Dear Mark: Eggs, More Eggs, and Marathon Man

EggsFor today’s edition of Dear Mark, we’re talking eggs, eggs, and marathons. First up are egg allergies/intolerances as determined by blood test. It’s not exactly clear what blood test was used to determine the inflammatory response to eggs, but regardless: the test was done and the reader is now worried about eggs, previously one of her favorite foods. Can she reintroduce eggs? Should she even worry at all? Next are eggs and blood lipids. Our reader’s naturopath has warned against four times daily egg consumption because of elevated LDL, and she wants to know if there’s really any reason to follow the advice. I lay out some of the evidence in favor of egg consumption; hopefully it’s enough to satisfy. Finally, I discuss the curious case of Stefaan Engels, the man who ran 365 marathons in 365 days. Does he discredit my whole view of fitness, chronic cardio, and endurance training? Should you therefore take up daily marathoning? Read on to find out.

Let’s go:

I had blood work done that showed eggs, and especially egg whites, were the number one food allergy causing inflammation in me. Eggs are one of my very favorite foods and because of the tests I have all but eliminated them from my diet. Is it possible that eggs can be reintroduced into my diet after some time on the primal blueprint?

Thank you for any suggestions!


I’d be interested to hear exactly what this blood work consisted of, because if it was IgG allergy testing, I’m not very convinced. Egg allergy is one thing, where you have a bite of food containing eggs and end up going into anaphylactic shock. That’s bad, that’s dangerous, and you can’t really ignore it. If eggs are an imminent threat to your life and you feel awful eating them, by all means, listen to the blood work and eliminate the eggs. The simple fact that they are one of your favorite foods, however, makes me think that eggs aren’t having a noticeable impact on your health.

Read next: How to Use Egg Yolks as a Thickener

If it was an IgG allergy test, there are serious doubts as to its accuracy and usefulness in identifying allergies or sensitivities. Chris Kresser, in one post, recounts how he once received back completely different results after sending two vials of his blood to the same lab for testing. And one study even found that every subject tested positive for ovalbumin-specific (egg white) IgG levels, whether they had active egg allergies, resolved egg allergies, or were completely free of egg allergies. The authors suspect that “strong IgG responses to OVA may be a normal physiological response to a protein frequently ingested from infancy.” Another study found that children who had higher IgG responses to egg protein as infants actually showed greater tolerance of egg protein later in life. If everyone has positive responses to egg-specific IgG levels regardless of allergic status, what’s the point of testing? And if higher IgG responses to proteins have even been shown to indicate greater tolerance of said proteins, are IgG tests really useful in determining intolerances?

How did they determine that they’re causing inflammation in your body? Did you get a C-reactive protein test? Did they test for specific inflammatory cytokines? Or do you get symptoms of inflammation upon egg consumption – achy joints, irritated skin, gastrointestinal upset? Or is the “inflammation” an abstract thing purely represented by numbers on a lab test? A blood test is rarely sufficient, particularly absent subjective symptoms.

You may very well be sensitive to eggs. Many people are. But most people who are sensitive to eggs don’t consider them a favorite food. You could be suffering from inconspicuous inflammation, doing damage to yourself without really knowing it. But in the absence of obvious symptoms, I’d hesitate to banish eggs entirely from your diet. Eggs are nearly unparalleled in the nutrition realm. They’re an excellent source of highly assimilable protein and vitamins like A, choline, K2, and folate, and they can be a good source of omega-3s if the hen’s diet is right.  Take them out for a few weeks to see how you react, sure. Nothing wrong with an elimination diet. That way, you’ll get actual answers in about 30 days, and you’ll be able to determine whether or not eggs are causing problems.

Look into your intestinal permeability, too. Oftentimes errant food proteins worm their way into our blood stream by way of an overly permeable intestinal wall, thereby prompting an immune response. Eat more gelatin and bone broth, consider probiotics, and eat some fermentable fiber to improve your gut health.

One final note: if it’s egg white you’re worried about and sensitive to, just eat the yolks. The yolks are the best part, anyway. If you trust your eggs, there’s no better multivitamin than a few raw pastured egg yolks in the morning.

I am seeing a naturopath and she is a bit worried about my LDL cholesterol, and is concerned I am eating too many eggs (3-4 for breakfast every day and the odd extra one with dinner). She says she normally doesn’t worry about eggs but in my case maybe it’s time to pull it back a bit….but hang on, everything I have read in paleo-land tells me that eggs are fine.

She said another comment that intruiged me, that because I fry my eggs (in coconut oil) or make an omelette that the yolk is exposed to air and they oxidise, and this may be the problem. She recommended cutting back to 2 eggs a day and only poaching under water or boiling. Have you ever heard such a thing and could it have any credence…or is it time to find a new naturopath!

