Saturated fat has a really bad rap.

Common belief is that a high intake of it will increase your likelihood of developing and dying from cardiovascular diseases, heart attacks and strokes. Others argue a link between saturated fat and diabetes.

But what does the evidence say?

When it comes down to testing these relationships with controlled studies, is there any significant association?

Is saturated fat really that bad for you, or is this a myth that should be retired?

What IS saturated fat?

Fat comes in several forms.

There’s saturated fat, monounsaturated fat and polyunsaturated fat.

The difference lies in the number of double bonds in the fatty acid chain (I won’t get too deep into the explanation of this here).

Unsaturated fats have one or more double bonds and fewer hydrogen atoms on their carbon chains. Saturated fats lack these double bonds.

Saturated fats tend to be solid at room temperature, while unsaturated fats tend to be liquid.

Here’s some sources of saturated fat:

• Fatty cuts of meat.
• Products with meat in them (pies, etc.)
• Animal fats like butter, lard, tallow.
• Coconuts and coconut oil.
• Cheese and other dairy products.
• Some oils, like palm oil.
• Cream and ice cream.
• A lot of snack and junk foods. This can vary depending on what type of oil is used to in them. Some are made with vegetable oils, which contain unsaturated fat. Others are made with palm oils, which contain saturated fat.

Why are we advised to limit saturated fat?

Saturated fat has been believed to be bad for human health since the 1950s.

This was originally based on observational studies that showed a link between higher saturated fat consumption and higher rates of death from heart disease.

Observational studies examine effects in “real world” settings, whereas randomised controlled studies or randomised clinical trials evaluate interventions under ideal conditions among highly selected populations.

Here’s a definition:

“Observational studies are seen to have limitations that are largely avoided with randomized controlled trials, leading to the view that observational studies should not generally be used to inform practice. For example, observational studies examining patient outcomes associated with blood transfusion often present higher estimates of adverse outcomes than randomized controlled trials”

These observational studies that showed a link between higher saturated fat consumption and higher rates of death from heart disease were used to create the “diet-heart hypothesis”.

A hypothesis is an idea that you propose, which you then attempt to prove or disprove using scientific evidence.

The diet-heart hypothesis states that saturated fat raises levels of LDL (bad) cholesterol in the blood, which lodges in the arteries, causing heart disease.

This hypothesis has never been scientifically proven but many official diet guidelines are based on it.

There are still lots of studies looking into and trying to prove this link, with many recent studies finding no association between saturated fat and heart disease.

The issue may be more nuanced than the diet-heart hypothesis makes it seem.

Why diet guidelines around saturated fat may need to be updated

There’s a lot of recent scientific evidence that does not show a link between saturated fat consumption and heart disease.

For example, this meta-analysis looked at 15 randomised controlled trials, totalling 59,000 participants in studies where saturated fat was reduced for at least 2 years.

The study found no reduction in deaths, heart attacks or strokes from reducing saturated fat.

However, it was found that replacing some saturated fat with polyunsaturated fat led to a 27% lower risk of cardiovascular events – but no significant findings for deaths, heart attacks or strokes.

This 2014 review looked at 76 studies, including 27 randomised controlled trials.

The conclusion was that current evidence doesn’t support guidelines to reduce saturated fats and increase consumption of polyunsaturated fatty acids.

Here’s another meta-analysis, this time looking at data from 75 studies.

No link was found between consuming higher levels of saturated fat and heart disease, stroke, type 2 diabetes or dying from any cause.

This review looked at 607 studies, analysing all of the data, and finding that saturated fats are not associated with all cause mortality, CVD, CHD, ischemic stroke, or type 2 diabetes.

Some Caveats

A limitation of these reviews is that they look at such a large amount of data from different studies, using different methods – so it’s hard to draw overall conclusions.

Even so, no associations were found between higher saturated fat intake and cardiovascular diseases.

Saturated fat may be neither positive nor negative for health, but other types of fats may be a positive for health. Lowering saturated fat intake doesn’t seem to reduce cardiovascular disease risk. However, an increase in unsaturated fats might be beneficial for health.

On the face of it, it might look like people have developed cardiovascular disease because of a high saturated fat intake, when in reality it could be what their diet is lacking that’s the real issue.

What the studies replace saturated fat with should therefore be scrutinised when analysing the results. In some studies it’s replaced with monounsaturated fat, in others it’s replaced with polyunsaturated fat, and in others it’s replaced with carbohydrates. In some studies, the replacement may not be controlled at all.

This study found that replacing saturated fat with polyunsaturated fat led to a 27% reduced risk of cardiovascular events. It may be that the addition of polyunsaturated fat is what drove this improvement, rather than the reduction of saturated fat.

This study found that polyunsaturated and monounsaturated fats, were equally beneficial for reducing CVD risk when replacing saturated fats. Other studies have found that monounsaturated fat has a better impact.

