Dietary fats have been demonised in the last 60 years. Many believe that eating eggs and bacon or butter can give you a heart attack. Even the world "fat" refers not only to the lipids that we eat but also to excess body flesh, inferring that eating fats make you fat. On the contrary, dietary fats are essential for our survival and have been our primary source of energy for 2.5 million years.
In part I of this article, I will review the main types of dietary and body fats, good and bad. I will explain how the "fat is bad for you" theory has been ingrained in our brains and talk about the extensive research that has debunked this myth, pointing to other risk factors as the catalysts for heart attacks and strokes.
In Part II, I will explain how to optimise your cholesterol levels to be as healthy as you can, which dietary fats are healthy or toxic, and how to reduce the risk of developing cardiovascular diseases.
So, forget everything you have heard or read about saturated fats and cholesterol being evil, at least for the time it takes to read this blog. Here we go!
Saturated fats, cholesterol, triglycerides... ?????
Triglycerides and cholesterol are 2 different types of fats found in our food and in our body. As fat cannot mix with water, they bind to lipoproteins (such as LDL and HDL) to travel in our blood.
Triglycerides - a type of fat
Most of the fat we eat is in the form of triglycerides (3 fatty acids bound by 1 glycerol), that can be saturated (the saturated fats) or not (the unsaturated fats).
Excess dietary carbohydrates ("carbs") can also produce triglycerides: the sugar and starches we eat can be converted into fat and stored to be used as energy at a later time. However, a high-carb / high-insulin-producing diet put us in a fat storage mode where these triglycerides are stuck in our fat cells and cannot be accessed for energy.
On the other hand, a low-carb nutrition opens the access to stored fats that can be then be used for energy production, resulting in fat loss. Yes, eating (healthy) fats can help you lose fat! Think about it when you have breakfast tomorrow: do you still fancy this bowl of sugary cereals & OJ or does an avocado & egg combo suddenly look really appetising?
Triglycerides are necessary for our health but can contribute to cardiovascular diseases when they are too high. This typically occurs in individuals with high blood glucose and high insulin levels resulting from a standard high-carb / low-fat diet. On the other hand, triglycerides are typically lower with a low-carb / high-fat nutrition.
Saturated fats - a type of triglycerides
Fatty meats, eggs, cocoa, coconut, seafood, butter, cheese and full-fat dairy products are all rich in saturated fats.
Cholesterol - a different type of fat
75 to 80% of our cholesterol is produced by our own body and only 20 to 25% comes from our food. This is why restricting dietary cholesterol is useless, as it results in the liver producing more (from fat, sugar and proteins) to satisfy our body needs.
Nutritious foods that are rich in cholesterol include eggs, cheese, shellfish, fatty meat, fatty fish, organ meat and full-fat dairy products. On the other hand, other cholesterol-rich foods are best avoided, such as fried food, fast food and baked goods.
HDL and LDL - the carriers of triglycerides and cholesterol
Neither cholesterol nor triglycerides can travel alone in our bloodstream (as fats cannot dissolve in water) and they are packaged in particles (the lipoproteins) than can mix in our blood. There are different types of lipoproteins, with different sizes, density and purposes. If you have ever had your blood tested for cholesterol, you may have heard of LDL (Low Density Lipoprotein) and HDL (High Density Lipoprotein). They both contain cholesterol and triglycerides.
LDL - the "bad" cholesterol? Not always...
LDL is known as the "bad" cholesterol because it is associated with the build-up of artery-clogging plaque. However, LDL itself does NOT cause cardio-vascular diseases. Some LDL particles are large and fluffy and others are small and dense. It is the small and dense LDL that can lodge in the artery wall and become oxidised and inflamed, increasing the risk of atherosclerosis.
LDL transports mostly cholesterol but also saturated fats, fat-soluble nutrients and antioxidants to the cell membranes. It protects us against bacteria, infections and toxins by binding to pathogens, preventing them to enter our cells. Not quite the bad guy it is supposed to be!
Traditional blood tests for total LDL are not really useful to assess the risk of heart disease, as they do not differentiate between the 2 patterns. Even having small dense LDL is not an issue per se. To reduce the risk of cardiovascular events, it is more important to have high HDL, low levels of triglycerides and other markers (such as HbA1C, a measure of blood sugar, fasting insulin, waist-to-height ratio...), and to avoid other risk factors. Besides, the majority of heart attack victims have a safe LDL level.
