In our YouTube Live event on July 1, 2020, we discussed both Nina Teicholz’s book “The Big Fat Surprise” and an article recently published in JACC (Journal of the American College of Cardiology). It was Dave Murphy who got me started on this when he brought this JACC article to my attention the week before.
The topic: saturated fat.
The title of the JACC article is “Saturated Fats and Health: A Reassessment and Proposal for Food-Based Recommendations” (Astrup, 2020).
This article covered not just case studies or reviews. There is even a meta-analysis of randomized critical trials. You can’t get a more powerful write-up than a combination of trials and meta-analyses of such trials.
Pardon the pun, but there’s a fat chance that debate is over. Be warned, though—the details around saturated fats can be confusing.
The Confusing Science of Saturated Fats
Because food is essential, many people started getting interested in food epidemiology—until they looked deeper.
I get nervous when I discuss food epidemiology. It’s a hazardous area of science. It reminds me of the quote about politics and sausage from Otto von Bismarck (or others would say came from Mark Twain):
Those that like law and sausage should watch neither one of them being made.
The saga of the epidemiology of saturated fats is no exception. It’s a story of failed guesses and frustration associated with saturated fats in our diet. But sometimes, the problem around saturated fats comes from looking for simplified answers when, in fact, the issue is complicated.
To minimize confusion in describing whether saturated fats are healthy, let’s start by asking some critical questions:
- What are saturated fats? How are they different from polyunsaturated and monounsaturated fats?
- Why is the topic of saturated fats so complicated?
- What did the science say before this JACC article?
- What about omega-3 fats & oils?
- What about processed meats and saturated fats?
What are Saturated Fats?
Before we describe saturated fats, let’s define first the terms “triglyceride,” “fatty acid,” “saturated,” and “unsaturated.”
Triglycerides and fatty acids
Fats are also called triglycerides. Triglycerides consist of 3 fatty acid molecules held together by a glycerine or glycerol molecule.
Triglyceride structure
Bermoda.hossein.m / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)
Fatty acids that make up fats are either saturated or unsaturated.
- Saturated fatty acids (SFAs) have no double bonds in their molecular chain.
- Monounsaturated fatty acids (MUFAs) have one double bond.
- Polyunsaturated fatty acids (PUFAs) have multiple double bonds.
Here is a good example to differentiate PUFAs, MUFAs, and SFAs.
Stearic acid, oleic acid, and linoleic acid are all fatty acids with 18 carbons. There are no double bonds in stearic acid, so it’s saturated. Oleic acid is monounsaturated because it has precisely one double bond. Meanwhile, linoleic acid is polyunsaturated as it has two double bonds.
Stearic acid (SFA) vs. oleic acid (MUFA) vs. linoleic acid (PUFA). Image from “How Lipids Work,” section 5.2 from the book “An Introduction to Nutrition” (v. 1.0) by Zimmerman & Snow.
Saturated vs. Unsaturated Fats
Fats are saturated or unsaturated, depending on the type of fatty acids they contain.
“Saturated” means that the fat has no double bonds between the carbon atoms in the fatty acid components. This means the fats only contain SFAs. Saturated fats are predominantly found in animal foods, butter, and lard.
Conversely, unsaturated fat has one or more double bonds in the molecular chain of its fatty acids. They can be polyunsaturated fats (made up of PUFAs) or monounsaturated fats (made up of MUFAs).
Good sources for polyunsaturated fats are fish, shellfish, and oils from flaxseed, soybean, walnut, rapeseed, corn, sesame, and sunflower. On the other hand, monounsaturated fats can be found in olive oil, canola oil, avocados, peanuts, and almond.
Relative amounts of types of fat acids in selected foods. (Image from Wikimedia Commons.) The composition of fat by fat acid type of various foods is shown. The data have been taken from Gebhardt, Susan E.; Robin G. Thomas (2002). “Nutritive Value of Foods” (PDF). Home and Garden Bulletin. Retrieved on 2006-07-27., which is a publication of the United States Department of Agriculture. Pie charts were made in MATLAB.
Saturated Fats and LDL Cholesterol
Dietary saturated fats increase blood levels of LDL cholesterol—at least that’s what many believe. And many believe LDL cholesterol leads to CV risk.
However, many people don’t think that way nowadays. Even those who still believe in the LDL theory are mainly concerned with a certain subgroup—the small, dense LDL subgroup.
Like the writers of the JACC article. Astrup and associate said saturated fats increase the larger, healthier LDL particles, not the atherogenic (plaque-causing) small and dense LDL particles (Astrup, 2020).
Although SFAs increase low-density lipoprotein (LDL) cholesterol, in most individuals, this is not due to increasing levels of small, dense LDL particles, but rather larger LDL particles, which are much less strongly related to CVD risk.
What Studies Before the 2020 JACC Article Say
At least 2 old studies showed a direct correlation between saturated fats and CV disease.
In the New England Journal of Medicine (one of the top 3 journals globally for medicine), Hu and associates (1997) found that “replacing saturated… fats… is more effective in preventing coronary heart disease… than reducing overall fat intake.”
