Eggs are a food product that is high in cholesterol, which raises concerns about their impact on blood cholesterol levels. High cholesterol can cause fatty deposits in blood vessels, causing the heart to overwork, and potentially leading to heart attack or stroke. Dietary cholesterol’s ability to raise blood cholesterol has been well-established by the scientific community, and has been shown to raise both total cholesterol and LDL cholesterol, the so-called “bad cholesterol” that causes the fatty buildups. 

However, dietary cholesterol’s impact on blood cholesterol remains a topic of study, and the potential for industry funding to influence research that may play a part in nutritional policy is an ongoing concern. The percentage of studies examining how eggs affect blood cholesterol that were funded by the egg industry has risen from 0% in the 1950s to 60% in 2010-2019. This review set out to examine whether industry-funded studies were more likely than non-industry-funded studies to report conclusions that were not supported by their objective data. 

To create this review, the authors searched through PubMed and the Cochrane Central Register of Controlled Trials for human study titles containing the words “egg” and “cholesterol.” The criteria for articles included in this review were:

1. Articles included observational studies, intervention studies, case reports, reviews, or meta-analyses involving adult humans
2. Articles focused on egg or egg yolk consumption
3. Articles reported total or LDL cholesterol levels in blood, serum, or plasma

Articles were excluded from the analysis for the following reasons:

1. The study lasted 24 hours or less
2. The effects of eggs couldn’t be separated from other factors (e.g., studies combining eggs with fatty foods or exercise)
3. Not enough data to determine the impact of egg consumption on total or LDL cholesterol
4. Conflicting results in study subgroups

211 articles met these criteria. Studies were considered to be industry-funded if they received money from companies, industry lobbies, or programs that promoted eggs, or egg-derived products. Findings that stated that eggs increased LDL or total cholesterol, posing cardiovascular risk, were labeled “unfavorable.” Findings that stated that eggs decreased LDL or total cholesterol, led to no change, or that the increase was made up for by other fat levels were labeled “favorable.”

For studies focused specifically on blood cholesterol, 58% published between 2010 and 2019 were industry-funded. 93% of non-industry-funded studies reported net increases in cholesterol, with 51% of these increases being statistically significant. 86% of industry-funded studies reported net increases in cholesterol, with 34% being statistically significant. No studies reported significant net decreases in cholesterol concentrations.

This review found that there was a notable difference in conclusions between industry-funded and non-industry-funded studies. 49% of industry-funded studies showed disagreement between their data and their conclusions (interpreting increases in cholesterol as favorable) versus 13% of non-industry-funded studies. Disagreement often involved non-statistically significant cholesterol increases being interpreted as no change or no negative impact. 

The review’s authors give the example of college freshmen being given an addition of 2 eggs at breakfast 5 days a week for 14 weeks. This was associated with an LDL increase of 15 mg/dL, a non-statistically-significant change, but which does not rule out any negative effects of eggs. Instead of noting this, the study’s authors concluded that the egg addition did not negatively impact blood cholesterol levels.

With these results in mind, advocates should take note of potential bias within industry-funded studies and alert the public about potential misinformation about the health benefits of egg or egg-derived products.