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Dietary Fats and Oils: The Good, The Bad and The Ugly

Nov 5th 2021 | By Jannell Baez, MS, RDN, LD/N

Healthy cooking oils

When I began studying nutrition in the 1990s, we were taught that the healthiest diet was a low-fat diet. Fat has been demonized for decades based on faulty research by Dr. Ancel Keys that correlated dietary fat with cardiovascular disease and obesity. The problem with this correlation is that it was merely a correlation. Other factors such as fruit and vegetable intake and lifestyle were not taken into consideration. For example, if crime rates increase and the rate of ice cream sales also increases during the same time period, can we say ice cream intake causes people to commit more crime?  Studies that correlate one thing with another can not necessarily determine causation. In his landmark Seven Countries Study which examined the association between dietary saturated fat and cardiovascular disease, Keys omitted data from countries like France, Germany, Switzerland and Sweden where fat intake is high yet they have less incidence of cardiovascular disease. This was done to help prove his hypothesis about fat causing heart disease.

fatty foods good bad and ugly

Newer research has found is that a low-fat diet may not be the answer to optimal health. When the food industry started formulating low-fat and fat-free products based on the incomplete research done in the past, Americans started consuming food products with little to no fat and higher amounts of carbohydrates and sugars. Chronic diseases such as obesity, diabetes, cancer and cardiovascular disease increased despite people avoiding dietary fats and cholesterol-containing foods such as eggs. Despite the newer information on fat metabolism, Americans are still wary of consuming fat and many believe dietary fat causes weight gain, cardiovascular disease, and other chronic conditions. Changing this narrative is important so that people understand that fat can be a healthy part of your diet and attention should be paid to lowering processed carbohydrates and sugars instead of avoiding fats. Dietary fats provide energy and are essential for health. Fats are the building blocks of all cell membranes, central nervous system tissues including brain tissue, they are involved in cell communication and are also needed for hormone production. Healthy amounts of the right fats and can also be helpful for weight management and maintaining insulin sensitivity. In this article, I will review which fats are best and educate you on how to choose the best quality healthy fats which are most physiologically compatible with your body’s needs.

Essential Fats

Essential fatty acids are fats that our body can not produce and must be consumed from the foods we eat. These fats include Omega 6 fats: Linoleic acid (LA), Gamma-linolenic acid (GLA), Conjugated linoleic acid (CLA) and Arachidonic acid (AA). These oils are found in vegetable oils, soybeans, animal proteins, nuts, seeds, safflower and sunflower oils and corn. The other family of essential fats are the omega 3 fats: alpha-linolenic acid (ALA), Eicosapentaenoic acid (EPA), Docosahexaenoic acid. Sources of omega 3 fats include: fatty fish such as wild-caught salmon, sardines, cod and mackerel, nuts, seeds, eggs (organic pasture-raised).

Omega 6 vs Omega 3 Oils

Omega 6 and omega 3 fats are necessary in the diet. They play important roles in structural integrity of cell membranes and influence inflammation in opposing ways. Omega 6 fats can be used to make inflammatory molecules in the body known as prostaglandins and leukotrienes. These are a part of your immune system. Omega 3 fats are more anti-inflammatory making different types of prostaglandins and leukotrienes that are less inflammatory compounds. These fats should be consumed in certain amounts so they are in balance. It is recommended to eat a 4:1 ratio of omega 6 to omega 3 fats for the body to be in balance. Unfortunately, our standard American diet tends to be very high in omega 6 fats with little to no consumption of omega 3 fats. Omega 6 fat intake in America has been found to be as high as a 25:1 ratio of omega 6 to omega 3 fats instead of 4:1. This is due to use of cooking oils high in Omega 6 fats, high intake of animal products, and commercial uses of these fats to make processed foods such as dressings, chips, crackers and even protein bars. Americans are also notorious for not eating enough vegetables, nuts, seeds fatty fish which are sources of omega 3 fats leaving us with more inflammation, pain and suboptimal cell membrane and central nervous system tissues.

Increasing your intake of omega 3 fats can disrupt the inflammatory effects of too much omega 6 fats in the diet. Choosing foods high in omega 3 fats such as fatty fish, organic pasture raised eggs, walnuts, chia seeds, hemp seeds and ground flax seeds. Many people find it helpful to take an omega 3 supplement containing both EPA and DHA but it is easy to get sufficient omega 3 fats from foods.

Healthy Fat Options: “The Good”

Choosing the right fats that provide your body with the building blocks it needs to make body tissues and cell membranes is essential for the body to function correctly. Healthy fats are physiologically more compatible than other fats and oils and are necessary for healing and rebuilding body tissues. So which fats are best and what makes them superior? We take many things into consideration including the chemical structure of the oil, how processed the oil is and how well it tolerates heat when cooking. Certain oils are more sensitive to heat and start to burn or smoke at lower temperatures. These oils are not recommended for cooking and are best used for dressing foods at room temperature. If an oil is heated past its smoke point, the chemical structure can change making it a more toxic and inflammatory oil.

