Eggs contain cholesterol. Eggs raise cholesterol. Cholesterol causes heart disease. Eggs cause heart disease…right?
No. Not even close. But for decades this was a popular belief. In this post we will discuss specifically the effect regular egg consumption has on blood lipids, including HDL, LDL, and total cholesterol, as well as the total/HDL cholesterol ratio, not egg consumption and risk of heart disease (future post).
This topic was suggested to me after I uploaded a video discussing LDL particle size and atherosclerosis, a rebuttal video intended to discredit the claims made by a vegan Youtuber named Vegan Gains. A different vegan goaded me with a comment claiming that there was no way I could debunk another “evidence-based” video, by Mic the Vegan this time, about the failure of eggs to raise HDL cholesterol, contrary to common dietary advice.
First, a note about bias. Mic the Vegan cleverly pointed out that some studies on this topic are funded by the Egg Nutrition Center (ENC), a branch of the American Egg Board, and the Egg Nutrition Council, the Australian version of the ENC. The ENC funded studies often come from the University of Connecticut and are performed by Maria Luz Fernandez’s research group (she is the last author listed in several studies on this topic). This certainly raises my eyebrows. Food politics drastically affects science. We cannot rely solely on studies funded by the Egg Nutrition Center or the Egg Nutrition Council to determine the effect eggs have on serum lipids.
Here is a quote from the ENC’s about page: “The Egg Nutrition Center (ENC) is the science and nutrition education division of the American Egg Board (AEB), a national checkoff program on all egg farms with more than 75,000 hens.”
Yikes, I don’t support those eggs. Those eggs are raised in disease-ridden environments but time to get back on topic.
The bias runs both ways. Just a note for vegans, it’s not as if this type of bias is only seen among the meat, dairy, and egg industries. The American dietary guidelines have been influenced by big agriculture for the last several decades. The American Diabetes Association and American Heart Association’s diets reflect the lobbying of these pro-grain industries. The bias is on BOTH sides, not just with eggs. It’s grains, sugar, vegetable oil, and eggs, but the first three have far more lobbying and industry backing than factory eggs. Here’s a talk I liked on the subject by Nina Teicholz, author of “Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet.”
Regardless, not all of the ENC-funded studies conclude that egg consumption raises HDL cholesterol, or the “good” kind (a major simplification). In fact, their research doesn’t show it all to well, as we will see. Throughout this post I will mention conflicts of interest in the studies I cite. There are a few studies that do not seem to have conflicts of interest, but you never know. Lastly, this isn’t a literature review; I will cite the studies I’ve found, and in the future if I find more interesting information this post will be updated.
Do Eggs raise total, HDL, and LDL cholesterol (or any of them)?
Short answer, no, not really. Long answer, it probably depends, partly on the fact that we don’t all absorb cholesterol the same, as indicated by different campesterol:lathosterol ratios. Wait what?
Basically, some people absorb more cholesterol than others. Some people endogenously produce more, and I’m sure both of these factors are modifiable through diet. Lathosterol is an intermediate in the numerous reactions involved in cholesterol biosynthesis. The final step in cholesterol synthesis is the conversion of lanosterol to cholesterol. It’s in this step where lathosterol is produced.
I don’t know exactly why, but lathosterol is correlated to whole body cholesterol production/synthesis better than the other intermediates. Campesterol is a plant sterol. But, it’s also found in our blood (maybe through the plants we eat I suppose) in small concentrations and indicates cholesterol absorption. I found a great article by BJJ Caveman that goes into more detail.
So lathosterol indicates PRODUCTION and campesterol indicates ABSORPTION. In a study involving 98 final participants (the number of people who’s data was analyzed) who consumed a lutein-enriched cholesterol drink daily for one year, the ratio of campesterol to lathosterol (C:L) had a significant effect on lutein absorption but not cholesterol levels. The purpose of this study was to determine if there were differences in the change in serum lipids and lutein absorption based on the ratio. Lutein is in important for eye health, and the participants in this study had early signs of age-related macular degeneration.
