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Written by
Taylor Foster
Medically Reviewed by
Dr. Danielle Desroche

The autoimmune protocol (AIP) diet is a specialized eating plan designed as a food-first approach to healing systemic inflammation from the inside out. Foods considered problematic are initially eliminated and then reintroduced at a later point. As with the less restrictive paleo diet, with the AIP dietary fats play a large role in treating autoimmune disorder symptoms.

While you may have been told that fat is bad for your health and you should avoid it, some fat is actually essential for good health. You need fat for energy, to absorb and store fat-soluble vitamins, to provide protection for your organs, for insulation, and to facilitate chemical reactions that regulate your hormones. Not all fats are created equal, though — there are different types, some healthier than others. To better understand how you can utilize dietary fats to impact your health positively, let’s dive into why fats are essential for your body to perform optimally, what fats to consume, and which fats to avoid on the AIP diet. (Source)

What Is Fat?

Over the last two decades, we have received mixed messages about fat, so it’s no surprise if you’re a little confused on the subject. With the overwhelming influence of social media, where anyone can tell you anything, it can be difficult to know what advice to follow. Fat is essential for our bodies to perform and function at optimal levels each day, so why the controversy?

First, we need to clarify the difference between dietary fat and body fat. Your body builds the fat it needs for good health from components in the foods you eat. The so-called building blocks of fat are called fatty acids, and your body can make most of them as needed. There are two fatty acids, however — alpha-linolenic acid (an omega-3 fatty acid) and linoleic acid (an omega-6 fatty acid) — that your body can’t make. They are called essential fatty acids, because your body needs them and relies on you to provide them in your diet.

Of course, these essential fatty acids aren’t the only kinds of fat found in foods, and the type of fat you eat plays a large role in body fat as well, because not all calories are created equal. Healthy fat sources, when eaten in conjunction with a nutrient dense diet, provide a satisfying feeling of fullness that may result in less caloric consumption overall. (Source, Source, Source)

avocado cut in half on a cream plate

Fat Function

In addition to the functions already mentioned, fats are necessary for brain health, keeping inflammation at bay, and clotting blood. All fats play a part in how our bodies function, but the essential fats, saturated and unsaturated, are important because we must get most of these through our food, preferably whole foods that contain them naturally. Essential fatty acids (EFA) can be broken down even further into omega-6 (linoleic acid) and omega-3 (alpha-linolenic acid) fatty acids.

It is important to note that due to the nature of the typical Western diet, it is not uncommon to be deficient in essential fatty acids, but also to be imbalanced as well. This is due to the fact that many foods included in the Western diet contain high levels of omega-6 EFAs and insufficient amounts of omega-3s. Consuming the right types of foods to get the EFAs you need may lower inflammation to treat some diseases, improve brain health and performance, and increase physical performance as well as body composition. (Source)

The Building Blocks of Fat

The building blocks of fat are fatty acids, which are categorized as saturated and unsaturated. These can be further broken down into monounsaturated fats, polyunsaturated fats, and trans fats. Fatty acids are the building blocks our bodies use to produce fat that forms cell membranes and provide us with the energy we need. During digestion, our bodies break our food down into usable fatty acids that are distributed to our cells and absorbed into our blood to play a cellular role in our cardiovascular, neurological, and endocrinological health. (Source, Source)

Saturated Fats

Saturated fats are solid when at room temperature, and are found in dairy products such as butter, lard, full-fat milk, yogurt, and cheese, as well as fatty cuts of meat, baked goods, and fried foods. Trans fat is a form of saturated fat that is found in dairy and red meat. It can also be artificially made by adding hydrogen to vegetable oil, and is more commonly known as partially hydrogenated oil. This form of oil has been banned from food products in the United States, and has been known to cause increased risk of heart attack and stroke. (Source)

Unsaturated Fats

Unsaturated fat is liquid at room temperature, and is found in vegetable oils, fish, and nuts. Unsaturated fat is categorized into two main types: polyunsaturated and monounsaturated fats. Polyunsaturated fats are found in seed oils (corn, sunflower, soybean, and cottonseed), walnuts, pine nuts, flaxseed, sesame, sunflower, and pumpkin seeds. Monounsaturated fats can be found in oils such as olive, peanut, safflower, sunflower, as well as avocados, peanut butter, most types of nuts, and animal fats such as chicken, pork and beef. Omega-3 fatty acids are a type of unsaturated fat that has been shown to improve blood pressure and cholesterol. (Source)

fat soluble vitamins on a marble counter

Fat-Soluble Vitamins

The fat-soluble vitamins A, D, E, and K, are important for blood clotting, vision and bone health, and you guessed it, immunity. These vitamins are absorbed in the small intestine with fat present for better absorption and utilization, and are best taken with a dietary fat source such as coconut oil.

Deficiencies of these fat-soluble vitamins may show up as night blindness, osteomalacia (softening of the bones), increased risk of oxidative stress, and difficulty clotting. Deficiency of dietary fats may increase the risk of disease such as cancer, diabetes, and autoimmune disorders. The AIP diet is centered around decreasing inflammation systemically and increasing immunity by fostering good gut health. With a food first approach to populating a healthy gut microbiome, we in turn are building up our immune system to strengthen our overall health. Needless to say, dietary fats are critical to our immune health. (Source, Source)

Essential Versus Non-Essential Fat

There are two types of fatty acids: essential and non-essential. Non-essential fatty acids can be synthesized through biochemical processes within the body, whereas essential fatty acids need to be taken in through the diet because our bodies can not make them. These are more commonly known as omega-6 and omega-3 fatty acids, and both are necessary for our body to perform normally.

