Is Saturated Fat Bad For Your Heart?

cardiology Mar 05, 2024
Is Saturated Fat Bad For Your Heart?

What Are Saturated Fats?

Saturated fats are solid at room temperature; butter, bacon, cheese, lard, margarine, tallow, ghee, coconut oil, chicken skin, fat on steak, sausage, cocoa butter, and suet. But they can also exist in a more liquid form. Some liquid oils have a bit more saturated fat, like palm oil. Milk and dairy are another exception. It looks liquid at room temperature, but it is a lipid emulsion (many solid fat particles floating around in a liquid).

 

Why Saturated Fats Matter?

If you want to live longer and optimize your health, you must begin with saturated fat. Why? Because of all the possible lifestyle modifications you could implement, reducing saturated fat makes the single biggest difference.

Saturated fats are defined as fatty acids that have no double bonds. They can be totally synthesized by the human body and thus their concentrations do not depend on diet. Let me say that again, you do not need to consume saturated fat. Your body can make it!

I am spending a lot of time on saturated fat because it is also a large area of contention. Many people will argue online about the role, or lack thereof, of saturated fat in heart disease.
These “Medfluencers” want people to believe that eating tons of saturated fat is harmless when it isn’t. They have books and supplements to sell. Saturated fat would cut into their sales.
In the medical community, however, saturated fat is not an area of contention. There are no nutritionists, or physicians with nutritional knowledge, that would suggest that eating excessive amounts of saturated fat is harmless and should be encouraged.

One of the first, and most effective ways to lower apoB, LDL-P and they cholesterol they carry, is by reducing saturated fat intake. Without question, this reduces apoB-cholesterol (non-HDL-C). Below are two charts that show a significant reduction in cardiovascular events, mortality, and morbidity with reduced saturated fat intake.

 

If you look at the above chart, you will see that as saturated fat intake increases per kcal of food per day, you have increased death rates per 100,000 persons, in this case males.
In other words, as saturated fat increases as a percentage of total calories, more people die.
Notice France is in red, more on the “French Paradox” later. But the same pattern exists. The more saturated fat, the higher the death rates, even when you include France.


The above chart tells a similar story. As saturated fat increases as a percentage of total calories, you have more heart related deaths.
This data comes from the 7 countries study. This study has received a lot of criticism over the past few years, but anyone who understands science and data knows it was very well done. These countries were not cherry picked; they are the ones that opted into the study, and they had reliable data. Other countries did not have reliable “cause of death” data.
https://www.nature.com/articles/s41430-018-0183-1 

Many people want to criticize Ancel Keys and the 7 countries study, but these are usually cholesterol disputers and conspiracy theorists. In the scientific community, we understand data and how to evaluate data. Many articles from various societies have had to publish editorials and reports on why this was well done because the public has grown quite skeptical.
Here is one such article from the European Heart Journal.
https://academic.oup.com/eurheartj/article/38/42/3119/4600167 

From the above:
“The contention that Keys had access to data from 22 countries and chose to use only seven for the SCS (seven countries study), reported as fact on the Wikipedia entry for the SCS at one point, likely stems from misinterpretation of a graph from Keys’ 1953 paper ‘Atherosclerosis: A Problem in Newer Public Health’. The paper, a 19-page review of available experimental and observational evidence, in which Keys hypothesized that rates of heart disease were linked with proportion of daily calories from total fat, was not a product of the SCS.”

I highly recommend that you read that study and the conclusions. No countries were excluded because they didn’t fit Ancel Keys forgone conclusion. They excluded countries that did not have enough data on mortality or food consumption.


Is The French Paradox Real?

What about France? Conspiracy theorists always ask why Ancel Keys did not include France in the 7 countries studies?
The 7 countries study excluded countries that did not have accurate food consumption data and mortality data. Further, they had to exclude data from the time when World War II ravaged most of the world and people’s dietary patterns were interrupted.

From the same paper above:
“Seven Countries Study critics have alleged that France was excluded because Keys and the SCS researchers were aware of the ‘French Paradox.’ However, as with the 22-countries argument, this is anachronistic. Reliable data, particularly on diagnoses and cause-of-death statistics were notoriously poor during the decades prior to the SCS, leading the SCS researchers to design their own classification system for coronary heart disease (CHD) and specific follow-up protocols for confirming cause of death. Reliable data allowing Keys and the team to pick cohorts based on outcomes did not exist.