This 2017 review found that replacing saturated fat with carbohydrates did not reduce CVD risk, but replacing it with unsaturated fats did. This is strong evidence that saturated fat doesn’t contribute to increased risk of cardiovascular diseases. Risk only reduced when unsaturated fats were added, not when saturated fat was reduced without this addition.

When studies claim a link between saturated fat intake and cardiovascular disease, you should question whether the levels of mono and poly unsaturated fats, carbohydrates, overall calories, etc. as well as BMI and other risk factors are being controlled for.

Sources of Unsaturated Fats

Monounsaturated fats can be found in olives, avocados, olive oil, almonds, hazelnuts, pecans, pumpkin and sesame seeds.

Polyunsaturated fats can be found in walnuts, butternuts, sunflower seeds, pine nuts, sesame seeds, brazil nuts, watermelon seeds, pecans, almonds and soybeans.

Polyunsaturated fats can also be found in seed oils like canola oil, rapeseed oil, “vegetable oil”, sunflower oil, etc.

There is a lot of debate about whether these oils, which are produced from seeds and go through a lot of industrial processing to become oils, are harmful for health. So far, scientific evidence has not proved conclusive. However, consuming too many omega 6 fats (which these oils are high in), in proportion to your omega 3 intake, has been linked to greater levels of inflammation.

It’s hypothesised that omega 6 fats may suppress or inhibit the anti-inflammatory properties of omega 3 – so your overall ratio is what matters. The modern diet leads to plenty of omega 6 fats and not enough omega 3, so trying to reduce omega 6 and increase omega 3 intake seems to be a wise approach.

The Source of Saturated Fat May be Important

It’s also worth thinking about the different sources of saturated fat.

Saturated fat is present in lots of junk foods, whereas unsaturated fat is present in a lot of whole foods.

It seems logical that regular consumption of avocados and olives is going to be better for you than regular consumption of chips and ice cream (if the amount of total fat is equated).

But is this because of the type of fat you’re consuming, or because you’re not consuming copious amounts of highly processed foods which also contain sugar (which is linked to heart disease – and which you are also more likely to overeat, contributing to weight gain)?

Being overweight increases your CVD risk

One thing that IS strongly linked to heart disease is obesity.

Whilst consumption of saturated fat hasn’t been proven to cause build-up of fatty material in arteries, there is strong evidence that being overweight and obese does.

This is the case even if you have a healthy lifestyle with many health seeking behaviours and “healthy foods”. Being overweight increases your risk of heart attacks by up to 28%.

It’s also been found that overweight individuals tend to have a higher intake of saturated fat.

This study found that a higher intake of saturated fat (>15.5% of calories) was strongly linked with a BMI of over 25 (overweight).

Correlation is not causation

Overweight and obesity is caused by consumption of more energy than you need over a prolonged period of time. As fat in all forms is the most calorie dense macronutrient, it explains why high intakes of saturated fat tend to be correlated with obesity. Obesity has been proven to increase risk of cardiovascular diseases. The evidence for saturated fat isn’t clear.

Saturated fat is also found in a lot of processed foods, fast food and junk foods, all of which are easy to overeat. Regularly consuming a lot of these foods is likely going to lead to obesity. This isn’t the fault of saturated fat itself – it’s caused by eating too many calories.

There was an interesting experiment done by Dr. Mark Haub, a nutrition scientist, where he lost 27 lbs whilst eating junk foods but controlling his calorie intake.

That’s interesting, and it proves that calories, not food quality, drive weight loss and weight gain. What’s more interesting is that his health markers also dramatically improved, despite living on a junk food diet!

His BMI went from 28.8 (overweight) to 24.9 (normal). LDL (bad) cholesterol was reduced by 20% and HDL (good) increased by 20%. His triglycerides dropped by 39%.

For all intents and purposes, he was healthier after eating a junk food diet for 2 months! (he also took a multivitamin and a protein shake each day – for micronutrients and to maintain muscle mass).

If this had been a controlled trial, with thousands of participants, you could deduce that eating junk food is good for your health. Obviously that’s not the case. Losing excess fat is good for your health. We have to be careful about jumping to similar conclusions about saturated fat. A high saturated fat intake correlates with being overweight or obese. That seems to be the real danger for CVD risk.

It seems logical, and a lot of official guidance and scientific evidence agrees, that the number one thing you can do to decrease your risk of cardiovascular diseases is to achieve a healthy bodyweight.

You could do this by reducing ANY type of food from your intake whilst increasing your physical activity (as many people do by fitting their favourite foods into their macros and losing fat).

Reducing calories from fat

If you have a high intake of dietary fat, reducing this may be an effective way to lose weight – as fatty foods are more calorically dense than other macronutrients. But you could have equally good results by reducing carbohydrates from your diet.

Monounsaturated fats appear to have a health benefit, so it would be wise not to limit these too much.

It should be mentioned that fat is an ESSENTIAL part of a healthy diet.

Many vitamins are fat-soluble, meaning you need fat in your diet in order to absorb them.

Excessively limiting your fat intake could lead to nutrient deficiencies as you would be unable to get these vitamins.

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