Dietary fat has been vilified for a really long time. In the '90s, the advice to avoid excess fat was everywhere. But as nutrition experts and researchers started to gain a deeper understanding of the macronutrients, tunes have started to change.
Although there are still some fats, like trans fats, that you should avoid as much as possible, there are some gray areas when it comes to the other types of fats, even saturated fat.
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Trans Fats and Your Organs
Trans fats have a detrimental effect on your heart. According to a report that was published in the Pakistan Journal of Medical Sciences in February 2014, trans fats contribute to heart disease by increasing LDL, or "bad," cholesterol levels while simultaneously decreasing good cholesterol, or HDL. But even though the connection to heart disease might be the most well-known negative effect of trans fats, they also affect your brain.
A study that was published in an October 2019 issue of Neurology found that high levels of elaidic acid, a specific type of trans fat, were connected to developing dementia and Alzheimer's disease later in life.
According to the Harvard T.H. Chan School of Public Health, the Food and Drug Administration (FDA) once said there were trans fats in about 100 percent of commercially-produced crackers, 95 percent of prepared cookies and 80 percent of frozen breakfast products. The good news is that, due to the overwhelming science about the adverse health effects of trans fats, the FDA mandated that all food manufacturers remove partially hydrogenated oils, the main source of trans fats, from their packaged food items by January 2021.
Saturated Fats and Your Organs
Saturated fat is one of the most controversial fats around. While most experts agree trans fats are bad, there seems to be a divided camp on saturated fats. However, recent research shows that saturated fat might not be as bad as previously thought.
A September 2013 report in the American Journal of Public Health found that the saturated fat from milk, cheese, butter and total dairy intake was not associated with an increased risk of heart disease or death, but there was modest increased risk when it came to the saturated fat in high intakes of meat, especially processed meat. An August 2012 review from The American Journal of Clinical Nutrition reported similar results.
However, a review that was published in an April 2019 issue of Lipids in Health and Disease found no associations between saturated fat (or total fat) intake and heart disease.
As Steven Nissen, MD, the chair of Cardiovascular Medicine at Cleveland Clinic says, you don't have to avoid saturated fats, even from meat. Just make sure you're keeping your excess fat intake of under control and including them in a diet that's also rich in monounsaturated fats, vegetables and lean proteins.
Polyunsaturated Fats and Your Organs
Unsaturated fats are often deemed the "healthy fats," but there are two classes — polyunsaturated and monounsaturated. Polyunsaturated fats can be broken down further into omega-3 fatty acids and omega-6 fatty acids — and it's important to know the difference.
While omega-3 fatty acids are anti-inflammatory and promote health, omega-6 fatty acids, which are found in the highest concentrations in vegetable oils, actually contribute to heart disease and promote inflammation in your brain and your lungs, especially when eaten in excess.
According to an August 2018 report in Current Neuropharmacology, the effect of polyunsaturated fats on your brain have a lot to do with the total ratio of omega-3 fatty acids to omega-6 fatty acids in your diet. If your intake of omega-6-rich polyunsaturated fats is too high, it can cause chronic inflammation, which is connected to brain conditions like depression and Alzheimer's disease.
On the other hand, if you eat a lot of omega-3s, it can help counteract the effects of omega-6s, preventing loss of brain function and dementia. It's recommended that you consume omega-3 fatty acids and omega-6 fatty acids in a 1:1 ratio. However, the average American consumes 20 times more omega-6 fatty acids than omega-3s, according to a March 2016 report in Nutrients. This not only increases your risk of chronic diseases, it also contributes to weight gain and obesity.
Read more: Why You Need to Eat Fat to Burn Fat
High-Fat Diet Benefits
While most of the focus is generally on the negative effects of too much of the wrong types of fat in your diet, there may actually be some pretty beneficial effects, too. Research from an August 2013 report in the European Journal of Clinical Nutrition says there's strong evidence that a ketogenic diet, which consists of mostly fat and very few carbohydrates, can help significantly reduce triglycerides and reduce the risk of heart disease.
There's also strong evidence that ketogenic diets have positive effects on the brain. In fact, the ketogenic diet was originally created as a way to control seizures in children and a May 2017 report in Expert Review of Neurotherapeutics says there's evidence that it can be used as an adjunctive treatment for brain cancer. That same report also notes that the high-fat diet can help improve social and cognitive skills in children with autism.
Even though eating an excess fat in the form of fatty food is often discouraged, a changing nutrition landscape shows there may actually be some benefits of including plenty of fat (even saturated fat) in a healthy, balanced diet. Just make sure you're also getting plenty of omega-3s and avoiding trans fats as much as possible.
- Pakistan Journal of Medical Sciences: "Trans Fatty Acids – A Risk Factor for Cardiovascular Disease"
- Harvard T.H. Chan School of Public Health: "Shining the Spotlight on Trans Fats"
- Current Neuropharmacology: "Impact of Dietary Fats on Brain Functions"
- Open Heart: "Omega-6 Vegetable Oils as a Driver of Coronary Heart Disease: The Oxidized Linoleic Acid Hypothesis"
- Neurology: "Serum Elaidic Acid Concentration and Risk of Dementia"
- American Journal of Public Health: "Food Sources of Saturated Fat and the Association With Mortality: A Meta-Analysis"
- Food and Drug Administration: "Final Determination Regarding Partially Hydrogenated Oils (Removing Trans Fat)"
- Nature Reviews Neuroscience: "Polyunsaturated Fatty Acids and Their Metabolites in Brain Function and Disease"
- Expert Review of Neurotherapeutics: "Ketogenic Diet and Childhood Neurological Disorders Other Than Epilepsy: An Overview"
- European Journal of Clinical Nutrition: "Beyond Weight Loss: A Review of the Therapeutic Uses of Very-Low-Carbohydrate (Ketogenic) Diets"
- American Journal of Physiology: "Lung Cellular and Molecular Physiology: "Dietary Omega-6, but Not Omega-3, Polyunsaturated or Saturated Fatty Acids Increase Inflammation in Primary Lung Mesenchymal Cells"
- The American Journal of Clinical Nutrition: "Dietary Intake of Saturated Fat by Food Source and Incident Cardiovascular Disease: The Multi-Ethnic Study of Atherosclerosis"
- Cleveland Clinic: "Your Diet and Heart Disease: Rethinking Butter, Beef and Bacon"
- Lipids in Health and Disease: "Dietary Total Fat, Fatty Acids Intake, and Risk of Cardiovascular Disease: A Dose-Response Meta-Analysis of Cohort Studies"
- Nutrients: "An Increase in the Omega-6/Omega-3 Fatty Acid Ratio Increases the Risk for Obesity"
- Merck Manual Home Health Handbook: Atherosclerosis