To start, we need to understand the different types of fats.
There are two main types of fats: Saturated and Unsaturated. This is mostly to do with the fats chemical structure.
Monounsaturated fats have one double bond – the double bond makes a kink in the structure
Poly unsaturated fats have 2 or more double bonds and they have lots of kinks in their structure.
These bonds effect how the fat looks and acts. For example, saturated fats are solid at room temperature – think: butter and the visible fat on red meat. Saturated fats are more stable (less likely to oxidise – react with oxygen and go rancid) and better for deep frying and high heat cooking.
Unsaturated fats are liquid at room temperature. They are more unstable, so are more likely to oxidise (react to oxygen and go rancid) and smoke at high temperatures. Different unsaturated fats have different cooking temperatures and stabilities.
Saturated fats have no double bonds. This means they can compact together closely which makes them solid at room temperature.
Unsaturated fats can have one or many double bonds. This means their fat strands have kinks in them, so they can’t pack up closely together. This means they are liquid at room temperature.
Unsaturated fats
There are a few different types of unsaturated fats, the ones you will commonly hear about are: monounsaturated (MUFA), polyunsaturated (PUFA), omega 3 and omega 6. The differences are to do with how many double bonds their chemical structure has 1 double bond = monounsaturated fat (MUFA) or 2 or more double bonds = polyunsaturated fats (PUFA). Omega 3 adn omega 6 are two polyunsaturated fats. The length of the chain and where the double bonds are on the chain also effect how they react when cooking, how heat resistant they are (good for cooking or not) and their effects on our health.
Generally, unsaturated fats are good for our health and worth including in our diet every day. Foods that contain unsaturated fats are: olive oil, olives, avocado, nuts, seeds, fish, salmon.
Omega 3 and 6
The omega’s are two essential fats that cannot be made in our body, so it’s essential we get them from food. Omega 3 and Omega 6 fats are long chain polyunsaturated fats. Their names are to do with their chemical structure eg. where the double bond is placed – in the 3rd or 6th position (more about these a bit later).
There are a two types of saturated fats: saturated fats and trans fats.
Saturated fats are found in loads of different foods, mostly animal foods but also plant foods such as coconut oil, palm oil, nuts and seeds are usually high in unsaturated fats, but some nuts, such as cashews, are high in saturated fats.
Foods are complex and made up of thousands of different components. So when we are talking about specific fats it doesn’t necessarily help us understand the foods we are eating. For example, whole milk contains around 400 different fats, around 70% of it is saturated fat and 28% mono unsaturated fats. The composition of milk changes with the season, diet of the cow and how the milk is processed etc! And looking at just the fats in the milk is short sighted. Milk is also a good source of calcium, vitamin B12, phosphorus and riboflavin. Milk is also full of protein. It is easy to store, relatively cheap, a great snack for growing kids and easily accessible to buy. All these factors are important when we consider what foods to eat.
Trans fats
Trans fats occur naturally in foods from ruminants (think cow, sheep and dairy) and in artificial forms. Studies show that naturally occurring trans fats are good for our health. But trans fats in highly processed foods, such as margarine’s, are very bad for our health – they increase our risk of type 2 diabetes, arthritis, cancer and heart disease. Trans fats occur from making oils that are unsaturated fats and liquid at room temperature in to solids. To make them solid at room temperature they are “hydrogenated” or partially hydrogenated – this process creates trans fats and trans fats are worth avoiding.
Cholesterol – and your blood results
When you get your cholesterol tested at the Dr’s they look at your:
- Total cholesterol – this is the total amount of cholesterol in the blood
- Triglycerides – a type of fat that floats around in the blood around 1 is good, but below 2 is within range.
- LDL-C – this is a measure of the concentration of a protein that carries fats in the blood from the liver to the rest of the body. In NZ this is not measured, it is calculated from the amounts of total cholesterol and HDL-C
- HDL-C – this is a measure of the concentration of a protein that carries fats in the blood from the body to the liver
- Cholesterol ratio – this looks at your total cholesterol and HDL-C and comes up with a ratio. High ratios indicate a high risk of heart attacks and low ratios indicate low risk.
I took part in the TOFI study (thin on the outside, fat on the inside)
There are two points I would like to make:
1. My LDL is much lower than everybody else’s (which is good!)
2. My HDL is much higher than everybody else’s (also good!)
So cholesterol is….
Cholesterol is a type of fat that is made in our liver and is found in animal foods. It’s a super important fat which is essential for life. Cholesterol is imperative for making hormones, such as testosterone and for sitting inside every cell membrane of our body.
Cholesterol and its effects on our heart, is a highly contentious topic which has resulted in nutrition experts hotly debating what’s known as the ‘diet heart hypothesis’. Traditionally, it was thought that when you ate cholesterol containing foods (think animal products containing fat, meat, dairy, eggs) that would increase the levels of cholesterol in your blood, clog up your arteries and cause heart disease. We now know that our liver makes all the cholesterol we need and cholesterol containing foods do not increase cholesterol levels in the blood or increase your risk of heart disease. Around 80% of the cholesterol in your body is made by your liver and diet contributes around 20%.
However, having too much cholesterol in our blood has been thought to increase our risk of heart disease. With this reasoning, current recommendations for Total cholesterol is under 5.0mmol/L – but this is highly contentious and there is some evidence to show that higher cholesterol levels are protective, especially in older people. And some evidence that it’s not the cholesterol that increases our risk of heart disease, but inflammation (and that’s a whole other topic)!