Participants were dived into a low, medium, or high campesterol: lathosterol group. A high ratio indicated greater absorption and a low ratio indicated more production. They drank a mixture of 1.5 egg yolks with 80 mL buttermilk. The egg yolks had higher lutein levels than normal, because of the type of feed that was used. Interesting design! The drink supplied 323 mg cholesterol, which is above the recommended daily limit of 300mg/day set by the American Heart Association . Over the course of a year, that’s 8,395 extra mg of cholesterol over a year! Sounds like a lot, but it’s pretty miraculous that our body knows how to stay in balance to an extent.
Total cholesterol levels on average increased 0.18 mmol/L which converts to roughly 7 mg/dl a small increase. The LDL increase was a little below that. HDL did not increase. And most importantly, the total cholesterol to HDL cholesterol ratio (an important predictor of cardiovascular disease risk) decreased on average a little bit, but the results were not statistically significant at all. Thus, no change in the ratio. Furthermore, the C:L ratio had no significant effect on total, HDL, or LDL levels after one year.
So, even in people who absorb more cholesterol (the higher C:L ratio group), there was no difference in lipids after one year. However, the high cholesterol absorbers showed increased lutein and zeathantin levels after a year compared to the low and mid-absorbers, which probably helps their eyes.
Summary of research
Here is a brief rundown of a bunch of other studies. Let’s start with the ones that have conflicts of interest and go through their design briefly, each.
Studies with conflict of interest:
- Low carb diet + 3 eggs a day (640 mg cholesterol). ML Fernandez.
- This study was funded by the ENC it involved a restricted carbohydrate diet which is a MAJOR confounder. I’m sharing this study not necessarily to answer our question, but to show how this study does not answer our question. It does provide some clues as to the methods those with conflicts of interest employ. Fernandez is involved in three additional studies that combine egg consumption with a low-carbohydrate diet. This makes me wonder if she purposely chose to restrict carbohydrates in the participants knowing that it was likely to favorably change lipids, just to make eggs look like they contributed in raising HDL cholesterol. Or, perhaps her research question was simply to investigate if consuming eggs with a low-carb diet improved blood lipids. Judging by the language in the introduction of this paper, where she extolls the virtues of eggs, it seems like perhaps her motive was to make eggs look good in the public eye. If that’s the case, none of her studies can be trusted and all her papers on the topic should be retracted.
- I gave her UConn phone number a call to ask more but haven’t heard from her yet, fyi.
- However, on the plus side, 3 eggs were consumed daily, supplying over 600 mg cholesterol, twice the daily limit set by the American Heart Association, and yet cholesterol levels still did not increase.
- 2 eggs (370 mg cholesterol) for breakfast versus oatmeal for breakfast in college students. ML Fernandez.
- In this study, total, HDL, and LDL cholesterol increased. There was no significant difference in the oatmeal versus egg group in the LDL to HDL ratio. However, they did not report the total to HDL ratio, but from a quick eyeball, it seems to have decreased in the egg group. Overall, not a huge change.
- They also measured satiety, which was higher in the egg group than the oatmeal group.
- Two eggs for breakfast a day for six weeks in diabetics. Egg Nutrition Council-funded study.
- In this study one group of participants was instructed to eat 2 eggs a day for breakfast daily for six weeks while the other group was instructed to eat less than 2 eggs a week, and obtain protein from lean sources.
- At the end of the three month period, the egg group consumed on average 11.8 eggs per week, while the low-egg group consumed 1 egg a week.
- Participants were also instructed to reduce their intake of saturated fats. This raises my eyebrow. What was the point of that?
- Results: no significant difference in the change in total, HDL, or LDL cholesterol between groups.
The studies with conflicts of interest, especially those authored by Maria L. Fernandez of the University of Connecticut, try desperately to show that eggs raise HDL cholesterol without raising LDL. But in the one Fernandez paper where people were not on a carb restricted diet, both HDL and LDL went up. In the Australian study, no differences were found between groups. HDL did not go up. Eggs do not raise HDL cholesterol without also increasing LDL, that’s for sure. Let’s look at the studies without conflicts of interest.