France falls into this category, since available evidence at the time of the SCS did not provide estimates for fat intake from animal or plant sources, which would have been proxies for saturated and unsaturated fat. Further, as reported by Yerushalmy and Hilleboe in 1957, available data from the Food and Drug Organisation of the United Nations (FAO) statistics suggested dietary fat intake in France was below 30% of calories, qualifying as a relatively low-fat dietary pattern. Thus, there was no evidence of a ‘French Paradox’, an idea not first mentioned in academic literature until 1981, over 20 years after the start of the SCS.

France was invited to join the SCS. A representative scientist from France participated in the 1957 SCS ‘dress rehearsal’, in Nicoterra, Italy where researchers met to standardize protocols before the start of the formal SCS, though France ultimately did not provide cohorts for the SCS.”
It makes no sense to continue to blame and discuss Ancel Keys 1958 study. Why? Because that was the 1950s. We now have 70 more years of data and evidence. We don’t need to worry about one single study from the 1950s.

The Brian Ference article referenced earlier looked at every single study that has ever been done on LDL cholesterol with 20 million-person years of follow-up. Same result.
Many more modern studies have been published showing that reducing saturated fat intake reduces all-cause mortality. For example…
Reducing saturated fat intake reduces All-Cause Mortality:
https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2530902 

From the article:
“Findings In this cohort study that included 126,233 participants followed up for as long as 32 years, higher intakes of saturated fat and trans-fat were associated with increased mortality, whereas higher intakes of polyunsaturated (PUFA) and monounsaturated (MUFA) fatty acids were associated with lower mortality. Replacing 5% of energy from saturated fats with equivalent energy from PUFA and MUFA was associated with reductions in total mortality of 27% and 13%, respectively.”

Meaning These findings support current dietary recommendations to replace saturated fat and trans-fat with unsaturated fat.
In another very well-done study, they examined what happens when you consume saturated fat below or above 10% of total calories.
Reducing saturated fat reduces all-cause mortality (free pdf):
https://www.who.int/publications/i/item/9789240061668 

From the Article:
“We identified 32 publications providing 34 data sets of SFA intakes and all-cause mortality. Data were available on 256,508 deaths in 1,509,268 people. Primary analyses relating to all-cause mortality are shown in Table 1, and replacement analyses of self-reported dietary intakes of SFA (saturated fat) and all-cause mortality in Fig. 2. Additional analyses are shown in Annex 3.

Higher reported intakes of SFA were associated with increased risk of premature mortality when compared with lower intakes, and when comparing dietary intakes above and below 10%TE (10% of total energy intake, calories). Fewer data were available regarding the source of SFA and tissue measurements, and there was no evidence of a dose–response effect. Reductions in risk of all-cause mortality were observed in analyses where dietary SFA was replaced by PUFA, MUFA (especially plant MUFA) or carbohydrates. Replacements of SFA with MUFA from animal sources or TFA were not associated with a change in the all-cause mortality rate.”

We have much more data on saturated fat intake reducing cardiovascular events, mortality, and quality of life. We don’t have to rely on one single study from the 1950s that the Medfluencer community is obsessed with. That’s just incompetence. Science continues to move forward. We aren’t stuck in the past.

 

How Does Saturated Fat Increase LDL Cholesterol?

Why does reducing saturated fat lower LDL-C?

As saturated fat intake increases in an individual’s diet, cholesterol synthesis will increase as well. However, the nuclear transcription factor (SREB1c) will reduce intestinal cholesterol absorption.

Article on reducing saturated fat intake increases LDL receptors:
In summary, reducing dietary saturated fat may be associated with decreased cholesterol synthesis, increased production of LDL-receptors, and reductions in apoB, LDL-P, LDL-C and, non-HDL-C. A reduction in saturated fat intake is associated with an increase in LDL-receptor abundance of magnitude similar to the decrease in serum LDL-cholesterol.
https://pubmed.ncbi.nlm.nih.gov/9101427/

A meta-analysis of 15 studies and nearly 60,000 participants demonstrating dose response to reduction in saturated fat intake. Reducing saturated fat lowered CVD event risk by 21%. Reducing saturated fat reduced serum cholesterol and LDL-C which directly correlated with reduced CVD events and mortality:
https://pubmed.ncbi.nlm.nih.gov/32428300/ 

And the revised edition of that study:
https://pubmed.ncbi.nlm.nih.gov/32827219/ 

And original publication:
https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD011737.pub2/full 

Another meta-analysis of 16 trials showed a 17% reduction in CV events when you reduce saturate fat intake.
https://pubmed.ncbi.nlm.nih.gov/32827219/ 

