The Short Answer

Dietary fat doesn’t raise cholesterol—sugar and refined carbohydrates do. For people managing autoimmune conditions, including those with Hashimoto’s low thyroid, consuming healthy, whole fats while eliminating processed oils and trans fats supports better inflammation control and cardiovascular health. Choosing the right fat sources matters far more than limiting fat intake overall.

The cholesterol myth and autoimmune health

It’s time to let go of the belief that fat raises cholesterol. Research is clear: it’s sugar, refined carbohydrates, and processed foods that cause unhealthy cholesterol levels and chronic inflammation. Too much sugar and processed carbs lower good cholesterol, raise triglycerides, and create the small, dangerous particles that cause arterial plaque. These factors raise the risk of heart disease and insulin resistance—conditions that complicate the management of any autoimmune condition.

Sugars and processed carbs are dangerous because they cause high blood sugar, which raises insulin levels and systemic inflammation. These two factors are foundational to heart disease and most chronic health disorders, including autoimmune conditions like Hashimoto’s low thyroid. Chronic inflammation stems from excess sugars and carbs, a diet lacking whole foods and vegetables, a sedentary lifestyle, chronic stress, food intolerances, and chronic infections.

Several widely believed cholesterol myths directly affect autoimmune health management:

Statins: Recent research shows that statin benefits likely stem from their ability to lower inflammation, not cholesterol levels.

Heart attack: Approximately 75 percent of people who experience heart attacks have normal cholesterol levels.

Age: In older adults, those with higher cholesterol actually have a lower risk of death than those with lower levels.

Inflammation: Harvard research demonstrates that high systemic inflammation is a stronger risk factor for heart disease than high cholesterol.

Healthy fats support autoimmune management

Conventional medicine promoted low-fat diets for decades, but emerging evidence shows we need more healthy fat than previously recommended. The key distinction is that not all dietary sources of fat are created equal. The type of fat you consume directly affects inflammation and metabolic health, which is especially important when managing autoimmune conditions.

To support autoimmune health, consume healthy, whole, unprocessed fats and eliminate processed vegetable oils from your diet. Completely avoid trans fats (hydrogenated and partially hydrogenated oils) as they raise cardiovascular disease risk and can damage brain function.

Omega-3 and monounsaturated fats raise healthy cholesterol and dampen autoimmune inflammation.

The dietary reference intake (DRI) for fat consumption is 20 to 35 percent of total calories. This equals 44–77 grams of fat for a 2,000-calorie diet. These ratios adjust if you’re following a low-carb or ketogenic diet, which replaces carbohydrate calories with fat calories.

These are the recommended fat ratios for conventional diets:

Monounsaturated fat: 15–20 percent

Polyunsaturated fat: 5–10 percent

Saturated fat: less than 10 percent (unless following a ketogenic diet)

Trans fat: 0 percent

Cholesterol: less than 300 mg per day

Unsaturated fats. Usually liquid at room temperature. Includes monounsaturated and polyunsaturated varieties.

Monounsaturated fats. Healthy sources include nuts, olives, and avocado. Avoid canola oil.

Polyunsaturated fats. Healthy plant-based sources include nuts, seeds, and fish. Avoid processed seed and grain oils (especially corn oil) due to their susceptibility to rancidity and oxidative damage.

Omega-3 fatty acids are polyunsaturated fats that actively dampen inflammation. Healthy sources include cold-water fish (salmon, tuna, herring, and anchovies), flaxseed, chia seed, and walnuts. For autoimmune patients, these are particularly important for managing systemic inflammation.

Saturated fats. Solid or waxy at room temperature, these are derived from animal products and tropical oils like coconut and palm. Excessive saturated fat is associated with increased “bad” LDL cholesterol and inflammation. Healthy saturated fat sources include:

Beef, pork, lamb, veal, and poultry skin

High-fat dairy products

Butter, lard, and bacon fat

Coconut, palm, and palm kernel oils

Low-carb and ketogenic diets. Fat intake guidelines shift on very low-carbohydrate diets because carb restriction affects how saturated fat behaves in the bloodstream. People following these diets can safely consume higher ratios of saturated fats. Many individuals find that low-carb or ketogenic approaches help them better manage autoimmune symptoms and inflammation.

Trans fats. These form when liquid fat is converted to solid fat through hydrogenation, making products more shelf-stable. However, trans fats raise “bad” LDL cholesterol, decrease “good” HDL cholesterol, increase inflammation, and damage brain tissue. Avoid them completely.

Trans fats hide in solid margarine, shortening, powdered and liquid creamers, and most convenience and prepackaged foods. Check ingredient labels; if it says “hydrogenated” or “partially hydrogenated,” avoid it completely.