LDL - the large and fluffy
The large and fluffy LDL tends to carry more fat-soluble vitamins and anti-oxidants to protect the body from oxidative stress. It is generally harmless. However, when other risk factors are elevated, it can also circulate in the blood for too long and become oxidised.
Lower levels of triglycerides, insulin and HbA1C - typically from a low-carb diet - are associated with this pattern of LDL.
LDL - the small and dense
This LDL is small enough to enter the walls of our artery, where it can oxidise, coagulate and form a plaque. If oxidation and inflammation continue, the plaque can calcify, rupture and block an artery, causing a stroke (artery heading to the brain) or a heart attack (artery going to the heart).
Higher levels of triglycerides, insulin and HbA1C - typically from a high-carb diet - are associated with this pattern of LDL.
HDL - the "good" cholesterol
HDL is called good cholesterol because it helps remove potentially dangerous small dense LDL from the bloodstream and return it to the liver for recycling or excretion. It has anti-inflammatory and anti-oxidant benefits, reduces the formation of blood clots and prevents cell death.
Unfortunately, high levels of triglycerides and insulin can affect the HDL ability to clear excess cholesterol. A low-carb / high-fat nutrition increases HDL levels (which is good), whereas replacing saturated fats by high carbs decrease them.
Dietary fats are essential for health and well-being
We need sufficient levels of blood cholesterol to function optimally.
Our brain needs cholesterol and even produces its own! 1/3 of the brain is made of cholesterol, which accounts for up to 25% of the amount found in our body. As a matter of fact, higher cholesterol levels are linked to better cognitive functions.
Our cells need cholesterol to maintain their structure (50% of most cell membranes are made of lipids) and our nervous system needs it to form the myelin that protects our nerve cells.
We also need cholesterol to make our hormones (testosterone, estrogen, cortisol, vitamin D...) and neurotransmitters, to produce the bile that helps us digest fats, to absorb fat-soluble vitamins (A, D, E and K) and to improve satiety signalling.
Similarly, saturated fats are essential for our health, to support our immune system, help destroy pathogens and fight tumours. They protect the liver from toxic substances and help improve cognitive functions. They also signal satiety, make us eat less and help us lose fat (in the absence of high carbs).
Not only eating less cholesterol- or saturated fat-rich foods does not work (as the body adjusts its own production or usage to compensate), but we need good levels of both to be healthy.
So, why are so many people afraid of saturated fats and cholesterol?
It all started in the 50's, when an American scientist named Ancel Keys published a paper suggesting that dietary fats raised cholesterol levels, thereby increasing the risk of heart disease. His theory was based on correlations derived from observational surveys conducted in 6 countries. However, correlation does not mean causation, as the results could have been affected by factors such as high-carb/sugar intake, processed vegetable oil consumption, smoking, stress....
In the 60's and 70's, the sugar industry funded Harvard research that downplayed the role of sugar as a cause of heart disease, blaming fats instead.
In 1961, the American Heart Association endorsed low-fat diets for the prevention of heart disease. Food manufacturers started replacing saturated fats by toxic hydrogenated fats and added sugar.
In 1977 and 1983, the US and the UK introduced dietary guidelines recommending a diet low in total and saturated fats, without asking for controlled trials to confirm the cause-and-effect relationship.
In the 80's, Ancel Keys published another observational study covering 7 countries. He concluded, again, that a higher saturated fat intake was associated with higher heart disease mortality. However, he discarded data from countries that where showing the reverse (higher saturated fats but lower mortality), such as France and Switzerland!
In 1997, Ancel finally conceded that there was no connection whatsoever between cholesterol intake and cholesterol in the blood...
Since then, many observational studies and randomised controlled trials confirmed (i) the lack of association between saturated fats and cardiovascular diseases, and (ii) that replacing saturated fats by polyunsaturated fats or carbs not only did not show any health benefits but actually increased the risk of death from heart disease or other causes.
In 2014, in her book Why Butter, Meat & Cheese Belong in a Healthy Diet, the journalist Nina Teicholz documents how the past 60 years of low-fat nutrition advice has amounted to a global experiment, with disastrous consequences for our health. She shows how the misinformation about saturated fats took hold in the scientific community and the public imagination and how recent findings overturned these beliefs.