I’ll end with a few more trials on saturated fat for your perusal:
https://pubmed.ncbi.nlm.nih.gov/26068959/ 
https://pubmed.ncbi.nlm.nih.gov/22592684/ 
https://pubmed.ncbi.nlm.nih.gov/27224282/ 
https://journals.sagepub.com/doi/10.1177/1753944717742549 
https://pubmed.ncbi.nlm.nih.gov/24034567/ 

In the 24-year Cohort Health Professionals Follow-Up Study (HPFS) and the 22-year and 20- year cohort NHS I and II, dairy fat consumption was not associated with the risk of total CVD. Isocaloric replacement of 5% energy from dairy fat by polyunsaturated fats (PUFA) or vegetable fat was associated with 24% and 10% reductions in CHD risk, respectively.
https://pubmed.ncbi.nlm.nih.gov/27557656/ 

A study by Jakobsen and colleagues of 11 US and European cohort studies showed similar results by replacing SFA with PUFA and the risk of CHD. During a 4–10 year follow up a 5% lower energy intake from SFA with an isocaloric intake from PUFA significantly reduced coronary events by 13% and coronary deaths by 26%.
https://pubmed.ncbi.nlm.nih.gov/19211817/ 

The 10-year Multi-Ethnic Study of Atherosclerosis (MESA) demonstrated that SFA from meat had a higher risk for CVD: hazard ratio (HR) (95% confidence interval [CI]) for +5 g/day (1.26 (1.02, 1.54) and a +5% of energy from meat SFA (1.48 (0.98, 2.23).
https://pubmed.ncbi.nlm.nih.gov/22760560/ 

In the 24-year Cohort Health Professionals Follow-Up Study (HPFS) and the 22-year and 20- year cohort NHS I and II, dairy fat consumption was not associated with the risk of total CVD. Isocaloric replacement of 5% energy from dairy fat by polyunsaturated fats (PUFA) or vegetable fat was associated with 24% and 10% reductions in CHD risk, respectively.
https://pubmed.ncbi.nlm.nih.gov/27557656/ 

But there is even more compelling evidence. Let’s examine what happened in North Karelia, Finland.


How North Karelia Finland Reduced Death From Heart Disease By 84%

In a beautiful example of how dietary and lifestyle interventions work, the country of Finland was able to reduce cardiovascular mortality by 84% in North Karelia by making a few simple dietary and lifestyle changes.

The year was 1972. North Karelia is a small rural town in northern Finland. They had the highest cardiovascular mortality in the world. They had 700 deaths per 100,000 people. That was the highest in the world. The government needed to act fast and sent a task force to evaluate the situation.

The people of North Karelia were noted to have very high intakes of saturated fat and salt. Two major contributors to heart disease. They were also noted to be smokers. They were farmers and consumed a lot of lard, margarine, butter, ghee, tallow, red meat, processed meats, dairy, eggs, and cheese. They also smoked and used salt extensively to preserve their meats and food.
The government put a plan into place and did some of the following, taken straight out of the publication….

“To reduce the cardiovascular risk factor of elevated serum cholesterol levels, the North Karelia project targeted dietary fat intake. The diet recommendation was to minimize the use of saturated fat products (ie, hard butters and margarines, high-fat and whole milk, and fatty meats) and transition to the use of products with low saturated fats and vegetable oils (ie, soft butters and margarines, vegetable oils, low-fat or nonfat milk, and lean fish, poultry, and meats).

These nutritional messages were spread through community channels and activities. Between 1972 and 1977, more than 1000 newspaper articles were published on nutrition and other risk factors. Furthermore, diet was discussed in more than 150 health education meetings and more than 300 local “parties of long life,” where healthy food was cooked and served by local housewives associations to village members. Hundreds of special training seminars were organized for health care workers, the general public, and mass catering personnel responsible for workplaces, schools, hospitals, and restaurants.

After the initial 5-year period for the project, the government became more involved and developed policies that increased consumers’ health consciousness through media campaigns and led to the food industry creating low-fat products. The mobilization of community members and local resources in addition to national health policies and initiatives led to major dietary changes.

From 1972 to 2012, the use of butter on bread had dropped by approximately 80%, and the use of butter for cooking had dropped by approximately 50%. Vegetable oils, such as rapeseed oil, and soft butters and margarines became the lower-fat alternative. As a result, serum cholesterol reduced by more than 20% in both men and women in North Karelia between 1972 and 2012.