I am one of your many readers from Australia and send you a big thanks for the work you do from Down Under.


The vast majority of the evidence shows that egg consumption has either no effect or a favorable effect on serum lipids, particularly if you’re eating low-carb/high-protein (terms which are usually synonymous in the medical literature):

Dietary cholesterol from eggs increases HDL in overweight men on a low-carb diet and reduces markers of metabolic syndrome.

As part of a high-protein diet, egg consumption improves blood lipid and blood glucose profiles in type 2 diabetics.

Heck, if you’re eating low-carb, eggs might actually make it work even better than a low-carb diet without eggs, probably due to the cholesterol increasing HDL and improving antioxidant function. Or, it might be the increase in HDL and LDL particle size (and probable reduction in HDL and LDL particle number) along with the higher levels of circulating antioxidants doing the trick. Or both. Either way, eggs fit quite nicely into a Primal eating plan.

Of course, you could be a rare poor responder to eggs. Some people experience increases in cholesterol (although it’s usually both HDL and LDL, so it ends up a wash in a sense). It probably won’t hurt to spend a few weeks at a lower daily egg intake just to see what happens to your lipids. They might drop. You might feel even better than before. They could also drop, and you end up feeling worse. After all, cholesterol is converted into important hormones like pregnenolone and testosterone and vital prohormones like vitamin D. Lipoproteins also deliver nutrients (beyond just cholesterol) to cells. Lower cholesterol – even LDL – isn’t always better. Don’t ignore subjective measurements of health, like energy levels, libido, workout performance, and general feelings of awesomeness.

Oxidized cholesterol from overcooked eggs might be able to increase the portion of oxidized cholesterol in your LDL particles, but I haven’t seen any evidence that it would increase circulating levels of LDL. It’s just that the LDL in your LDL particles might be a bit more oxidized and therefore prone to trigger atherosclerosis. Overall, I think the fear of oxidized cholesterol because you cooked up an omelet is overblown. High-heat, high-pressure spray drying of eggs? Yeah, that’ll oxidize the cholesterol. Cooking them up in coconut oil? Scrambling and subjecting them to a hot buttered pan for a couple minutes? I don’t think you have much to worry about.

That said, I am quite partial to soft boiled eggs. I just pop three or four in my pressure cooker with a cup of water, set it to steam for three minutes, and immediately immerse them in cold water. The white comes out soft, smooth, and fully-cooked while the yolk remains warm and runny. I mostly do it because it’s easy (I can just set the timer and walk away) and tasty (a runny yolk is paramount), but I can see it being “healthier” in that it eliminates any chance of cholesterol oxidation (not that I think we need to worry too much).

How do you explain Stefaan Engels? He ran a marathon everyday for a year, ate whatever he wanted, and showed no muscle or cartilage damage.


Engels is certainly impressive, but he’s pretty easy to explain.

He’s an outlier, well-suited for marathon running. I’ve never argued that you can’t run marathons and be healthy. I’ve merely argued that running and (most importantly) training for marathons at an elite level usually means avoiding other beneficial ways to train, and results in aches, pains, and injuries. Just because lots of slow moving, some sprinting, and heavy lifting (and even some endurance work alongside) builds more lean mass and more well-rounded fitness in a fraction of the time doesn’t mean marathoning means certain death.

Not to take anything away, but it was a parlor trick. He took an average of four hours to complete each marathon, which means he was taking a little over nine minutes per mile. For him, an elite endurance athlete (and accomplished triathlete), he probably never got past 60% of his max heart rate, which might not even qualify as chronic cardio in his case. A 9+ minute/mile pace is far better than most people could do, but it’s not very hard for him. He was taking it relatively easy. Engels’ best time was 2:56, and 4:00 is an easy jog for a guy with a sub 3:00 marathon.

As for eating whatever he wanted, exactly! When you’re training for marathons like I was, you have to be willing to shovel just about anything in, purely for the easy and quick calories. Superhuman levels of athletics often require superhuman levels of consumption – just look at Michael Phelps.

Nothing against Engels or his feats, mind you. But his situation really isn’t applicable to the average Joe, for whom I write my books and my blogs.

There were runners in the 1970s who regularly did 250 training miles a week and then raced hard and fast. My friend Dave McGillivray ran across the USA (3,452 miles) in 80 days. He turned out fine, but most of the other guys are dead or ailing now. Many of my triathlon buds had no signs of damage during their careers, but years later had big problems.

So yeah, you can do it, but it doesn’t mean you should.

That’s it for this week, guys. Thanks for reading and be sure to leave a comment!

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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