The Western diet tends to be higher in omega-6 fatty acids, which means that most individuals who follow a Western diet could be deficient in omega-3 fatty acids. The health implications of this ratio being off kilter may contribute to chronic inflammatory conditions such as cardiovascular disease and cancer, but this concept has not been proven entirely and the perfect ratio of omega-6 to omega-3 fatty acids has not been defined as of yet. (Source, Source)

hand pouring olive oil out of a bottle onto a slice of bread

Sources of Dietary Fats

We know that dietary fat is essential for our bodies to function normally and optimally, but do you know where to find the best sources of dietary fat?

Natural Fat

Naturally fatty foods include cold-water fish like salmon, mackerel, tuna, herring, and sardines, nuts and seeds, plant oils, and animal products. Some of these foods may be high in omega-6 or omega-3 fatty acids, but not all fats are created equal! You should aim to get the majority of your fat intake from food sources, but supplements that are high in omega-3 fatty acids, such as fish or krill oil, can be part of a healthy, rounded diet. (Source)

Chemically Altered Fat

Hydrogenated trans fat has quite a different structure than plant and animal fat because it has been chemically altered. Consumption of these trans fats have been found to cause damage inside the body including excess inflammation, increased risk of coronary heart disease, and cancer. Reducing or, preferably, completely eliminating trans fat from your diet will decrease your chance of developing health risks associated with consumption. (Source)

hand reaching for a piece of cheese on a white plate


Dairy products such as cheese, butter, and whole milk contain saturated fats. Though these foods are high in nutrients, saturated fats have gotten a bad reputation for increasing the risk of cardiovascular disease and have been linked to high mortality rates. As of now, there is not a whole lot of research to back these claims up, but there is some evidence that high-quality, full fat dairy products may be a good addition to your diet as long as you tolerate them well. Consuming dairy regularly has been suggested to decrease the risk of obesity in children, as well as improve body composition, and decrease the risk of cardiovascular disease and type two diabetes in adults. (Source, Source)

Refined Oils

Refined oils cannot be used in their crude or raw form, and must be refined or purified before human consumption. Examples of refined oils include soybean, rapeseed, corn, and sunflower oils. Whether physically or chemically refined, this process is necessary to make the oils more shelf stable, to improve quality with lower odor and lighter color, and to eliminate any possible contaminants or pollutants the oil may have had. The refining process removes some essential nutrients from the oils, and downgrades the oil quality even further due to harmful trans-fatty acids and esters that are produced from the refining process. (Source)

Nut and Seed Oils

Nuts and seeds both are high in unsaturated fats as well as other important nutrients that may decrease inflammation, possibly reducing the risk of cardiovascular disease and diabetes. Seed oils, though, are refined and altered, making them not the purest or best choice of oil to consume. Unrefined seed oils such as flaxseed oil, are high in omega-3 fatty acids. Flaxseed oil consumption may reduce the risk of inflammatory diseases such as cardiovascular disease, diabetes, cancer, autoimmune, and neurological disorders. (Source, Source)

small wooden bowl of olives

Fats Allowed on The AIP Diet

On the AIP diet, your dietary fat will either come from a whole food or a rendered animal or plant source. Whole food sources of dietary fats could include those fatty cold-water fish mentioned earlier, avocado, olives, oils such a: extra-virgin/naturally refined/expeller-pressed coconut oil, palm oil, cold-pressed avocado oil, extra-virgin olive oil, palm shortening, or red palm oil. (Source)

Fats from animal sources that are allowed on the AIP diet and are nourishing to gut health include duck fat, lard from pork products, tallow from lamb, beef, and bison, and schmaltz from chicken. Each cooking fat, whether from plant or animal sources, has properties that define how you should cook with it. While all fats do have a smoke point that can be taken into consideration before using for cooking and baking, it’s also important to factor in how the oil presents at room temperature.

Unsaturated fats such as olive oil and avocado oil are liquid at room temperature, while saturated fats such as tallow and lard are solid at room temperature. Some liquid fats lose nutritional value and form trans fats when heated to high temperatures, and should be used over low heat or no heat at all (as in a salad dressing). Fats that are solid at room temperature are a better choice for roasting, sautéing, grilling, and frying because the fat properties will remain stable in high heat conditions. (Source, Source)

The Bottom Line on Fats

Fats are a critical source of nutrients in any diet. Fats support health throughout the body, but they are especially important in the AIP diet to promote optimal health with a food-first approach to treating autoimmune disorders. Choosing the right fats is key for fueling the brain and body with the essential nutrients necessary for your body and brain to function normally on a daily basis. The bottom line is that knowing the skinny on fat sources can play a huge role in treating your autoimmune symptoms. Learn more about how WellTheory can support you in using food as medicine and get guidance from a WellTheory Nutritional Therapy Practitioner to manage your inflammation and autoimmune symptoms.

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Rheumatoid Arthritis
January 6, 2023

The AIP Guide to Fats

High quality fats in the AIP diet are important for optimally supporting autoimmune disorders with a food first approach.
Medically Reviwed
Written by
Taylor Foster
Medically Reviewed by
Dr. Danielle Desroche
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