The intake of saturated fats reduced from 20% to 12% in 2007 and increased from 2007 to 2012 to 14%. Most of the decline in serum cholesterol was explained by dietary changes, with minimal contribution from statin use.”

What were the results? They were so good, they had to expand the program across all of Finland. A picture is worth 1000 words, right?

 

By 2012, you had an 84% reduction in mortality in North Karelia and 82% across all Finland when the program was expanded. They went from being number one in the world for cardiovascular death to being nearly last.

This is one of the most incredible turnarounds in the history of the world!

Additionally, they educated the public on reducing salt intake and blood pressure control as well as smoking cessation.

Here’s the kicker….
Obesity rates increased and smoking rates were reduced initially, but then stayed the same throughout most of the study. The study is still on-going, and we have data now out to 2018. The data will keep coming in.

Based on further statistical analysis, the researchers concluded that 67% of the reduction in mortality was due to reduction in serum cholesterol levels. Additionally, life expectancy increased by 10 years.
The study is a very easy read and I highly recommend everyone read it:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7444010/ 


Saturated Fat And LDL Receptors

Increasing saturated fat intake has been shown to increase cholesterol synthesis in liver cells and reduce the number of LDL receptors at the liver, thereby not allowing the liver to capture and clear LDL particles.

The newly synthesized pool of cholesterol in liver cells is sensed by "cholesterol sensors" (called nuclear transcription factors), that influence liver gene production. The gene that regulates LDL receptor synthesis is turned off, which will result in decreased clearance of plasma apoB particles (most of which are LDL particles). This results in more circulating apoB particles which can cause increases in apoB, LDL-P, LDL-C, and non-HDL-C.

Saturated fat has also been shown to make lipoproteins more retainable inside the arteries by affecting the proteoglycans. Proteoglycans in the presence of saturated fat are better at retaining lipoproteins.
It has also been found that substituting saturated fat for polyunsaturated fat confers favorable lipid profile changes and reduces ASCVD by 30% over a 4-8 year time span.
It has also been shown that for every 5% reduction in saturated fat from total energy intake, called 5 E%, and concomitantly increase in 5 E% in PUFA associates with a 25% reduction in ASCVD over the course of 24-30 years. Similarly, every 5E% replacement of saturated fat for 5E% of MUFA or whole grain carbohydrates associates with a 15 and 9% reduction in ASCVD, respectively.
Study:
https://pubmed.ncbi.nlm.nih.gov/28620111/ 

Polyunsaturated fats appear to decrease overall cholesterol synthesis and upregulate (increase) LDL receptors to help clear more LDL particles. This is the opposite effect of saturated fat.
I am not telling you that you can never eat these things ever again. I am just saying that you should try to limit your intake. My kids love steak, and we eat burgers and lunch meat. It’s not every day, and it’s not all the time. To reduced saturated fat intake, we mostly use leaner sources of protein, egg whites, chicken, turkey, and salmon. Salmon and fish is in another post.

Saturated fat has also been linked to nonalcoholic fatty liver disease (NAFLD). Calorie for calorie, saturated fat worsens NAFLD. In fact, studies have shown that when you substitute any other macronutrients for saturated fat, it actually takes less saturated fat to cause the same amount of NAFLD.

A study was done where they overfed humans excess calories. They used different macronutrient breakdowns. They tested protein, carbohydrates, fats (saturated vs unsaturated). They found that saturated fat increased fat in the liver by 55% versus an increase of only 15% due to simple carbohydrates (sugar). This was an isocaloric overfeeding study. All participants were in a calorie surplus, obviously you aren’t going to store fat if you aren’t. They did an isocaloric swap between various macronutrients. Saturated fat worsened NAFLD more than any other macronutrient.

Saturated fat more harmful to liver than sugar, unsaturated fat, and excess calories:
https://pubmed.ncbi.nlm.nih.gov/29844096/ 
https://pubmed.ncbi.nlm.nih.gov/33665203/ 
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5272176/ 
https://pubmed.ncbi.nlm.nih.gov/31369090/ 
https://pubmed.ncbi.nlm.nih.gov/24550191/ 
https://pubmed.ncbi.nlm.nih.gov/22492369/ 

Great summary article on saturated fat and ASCVD:
https://www.atherosclerosis-journal.com/article/S0021-9150(23)05354-6/fulltext 
Further reading:
https://pubmed.ncbi.nlm.nih.gov/9430388/ 
https://pubmed.ncbi.nlm.nih.gov/1438279/ 
https://pubmed.ncbi.nlm.nih.gov/9101427/ 
https://pubmed.ncbi.nlm.nih.gov/8369151/ 
https://pubmed.ncbi.nlm.nih.gov/28620111/ 


