decade or so to make sure we’re all getting our daily dose of Omega 3 oils.  Fish and krill oil sales have gone through the roof, and we’re all trying to get a couple of portions of fatty fish into our weekly meal plans.

However, did you know that there are two other Omega oils?  Omega 6 and Omega 9 are also important for our health, but quite often we eat far too much Omega 6 which can cause an imbalance. As you know, Omega 3 is found in our SMASH fish (salmon, mackerel, anchovy, sardines, and herrings), flax seeds, chia seeds, and walnuts among others.  The health benefits they offer are pretty significant.  For example:

• Fighting inflammation

• Promoting bone health

• Decreasing liver fat

• Supporting mental health

Omega 6’s are generally used for energy and also play a role in brain function, growth, and development.  Good sources of this fatty acid can be found in many of the same foods as Omega 3, as well as sunflower oil, soy oil, and sesame oil.

And let’s not forget Omega 9!  These fatty acids can be produced by the body and are pretty abundant.  Omega 9 has anti-inflammatory properties and has been found to be important for healthy brain function.  As I said, these fatty acids are non-essential as they are produced naturally but they can also be found in olive oil, avocado oil, almonds, and walnuts.

Finding the right Omega balance

The recommended ratio of Omega 6 to Omega 3 in the diet is around 4:1 – but did you know that the average Western diet generally has a ratio of around 20:1?  This level of imbalance can cause health problems and so should be addressed.

A good approach is to identify the sources of Omega 6 in your diet (look out for the oils you’re using to cook with, for example) and reduce them, rather than just trying to increase the levels of Omega 3 to balance the ratio out.

Friendly fats that we can include in our diet

Let’s be honest, fats make our food taste good and they help to keep us feeling full for longer after we’ve eaten.  What can we include in our diet that will give us these benefits in a more healthy way?  In the next post, I'll go through a few options that you could try, along with some reasons why they can be good for us (in controlled amounts, of course!).