Nutrition Diet: What are the worst fats for heart disease?

October 15, 2025 •

3 min read

According to the World Health Organization, more than 278,000 deaths each year can be attributed to the intake of industrially produced trans fat, highlighting the critical role of fats in cardiovascular health. This comprehensive guide examines what are the worst fats for heart disease and provides actionable dietary advice to protect your heart.

Quick Summary

This guide details the harmful effects of trans fats and saturated fats on heart health, explaining their impact on cholesterol levels and identifying common food sources to avoid. It also provides strategies for replacing unhealthy fats with beneficial ones for a healthier diet.

Key Points

Avoid Trans Fats Completely: Industrially produced trans fats from partially hydrogenated oils are the most harmful type of fat for your heart and should be avoided entirely.
Limit Saturated Fats: Found mainly in animal products and some tropical oils, saturated fats can increase 'bad' LDL cholesterol and should be consumed in moderation, with the AHA recommending less than 6% of daily calories from saturated fat.
Prioritize Unsaturated Fats: Replace bad fats with heart-healthy monounsaturated and polyunsaturated fats, including beneficial omega-3s found in fatty fish, nuts, and plant oils.
Read Food Labels Carefully: Always check the ingredients list for 'partially hydrogenated oils' to detect hidden trans fats, even if the nutrition panel claims '0 grams' due to rounding rules.
Choose Healthier Cooking Methods: Opt for cooking methods like baking, grilling, or roasting, and use liquid vegetable oils over solid fats like butter and shortening.
Shift to Whole Foods: Reduce your intake of ultra-processed foods, baked goods, and fried items, which are common sources of unhealthy fats, in favor of fruits, vegetables, and whole grains.

Fats are an essential part of our diet, but not all fats are created equal. For heart health, certain types of fat can be detrimental, primarily by affecting cholesterol levels and contributing to arterial plaque buildup. Understanding which fats to limit or avoid is a critical step toward a heart-healthy diet.

The #1 Culprit: The Dangers of Trans Fats

Industrially produced trans fats are considered the most harmful type of fat for heart health. They are formed through hydrogenation, turning liquid vegetable oils into solid fats to enhance shelf life and texture. Trans fats negatively affect cholesterol by raising LDL ('bad') cholesterol, which contributes to atherosclerosis (plaque buildup in arteries), and by lowering HDL ('good') cholesterol, which helps clear excess cholesterol. Due to their clear health risks, the WHO advocates for the elimination of these fats, and many countries have implemented bans.

Common Sources of Industrially Produced Trans Fats

To minimize trans fat intake, be aware of foods that may contain them, including fried foods, baked goods, stick margarine, processed snacks, refrigerated dough, and pre-made frosting.

How to Spot Trans Fats on Food Labels

Check the ingredients list for 'partially hydrogenated oil'. This indicates the presence of artificial trans fats, even if the label states '0 grams trans fat' due to regulations allowing rounding down if the amount is less than 0.5 grams per serving. Paying attention to total fat content can also help identify foods to consume in moderation.

Understanding Saturated Fats and Their Risks

Saturated fats, typically solid at room temperature and found mainly in animal products and some tropical oils, can also harm heart health when consumed excessively. A high intake can raise LDL cholesterol, increasing heart disease risk. The American Heart Association recommends limiting saturated fat to less than 6% of daily calories.

Common Sources of Saturated Fats

Sources of saturated fats include fatty meats, high-fat dairy, poultry skin, lard, tallow, tropical oils, and many processed foods.

Replacing Bad Fats with Heart-Healthy Alternatives

Improving heart health involves replacing unhealthy fats with beneficial monounsaturated and polyunsaturated fats. Monounsaturated fats, found in olive oil, avocados, nuts, and seeds, can lower LDL cholesterol. Polyunsaturated fats (including omega-3 and omega-6), present in fatty fish, walnuts, flaxseeds, and certain vegetable oils, are essential fats, with omega-3s known for reducing inflammation and triglycerides.

A Comparison of Fats for Heart Health


Feature	Trans Fat	Saturated Fat	Unsaturated Fat (Mono & Poly)
Heart Health Impact	Worst for heart; raises LDL, lowers HDL, increases inflammation.	Poor for heart in excess; raises LDL.	Best for heart; lowers LDL, may raise HDL, reduces inflammation.
State at Room Temp	Solid.	Solid.	Liquid.
Primary Sources	Fried foods, baked goods, processed snacks.	Animal products, full-fat dairy, some tropical oils.	Fish, nuts, seeds, avocados, olives, plant oils.
Chemical Structure	Contains hydrogenated oils with altered molecular bonds.	Carbon chain fully saturated with hydrogen atoms.	Contains one (mono) or more (poly) double bonds.

Building a Heart-Healthy Nutrition Diet

Creating a heart-healthy diet involves making conscious choices about fat intake. Key strategies include:

Prioritize Plant-Based Proteins: Replace some red and processed meats with legumes, beans, nuts, and seeds.
Choose Lean Protein: Opt for lean cuts of meat and skinless poultry, cooked using healthy methods like baking or grilling.
Use Healthy Cooking Oils: Substitute solid fats with liquid vegetable oils such as olive or canola oil.
Embrace Whole Foods: Focus on minimally processed foods like fruits, vegetables, and whole grains, which are lower in unhealthy fats, salt, and sugar.
Be Mindful of Portion Sizes: Manage overall calorie intake and body weight by being aware of portion sizes for all foods, including healthy fats.

Conclusion: Making Smarter Fat Choices for a Healthier Heart

Identifying what are the worst fats for heart disease is essential for a heart-healthy diet. Industrially produced trans fats are the most detrimental and should be avoided. While less harmful, saturated fats should be consumed in moderation and replaced with unsaturated fats as recommended by health organizations. Simple dietary swaps, like using olive oil instead of butter and choosing nuts over fried snacks, can significantly improve cardiovascular health, manage cholesterol, and reduce inflammation, contributing to a healthier life.

Heart Foundation Australia: A heart healthy eating pattern

Frequently Asked Questions

Saturated fats are naturally occurring and mainly found in animal products and tropical oils. Industrially produced trans fats, however, are a byproduct of a manufacturing process and are particularly harmful because they both raise 'bad' LDL cholesterol and lower 'good' HDL cholesterol.

When shopping, the most important step is to read the ingredient list on packaged foods. Look for the words 'partially hydrogenated oil' and avoid any products containing it. Do not rely solely on the '0 grams trans fat' claim on the nutrition label, as manufacturers can round down small amounts.

While excessive intake of most saturated fats increases heart disease risk by raising LDL cholesterol, some research suggests the effect can depend on the food source and what it is replaced with. Replacing saturated fat with polyunsaturated fat is consistently shown to be beneficial.

For heart health, it is best to use oils high in monounsaturated and polyunsaturated fats, such as olive, canola, sunflower, and corn oil. These are healthier alternatives to solid fats like butter, shortening, and tropical oils like palm and coconut oil.

Yes, diet plays a significant role in managing cholesterol levels. A diet high in saturated and trans fats can raise 'bad' LDL cholesterol, while replacing them with unsaturated fats and increasing fiber can help lower LDL and improve overall cholesterol profiles.

For healthier snacking, choose options like a handful of unsalted nuts, apple slices, carrot sticks, or plain yogurt. These provide healthy fats and other nutrients while helping you avoid processed snacks containing unhealthy fats.

Naturally occurring trans fats from ruminant animals like cows are present in small amounts in some meat and dairy products. Unlike industrially produced trans fats, these have not been shown to pose the same significant health risks at typical consumption levels.