Saturated Fat: Modern Data On Heart Disease

While the data from the 1950s studies still holds true, we have 66 more years of data on saturated fat intake and mortality. We don’t have to rely on studies from the 1950s.
Medfluencers will sometimes flash up a study on screen and say it is evidence that they are correct, but when you do some digging, it turns out to be from 1934, or a mouse study, or a petri dish experiment, or a study with only 29 participants.
Study after study has shown that reducing saturated fat intake will reduce cardiovascular mortality. Without question.

Perhaps one of the best studies on saturated fat was published in 2020 in Cochrane Reviews using data from 15 studies and about 60,000 participants.
https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD011737.pub2/full 

Take a look at this chart from that study.

The chart shows that the risk of all events is on a sigmoidal curve. The chart plots saturated fat intake as a percentage of total calories vs cardiovascular events and death rates. You’ll notice that very low levels of saturated fat intake, below 8% of total calories, is a flat line and that saturated fat intake above 10% of total calories in a flat line. There appears to be an inflection point around the 9% mark where the graph shoots up.

Why does this matter?

It’s very easy to design a study that shows that decreasing saturated fat intake did not affect mortality and CV event rates by showing that reducing saturated fat intake from 23% down to 12%. You can also show that reducing saturated fat intake from 8% down to 3% also had no effect on mortality or cardiovascular event rates.
This is very important! Many critics of the saturated fat hypothesis have looked at studies that fall into the above criteria where they did not show any difference because they were on the wrong part of the sigmoidal cure.

Notice also that the change in saturated fat intake also showed a significant increase in cardiovascular mortality as was shown in the previous charts. Also, you will notice that all-cause mortality increased as well. All-cause mortality is your chance of dying from any cause, medical or not.

Many other studies have shown a log-linear relationship between saturated fat and all-cause mortality and cardiovascular mortality. This means that decreasing saturated fat intake causes a linear reduction in cardiovascular events, cardiovascular mortality, and all-cause mortality. As saturated fat goes up, so does mortality and events. As saturated fat goes down, so does mortality and events. It’s a straight line.


The relationship between saturated fat intake and all negative outcomes, is a straight line, like the graph above.
From:
https://analystprep.com/study-notes/cfa-level-2/linear-or-log-linear-model/ 

And the studies on saturated fat go on and on. It’s a very well-established relationship in scientific literature.

 

How Can You Lower Heart Disease Risk With Lifestyle Changes And Diet?

In a study titled, Association of Specific Dietary Fats With Total and Cause-Specific Mortality, the authors were able to demonstrate that reducing saturated fat intake actually reduced all-cause mortality. Showing a reduction in all-cause mortality is quite difficult, as you have learned from this book.

People who consumed the most amount of saturated fat had an 8% higher all-cause mortality. This is pretty significant.

The participants eating more monounsaturated and polyunsaturated fat had a 13% reduction in all-cause mortality. This is also quite significant.

When you looked at cause-specific mortality, the margins and benefits widened. For example, dietary intake of saturated fat was associated with a 7% higher rate of cancer. Whereas PUFA intake, especially linoleic acid, was associated with a 7% reduction in cancer rates.

Further, higher intakes of saturated fat were associated with neurodegenerative diseases.

The investigators also did a great job analyzing substitutions. What happens if you substitute saturated fat with carbohydrates? PUFAs? MUFAs? I highly recommend you read the article.
Read the article:
https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2530902 

Another study found that adhering to the Healthy Eating Index 2015 dietary pattern, reduced cardiovascular disease rates, cardiovascular mortality, and all-cause mortality. You can read the study below.
https://pubmed.ncbi.nlm.nih.gov/31529069/ 

Another large meta-analysis that had over 3 million person years of follow up, found that reducing saturated fat intake reduced mortality rates up to 27%. They followed people for 32 years.
https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2530902 

Reducing saturated fat intake has also been shown to reduce all-cause mortality especially if replacing saturated fat with polyunsaturated or monounsaturated fats.
https://www.who.int/publications/i/item/9789240061668 

 

Why Is Saturated Fat Bad For You?

