Are eggs bad for your cholesterol? What two randomised trials found

The fear that eggs wreck your cholesterol is largely a hangover from older nutrition advice, and the randomised evidence does not support it. When researchers actually assign people to eat a lot of eggs or almost none and then measure their blood, the cholesterol numbers barely budge. A 2024 trial in patients at cardiovascular risk found no meaningful difference in LDL or HDL cholesterol between a dozen eggs a week and near-abstinence [s1]. A year-long trial in people with diabetes reached the same conclusion [s2]. The dietary cholesterol in an egg is not the same thing as the cholesterol in your arteries.

The 2024 trial, in detail

The PROSPERITY trial set out to test the specific worry directly. It was an unblinded, two-by-two factorial study that randomised 140 patients — each with either a prior cardiovascular event or two cardiovascular risk factors — to fortified eggs versus a non-egg diet, and separately to time-restricted eating versus usual care [s1]. Patients in the egg group were given eggs and asked to eat at least 12 fortified eggs a week; the comparison group kept egg intake below 2 a week [s1]. The participants were older and higher-risk than average: median age 66, half were women, 27 percent were Black and 24 percent had diabetes [s1].

The co-primary endpoints were LDL and HDL cholesterol at four months. Neither moved in a way that mattered. Comparing the high-egg group with the non-egg group, the difference in change from baseline was -0.64 mg/dL for HDL (95% confidence interval -3.86 to 2.58) and -3.14 mg/dL for LDL (95% CI -10.81 to 4.52) [s1]. Both intervals straddle zero, meaning no statistically or clinically significant effect from eating a dozen fortified eggs a week. The authors' own conclusion was that the data "did not demonstrate clinically relevant differences" in LDL and HDL over four months [s1]. A prespecified subgroup hinted at a nonsignificant HDL rise and LDL fall with eggs in patients aged 65 and over, but that is a signal to test further, not a result [s1].

The longer trial agreed

PROSPERITY was not the first randomised test. The Diabetes and Egg (DIABEGG) study followed 128 people with prediabetes or type 2 diabetes — a group often told specifically to limit eggs — through a three-month weight-loss phase and out to 12 months total [s2]. One group ate at least 12 eggs a week, the other fewer than 2, with both diets built to replace saturated fats with mono- and polyunsaturated fats [s2].

Weight loss was identical: -3.1 kg in the high-egg group versus -3.1 kg in the low-egg group (P = 0.48) [s2]. More to the point for the cholesterol question, there were no differences between the groups in blood lipids, in glycaemic markers such as glucose and glycated haemoglobin, or in markers of inflammation and oxidative stress, whether measured from 3 to 12 months or across the full 0 to 12 months [s2]. A high-egg diet, in the population most often warned off eggs, did nothing detectable to their cardiometabolic risk factors.

Why dietary cholesterol matters less than assumed

The mechanism explains the null. For most people, the liver adjusts its own cholesterol production in response to what arrives in the diet, so eating cholesterol raises blood cholesterol far less than the arithmetic suggests. That is why national guidance quietly dropped its strict daily cholesterol cap years ago, and why the saturated-fat content of a meal generally predicts its effect on LDL better than its cholesterol content — the same re-examination running through the evidence on whole-fat dairy and red and processed meat.

Two honest limits. Both trials measured blood markers over months, not heart attacks over years, and neither was blinded. There is also long-running debate about egg intake and diabetes risk in observational cohorts, and people vary — a minority are "hyper-responders" whose LDL does climb on a high-cholesterol diet. But the randomised evidence, where it exists, is consistent: for most people, including those at elevated cardiovascular risk, a dozen eggs a week does not move cholesterol in a way that matters [s1][s2].

So, are eggs bad for your cholesterol?

On the best available randomised evidence, no — not for most people. Two trials that deliberately fed people many eggs or almost none found no clinically meaningful difference in LDL or HDL cholesterol [s1][s2]. What still counts is the company eggs keep: the butter, bacon and fried bread carry the saturated fat that does move LDL. As with most single-food scares, the villain was oversold and the context underrated.

This article is informational and is not medical advice.

Sources

• Effects of fortified eggs and time-restricted eating on cardiometabolic health: The PROSPERITY trial — American Heart Journal, 2024
• Effect of a high-egg diet on cardiometabolic risk factors in people with type 2 diabetes: the DIABEGG Study — The American Journal of Clinical Nutrition, 2018