In a groundbreaking clinical trial, researchers have reexamined the roles of cholesterol and saturated fat, revealing that eggs may be much less harmful—and possibly even beneficial—than once believed. This latest study adds to a growing body of evidence challenging long-held dietary assumptions.
In a world-first investigation, scientists from the University of South Australia (UniSA) explored how dietary cholesterol and saturated fat separately affect levels of “bad” cholesterol, or LDL. Their findings showed that consuming two eggs daily as part of a high-cholesterol, low-saturated-fat diet actually reduced LDL levels and lowered the risk of heart disease.
“Eggs have been unfairly blamed due to outdated nutrition advice,” said lead researcher Professor Jon Buckley from UniSA. “They’re unique—high in cholesterol, but low in saturated fat. Yet it’s their cholesterol content that has often made people question whether they belong in a healthy diet.”
Study Pits Egg-Rich, Egg-Free, and High-Fat Diets Against Each Other
In a randomized, controlled crossover study, 61 healthy adults followed three different five-week diets, each separated by a break. All diets had the same number of daily calories, but varied in cholesterol and saturated fat. The egg diet included two eggs per day, making it high in cholesterol but low in saturated fat; the egg-free diet was low in cholesterol but high in saturated fat; the control diet was high in both, including just one egg per week.
Specifically, the egg diet delivered 600 mg/day of cholesterol (6% saturated fat), the egg-free diet had 300 mg/day (12% saturated fat), and the control had 600 mg/day (12% saturated fat).
Results showed that the egg diet significantly lowered LDL (“bad”) cholesterol compared to the control (103.6 µg/dL vs. 109.3 µg/dL). The egg-free diet, despite its lower cholesterol content, had no significant effect on LDL levels. Saturated fat, not cholesterol, appeared to drive LDL changes.
Digging deeper, researchers found changes in the types of LDL particles. The egg diet reduced total LDL but also altered particle composition—fewer large, less risky particles and a slight increase in smaller, denser ones linked to plaque buildup. While this shift isn’t clearly harmful, it raises new questions and highlights the need for further research.
Saturated Fat, Not Egg Cholesterol, Identified as Key Factor in LDL Levels
The no-egg diet also led to a rise in small LDL particles and a drop in large ones, but didn’t significantly lower overall LDL cholesterol. The study’s findings pointed to saturated fat—not cholesterol from eggs—as the real driver of elevated LDL. This suggests that avoiding eggs without reducing saturated fat intake is unlikely to improve cholesterol levels
Additional results showed that the egg-rich diet increased blood levels of lutein and zeaxanthin—antioxidants found in egg yolks that support brain and eye health and reduce inflammation. Interestingly, higher levels of these carotenoids were linked to increased spontaneous physical activity among participants. Though not a proven cause-and-effect relationship, researchers suggest these compounds might influence motivation or energy regulation in the brain.
“We isolated the effects of cholesterol and saturated fat and found that high cholesterol from eggs, when combined with low saturated fat, doesn’t raise LDL,” said Professor Jon Buckley. “Instead, saturated fat is the main culprit.”
This trial builds on earlier observational research from Monash University, which reported that eating up to six eggs per week was associated with a 29% lower risk of heart disease compared to rarely eating them.
New Research Challenges Decades of Misguided Fears About Eggs
Although skeptics might dismiss such findings as egg industry propaganda, these studies challenge outdated thinking shaped by the era of “nutrient reductionism”—when foods were judged based on single components like fat or cholesterol. For decades, eggs were demonized due to their cholesterol content, despite weak evidence linking dietary cholesterol directly to heart disease. By the 1980s and ’90s, the yolk was vilified again during the low-fat craze, even though it contains most of the egg’s nutrients and primarily healthy fats.
This reductionist view overlooks the complexity of how our bodies process whole foods within the context of meals, metabolism, and lifestyle. Nutritional science is now shifting toward a more holistic understanding.
“So when it comes to breakfast,” Buckley noted, “it’s not the eggs you should worry about—it’s the bacon or sausage that poses more risk to your heart.”
Still, the study underscores the need for more research on how eggs affect not just LDL levels, but the specific types of LDL particles.
Currently, the American Heart Association recommends that healthy individuals can safely eat one egg per day—and that older adults with healthy cholesterol can have up to two—due to eggs’ strong nutritional profile.
Read the original article on: New Atlas