Saturated fat intake increases cholesterol synthesis and reduces the number of LDL receptors. LDL receptors are used to clear LDL particles from circulation.
https://pubmed.ncbi.nlm.nih.gov/9101427/ 

But does everyone who consumes saturated fat have an increase in LDL cholesterol? The short answer is yes. But then why do some studies show that not all participants had an increase? Sometimes there is statistical error and regression to the mean. For example, someone may have an elevated LDL-C to begin with and as they begin a study that adds extra saturated fat to their diet, they just regress to the mean. Their LDL-C would have decreased regardless. A few papers have looked at these phenomena as well as predictive models to try and figure out how people will react to increased saturated fat intake.

Studies:
https://www.atherosclerosis-journal.com/article/S0021-9150(21)00145-3/fulltext 
https://pubmed.ncbi.nlm.nih.gov/11592728/ 

A meta-regression analysis by Mensink found that isocaloric substitutions of carbohydrates for palmitic acid (the main fatty acid found in meats) raised both LDL-C and HDL-C substantially.
This same study found that isocaloric substitutions of carbohydrates for myristic acid (the main fatty acid found in butter) had the greatest effect on raising LDL-C levels. It was closely followed by palmitic acid (butter, meat, milk, and cheese), then lauric acid (coconut oil).

Study:
https://pubmed.ncbi.nlm.nih.gov/1386252/ 


What About PURE Study?

A recent study looked at the eating patterns of 18 countries based on memory-based dietary assessments. This is different than food frequency questionnaires that are verified by calibration to food tracking logs. The writers of the study made implausible and scientifically impossible claims. One of their conclusions was that total fat intake (and specific fat intake) had no effect on cardiovascular outcomes. They attempted to conclude that saturated fat did not adversely affect cardiovascular outcomes.

Harvard and multiple other organizations have published swathing critiques of the study methods and conclusions. Many parts of the study were not reliable. For example, the authors reported that Chinese participants had an average fat intake of 17.7% of total daily caloric intake whereas most other studies report that Chinese usually get approximately 30% of their calories from fat. This calls into question the reliability of their data.

The PURE trial has also been criticized because it was mostly done in very poor nations with very little healthcare spending power. Most prior studies have demonstrated better outcomes with increasing spend on healthcare. It’s very hard to generalize this data to wealthier nations. It’s also very difficult to get accurate medical data from poorer countries.

They also criticize the study because in Europe, the increase in saturated fat intake likely came from milk and cheese, whereas in the United States it is mostly from red meat intake. They did not control for such confounders.

Harvard and other criticisms:
https://www.hsph.harvard.edu/nutritionsource/2017/09/08/pure-study-makes-headlines-but-the-conclusions-are-misleading/ 
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7270973/ 

 

Fat Quality and ASCVD Risk

Because of all of the conflicting reports or groups trying to muddy the waters regarding fat intake and heart disease, a review article was published on December 23, 2023 in a journal called Atherosclerosis to help summarize all of the data and studies on dietary fat. It was titled, “Dietary fat quality, plasma atherogenic lipoproteins, and atherosclerotic cardiovascular disease: An overview of the rationale for the dietary recommendations for fat intake”.

They wanted to review all available evidence and literature on dietary fat intake and fat quality with regards to ASCVD. They did a fantastic job, and the references alone make it worth taking a look.
One of their conclusions was that dietary fat quality causally affects the risk of ASCVD via modulation of the plasma concentration of apoB containing lipoproteins. This means that fat quality (certain fats) actually cause ASCVD by increasing apoB in plasma and increasing apoB retention in arteries.

They also stated that the reason there may be confusion in dietary guidelines is because people may not understand the process of developing dietary guidelines and they hoped to shed some light on that as well. They looked at controlled feeding trials, where participants had 100% adherence rates because their entire diet was controlled by the researchers.

They concluded that the ingestion of trans fats, saturated fats, and cholesterol increased apoB concentration in plasma. They also found that PUFAs lower apoB in plasma. They also concluded that MUFAs and long chain PUFAs (EPA and DHA) are close to neutral on apoB concentrations.

Read the Review:
https://www.atherosclerosis-journal.com/article/S0021-9150(23)05354-6/fulltext 


Saturated Fat Worsens Insulin Resistance

Perhaps the most well done study on this topic was just published on October 19, 2023 in the American Journal of Clinical Nutrition by the Harvard research team looking at 216,695 participants in the Nurses’ Health Study (NHS 1), NHS 2, and Health Professionals Follow-up Study (HPFS). This was a prospective cohort study with over 5.4 million person years of follow-up. This was a collection of health professionals. You can argue that they are well educated and more health conscious than the general public.

