Is saturated fat bad for you?
Is saturated fat bad for you? Here’s what the latest studies say about this controversial nutrient
Is saturated fat bad for your health? For decades, saturated fat consumption was routinely linked to coronary heart disease and high blood cholesterol levels. It was also vilified by medical professionals and governmental bodies alike. The rise of this low-fat craze appears to link back to the publication of the famous Ancel Keys’ study back in the 1950s. Except we now know that his research paper was deeply flawed, and recent scientific studies have thrown the notion of harmful saturated fats into question. Some scientists even believe that there are some tangible health benefits to this controversial nutrient.
It is not surprising then that many of us are left confused as to whether we should include saturated fat in our diets, or cut down on it as much as possible. In truth, dietary fat is a complex subject. The answer to the question, ‘is saturated fat bad for you’ may not be as black and white as we want it to be, and recent scientific advancements have demonstrated that many different factors may affect our relationship with saturated fats.
Here, we’ll look further into what saturated fats are, and what we know so far about their impact on our bodies.
What is saturated fat?
Most dietary fats belong to a group called glycerides. Glycerides are made of two types of molecules: glycerol and a number of fatty acids, which are long linear or branched chains of carbon atoms. How these carbon atoms are connected with each other will determine whether a glyceride molecule is considered to be saturated or unsaturated.
A saturated fat is a type of fat in which the fatty acid chains all have single chemical bonds. Single bonds stabilize the fat molecule and make it more rigid. That’s why saturated fats are solid at room temperature.
Saturated fats can be mostly found in animal-based foods like lard, red meats and dairy products.
Foods high in saturated fat
- Whipped cream: 23.2g per cup / 19.3g per 100g
- Dried coconut: 16.2g per oz / 57.2g per 100g
- Fatty red meats (eg. pork ribs and beef steak): 15.1g per 3 oz / 17.8g per 100g
- Processed meats (eg. pepperoni and salami): 15.1g per 3 oz / 17.7g per 100g
- Dairy-based desserts (eg. ice cream and chocolate mousse): 13.8g per cup / 4.5g per 100g
- Palm oil: 11.1g per tablespoon / 81.5g per 100g
- Full-fat milk: 9.1g per cup / 1.9g per 100g
- Full-fat cheese: 8g per half a cup / 6.4g per 100g
- Butter: 7.2g per tablespoon / 50.5g per 100g
- Dark chocolate: 7g per 1 oz square / 24.5g per 100g
- Peanut butter: 3.3g per 2 tablespoons / 10g per 100g
Saturated fat: A brief history
The claim that a high saturated fat intake is directly linked to cardiovascular disease — the so-called ‘fat-heart hypothesis’ — began in the 1950’s. During this time, the rate of coronary heart disease among middle-aged Americans was continuously growing, and medical professionals were unsure why this was happening. The turning point came in 1955, when the 34th U.S. president Dwight D. Eisenhower suffered a major heart attack while playing golf. When this incident was reported in the media, the stock market suffered one of the biggest crashes in modern history.
This economic downturn mobilized scientists to find effective ways to prevent heart disease. Diet became the primary target. It’s worth mentioning, however, that throughout this time, cigarettes were considered to be healthy, and the link between smoking and adverse health outcomes was not yet made.
Ancel Keys, a pathologist from the University of Minnesota, believed that he had found the answer to the problem. He conducted a study that looked into the lifestyle factors of more than 12,000 middle aged men in seven different countries. According to his findings, a higher consumption of saturated fat in north European countries was associated with a higher incidence of heart disease. At the same time, a higher intake of polyunsaturated fat in Mediterranean countries appeared to protect against cardiovascular problems. This study contributed to subsequent public health initiatives aimed at reducing saturated fat intake.
However, it was deeply flawed. Not only did Keys cherry-pick data, he also did not account for any other potential factors, such as smoking or fiber consumption. But these facts came to light much later.
Following the publication of Keys’ findings, public health authorities began recommending an increased consumption of carbohydrates, and downplaying potential risks of excessive sugar consumption. In fact, the U.S. dietary guidelines from the late 1970s recommended a whooping 7 to 11 servings of bread everyday. It’s also a time when the rates of chronic disease in the U.S. started to rise rapidly.
Saturated fat: What does recent evidence say?
The science surrounding dietary fats is constantly evolving, and many aspects of this topic are still a matter of heated debate among researchers and medical professionals.