Studies without any apparent conflicts of interest: summary
- 1 egg a day. Japan.
- 14 healthy male volunteers consumed one egg a day for breakfast for 4 weeks.
- HDL cholesterol increased significantly, and the LDL/HDL cholesterol decreased.
- LDL cholesterol did not increase.
- However there was a statistically significant increase in polyunsaturated fat (PUFA) consumptoin as well, perhaps in the margarine that was added to the breakfast. Yuck. This could possibly be a confounding factor, and the researchers note that the ratio of PUFAs to saturated fatty acids (SFAs) did not change in the study and therefore it was not likely a factor.
- Association of serum lipids with coffee, tea, and egg consumption. Israel.
- This study was not an intervention study. The researchers examined associations between the number of eggs people reported to consume on average per day and their serum cholesterol levels. What’s fascinating here is that some people ate more than 10 eggs a day, yet their total, HDL, and LDL cholesterol, plus triglyceride levels, were no different than those in the other groups. See table 5 in the paper.
- In fact, those who ate the most eggs had lower LDL cholesterol and triglycerides, but these results were not significant at all
- What these studies are all showing me is that there is immense variability in the cholestersol response from egg consumption. This is evidenced by the high p values and standard errors I’m seeing throughout these papers.
- Note however that in all groups, serum cholesterol was below 200 mg/dl, the cut off for having “high” cholesterol. I wonder what else they were eating up there.
- Two or seven eggs a week for eight weeks on a low-fat diet.. Oxford, UK.
- Their aim was to determine if egg cosumption would increase cholesterol levels in subjects following a low-fat diet, the recommended heart-disease-preventing diet at the time that was shown to lower total cholesterol levels.
- This thirty-year-old study found a small but significant increase in total cholesterol at four weeks but not eight weeks in the group that consumed seven eggs a week.
- “Short term changes, reflecting a transient response with insufficient time for metabolic adaptation, have occurred after other dietary changes-for example, temporary hypertriglyceridaemia after a change to a high carbohydrate diet and should not form the basis of dietary recommendations.”
- Two eggs for six weeks in a crossover design. Denmark.
- Twenty-four adults consumed two eggs a day for six weeks and their total cholesterol went up 4% on average, with HDL rising 10%, and no significant change in the total:HDL cholesterol ratio.
There are many more studies that have investigated the effect of egg consumption on blood lipids. Overall, it seems that egg consumption does not adversely affect the lipid profile. That means, you are not likely to see a significant increase in your total to HDL cholesterol ratio, or a huge jump in your LDL cholesterol ratio. Eating just one egg daily, for weeks, had no significant effect on blood lipids in multiple studies. Over eight weeks, that’s 9800 mg of cholesterol, that does not end up in your blood. It ends up synthesizing hormones and transporting carotenoids like lutein and zeaxanthin as well as vitamin E to your cells. But about eggs increasing HDL cholesterol…the data are inconsistent. In some people it will raise it without a rise in LDL and in others maybe not.
Context matters. The rest of your lifestyle matters. And your absorbtion to production ratio matters a little bit but not much. Egg consumption, even more than ten eggs a day, does not significantly change blood lipids. Dietary fat is a stronger modulator of blood lipids than dietary cholesterol. In some people, eggs will raise HDL cholesterol, without a change in LDL.
As I find more studies on this topic I will update this post but for now, it’s a start. Do not be afraid of eggs. One of my readers told me that she thought eating one egg would cause severe health issues. This is far from the truth.
On another note, I wonder how pasture-raised eggs differ from the type most likely used in these studies. Eating whole foods, and considering a balanced approach to diet is a far better expenditure of your time than trying to discern the minutiae about dietary cholesterol and eggs.
We must be aware of industry bias in this research, but there does seem to be plenty of research free from this type of bias that reports similar results, where eating eggs does not seem to elevate the “bad” cholesterol. Enjoy your breakfast!