In the American Journal of Epidemiology, McGee and associates (1984) stated, “Men who developed coronary heart disease also had a higher mean intake of… saturated fatty acids… than men who remained free of coronary heart disease.”
However, newer studies challenged the earlier theory about saturated fats and CV disease:
In Annals of Internal Medicine, Chowdhury and associates (2014) stated, “High levels of saturated fat intake had no effect on coronary disease… Monounsaturated (nine studies), alpha-linoleic (seven studies) and omega-6 (six studies) fatty acids were found to have no association with disease.”
In the American Journal of Clinical Nutrition, Siri-Tarino and associates (2010) studied the experience of 347,747 people. Researchers followed the subjects from 5 to 23 years. They found “no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD or CVD.”
In BMJ, de Souza and associates (2015) found that, “Saturated fats are not associated with all cause mortality, CVD, CHD, ischemic stroke, or type 2 diabetes…”
In BMJ Open, Schwingshackl and Hoffman (2014) also echoed the 3 studies above. “No significant risk reduction could be observed considering all-cause mortality… and cardiovascular mortality…, combined cardiovascular events… and myocardial infarction… comparing modified fat diets versus control diets.”
These new findings didn’t surprise some people (including “the Big Fat Surprise” author Nina Teicholz). Even before the studies debunking “saturated fats are bad” appeared, there were already signals that the issue might not be so simple.
But again, the science is confusing and conflicting.
What Makes Saturated Fats So Complicated
1. Saturated fat is biologically complex and not a single chemical entity.
SFAs that make saturated fats differ in the number of carbon atoms. Such differences bring forth different physical and chemical characteristics. The differences can also lead to varying health effects, or so the theory goes.
Marion Nestle, a professor of Nutrition Food Studies and Public Health at NYU, laid this fact nicely in an article titled “The fuss over saturated fat.” In an email to Medscape in 2011, Nestle stated:
All food fats, without exception, are mixtures of the three kinds of fatty acids, so it is not surprising that the effects of foods and diets differ. (Ward, 2015)
There were further complications, though, with SFAs’ effect on saturated fats. For example, stearic acid is an SFA, but researchers gave it a pass since stearic acid seemed to raise LDL cholesterol less than that of PUFAs (Hunter, 2010).
In an interview with Medscape, Dariush Mozzaffarian, Dean of the Friedman School of Nutrition Science and Policy at Tufts in Boston, stated:
The US view on saturated fats focuses on the effects on LDL-C (LDL cholesterol). That’s why they have dietary guidelines to lower our saturated fat intake. That’s why stearic acid is given a free pass. They (saturated fats) don’t affect just LDL cholesterol. They affect particle size, and they affect HDL cholesterol and triglycerides. It’s not clear which ones are better or worse if you begin to look at all of those different effects. (Ward 2015)
2. Source of saturated fat matters.
What you replace saturated fat with matters.
Professor Nestle acknowledged this information. She thinks that saturated fats should be replaced, but not with carbohydrates. (So prediabetics and diabetics, beware.) She recommends that SFAs should be replaced with PUFAs (Nestle, 2011).
At least one study appears to support Nestle’s claim. A pooled analysis of 11 prospective studies of 340,000+ healthy adults older than 35 has shown that consuming PUFAs instead of SFAs lowers coronary artery disease risk (Jakobsen, 2011).
The Mediterranean Diet
The Mediterranean diet is touted to be one of the healthiest. It’s based on vegetables, fruits, herbs, nuts, beans, and whole grains.
Now, to compare the risk of other diets to the Mediterranean diet, the PREDIMED (Prevención con Dieta Mediterránea) was conducted. Calories were unrestricted and came in between 37 and 41% fat. Appel and Van Horn (2013) pointed out that “saturated-fat intake was low and similar in (all) groups, approximately 9% of energy intake.”
The result: 7,500 high-risk study participants experienced a 30% decrease in CV events. Many interpreted the PREDIMED trial as a strong indictment of saturated fat.
Is that true?
Not exactly. PREDIMED was designed not as a comparison between high and low saturated fat diets. Instead, the trial turned out to be a comparison of diets supplemented and not supplemented with olive and nut oils.
What makes olive oil and nuts somewhat special? They are both good sources of MUFAs. But there’s another thing—they are also abundant in omega-3s.
Omega-3
Omega-3 fatty acids are known to help with inflammation and decrease CV risk. They are not saturated. They are PUFAs, with a specific double bond between the 3rd and the 4th carbon atoms from the end of the carbon atom chain.
Two of the main omega-3s are EPA (eicosapentaenoic acid)…
…and DHA (docosahexaenoic acid).
Aside from olive oil and nuts, omega-3s are also present in vegetables and oily fish. In fact, you may have been familiar with EPA and DHA, as you would see them listed as components of OTC fish oil supplements.
The MESA Study
MESA (Multi-Ethnic Study of Atherosclerosis) is an extensive database study, even rivaling the Framingham study in its influence and scope. It’s the basis of many sub-studies, though these sub-studies show conflicting results.