Trans fats are a good example. A significant amount of evidence points to their harmful effects, particularly in relation to cardiovascular disease and cancers. However, it may not be as clear cut as it seems. According to a review recently published in the Advances in Nutrition, there is a significant difference between industrial trans fats, and trans fats that are naturally present in meat and dairy products. Industrial trans fats promote inflammation and inflict damage on the cells in our body, while ruminant trans fatty acids may not have the same negative impact on human health.
The issue of saturated fats may be even more complex. Despite decades of research, scientists are still unsure about the exact role these nutrients have on health and disease. Early study findings were often contradictory and blighted by flawed methodology. Some papers were even suspected to be biased by sugar industry sponsorship.
However, the quality of modern research is continuously improving.
Our understanding as to why similarly designed studies may produce vastly different results is also growing. To start with, saturated fats are not a homogenous group — they include multiple different nutrients, containing either short, medium or long fatty acid chains. As a result, it’s unlikely they share the same properties.
“There has been some speculation that some of the saturated fats in particular foods, for example lauric acid in coconut oil, may be better for us than other saturated fats,” says Sarah Coe, nutrition scientist at the British Nutrition Foundation. “There is not enough good quality research to show this, and it cannot be said that one saturated fat should be chosen over another.”
Coe graduated with a BSc in Nutrition from the University of Surrey, U.K., where she also completed a professional training year working in the nutrition team at Unilever. She joined the science team at the British Nutrition Foundation in 2009 as a research assistant and is now a nutrition scientist.
Scientists from The American Journal of Clinical Nutrition have recently proposed a novel model called the Homeoviscous Adaptation to Dietary Lipids (HADL). According to this hypothesis, how our bodies respond to dietary fat intake may be more flexible and based on individual circumstances than previously thought. For example, the rise in ‘bad’ blood cholesterol caused by saturated fats may be a normal, rather than a pathogenic, response. What’s more, different dietary factors, as well as our gut microbiome, may play a role in mediating this relationship and determining whether it's harmful or not.
So while we try to answer the most common questions about the links between saturated fats and different aspects of our health, keep in mind that there is still a lot to discover about these nutrients. As such, contradictory findings may not necessarily be wrong, or skewed by poor study design.
Let’s begin with the most widely-researched issue - the ‘fat-heart hypothesis’.
“Medical opinion remains behind the idea that we should lower our saturated fats and that will reduce our risk of cardiovascular disease,” says Dr. Brian Fisher, medical doctor and clinical director at Evergreen Life. “However, there is also evidence that the link between sa
turated fats and heart disease may be weaker than previously thought.”
Dr. Fisher has over 42 years’ experience as a general practitioner in the United Kingdom. He has a Bachelor of Medicine and a Bachelor of Surgery, and an MSc in primary care.
So why is that the case?
“An increased intake of saturated fatty acids (SFA) increases the blood total cholesterol level,” explains Dr. Fisher. “These findings suggested that they are a causative factor of coronary heart disease (CHD). In contrast to saturated fatty acids, polyunsaturated fatty acids (PUFA) lower the total cholesterol. These findings led to the conclusion that substituting PUFA for SFA should help prevent the disease.
“This possibility was tested in several major randomized controlled trials. The findings from these trials have been generally interpreted as indicating that the risk of CHD can be reduced by partially replacing SFA with PUFA.”
- Related: How body fat is calculated
But he says serious flaws with this hypothesis have steadily emerged.
“Many cohort studies were published after 1990 that have provided a wealth of information on the relationship between diet and risk of coronary heart disease,” he explains. “Meta-analyses of cohort studies have clearly shown that intake of SFA has only a weak, non-significant association with risk of CHD. The possibility must be considered that due to methodological errors, the true association is much larger than is indicated by cohort studies. [But] this is very unlikely as demonstrated by the fact that cohort studies have reported that several other components of the diet have much stronger, significant associations with risk of CHD. So when cohort studies report a weak association between SFA and risk of CHD, this cannot be dismissed as methodological error.
“Moreover, none of the dietary trials that lowered total and LDL cholesterol through dietary changes (i.e. a reduction in saturated fat) have shown a reduction in the incidence of heart attack, stroke or death. And this was the case even before the introduction of the change in dietary guidelines advising us to cut down on saturated fat.”
