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Healthy Fats and Thyroid Health

Published March 12 2018

Fats are an essential macronutrient of the human diet.  Many people still have a “fat phobia”, as some are concerned about dietary fat causing heart disease, although eating healthier forms of fat can actually have the opposite effect.  As a result, I encourage my patients with thyroid and autoimmune thyroid conditions to eat healthy fats.  I prefer for my patients to get most of their healthy fats from whole foods because fats found in food are more nutrient-dense than oils on their own.

Why Eating Fat Is Important

Fats are essential in providing the body with energy.  Every single cell in your body has a membrane that protects it from damage.  Those membranes are made of proteins, fat, and cholesterol.  Fat keeps us warm and protects the organs in our body.  Fats are crucial for proper absorption of the fat-soluble vitamins A, D, E & K.

The Different Types of Fat

1. Saturated Fat.  These fats are found in animal products (beef, pork, chicken, dairy, etc.) and tropical oils (coconut oil, palm oil).  They are called saturated because each saturated fat molecule’s carbon has two hydrogens attached, making saturated fats solid at room temperature.  While some claim that eating a lot of saturated fat causes oxidative stress, some studies show that a diet high in saturated fat doesn’t cause an increase in inflammation and oxidative stress (1) [1].  On the other hand, there is evidence that polyunsaturated fatty acids (PUFA) are more easily attacked by free radicals (2) [2] (3) [3].

2. Monounsaturated Fat.  These fats are found in nuts and fruits (olives, avocados, peanuts, ground nuts, tree nuts, etc.) and contain one double bond.  Not all carbons in the molecule have hydrogens stuck to them.  This breaks the chain, and makes these types of fats liquid at room temperature.   Most foods that are high in monounsaturated fats are considered to be healthy forms of fats, although there are exceptions (i.e. peanuts).

3. Polyunsaturated Fat.  These fats are found in foods such as fish, nuts, seeds, and vegetable oils. They contain more than one double bond, and not all carbons in the molecule have hydrogens stuck to them so they are also liquid at room temperature.  There are four types of polyunsaturated fats:

Omega 3’s – Found in fish as EPA and DHA, but also include walnuts, flax seeds, soybeans, and canola,.

Omega 6’s – Nuts and seeds, whole grain cereals and breads, meat, and vegetable oils (soybean oil, corn and safflower oils).

Omega 9’s – Oleic acid is the most well known omega-9 fatty acid.  As for food sources of oleic acid, some examples include olive oil, avocados, and macadamia nuts.  Erucic acid also a type of omega-9 fatty acid, and is commonly found in rapeseed and mustard seed.

4. Conjugated Fatty Acids (CLA).  CLA is mainly consumed by humans in the form of meat and dairy products.

While all of these polyunsaturated fats are important, the problem is that many people eat too many omega-6 fatty acids.  Regarding the ratio of omega-6 to omega-3 fatty acids, most people eat within a range of 10:1 to 20:1, when the ideal ratio should be between 1:1 and 4:1.  So you want to make sure to eat a sufficient amount of omega-3 fatty acids, and you can test for the omega-3 index, which ideally should be above 8%.

TransFats – These types of fats naturally occur in meat and dairy products in small amounts but are also made when unsaturated fats are altered during processing to extend shelf life.  Anything that has the word “hydrogenated” on the label is considered a trans fat.  Trans fats are used for many different reasons, as they are less likely to go rancid, can be used for deep frying, but the main reason is because they are cheap to use.

Foods That Contain High Quality Fats

Although I listed some of the healthier fats earlier, I want to dive a little deeper into some of the fats that most people should be consuming.


Avocados are nutrient-dense and rich in fats.

According to the research, avocado consumption is associated with improved overall diet quality, nutrient intake, and reduced risk of metabolic syndrome (4) [4].  There are eight preliminary clinical studies showing that avocado consumption helps support cardiovascular health. Exploratory studies suggest that avocados may support weight management and healthy aging (5) [5].

Avocados are a well-known source of carotenoids, minerals, phenolics, vitamins, and fatty acids. The lipid-lowering, antihypertensive, antidiabetic, anti-obesity, antithrombotic, antiatherosclerotic, and cardioprotective effects of avocado have been demonstrated in several studies (6) [6].