A good rule of thumb is to choose fats that are stable in at higher temperatures such as avocado oil, coconut oil, grass-fed butter or ghee (organic). Save olive oil or nut oils for dressing your food. Traditional animal fats are also an option for cooking but are saturated fats and are best used in small amounts. Animal fats are best from clean sources that are organic and pasture raised. Some people that have elevated blood lipids or genetics that affect saturated fat metabolism should monitor their intake of animal fats using small amounts and rotating them in and out of the diet in balance with healthy plant fats. The following table was adapted from educational documents from the Institute of Functional medicine and reviews common fats and oils that are acceptable for cooking and dressing.

Fat/OilSmoke PointBest UsesNotes
Avocado Oil520ᵒHigh heat cooking, low-heat cooking, dressing, finishing   
Butter, Ghee300ᵒ/480ᵒHigh-heat cooking, bakingGhee is butterfat with the animal solids removed. Some people who are sensitive to dairy may not be sensitive to ghee
Coconut Oil350ᵒ/450ᵒHigh-heat cooking, sauteing, bakingCoconut oil is solid at room temperature because it is a saturated fat. If sold as a liquid at room temperature it has been blended with another oil
Duck Fat375ᵒHigh-heat cooking   
Lard (pork, bacon fat)375ᵒHigh-heat cookingSource should be pasture-raised, sustainable raised and organic
Macadamia Nut Oil410ᵒLow-heat cooking, dressing, finishing   
Olive Oil320ᵒ/465ᵒHigh heat cooking, Low heat cooking, dressing, finishingOlive oil can be used for cooking but it is best to use lower heat to maintain its healthful properties. Extra-virgin olive oil is best used at room temperature
Peanut Oil230ᵒ/450ᵒHigh-heat cookingProne to rancidity and oxidation making it inflammatory. Not top choice for health
Rice Bran Oil415ᵒLow-Heat Cooking   
Sesame oil450ᵒDressing, FinishingSesame oil has high antioxidant content.
Tallow400ᵒHigh-heat cooking   
Walnut Oil400ᵒDressing, Finishing   

Refined Fats and Oils That Should be Avoided: “The Bad”

circle w/ slash

Many commonly sold and used oils are heavily processed in order to tolerate high heat cooking. When any food is processed, it is stripped of nutrients and beneficial phytochemicals needed for health. Once refined these oils are not the most compatible with your body to create cell membranes and tissues so it would be like building yourself a house using poor quality materials that will not hold up or function properly.  These oils are also high in Omega-6 fatty acids which can cause chronic inflammation in the body. Keep in mind that most restaurants use these kinds of oils for cooking which is why I always recommend for people to cook most meals at home to have more control over the quality of ingredients. The following refined fats and oils listed are not recommended.

Canola oil (Grapeseed oil)             Safflower oil

Corn oil                                         Soybean oil

Cottonseed oil                              Sunflower oil

Grapeseed oil                               Vegetable shortening

Trans fats: “The Ugly”

Trans fats were introduced into the American diet in 1911 as hydrogenated vegetable oil shortening for baking. When cholesterol and fat were deemed unhealthy, people were encouraged to stop eating butter and eggs and instead choose margarine or low cholesterol food products resulting in a high intake of trans fats.  Vegetable oils had to be chemically modified to make them solid at room temperature so they could make butter substitutes and be used in processed food products.

Trans fats are a type of fat in some foods that are created commercially by adding hydrogen to a liquid vegetable oil to make it more solid in food products such as margarine, pastries and other baked goods, and processed snack foods. These fats have been found to be bad for your health because they promote cardiovascular disease, diabetes and have even been implicated in promoting dementia and Alzheimer’s disease. Trans fats have an adverse effect on the brain and nervous system. They are used to build central nervous system tissues. These industrial fats are not compatible with the body and cause inflammation and poorly functioning cell membranes and brain tissues. Trans fat from the diet is incorporated into brain cell membranes and alter the ability of neurons to communicate diminishing cognitive performance.  In 2015, the FDA made regulations that made food manufacturers eliminate all industrial partially hydrogenated oils from their products. A small amount is still allowed in some food products. You can avoid these dangerous fats by eating a whole foods diet and avoiding processed foods.

Choosing The Best Oils

When reading oil labels, it can be difficult to decipher what type of oil you are buying. The table below will help you ease through the common descriptors on the label.