So depending on how researchers collate the data, they may come to different conclusions. For example, according to a major systematic review, reducing saturated fat intake for at least two years causes a potentially important reduction in combined cardiovascular events. At the same time, systematic reviews published in the Journal of the American Heart Association and The American Journal of Clinical Nutrition did not find a similar link.
According to the Frontiers in Immunology journal, a diet high in dietary fats may negatively affect our gut health, which in turn can increase our inflammation levels — a known risk factor for cancer. However, it may not be as clear cut. Individual genetic factors and gut microbiota profile may impact this connection. Certain saturated fats, such as lauric and myristic fatty acid found in coconut oil, may actually protect against inflammation. And as researchers from the International Journal of Molecular Sciences point out, there is no evidence that lowering your total fat intake can combat cancer, or that a moderate intake of SFA poses a health risk within a balanced diet.
Non-Alcoholic Fatty Liver Disease (NAFLD) is a condition in which fat accumulates in the liver tissues, leading to decreased function. It’s commonly associated with obesity. According to a review published in the Molecular Nutrition & Food Research journal, saturated fat may contribute to fatty liver, while unsaturated fatty acids appear to protect against this disease. However, this link may depend on whether the liver mitochondria (cell compounds responsible for generating energy) are in good condition or not.
Bones and joints
Evidence is growing that saturated fat may affect our bone health. According to the Osteoporosis International journal, there is a significant link between SFA intake and an increased risk of hip fracture. And as stated in a review published in the Joint Bone Spine journal, SFA consumption appears to increase the degradation and inflammation of chondrocytes — cells responsible for cartilage formation. As such, it may contribute to the development of osteoarthritis.
Saturated fat may negatively affect cognitive health. According to the Current Alzheimer Research journal, high SFA consumption increases the risk of Alzheimer's disease by 39%, and the risk of dementia by almost 105%. In a dose-response analysis, a 4 g/day increment of SFA intake was related to 15% higher risk of Alzheimer’s disease.
How much saturated fat should you eat?
There are no universal guidelines regarding the most optimal intake of saturated fat. Depending on the source, the recommended amount ranges from 5% to 11% of total calories. The American Heart Association endorses around 5% to 6% of your total energy intake — if you eat 2000 calories a day, that comes down to 13g of saturated fat.
At the same time, the latest Dietary Guidelines for Americans suggest limiting saturated fat to less than 10% of your total energy intake. Scientists from the International Union of Nutritional Sciences (IUNS) Task Force on Dietary Fat Quality recently published a review of dietary guidelines, which stated that a range of 7% to 11% of total energy intake is the most appropriate.
Most medical professionals and nutritionists tend to abide by the latest IUNS statement.
“Our saturated fat intake should not be more than 11% of food energy, which is roughly 30g per day for men and 20g per day for women,” says Sarah Coe.
Fisher adds: “About a third of our energy should come from fat. That’s about 70g for a woman and 90g for a man per day. Saturated fats should make up no more than a third of this.”
Should you eat a low fat diet?
A low fat diet provides less than 30% of total calories from fat, with some ultra-low fat diets containing less than 15%. Since our bodies need a certain amount of dietary fat to function properly, cutting down on this important nutrient may do more harm than good.
Several vitamins — namely A, D, E and K — need fat in order to be distributed across the body. Without this nutrient, you’re more likely to develop deficiencies. Excessively low dietary fat intake may also contribute to problems with skin and reproductive health.
On the other hand, a well-balanced low fat diet may improve the nutritional value of your foods. Incorporating more complex carbohydrates and fiber may help reduce the risk of certain cancers, type 2 diabetes and cardiovascular disease. Low fat diets may also be beneficial for those who had their gallbladder removed, as those who have undergone this procedure do not produce enough of the enzyme lipase which breaks down fat.
This article is for informational purposes only and is not meant to offer medical advice.
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Anna Gora is a health writer at Live Science, having previously worked across Coach, Fit&Well, T3, TechRadar and Tom's Guide. She is a certified personal trainer, nutritionist and health coach with nearly 10 years of professional experience. Anna holds a Bachelor's degree in Nutrition from the Warsaw University of Life Sciences, a Master’s degree in Nutrition, Physical Activity & Public Health from the University of Bristol, as well as various health coaching certificates. She is passionate about empowering people to live a healthy lifestyle and promoting the benefits of a plant-based diet.