Triglycerides
Triglycerides are lipids that float around in our blood. These levels fluctuate a lot each day. For example, after a meal they will be much higher, then your body stores triglycerides away into fat cells and releases them again, between meals, to keep your body fueled. You don’t want triglycerides to be too high and when you do this test it’s only valuable if you’re fasting (because they’ll likely be super high, depending on what you just ate, and you’ll think your about to die, but actually you’re not). Around 1 is brilliant, under 2 is the recommendations.
HDL and LDL – the low down
HDL and LDL are actually proteins that carry fat and cholesterol, in your blood, from your liver to the cells around your body and back again.
HDL is like a vacuum cleaner. It cruises around picking extra fat and cholesterol and takes it back to the liver (reducing the amount of fat in your blood). Higher HDL levels are good as HDL is protective against heart disease. Over 1 is the aim, but higher is better.
LDL is like a bus and drops fat and cholesterol from the liver to the cells in your body, so they can use it for energy and other things. LDL is considered the ‘bad’ cholesterol because higher LDL levels are thought to be associated with higher risks of heart disease. BUT there are different types of LDL proteins. The main ones are type A, which are big and fluffy and do not increase your risk of heart disease and Type B which are small and dense and do increase your risk of heart disease. These are not currently tested for in NZ. Which is unfortunate, as they are an important marker of health.
Also, we (in NZ) measure concentration eg. LDL-C but what is super useful is the particle number LDL-P. You could have the same LDL-C result as Joe Blogs but you might have a lower LDL-P comparative to Mr Blogs and this would indicate his cardio-vascular disease risk is WAY higher. This is because you might have 5 large fluffy particles and Mr Blogs might have 10 small dense ones. His particle number is double, but both your concentration results are the same. Poor Mr Blogs has an increased risk, but the current testing doesn’t give us that information.
You can’t look at these numbers in isolation, you need the whole picture, just one cholesterol reading is not particularly helpful and the amount of cholesterol your liver makes is impacted by age and genetics. When we look at health the over-all big picture is the most important.
It was thought that saturated fats caused heart disease.
The “diet heart hypothesis” was created by Dr. Ancel Keys who completed the infamous 7 countries study. He hypothesised that the more saturated fat a person ate, the higher their risk of heart disease. This was believed to be caused by saturated fat intake increasing cholesterol in the blood, clogging arteries (called atheroscleorsis) and increasing risk of heart attacks. His studies were problematic and there were massive flaws in his research and the data that he presented (he took out countries which had results that didn’t fit into his hypothesis). Despite all this, his studies and theories have hugely influenced our National Nutrition guidelines and food recommendations.
The official advice used to be limit foods containing saturated fats, as that is thought to increase the ‘bad’ cholesterol in your blood and increase your risk of heart disease. BUT there is growing evidence that this is not the case. We know, for example, that some saturated fats, like stearic acid (found in chocolate!) actually increases our HDL or ‘good’ cholesterol and other saturated fats reduce our HDL and increase our LDL. AND we now know that the saturated fats in dairy don’t increase our risk of heart disease (you can read more about that here, in the Heart Foundations Position Statement).
There is good research that shows that when you eat saturated fats you increase cardiovascular risk factors, for example increasing blood levels of cholesterol. BUT! when studies are done in free living humans, increases in eating saturated foods doesn’t increase actual heart attacks or death from heart attacks.
So what gives?
Nutrition and health is WAY more complicated and nutrition science, is generally pretty rubbish. There are so many factors that can increase a persons risk of heart attacks (overall diet quality, diet composition, exercise, genetics, age, gender, poverty, discrimination, access to health care etc!) This stuff is pretty hard to pick apart in studies.
Back to Omega 3 and Omega 6 – they have very important roles around inflammation.
Omega 3 reduces inflammation and Omega 6 increases it. And yes, increasing inflammation can be a good thing! When we have an infection, are sick, or our body requires healing processes, we need Omega 6 to help drive that. When we are well we need those responses dampened down by Omega 3’s.
The important thing about Omega fats is getting the RATIO right. We want the right amounts of each fats for our bodies to work optimally.
This is where it gets a bit tricky because in most Western countries we get WAY too much Omega 6 fats and not nearly enough of the Omega 3’s. The ideal omega 6:omega 3 ratio is around 4:1, currently Westerners eat more like 16:1.
Omega 6 fatty acids are in most plant based foods and their oils, such as wheat bran, corn, nuts, seeds as well as poultry and eggs. Most processed food is high in Omega 6 due to the types of oils they add to the products.
Omega 3 fats are found in very few foods. Fatty fish such as sardines, tuna and salmon and a few vegan options such as chia seeds, walnuts and linseeds.
So what do we know?
- Cholesterol in foods does not affect the cholesterol levels in our blood.
- Full fat dairy is beneficial for health – butter and cream are neutral to health
- Margarine’s no longer carry that health halo and are neutral to our health
- Trans fats found in processed foods are fats worth avoiding completely.
- Eating more foods high in MUFA’s is beneficial for reducing cardio-vascular risk factors.
- Processed meats do increase risk of cardio-vascular disease and mortality
- Red meat and full fat dairy do not increase risk of cardio-vascular disease
- Saturated fats and Omega 6 have similar effects when looking at risk of cardio-vascular disease
Confused? Let’s strip it all back down to heart health 101:
Overall diet quality is more important than the amounts and types of fats in our diet.
Focus your food choices on mostly plants, don’t worry about the total fat in your diet, but choose most of your fats from sources we know are brilliant for us, olive oil, avocado, fatty fish, nuts, seeds, peanut butter, full fat dairy etc. Make sure you exercise, get 8 hours sleep most nights and take time out to relax.
Getting regular health checks at your GP is a great idea, but keep in mind your cholesterol results are one small part of a very big picture.
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