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Seasonality for the Birds

Last week, we determined a common thread of seasonality running through historical fructose consumption [1]. Warm weather with plenty of sunshine generally meant fruit was available. Those living in the tropics (as we humans did for most of our history) thus had year-round access to sweet fruit, while cold climate Grok [2] had seasonal, intermittent access. Plus, there are many symptoms shared between folks with vitamin D deficiency and fructose-induced metabolic syndrome. Eating fruit seasonally (if you’re into that sort of thing) in the modern world, then, probably involves getting some sunlight with your berries.

What about other clearly seasonal foods – can they be consumed freely and wantonly?

Consider birds. The bird is especially sensitive to environmental and seasonal fluctuations, as anyone who’s ever been woken up by hungry birds chirping at the morning light can attest. You’re all familiar with the “flying south for the winter” phenomenon, and you’ve probably seen the highly efficient flying V formation employed by migratory ducks or geese.  They’re just following the food. Ever watch “The Endless Summer”? It’s like that, except with grubs and seeds instead of big waves. Not all birds are migratory, though. If they can stay put and get enough food to survive, migration to a warmer climate is unnecessary.

We’ve been eating birds for millennia. They can be a bit hard to catch, sure, but the payoff is incredible: juicy thighs, fatty skin, delicious edible bones. And if you were to nab a big one like an ostrich or a wild turkey, that’s dinner for a week! Birds are definitely seasonal, though, and depending on where Grok was living, bird meat wasn’t always available. Does that mean poultry should only be eaten seasonally? Of course not. Meat is meat (well, dark meat is definitely not white meat, but it’s all meat).

What about the eggs [3]? Egg laying is absolutely seasonal. Birds are wired to lay eggs in warmer weather, when food abounds. Even birds that stick around all year long aren’t constantly laying eggs. Grok undoubtedly loved eggs (he never had to deal with the egg yolk fear campaign), but he didn’t have steady access to them. Still, if eggs are just another form of meat, there shouldn’t be an issue with steady consumption of them… right?

Maybe, but there’s a bit more to the story.

Remember that health issues with food generally arise when we eat food that really doesn’t want to be eaten. Take grains [4], for example. Grains house the little plant embryos; in order to deter consumption and ensure growth, the grain employs lectins and other anti-nutrients [5]. These are chemical self-defense mechanisms that can trigger auto-immune diseases and irritate the intestinal lining. Meat [6], on the other hand, comes with claws and teeth and legs (and sometimes poison) to dissuade consumption. Once the animal is dead, though, it’s dead. It no longer cares whether it’s eaten, so dead meat is pretty safe to eat. Just watch out for the ostrich’s legs when it’s alive.

What about eggs? Eggs are a different beast altogether – almost like a meat seed. A meat precursor. An egg has no active physical defenses (unless the mother’s around). It can’t sprout legs and run away. It does have the shell, which appears fragile but is actually incredibly resilient. Note the shape, which varies according to the nesting environment; cliff-nesting birds have the most conical eggs, ensuring a loose egg will roll around in a tight circle rather than roll off, while hole nesters produce more spherical eggs. Shells are meant to keep predators, faunal and microbial alike, away from the interior goods.

If you get past the shell, there’s another line of defense: the white. The egg white [7] serves three purposes.

It stores protein for the growing organism – about 50% of the total egg protein [8].

It helps transport nutrients into the growing embryo.

It protects the egg from microbial attack.

That last one is where things get potentially hairy for us egg-loving hominids who only had historically seasonal access to them. Because the egg is a stationary, otherwise helpless bird “seed,” it has selected for toxic, antimicrobial proteins in the white to bolster defenses. In fact, other than ovalbumen, which accounts for 54% of an egg white’s protein content, the thirteen other proteins in a white are antimicrobial. They aren’t explicitly meant to hurt mammalian interiors, but what harms the microbes can hurt us, too.

Lysozyme is the most problematic egg protein, but in a strange, roundabout way. By itself, pure lysozyme is probably harmless. We even produce it in our own bodies. But because it has an alkaline isoelectric point, it can form strong bonds with other egg white proteins. It binds with the white’s other protease inhibiting proteins, like ovomucoid or ovoinhibitor, to avoid digestive breakdown by protease enzymes, and it can form hardy, potentially harmful protein compounds that pass through the intestinal lining and produce or exacerbate autoimmune or digestive issues.

Now, certain animals can adapt to chemical defenses, given enough time and exposure. Birds, for example, are wild seed-and-grain-eaters. They’ve adapted to the lectins given their steady exposure to them. Primal folks eat a lot of eggs [9]. I’m one of them, and I probably eat them five days out of the week. But how long have we been eating eggs year-round? The first fowl domestication probably occurred 8,000 years ago in Thailand with the red junglefowl, but I imagine year-round egg production took a bit longer to perfect. Have we adapted to year-round egg consumption?

I’m not sure. Egg white allergy is relatively common, ranging from between 1.6-3.2% of the population. According to Cordain, it’s the second most common food allergy. That, plus the inherent purpose of the egg white itself, makes me suspect that there is something there. I don’t think year-round consumption of eggs is a problem for most people; I just think that certain individuals may be sensitive to the egg white protein, while others can down them without issues. I have heard of people developing egg allergies or negative reactions in adulthood, but that usually happens with people who eat a ton of eggs. I don’t hear about people developing lamb allergies.

Egg consumption doesn’t have to be seasonal, but our understanding of eggs [10] is informed by the seasons. Seasonality merely limited historical access to eggs, which in turn limited our ability to develop universal adaptations to egg whites. That’s it. Frying up a scramble in the dead of winter may not be historically accurate, but who the hell cares? It’s not the timing of consumption that matters, but the frequency – and even that isn’t set in stone [11]. If you love eggs, don’t stop eating them. They’re a fantastic source of fat [12], protein [13], and vitamins [14]. If you have a preexisting autoimmune issue, though, filling up on eggs could make it worse. And if you start feeling like crap after every egg meal, you should probably ease up. Don’t make eggs your primary protein source (I’m talking five or six eggs each meal), and most of you should be fine. Just be aware that the ability to eat a dozen eggs every day is relatively novel, evolutionarily. I’m not saying that problems will always arise when we introduce dietary novelties, or even that they’ll be more likely to arise. I’m just saying that they may arise for some.

(I find it highly ironic that the only thing you really have to worry about is the egg white. Hmm, next time I’m at a diner I’ll try to order an egg yolk omelet. It might be even cheaper.)

By now, it’s clear that the seasons affect everything: organisms (sentient and inanimate) respond to changes in temperature, rainfall, weather, availability of sustenance by adapting, migrating, or dying; certain geologic features are molded by rain, wind, or glacier, while coastlines are obscured or revealed by changing sea levels. It’s not even so much that things are affected by seasonality so much as they are imbued with it. You know how space and time are forever linked and wholly dependent on one another? How the two are contextual and relative? Think of the seasons, life, and this planet [15] the same way. It’s all linked.

Anyone have egg white allergies? Did you develop them recently, or have you always had them?