Ah, eggs: Incredible and edible, as the commercial goes. A quintessential staple of American breakfasts, loaded with protein, packed with cholesterol. Bodybuilders chug ’em down en masse, and raw foodists sometimes experiment with them—but could they raise your risk of disease, as T. Colin Campbell claims all animal foods do? Let’s take a look at the original China Study data and find out.

Egg consumption in rural China

There’s no doubt about it: Eggs aren’t exactly a staple in China. In the China Project counties, egg consumption ranged from zero grams per day to 14.8 grams per day, which is the equivalent of about two or three chicken eggs per week. Not a lot. Although the data is still relevant, whatever we find here only reflects modest egg consumption—not a daily four-egg-omelet habit, for instance.

Unfortunately, we don’t have much information on what kind of eggs these people were eating. You wouldn’t guess it by strolling through an American supermarket, but chickens are, in fact, not the only birds that lay edible eggs. (Shocking, eh?) In China, meals can include eggs from ducks, quail, geese, pigeons, and other poultry, along with those of chickens. And rather than our familiar omelets and souffles, Chinese cuisine embraces things like salted duck eggs (which are soaked in brine for a month) and century eggs (which are soaked in a mixture of ash, salt, clay, lime, and rice straw for a few months—’til the yolks turn green and the eggs develop a delightful ammonia smell).

Alas, the only variable we have in the China Project data is “egg intake,” so we can’t see if particular types of eggs or preservation methods have different effects than others. An unfortunate limitation indeed. But we’ll work with what we’ve got.

In China, egg consumption tied in with a number of other variables. The folks who ate eggs tended to also have low triglycerides (-42), got a larger portion of their total calories from fat (+37), loved them some sea veggies (+41), indulged in a bit of processed starch and sugar (+33), piled on the soy sauce (+45), used a fair amount of soybean, cottonseed, sesame, and peanut oil (+32), gulped down the beer (+38), and smoked cigarettes (+34). Like fish eaters, eggy folks worked more often in industry than in agriculture (+37 and -49, respectively). Whew! Lots of variables there.

Here’s what egg-related correlations look like without adjusting any variables. Again, I’ll just be discussing the statistically significant ones.

NEGATIVE CORRELATIONS (more eggs = fewer of these diseases)

Liver cirrhosis: -46***
Peptic ulcer: -43**
Diseases of the blood and blood-forming organs: -35*
Death from all causes: -33*
Digestive disease other than peptic ulcer: -30*
Hypertensive heart disease: -28
Oesophageal cancer: -26*
Death from all non-cancer causes: -26

It’s questionable how many of these ailments (apart from heart disease and blood-related woes) are even related to diet, so I won’t gush over these happy correlations too much. Things like liver cirrhosis are probably related more to hepatitis B infection, peptic ulcers are linked to the bacterium Helicobacter pylori, and digestive diseases (whatever those consists of) could be related to infection or parasites. But I will say that eggs, in the modest amounts the Chinese consumed, don’t appear to tarnish heart health in any way. Along with hypertensive heart disease, other cardiovascular problems have inverse or neutral correlations with egg intake (-21 for rheumatoid heart disease, -13 for myocardial infarction, and -8 for stroke).

POSITIVE CORRELATIONS (more eggs = more of these diseases)

Colorectal cancer: +35*
Colon cancer: +34*
Rectal cancer: +30*

Look familiar? It should. If you’ll recall, we saw high rates of colorectal cancers (colon and rectal) with meat in an earlier post—a trend that turned out to be related to schistosomiasis infection, not meat itself. And as it just so happens, egg intake correlates strongly with schistosomiasis as well, at the statistically significant rate of +40. Could that pesky little parasite be causing colorectal cancers in egg eaters?

Yep, that’s right… graph time! You know you love it.

Here we have three charts mapping the correlation between eggs and rectal cancer, colon cancer, and all colorectal cancers—using only the counties free from schistosomiasis infection.

Voila; we no longer have a statistically significant correlation between eggs and any form of colorectal cancer. As you can see, even our counties with the highest egg consumption didn’t have considerably more or less of these cancers than the eggless populations.

In conclusion:

We can’t say too much about eggs one way or another, simply because our data pool is limited and we lack some pertinent info—like what kinds of eggs these people ate and in what form. However, based on what we do know from the China Project, there’s no reason to think eating a couple of eggs per week (hopefully organic and free-range) would have any negative health repercussions. More than that may be fine, too; we just can’t say for sure based on this data alone. In fact, egg consumption may even offer benefits for heart health and “diseases of the blood and blood forming organs,” as the variable is titled.

Next up is the last of our animal products: dairy.