Fat is often seen in a negative light, when the fact is that we need fats.  Fat have many important biological functions such as;

healthy fats

  • Being a source of energy, 1g of fat provides 9Kcal, (although the body must use up more oxygen to burn fat for energy than if it was using carbohydrate for energy).
  • Heat – there’s a layer of fat under our skin called adipose tissue which acts as an insulator to keep us warm.
  • A layer of fat protects delicate organs such as the kidneys.
  • Cholesterol is a type of lipid which is vital for making hormones, vitamin D and other substances. 
  • Fat acts as a major structural component of the billions of cells that make up our body in the form of cholesterol.  Our brains are 60% fat!
  • Fat supports the absorption of essential fat-soluble vitamins A.D.E and K.  You get these vitamins from foods which contain fat.
  • Monounsaturated and polyunsaturated fats are known to improve heart health.
  • Polyunsaturated fats, which contain Omega 3 and Omega 6’s, are known for a variety of health benefits including brain, heart and joint health. (Facts about Fats: (EUFIC), 2015)

What you need to know about fat is that there are different types of fats, and yes, some of them should be avoided, but some of them are important for our health.  I’m going to start with fats we should include in our diet and why they are important.

Fats can be saturated or unsaturated.  Unsaturated fats can be monounsaturated or polyunsaturated, and these unsaturated fats are the fats we need in our diet.  When we think about heart health and diet we usually think about lowering our fat intake, but unsaturated fats are actually really good for heart health, it’s the saturated and trans fats that you get from fried foods, cakes, biscuits and most animal products that are bad for the heart.  Coronary Vascular Disease (CVD) is the greatest cause of death worldwide, and it is closely related to eating too much saturated and trans fats  (Lovegrove, 2020).  Studies have shown that replacing saturated fats in the diet with polyunsaturated fats, monounsaturated fats or wholegrain carbohydrates have a beneficial effect on heart health by lowering the risk of developing Coronary Heart Disease Significantly (Li Yanping et al., 2015).  In fact, replacing as little as 5% of your energy intake from saturated fats with polyunsaturated fats, monounsaturated fats and wholegrain carbohydrates lowers your risk of developing CHD by 25%, 15% and 9% respectively (Li Yanping et al., 2015)! 

A well-known study called “The seven countries study” showed that people from Mediterranean countries typically suffered less incidences of heart disease, despite their diets being high in fat.  The main sources of fat in their diets where monounsaturated fats from olive oil (Keys et al., 1984).  Other sources of monounsaturated fats include peanut oil, canola oil, sunflower oil and sunflower seeds, avocados and most nuts (Publishing, 2019).  Take a look at my Mediterranean diet blog

Polyunsaturated fats are also essential in the diet.  They are used to build the membranes of the billions of cells that make up our bodies, as well as the coverings of our nerves.  They are also needed for blood clotting, controlling inflammation in the body and muscle movement (Publishing, 2019).  Polyunsaturated fats come as omega 3’s or omega 6’s.  Both are important.  Unfortunately, we tend to not get enough omega 3’s and too much omega 6’s due to omega 6 being present in most foods eaten in the western diet.  Sources of omega 3’s include;

  • Oily fish (salmon, mackerel, tuna)
  • Flaxseeds
  • Chia seeds
  • Walnuts
  • Soya beans
  • Olive oil

There are many health benefits associated with omega 3, these include;

  • Preventing and even treating heart disease and stroke.  Dieticians typically advise people who need to improve their heart health to go on a diet called the DASH diet, which is really the Mediterranean diet, full of omega 3’s.
  • Reducing blood pressure
  • Lowering bad LDL cholesterol and increasing good HDL cholesterol
  • Lowering triglycerides in the blood, too much triglycerides in the blood can cause the hardening of the arteries (atherosclerosis).  This increases the risk of heart attack, stroke and heart disease (Beckerman, 2019). 
  • They’ve also been shown to help treat rheumatoid arthritis by improving joint health.