They looked at the relationship between red meat intake and cases of T2D (type 2 diabetes). They examined the intake of total, processed, and unprocessed red meat intake. They found a positive and linear correlation between red meat intake (total, processed, and unprocessed) and higher risks of T2D.

Comparing the highest to the lowest quintiles of intake, you had a 62% higher chance of having T2D in those that consumed the most total read meat, 51% increase for processed red meat, and 40% for unprocessed red meat. This is a quintiles comparison. The consumption of red meat is divided up into 5 parts. The top 20%, the next 20% and so on until you have 5 different levels of red meat intake from the top 20% to the bottom 20%.

The skeptics may argue that this was an epidemiological study based on food frequency questionnaires and that those are not that reliable? Wrong. This was a prospective cohort study. It was not a retrospective epidemiological study based on food recall.

Also, food frequency questionnaires have been validated by research and data. They have been validated over time. But wait, there’s more.

They also had participants weigh every morsel of food they ate and record it in grams for 7 days. The food frequency questionnaires were done every 2-4 years and calibrated against their food logs. They did this for 30 years.

When they re-analyzed the data against the calibrated food logs, the association between total, processed, and unprocessed red meat intake was actually stronger.

They also found that for every 1 serving of total red meat that was substituted for nuts or legumes, you had a 30% reduction in T2D, 41% reduction for processed red meat, and 29% for unprocessed.
What about healthy user bias? Aren’t people that eat red meat generally unhealthy? Don’t they smoke more? Eat more processed foods? Eat mostly hotdogs, cheeseburgers, chips, and mayo? Aren’t they more likely to be sedentary? The researchers corrected for all of that. They corrected for every confounder and covariate.

They also looked at the overall dietary eating patterns, so you were comparing someone with high red meat intake that eats lots of processed sugar to someone with high red meat intake that eats no processed sugar. They did this for disease states, race, ethnicity, socioeconomic factors, income levels, geographic regions, smoking status, BMI, gender, age, and many other factors you wouldn’t normally consider.

This was one of the most well done red meat studies that has validated prior data and research suggesting red meat intake was associated with higher incidence of T2D.

The graphics from that study are quite impressive and located in the Red Meat chapter of this book.
Read the study:
https://ajcn.nutrition.org/article/S0002-9165(23)66119-2/fulltext 

This confirms data from many other studies that have shown that red meat intake is associated with more T2D. Multiple previous studies have shown that saturated fat intake worsens insulin sensitivity, insulin resistance, and causes fatty liver disease. When you substitute saturated fat for other healthier fats, MUFAs and PUFAs, you improve insulin sensitivity and reduce fatty liver disease. This has been demonstrated in the KANWU study. It didn’t matter if you looked at total red meat, processed red meat, or unprocessed red meat intake. Increased intake correlated with higher incidence of diabetes.

Studies On Saturated Fat Worsening Insulin Sensitivity and Resistance:

https://pubmed.ncbi.nlm.nih.gov/15297079/ 
https://pubmed.ncbi.nlm.nih.gov/11317662/ 
https://pubmed.ncbi.nlm.nih.gov/27578132/ 
https://pubmed.ncbi.nlm.nih.gov/12079860/ 
https://pubmed.ncbi.nlm.nih.gov/27733250/ 

Reducing saturated fat improved insulin sensitivity:
https://pubmed.ncbi.nlm.nih.gov/30072407/ 
https://pubmed.ncbi.nlm.nih.gov/15613251/ 

Studies on saturated fat worsening Fatty Liver:
https://pubmed.ncbi.nlm.nih.gov/31369090/ 
https://pubmed.ncbi.nlm.nih.gov/29936596/ 

Food frequency questionnaires have been validated:
https://pubmed.ncbi.nlm.nih.gov/28024800/ 
https://pubmed.ncbi.nlm.nih.gov/29202890/ 
https://pubmed.ncbi.nlm.nih.gov/31501691/  
https://pubmed.ncbi.nlm.nih.gov/37242272/ 

Reducing Saturated Fat May Cause Plaque Regression:

https://pubmed.ncbi.nlm.nih.gov/1347091/ 

Foods with the highest content of saturated fat from Harvard University:
https://puntocritico.com/ausajpuntocritico/documentos/The_Nutrition_Source.pdf 

Please remember that gaining weight from over consumption of any calories can lead to fatty liver disease as well. But calorie for calorie, saturated fat worsened fatty liver disease more than any other macronutrient. More on weight loss and weight gain in my Actual Weighty Loss Book: https://DrAlo.net/book

Minnesota, Sydney, and Rose Corn Oil

Sometimes these Medfluencers will point to studies like the Minnesota Coronary Experiment, the Sydney Diet Heart Study, or the Rose Corn Oil Study as evidence that eating saturated fat, like butter is healthier than vegetable or “seed oils”. Unfortunately, these studies were poorly done and did not actually yield useful results. They should have looked at the very well done LA Veterans Study.

