Dispelling the Myth: Do All Fats Raise LDL?

October 15, 2025 •

3 min read

While it's a common belief that all dietary fat is bad, the reality is more nuanced. A heart-healthy diet requires distinguishing between the different types of fat to understand their specific impact on LDL cholesterol, not assuming do all fats raise LDL is a universally true statement.

Quick Summary

The impact of fat on LDL cholesterol depends on its type. Saturated and trans fats, found in sources like red meat and processed foods, raise LDL levels. In contrast, unsaturated fats from plants and fish can help lower LDL cholesterol and improve heart health.

Key Points

Not all fats are equal: Saturated and trans fats raise LDL cholesterol, while unsaturated fats can help lower it and improve heart health.
Trans fats are the most harmful: Artificial trans fats not only raise LDL but also lower HDL, posing the highest risk to heart health.
Replace wisely: Swapping saturated fat with healthy unsaturated fat is beneficial, but replacing it with refined carbohydrates is not.
Source matters for saturated fats: The food matrix affects how certain saturated fats influence cholesterol, with sources like cheese having a different impact than butter.
Eat unsaturated fats in moderation: Prioritize monounsaturated fats (like olive oil and avocados) and polyunsaturated fats (like fatty fish and nuts) to help manage cholesterol.
Focus on overall diet: A healthy eating pattern emphasizing fruits, vegetables, whole grains, and lean protein is key, rather than focusing solely on eliminating fat.

The idea that all dietary fats are villains in the story of heart health is a widespread and persistent myth. For decades, low-fat diets were promoted as the solution to cardiovascular disease, but modern nutritional science has painted a much clearer, and more complex, picture. The truth is that fats are a necessary part of a healthy diet, providing energy, supporting cell function, and helping the body absorb vital vitamins. The key lies in understanding the different types of fat and their distinct effects on low-density lipoprotein (LDL) cholesterol, the so-called "bad" cholesterol.

Understanding LDL Cholesterol and Its Particles

LDL cholesterol is a fatty substance carried in the blood, responsible for transporting cholesterol from the liver to the body's cells. While essential, an excess of LDL can lead to plaque buildup in the arteries, increasing the risk of heart disease and stroke. LDL exists in different sizes and densities, and some research suggests that small, dense LDL particles are more atherogenic (plaque-forming) than larger ones. The type of fat consumed can influence the total amount of LDL and the size of these particles.

The Different Types of Dietary Fat

There are four major types of dietary fat: saturated, trans, monounsaturated, and polyunsaturated. Each has a different chemical structure and effect on blood cholesterol levels.

Fats That Increase LDL

Saturated Fats

Saturated fats, found primarily in animal products like fatty meat and full-fat dairy, are generally solid at room temperature. While needed in small amounts, excessive intake can raise LDL cholesterol. The impact isn't uniform; different saturated fatty acids have varied effects, and the food source matters. Limiting saturated fat intake as part of a balanced diet is recommended.

Trans Fats

Artificial trans fats, created by adding hydrogen to liquid vegetable oils, are particularly harmful. They raise LDL cholesterol and lower HDL ("good") cholesterol. Found in many fried and processed foods, regulations have led to reduced use of trans fats.

Fats That Improve Cholesterol Profiles

Monounsaturated Fats (MUFAs)

MUFAs are heart-healthy fats, liquid at room temperature, that can lower LDL and maintain or increase HDL. Good sources include olive oil, avocados, nuts, and seeds.

Polyunsaturated Fats (PUFAs)

PUFAs, including omega-3 and omega-6 fatty acids, are also liquid at room temperature and can help lower LDL cholesterol. These essential fatty acids must come from food.

Omega-3s: Found in fatty fish, flaxseeds, and walnuts, also helping lower triglycerides.
Omega-6s: Found in vegetable oils like sunflower and corn oil.

What to Replace Fat With?

Replacing saturated fats with polyunsaturated fats is most beneficial for reducing LDL. However, replacing saturated fats with refined carbohydrates can negatively impact triglycerides and LDL particle size. The quality of the replacement matters significantly.

Fat Type Comparison


Feature	Saturated Fats	Trans Fats	Monounsaturated Fats	Polyunsaturated Fats
Physical State	Solid at room temperature	Solid at room temperature (artificial)	Liquid at room temperature	Liquid at room temperature
Primary Sources	Red meat, butter, cheese, coconut oil	Fried foods, baked goods, shortening	Olive oil, avocado, nuts, canola oil	Fatty fish, flaxseed, walnuts, sunflower oil
Effect on LDL	Raises LDL cholesterol	Significantly raises LDL cholesterol	Lowers LDL cholesterol	Lowers LDL cholesterol
Effect on HDL	May slightly raise HDL	Lowers HDL cholesterol	Maintained or slightly raised HDL	Can lower HDL slightly, but less than LDL
Overall Heart Impact	Limiting recommended	Avoid completely; most harmful	Highly beneficial	Highly beneficial

Conclusion: The Key Takeaway on Fats and LDL

Not all fats negatively impact heart health and raise LDL cholesterol. Trans fats and, to a lesser extent, saturated fats can raise LDL, while unsaturated fats can improve cholesterol profiles. A healthy approach focuses on replacing unhealthy fats with healthy ones and prioritizing whole foods. Making informed dietary choices can help manage cholesterol and reduce heart disease risk.

For more information on dietary fats and heart health, consult the American Heart Association.

What are dietary fats?

Frequently Asked Questions

Excessive intake of saturated fat can raise your LDL ("bad") cholesterol levels. It's important to limit your intake and opt for healthier, unsaturated fats when possible.

Trans fats are particularly damaging to cholesterol levels. They raise your LDL cholesterol while simultaneously lowering your HDL ("good") cholesterol.

Not effectively. Replacing saturated fats with refined carbohydrates can lower LDL but also increases triglycerides and reduces HDL, which is not beneficial for heart health.

Excellent sources include olive oil, avocados, nuts, seeds, and fatty fish like salmon and mackerel.

For most people, dietary cholesterol has a much less significant effect on blood cholesterol levels compared to saturated and trans fats. Organizations like the British Heart Foundation recommend focusing on lowering saturated fat intake instead.

Not all LDL particles are the same. Smaller, denser LDL particles are considered more harmful (atherogenic) than larger, more buoyant ones. Diet can influence particle size and density.

Focus on an overall healthy dietary pattern. This includes reducing saturated and trans fat, increasing intake of fruits, vegetables, whole grains, and healthy unsaturated fats, and limiting processed foods and added sugars.