Omega 6’s have also been associated with heart health, and like I mentioned above they have an abundance of sources such as Poultry, eggs, wholegrains, nuts, vegetable oil, sunflower oil, corn oil and soya bean oil. 

In terms of how much fat you need in your diet the European food safety Authority gives these guidelines;

Table 1: Recommended amount of fat in the diet of males and females (EFSA, 2019)

AgeALAEPA + DHALATotal fats
Infants 7-11 months0.5% of your overall calorie intake100mg/day4% of your total calorie intake40% of your total calorie intake
Children 1 year0.5% of your overall calorie intake100mg/day4% of your total calorie intake35-40% of your total calorie intake
2-3 year0.5% of your overall calorie intake250mg/day4% of your total calorie intake35-40% of your total calorie intake
4-17 year0.5% of your overall calorie intake250mg/day4% of your total calorie intake20-35% of your total calorie intake
≥18 years0.5% of your overall calorie intake250mg/day4% of your total calorie intake20-35% of your total calorie intake
Pregnant women0.5% of your overall calorie intake250mg + an additional 100-200mg/day4% of your total calorie intake20-35% of your total calorie intake
Lactating women0.5% of your overall calorie intake250mg + an additional 100-200mg/day4% of your total calorie intake20-35% of your total calorie intake
  • Key: Alpha-Linoleic Acid = ALA, an omega 3 fatty acid.
  • Eicosapentaenoic acid = EPA, and Docosahexaenoic acid = DHA, are long-chain omega-3 polyunsaturated fatty acids mainly found in fish. 
  • Linoleic Acid = LA is an omega 6 fatty acid

Saturated fats and trans fats have to recommendation except to consume as little as possible.

            So now we know about the fats we should eat, but what about the saturated and trans fats we should avoid?  Why are they so bad for us?  First, we’ll look at the main sources of saturated fats.  Natural sources come from animal products such as meat, eggs and dairy, but you can also find it in plant sources such as coconut, coconut oil, palm oil, and palm kernel oil.  Eggs do contain some saturated fats, and for a time it was thought that eating egg raised cholesterol levels.  However, the type of saturated fats found in eggs is in the form of phospholipids and they actually increase the ‘good’ High Density Lipoprotein (HDL) cholesterol which helps remove excess Low Density Lipoprotein (LDL) cholesterol, also known as ‘bad cholesterol’ from the blood, so eating eggs in moderation is fine (Gunnars, 2018).  Other sources of saturated fats are fried foods, cakes, pastries, biscuits and crisps. 

            we know saturated fats and trans fats are bad for heart health and eating too much saturated and trans fats can lead to major health problems.  When you hear the word ‘Diabetes’ you probably think of sugar, not fat.  However, many studies have linked a diet high in saturated and trans fats to insulin resistance, in other words, type 2 Diabetes.  I will do another blog explaining how there is more than one type of diabetes a person can get, but there is only one that is solely caused by poor diet and lifestyle.  That is type 2 diabetes. 

A study was carried out on two groups of healthy people.  One group was given a high saturated fat diet, and the other group was given a diet high in carbohydrates (sugar, sweets, white bread, syrup, baked potatoes, white rice, banana, oatmeal).  After only two days the group on the high fat diet had blood sugar levels twice as high as those on the high carb diet (Sweeney, 1927)!  Once the group on the high fat diet went back to a diet lower in saturated fats their sugar level normalised.  This study showed that as the amount of fat in the diet increased so did blood sugar levels.  High blood sugar levels are a typical characteristic of diabetes. 