For example, components of MESA indicated that for every 5 grams per day of saturated fats in the diet, CV risk declined by 16%. On the other hand, 5 grams per day of saturated fats from meats raised the CV risk by 23% (de Oliveira Otto, 2012).
The confusion lingers.
Processed Meats vs. Saturated Fats
What about processed meats and saturated fats?
The EPIC trial (European Prospective Investigation into Cancer and Nutrition) followed almost half a million middle-aged adults from 10 countries. The authors linked processed meats, but not red meat, to CV risk (Rohrmann, 2013).
That leads to more confusion, and confusion leads to frustration. Many are now beginning to say (and I tend to agree) to stop emphasizing macronutrients (e.g., fats, carbs, and protein), and instead highlight real foods. I think there’s a reality to that.
3. It’s not just about diet.
Diet is, by far, the biggest determinant of health.
But it’s not just diet. There’s also lifestyle. “Diet is one factor that affects heart disease among others: lifestyle, physical activity, cigarette smoking, genetics, and others,” Nestle noted (Ward, 2015).
Brisk walking exercise, high-intensity intervals, stress release, proper sleep—all of those are also very important. For instance, in one small study, a single aerobic exercise session appeared to counteract the postprandial endothelial dysfunction induced by some diets (Johnson, 2011).
Nina Teicholz’s “The Big Fat Surprise”
“The Big Fat Surprise: Why Butter, Meat, and Cheese Belong in a Healthy Diet” is the title of a book written by Nina Teicholz (Teicholz, 2014). It contains 497 pages, discussing the science and history of saturated fats in human diets. It focuses on the politics and the money that went into turning beliefs into policy.
After the book came out in 2014, it became a big deal. It was one of the first journalistic events questioning the assumption that saturated fat is causing CV risk.
The book was also a New York Times bestseller. It won many book awards from The Economist, Wall Street Journal, Kirkus Reviews, and Forbes.
So many reviews described how phenomenal Teicholz’s book is. But perhaps my favorite is this one from the American Journal of Clinical Nutrition. The quote describes the arrogance that a lot of the professionals have.
This book should be read by every nutritional science professional as a guide to risks of hubris, and to the consequences of basing public policy on belief as opposed to evidence of positive beneficial effects. All scientists should read this as an example of how limited science can become federal policy.
If you read Teicholz’s book, you’ll get a clear understanding that people reported and put “facts and science” out there that just were not facts or science. If that’s the first time you’ve ever heard that, where have you been?
So, Are Saturated Fats Good or Bad?
The abstract of the JACC article gives a pretty good view of whether saturated fats are indeed good or bad.
The recommendation to limit dietary saturated fatty acid (SFA) intake has persisted despite mounting evidence to the contrary. (Astrup, 2020)
30 years ago, the science around saturated fats was not that clear. The science is improving, though, and public policy is following it.
Most recent meta-analyses of randomized trials and observational studies found no beneficial effects of reducing SFA intake on cardiovascular disease (CVD) and total mortality… (Astrup, 2020)
This quote is worth repeating.
Although SFAs increase low-density lipoprotein (LDL) cholesterol, in most individuals, this is not due to increasing levels of small, dense LDL particles, but rather larger LDL particles, which are much less strongly related to CVD risk. (Astrup, 2020)
The JACC article concludes:
Whole-fat dairy, unprocessed meat, and dark chocolate are SFA-rich foods with a complex matrix that are not associated with increased risk of CVD. (Astrup, 2020)
The final quote:
The totality of available evidence does not support further limiting of the intake of such foods. (Astrup, 2020)
What are the authorities saying in terms of public policy?
If you live in the UK, the major authority is the NHS (National Health Service). If you go to the NHS website, the authorities there will still tell you to eat less saturated fat.
How about the American Heart Association in the US? Same. Limit saturated fat.
Decades of sound science has proven it can raise your “bad” cholesterol and put you at higher risk for heart disease.
As you see, there’s a significant disconnect in terms of science. You have the highest level of science from JACC, yet the American Heart Association still says saturated fats are bad.
How Should We React To The Confusion?
There is nothing more critical to our health than our food habits. What are we to do with this apparent confusion?
I find this topic similar to many patients’ fear when they find out they have both ApoE4 and prediabetes. I even have patients with both issues as well as kidney disease.
The standard ApoE4 dietary recommendations are low fat. For kidney disease, the nutritional recommendations are to cut protein. And of course, prediabetes patients should watch their carbs.
With all 3 macronutrient sources appearing to be unsafe, how do patients choose a healthy diet?
After wading through the confusing pieces of information, these patients develop an assurance that they can eat well and stay safe. Experience teaches them that the real dangers are in processed food and dietary excesses. They find that maintaining a healthy BMI with natural foods is the key to health.
They also know that it might be a long time before the scientific community will sort out the food science debates.
If you found this article helpful and want to start taking steps toward reversing your chronic disease, Dr. Brewer and the PrevMed staff are ready to serve you no matter where you’re located.
To find out more, schedule a consult here: prevmedhealth.com
References
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