Minnesota Coronary Experiment

The Minnesota Coronary Experiment had a great design. They wanted to look at 9570 participants who were institutionalized in a mental hospital who were provided food. They wanted to test what would happen if butter (saturated) was substituted for vegetable oil (non-saturated). The plan was to follow them for 5+ years, since they were institutionalized, it should be easy right?

Wrong.

The laws changed and 83% of the original 9570 had to leave. The remaining 2300 or so also had high dropout rates and they ended up with only 1100 participants. The original plan of 5 years also did not work. It only lasted 1 year. They had wanted to substitute saturated fat for linoleic acid, but they ended up giving it as a soft margarine, which is a trans-fat. Trans fats are extremely inflammatory and atherogenic. This obviously destroyed the outcomes, as the “vegetable oil” group received a very atherogenic trans-fat.

Could it get any worse?

Yes. The original authors realized this was a bad study and discarded it. It was severely underpowered, the placebo was atherogenic, nearly 90% of participants dropped out of the study.

Some scientists wanted to go back and look at the data and recovered the old notebooks in a “dusty basement”. They tried to publish the data later. But it gets worse.

Patients with higher BMI, were smokers, and were diabetic actually did better. This invalidates the data as being reliable. There were also many missing participants in the control group, lost files, unaccounted for deaths, and it was overall just poor-quality data.

It was also in 1958. We have 60-70 more years of really good data. We don’t need to go digging in an old basement for a worthless study.

Read the study:
https://pubmed.ncbi.nlm.nih.gov/27071971/ 


Sydney Diet Heart Study

This was a much smaller group of only 400 participants, 200 in each arm. They also wanted to substitute saturated fat for linoleic acid. This time they used safflower oil and soft margarine. Again, it was a trans-fat. Trans fats are very atherogenic. We did not know that back then, but we know that now. The authors argued later that they also knew that.

The linoleic acid levels were minimal in the study and the study authors also discarded it. Yet Ramsden and his group went back to the “dusty basement” in Sydney Australia to find the old notebooks and try to reclaim this data.

This was also a study from 1966. Even the authors realized it was not helpful. The placebo was an atherogenic trans-fat, and it was only 200 participants in each arm. Again, we have much more reliable data.

Read the study:
https://pubmed.ncbi.nlm.nih.gov/23386268/ 


Rose Corn Oil

The idea was to test various levels of unsaturated oils against each other. This also from 1965. There were 28 participants in the corn oil group, 26 in the olive oil group, and 26 in the control group. Yes, that’s it. After 2 years, 2, 1, 0 deaths occurred in each group due to heart attacks, respectively. There were also very high dropout rates. By 18 months, there were only 13 participants left in each of the oil groups. Most dropped out due to distaste and the amount of oil prescribed was not being consumed because of upset stomach.


I probably don’t need to explain why this is not a well done study nor should be used for evidence of anything. Having a very low number of participants, very low number of event rates, high dropout rates, and the participants not even consuming the oil.

This study really didn’t add anything to our current level of understanding.

Study:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2166702/ 

 
LA Veterans Trial

This was a brilliantly designed study. Veterans in Los Angeles were given oils high in saturated fat, versus oils lower in saturated fats (corn, soy, cottonseed, safflower, soybean). They were followed for 8 years. Tissue biopsies from adipose cells were taken to see if the participant were actually consuming the saturated fat or seed oils.


The design was that they were either given an institutional diet high in animal saturated fat versus the same diet with 2/3rds of the fat replaced by aforementioned seed oils (unsaturated fats). Food was provided so it remained blinded.

The results were pretty clear. There were fewer cardiovascular events and deaths in the group that had 2/3rds of their fat mot be saturated fat.

Read the study:
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(68)91531-6/fulltext 

 

This blog post is adapted from my Cholesterol Book. Click here to sign up to be the first to know when it will be released and to be a part of the launch teach and get exclusive access to additional charts, graphics, audiobooks, and bonus chapters! https://dralo.net/cholesterol 

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