Does the Type of Dietary Fat Affect Your Risk of Heart Disease?

Controlled dietary trials consistently show that replacing saturated fats with unsaturated fats lowers LDL cholesterol, a major contributor to atherosclerosis.

The benefits are particularly clear when saturated fats are replaced with polyunsaturated fats from vegetable oils, nuts and seeds.

Long-term evidence also supports lower coronary heart disease risk.

A previously published analysis of four major dietary intervention trials, discussed in this review, reported approximately 29% lower coronary heart disease risk when saturated fats were replaced with polyunsaturated fats.

Simply reducing saturated fat is not enough.

Replacing butter or fatty meat with refined starches and added sugars does not provide the same cardiovascular benefits as replacing them with unsaturated fats.

Such substitutions may also worsen triglyceride levels and metabolic health.

Replacing saturated fats with fiber-rich whole grains is more favorable than replacing them with refined carbohydrates.

The key consideration is therefore not only what is removed from the diet, but what takes its place.

A network meta-analysis of 54 randomized trials found that replacing butter with various vegetable oils lowered LDL cholesterol.

Olive, sunflower and other non-tropical vegetable oils generally produced more favorable cholesterol profiles than butter.

However, margarine requires an important distinction.

Older margarines made with partially hydrogenated oils contained industrial trans fats, which adversely affect cholesterol levels and cardiovascular health.

Some older dietary trials used these products, making their findings difficult to apply to modern margarines.

Contemporary soft vegetable-oil spreads containing mainly unsaturated fats and little saturated fat may provide a healthier fatty acid profile than butter.

However, the review did not directly compare every modern margarine formulation.

Milk, yogurt, cheese and butter differ in fat content, protein, minerals and fermentation.

Clinical studies found lower LDL cholesterol after consuming cheese compared with butter containing similar amounts of saturated fat.

However, cheese may still raise LDL cholesterol compared with certain plant-based alternatives.

The authors emphasize that the health effects of dairy depend on the specific product, its quantity and the foods it replaces.

Moderate dairy consumption can be compatible with a heart-healthy diet.

Eating fish rich in omega-3 fatty acids is associated with favorable cardiovascular outcomes in observational studies.

However, clinical trials of omega-3 supplements have produced mixed results.

High-dose prescription EPA reduced cardiovascular events in selected high-risk patients, but another trial using an EPA–DHA formulation did not show similar benefits.

These results should not be interpreted as proof that ordinary fish-oil supplements prevent heart disease in everyone.

The review also challenges claims that omega-6-rich seed oils are inherently inflammatory or harmful.

Human studies generally support their cardiovascular benefits when they replace saturated fats.

The authors emphasize that people eat foods, not isolated fatty acids.

Replacing processed meat with nuts, legumes or whole grains is not equivalent to replacing it with refined carbohydrates.

The review also identifies a potential inconsistency in the 2025–2030 Dietary Guidelines for Americans.

Although the guidelines recommend limiting saturated fats to less than 10% of daily energy intake, they also emphasize certain animal foods rich in saturated fat.

The authors argue that clearer recommendations about healthier food substitutions would help resolve this confusion.