When we eat carbohydrates or body breaks them down into glucose (sugar) which then travels through the blood to our cells where it gives us energy.  Blood sugar is a bit like a vampire, it needs to be invited into the cells, and insulin which is a hormone made in the pancreas is the key to the cells that lets the sugar in (Sweeney, 1927).  In type 2 diabetes the body makes insulin, it just doesn’t work well or at all.  This is referred to as insulin resistance and it occurs when fat is blocking the ‘locks’ in our muscle cells so insulin can’t unlock the cells to let the sugar in to do its job and give us energy.  This means the sugar is just floating around in our bloodstream leading to high blood sugar levels which can be life threatening if not treated.  A diet high in saturated fat can lead to fat building up in the muscle cells creating toxic fatty breakdown products and free radical (read the blog on vitamin C to learn more about free radicals.  These then block the signalling pathway for insulin (Krssak et al., 1999).  As little as one meal high in saturated fat can cause mild insulin resistance within three hours (Roden et al., 1999)!  That is why some sources say a ketogenic diet could mean insulin is not as effective (Santomauro et al., 1999). 

Insulin is made by cells in the pancreas called Beta cells, and it has been shown that fat breakdown products actually interfere with the functions of these Beta cells leading to death of the cells (Estadella et al., 2013).  So saturated fats not only impair the function of insulin by blocking the ‘lock’, it also impairs secretion by killing the cells that make insulin.  That is why some type 2 Diabetics who don’t make healthier food choices and reduce their saturated fat intake actually end up having to take insulin injections like a type 1 diabetic (Xiao et al., 2006).  The ingestion of saturated fat reduces the effectiveness of insulin within a few hours even in non-diabetics (Xiao et al., 2006). 

Saturated fats are also toxic to liver cells, and a diet high in saturated fat can lead to what’s called fatty liver disease (Leamy et al., 2013).  When liver cells are exposed to unsaturated fats nothing happens, but when exposed to saturated fats 1/3rd of them die (Leamy et al., 2013).  Overall a diet high in saturated fat and abdominal obesity (a lot of weight around the abdominal area) puts you at very high risk for many health complications including heart disease and type 2 diabetes (Taylor, 2008).   

So that’s saturated fats.  Now we’ll look at trans fats.  In America the death of healthy people (people without chronic illnesses), caused by a diet high in trans fats is comparable to the death from E.coli infection, meningitis, cancer of the larynx, cervical cancer, MS and drowning (Cohen, 2014).  Trans fats exist naturally in small amounts in the fat in red meat, dairy and vegetable oil due to the refining process it goes through.  Trans fats can also be added to processed foods.  Whether they occur naturally or artificially they effect cholesterol the same.  They make good cholesterol (HDL) go down and bad cholesterol (LDL) go up (Cohen, 2014).  Many countries have tight regulations around the use of trans fats in food manufacturing.  The addition of trans fats is actually banned in both Canada and the US (Canada, 2018; Artificial trans fats banned in U.S. | News | Harvard T.H. Chan School of Public Health, 2018).  There is no ban on trans fats in Ireland as of now, but the Food Safety Authority Ireland (FSAI) recommends limiting the amount we consume by looking out for the ingredient “partially hydrogenated oil”, as this indicates the presence of trans fats.  You would find partially hydrogenated oil in foods such as baked goods, shortening, microwave popcorn, frozen pizza, fried foods, margarine block, non-dairy coffee creamer (Trans fat is double trouble for your heart health – Mayo Clinic, 2020).    

My advice when it comes to fats is to eat plenty of unsaturated fats, so oily fish, avocados, nut, seeds, olive oil, rapeseed oil etc.  Limit the amount of red meat and dairy you eat.  Dairy is a good source of calcium, but in order to get your recommended amount of calcium per day you don’t need that much.  One 200ml glass of skimmed cow’s milk provides about ¼ of an adults daily need of calcium (check out https://www.efsa.europa.eu/en/interactive-pages/drvs for you daily need of calcium which depends on age and gender).  Milk is actually very low in fat overall, it’s mainly the cheese and yoghurts that you need to go easy on.  Try to stay away from highly processed, greasy fried foods as much as possible.


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