Unfortunately, the old US and UK guidelines have been adopted globally and have remained mostly unchanged to this date. In the meantime, 60 years of this low-fat / high-carb regime have led to epidemic rates of obesity, diabetes and other modern diseases including Alzheimer's, heart diseases and cancers.
Saturated fats and cholesterol do NOT cause cardiovascular diseases!
In the past decade, more and more observational studies and randomised controlled trials have shown that there was no association between saturated fat or cholesterol intake and cardiovascular diseases (heart attacks, strokes...) or all-cause mortality. On the contrary, people with the highest consumption of saturated fats and cholesterol have the lowest risk of dying from cardiovascular diseases. Yeah for eggs, cheese, fatty meat and butter!
Here is a summary of the key findings:
(TC = Total Cholesterol, TG = triglycerides, CVD = cardiovascular disease)
Dietary saturated fats do no increase blood levels of saturated fats: even when the saturated fat intake was tripled, blood levels of saturated fats did not increase.
Dietary cholesterol does not affect total blood cholesterol. When we eat more cholesterol, our body makes less and vice-versa.
Increased consumption of total fats, saturated fats or any type of fats reduces total mortality rates and improve the blood lipid profile (reduced TC/HDL, TG/HDL, ApoB/ApoA1 and TG; increased HDL).
Replacing saturated fats by polyunsaturated fats does not reduce the risk of cardiovascular diseases and all-cause mortality, on the contrary, it increases the risk when the polyunsaturated fats come from toxic processed vegetable oils. See my blog Stay away from vegetable oils.
Replacing saturated fats by monounsaturated fats improves LDL and blood pressure but worsens HDL and TG.
Replacing saturated fats with higher carbs (especially refined carbs and sugar) worsens the blood lipid profile (increased TG, small LDL, TC/HDL, TG/HDL, ApoB/ApoA1; reduced HDL) and increases the risk of obesity, diabetes, CVD and all-cause mortality. Combining fats with carbs gives the worst outcome in terms of inflammation and CVD.
The main risk factors for CVD include: smoking, excess weight or obesity, excess stress, diabetes, hypertension, inflammation, poor diet, over-consumption of sugar, low physical activity and bad lipid profiles.
A low-carb / high-fat nutrition increases total cholesterol levels, as fat becomes the primary source of fuel (instead of glucose) and requires more transporters (HDL and LDL) to deliver the cholesterol to the cells for energy. However, it improves the lipid profile (decreased TG, small LDL, TC/HDL, TG/HDL, ApoB/ApoA1; increased HDL) and reduces the risk of CVD. It also improves other markers of the metabolic syndrome and CVD risk, including reduced inflammation, blood pressure, blood glucose and insulin, BMI and fat mass. These improvements are even more significant when the carbs are kept below 50g per day.
On the other hand, high-carb / low-fat diets negatively affect the blood lipid profiles and increase the risk of CVD and all-cause mortality.
In short, eating more (healthy) fats, including saturated fats and cholesterol and less carbs (especially sugar) improves our blood cholesterol levels and reduces the risk of mortality. Dietary fats are efficiently metabolised in the presence of low carbs.
So, why - despite all these studies - do the current dietary guidelines still restrict the consumption of saturated fats, whilst promoting certain high-carb foods? And why are so many health professionals, health institutions and the general public still afraid of dietary fats?
The standard high-carb diet in America, Europe and Australia, together with other unhealthy lifestyles (chronic stress, smoking, lack of physical activity, poor sleep...) are the main culprits for the modern epidemy of obesity, diabetes, cardiovascular diseases and other chronic diseases.
It is time for a change! A shift to a well-formulated nutrition lower in carbs and higher in healthy fats could not only reduce cardiovascular diseases but also promote global health. It could help with weight and fat loss and reduce inflammation, which is at the source of so many modern chronic diseases.
In part II, I will cover cholesterol levels optimisation, which fat-rich foods are healthy and which ones are toxic, and what other lifestyle practices can reduce the risk of developing cardiovascular diseases. Don't miss it!
This article is for educational purposes only. It is not a substitute for professional medical advice and is not intended to diagnose, treat, cure, heal or prevent any disease or medical condition. See full Disclaimer here. I encourage you to do your own research and to discuss with a qualified healthcare practitioner the options that could work the best for your specific circumstances.
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