It’s also worth mentioning that avocados are on the Environmental Working Group’s “Clean 15” list, which means that they are very low in pesticide residues.  So while it’s great if you eat organic fruits and vegetables, it’s also fine if you eat non-organic avocados.


Coconuts are a super food that can be eaten raw, dried, flaked, and coconut flour can be used in baking and other recipes.  Coconut oil can be used for cooking, oil pulling, and it can be used topically as well.

One study researched all components of the coconut plant, and found it to have antiviral, antiparasitic, antibacterial, and antifungal properties (7) [7].  The same study showed that it has antioxidant, renal protective, cardioprotective, hepatoprotective, and antidiabetic properties, and it increases bone volume (7) [7].

Coconut oil raises HDL cholesterol, which is known as the “good” cholesterol, and it helps to keep triglycerides within desirable limits (8) [8].  Consuming coconut oil may aid in weight loss (9) [9].  Coconut oil decreases waist circumference and body mass in patients with coronary artery disease (10) [10].  Consuming coconuts may also help to prevent Alzheimer’s disease (11) [11], as the phenolic compounds found in coconuts may assist in preventing the aggregation of amyloid-β peptide, which is a factor in the pathogenesis of Alzheimer’s.

Recent Coconut Oil Controversy

Coconut oil has gotten some bad press lately, and I wanted to briefly mention the study that prompted the American Heart Association to vilify coconut oil. I first want to point out that this study represents a severe conflict of interest.  It was written by authors who were funded by The Canola Oil Council, The Walnut Commission, The National Cattlemen’s Beef Association, and a long list of major pharmaceutical companies.  You can understand why competing industries would want to vilify their competition, and pharmaceutical companies have a deep vested interest in selling statin drugs.  With all the positive studies citing coconut oil’s benefits, it’s hard to conclude that coconut oil is unhealthy from this one clearly biased study.  If you’re still not convinced I’d recommend reading this article by Chris Kresser [12].


Eating meat is a good way to get high-quality saturated fats along with B vitamins, minerals and quality protein.   Although I do have patients who are vegans and vegetarians who receive good results, one of the challenges with vegetarian and vegan diets is they do not contain an adequate amount of B vitamins.   Meat is nutrient dense and it compliments a diet rich in fruits and vegetables (12) [13].

Poultry has significant amounts of monounsaturated fatty acids, and one study showed that eating poultry reduces the risk of obesity, cardiovascular disease, and type 2 diabetes (13) [14].

I recommend for my patients to eat organic, free-range, and pasture-raised meat whenever possible, as these types of quality meats are higher in their nutrient content.  For example, numerous studies show that grass-fed beef has a significantly higher level of total omega-3 fatty acids when compared to grain-fed beef (14) [15] (15) [16].


Seafood is a clear nutrient powerhouse of fat content.  Fish and shellfish are the richest sources of the omega 3 fatty acids DHA and EPA, which decrease inflammation in the body.  Seafood effectively prevents cardiovascular disease, regulates body weight, decreases the risk of type 2 diabetes, reduces inflammation, and it protects against Alzheimer’s (16) [17].  I frequently recommend a fish oil supplement to my patients to reduce inflammation.  Some will ask about krill oil and cod liver oil, and I do think these are good “wellness” sources of EPA and DHA, but they aren’t as effective as fish oils in reducing inflammation.  And the reason is because these have lower levels of EPA and DHA.

Fish is the greatest food source of vitamin D.  I find a lot of my patients have a vitamin D deficiency, and while most people with a vitamin D deficiency will need to take a supplement, eating a diet rich in seafood is one way to increase these levels.  Getting regular sunlight is also important.  Patients with both Graves’ disease and Hashimoto’s commonly have low vitamin D levels (17) [18].  Evidence suggests that a vitamin D deficiency may contribute to the development of thyroid autoimmunity, and that supplementation of vitamin D can help to decrease thyroid antibodies (18) [19] (19) [20].