Essential cooking oils
RefinedOils that are extracted and treated with heat or chemicals to remove flaws. This process can also destroy the beneficial properties of oils. Refined oils are generally more stable than unrefined oils, so they tolerate high heat cooking better. “Light” oils are examples of refined oils.
UnrefinedOils that are made from cold-pressed source ingredients and are never treated with chemicals or heat. These oils retain the minerals, enzymes, vitamins and phytonutrients of the source ingredient. Virgin and extra virgin oils fall into this category
Extra-VirginOils that are unrefined and cold-pressed, generally from the first pressing of the source ingredient. These oils can be fragile and should be reserved for dressing, drizzling, and dipping. Note that olive oil needs to meet specific requirements for acidity in order to be labeled “extra-virgin”
VirginOils that are unrefined and cold-pressed from the second pressing of the source ingredient. These oils are also fragile and should be reserved for low-heat cooking, dressing and drizzling. Virgin olive oils must pass standards for taste and quality but the standards aren’t as rigid as the “extra-virgin” qualification.
PureOils that are a blend of refined and unrefined oils. All of the oil comes from a first pressing but some batches of oil may be treated with chemicals or heat to remove impurities before bottling.
Cold-PressedOils that are extracted from their source using pressure only. Chemicals and heat are not used in this process. This helps the oils retain all of the nutritional benefits of the source ingredients

* Table adapted from the Institute of Functional Medicine “Guide to cooking with Fats and Oils”

Once you have your healthy oils there are ways you can extend the shelf life of your oil to ensure you are not consuming a rancid oil. Oils are sensitive to light and temperature. The following tips will help you store and use your oils properly.

  • Purchase oils in dark glass bottles
  • Purchase oils with a tight fitting seal/lid
  • Store fats and oils away from the stove and other heat sources
  • Store your fats and oils in a dark place
  • Measure and separate cooking fats and oils from their containers before placing them in a hot pan
  • Do not purchase oils that are packaged in plastic containers
  • Do notpurchase oils with a loose-fitting seal or lid
  • Do notstore your oils next to the stove, oven, microwave, or other heat source
  • Do notstore your oils in a place that gets a lot of artificial or natural light
  • Do notpour oils directly into the pan from the bottle or container. The heat or steam from the pan can damage the oil in the bottle.

Take Home Message:

Oils and fats are an essential part of our diet so our body can rebuild cell membranes and tissues. The more the oil is in its natural state, the healthier it usually is. As with all processed foods, the healthful properties of oils are removed when refined. Know that oils used in restaurants and fast food outlets are usually inflammatory and refined. They may also be oxidized and rancid from poor storage or overuse (think deep fryers). The best oils for cooking are Coconut oil, avocado oil, grass-fed butter and grass-fed ghee.

Authentic Argentinian Chimichurri Sauce

a lovely dish of food

Chimichurri sauce is usually paired with steak but is a very versatile sauce you can use to dress everything from meats to vegetables. The recipe is full of wonderful nutrient rich herbs and made with extra-virgin olive oil.


  • ½ cup extra-virgin olive oil
  • 2 Tbs red wine vinegar
  • ½ cup finely chopped parsley
  • 3-4 cloves garlic, finely chopped or minced
  • 2 small red chilis, or 1 red chili, deseeded and finely chopped (about 1 Tb finely chopped chili)
  • ¾ teaspoon dried oregano (if you use fresh oregano use 1 Tb)
  • 1 level teaspoon coarse salt
  • Pepper to taste (approx. 1 tsp)


Mix all ingredients together in a bowl. Allow to sit for 5-10 minutes to release all of the flavors into the oil before using. Ideally let sit for more than 2 hours if time allows.

Chimichurri can be made in advance and refrigerated for up to 24 hours

Chimichurri is best used for dressing and basting.


 US Department of Health and Human Services; US Department of Agriculture., 1985 Dietary Guidelines for Americans. Washington, DC: US Dept of Health and Human Services; 1985.

Austin GL, Ogden LG, Hill JO. Trends in carbohydrate, fat, and protein intakes and association with energy intake in normal-weight, overweight, and obese individuals: 1971-2006. Am J Clin Nutr. 2011;93(4):836–843. doi: 10.3945/ajcn.110.000141.

Calder PC. Functional Roles of Fatty Acids and Their Effects on Human Health. JPEN J Parenter Enteral Nutr. 2015 Sep;39(1 Suppl):18S-32S. doi: 10.1177/0148607115595980. Epub 2015 Jul 15. PMID: 26177664.

Institute of Functional Medicine (2017). A Guide To Cooking With Fats and Oils. Retrieved from

Ginter E, Simko V. New data on harmful effects of trans-fatty acids. Bratisl Lek Listy. 2016;117(5):251-3. doi: 10.4149/bll_2016_048. PMID: 27215959.

Oteng AB, Kersten S. Mechanisms of Action of trans Fatty Acids. Adv Nutr. 2020 May 1;11(3):697-708. doi: 10.1093/advances/nmz125. PMID: 31782488; PMCID: PMC7231579.

Islam MA, Amin MN, Siddiqui SA, Hossain MP, Sultana F, Kabir MR. Trans fatty acids and lipid profile: A serious risk factor to cardiovascular disease, cancer and diabetes. Diabetes Metab Syndr. 2019 Mar-Apr;13(2):1643-1647. doi: 10.1016/j.dsx.2019.03.033. Epub 2019 Mar 16. PMID: 31336535.

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