Fish is a good source of iodine.  And while this might concern some people with thyroid and autoimmune thyroid conditions, keep in mind that iodine is crucial to thyroid function, it improves fertility, regulates the immune system, and speeds up wound healing.  An iodine deficiency can cause hypothyroidism, stunts growth and speech in children, and can even cause thyrotoxicosis in some cases (20) [21].  However, while I do think that an iodine deficiency eventually needs to be corrected, not everyone does well with iodine, and so before trying to correct an iodine deficiency you need to take certain precautions.  I talk more about iodine in an article I wrote entitled “An Update on Iodine and Thyroid Health [22]”.

Fish is also high in selenium.  Selenium has many benefits, as it is a cofactor of glutathione, plays a role in the conversion of T4 to T3, and there is also evidence showing that selenium reduces TPO antibody levels, improves thyroid ultrasound features, and can delay the progression of thyroid eye disease (21) [23].

This study specifically links fish consumption to a reduced risk of all-cause mortality.  You are less likely to die of any cause if you eat a diet rich in seafood (22) [24].  I typically recommend for my patients to eat at least 2-3 servings of seafood per week, and I recommend fresh wild-caught fish versus farmed varieties.

While there is no question that seafood has many health benefits, there are also risks associated with seafood consumption.  One of the main concerns is the mercury found in fish, although keep in mind that there are other environmental toxins as well, including polychlorinated biphenyls (PCBs).  As a result, while some healthcare professionals recommend to eat fish on a daily basis, I would try to limit your consumption of seafood to 2 to 3 times per week.

Nuts and Seeds

Nuts are off limits for my patients following a strict autoimmune Paleo (AIP) diet, but for those who have reintroduced nuts back in and they are well tolerated, nuts are a wonderful source of healthy fats.  Nuts are nutrient rich foods with wide ranging cardiovascular and metabolic benefits, which can be readily incorporated into healthy diets (23) [25].

Higher nut consumption equals lower body weight. In addition, several independent prospective studies found that increasing nut consumption was associated with lower weight gain over relatively long periods of time. Moreover, high consumption of nuts (especially walnuts) has been associated with lower diabetes risk (24) [26].

Brazil nuts can cause a significant increase in blood plasma selenium levels, and this study shows that the ingestion of a single serving of Brazil nut can acutely improve the serum lipid profile of healthy volunteers (25) [27].  However, the amount of selenium in a Brazil nut is variable, which is one reason why you might not want to rely on Brazil nuts to bring your selenium levels up.

Paleo-Friendly Fats and Oils:

Paleo Oils that are NOT AIP Compliant:

Oils To Always Avoid:

Why You Should Avoid Trans Fats

I briefly spoke earlier about trans fats, and there are a few reasons to avoid them.  First of all, trans fats have been shown to increase the ratio of LDL cholesterol to HDL cholesterol (26) [28].  Consumption of trans fats has proinflammatory effects in the body.  It increases CRP (inflammation marker) levels, and consumption of trans fats from partially hydrogenated oils adversely affects multiple cardiovascular risk factors and contributes significantly to increased risk of CHD events.

Final thoughts

In conclusion, I always prefer for my patients to get most of their daily fat intake from whole foods, because whole foods are more nutrient-dense than the isolated oils themselves.  When eating whole foods, it’s difficult to eat too much fat.

When using an oil for cooking, making salad dressing, etc., always choose fats from the healthy Paleo fats list and avoid anything processed or hydrogenated.

Cooking your own meals ensures you know exactly what oils are being used.  When eating out, it’s more difficult to control what oil is being used to cook your food.  Most restaurants use low quality, cheap vegetable oils for cooking, and so unless you know the chef, or the menu states what oils are used in cooking, you can assume anytime you eat out, you are consuming unhealthy fats.  This is one reason why I prefer to dine in most of the time.

Eating fat won’t make you fat. In fact, many studies in this article proved just the opposite.  Your body needs fat to function properly, so don’t be afraid of fats!  At the end of the day, industry-funded studies and mainstream media all have an agenda – to sell you something!  My agenda is proper nutrition to support thyroid health and reversing thyroid autoimmunity.