This post was written by Amy Berger. Amy is working on her Masters Degree in Nutrition and holds a Bachelors in Creative Writing. She has put together an excellent primer on all things antinutrient. Enjoy!
Phytates, oxalates, and goitrogens, oh my! If you’re new to the world of antinutrients, these harmful substances can seem as scary as the lions, tigers, and bears Dorothy and the others thought they might come across on their way to see the Wizard of Oz. Maybe you know all about the properties of antinutrients, or maybe you’re scratching your head, bewildered, because you thought antinutrients only came in the form of delicious cookies and the nefarious but well-meaning girls who sell them. Either way, here’s a primer on just what the heck these things are, and some advice on how much you should—or shouldn’t—freak out about them.
What are antinutrients?
Let’s think about this logically. Animals have ways to make sure they don’t become some other animal’s dinner (including a human being’s). They can run away, or they can stay and fight with claws, horns, or teeth. If they win, great. If not, fire up the BBQ! Plants aren’t so lucky. Since they can’t defend themselves physically, they’ve evolved multiple insidious ways of warding off predators biochemically. Plants produce a variety of harmful substances collectively known as antinutrients. (Not harmful to the plants, but harmful to the poor saps who eat them.) They’re exactly what they sound like: they work against you absorbing nutrients from those foods.
One of these antinutrients you’re likely already familiar with: phytic acid. It’s found mostly in grains and legumes, so if you’re following a fairly strict paleo diet, it’s not much of an issue for you. Still, it’s worth knowing a little about, since it’s one more nail in the coffin of these problematic foods. (Not to mention, nuts contain a small amount, so if you’re eating copious amounts of nuts and nut flours it’s something you should be aware of.) Phytic acid binds to minerals and makes them unavailable to the body. Specifically, it binds to things like calcium, magnesium, zinc, and iron. There are ways to neutralize some of the phytic acid in foods, like soaking, sprouting, or fermenting (hence the “sprouted grain” breads or natural sourdoughs you see in artisan bakeries), but it should be no surprise that the vast majority of commercially available grains do not undergo this kind of meticulous preparation. In our grain-centric society, is it any wonder there’s rampant magnesium deficiency and osteoporosis?
But that’s not your problem. You’re off grains and legumes. Whew! In the clear, right? Wrong.
Unfortunately, many foods that are indisputably wonderful from a nutritional standpoint contain other antinutrients besides phytic acid. One class of these is goitrogens – yes, goitrogens, which means—you got it—they depress thyroid function. Goitrogens are found in some of the most benign foods you can imagine: broccoli, kale, Brussels sprouts, collard greens, cauliflower, and all types of cabbage, including Asian varieties like bok choy. (Anything in the Brassica category, for you plant geeks.) You can also find goitrogens in most legumes, especially soybeans (as if you needed another reason to steer clear). The good news is, goitrogens are mostly neutralized by cooking or fermenting. Kind of makes sense—have you ever tried to eat a raw Brussels sprout? Or collard greens? Have fun chewing; I’ll see you in about a week.
A third class of antinutrients is oxalates. Oxalates do pretty much the same thing as phytic acid—they bind to minerals, making it difficult for our bodies to get at them. Like goitrogens, oxalates are found in many foods you may have come to think of as paleo staples: spinach, chard, blueberries, and cocoa/chocolate, among others. (Okay, so maybe that last one’s not a staple, but admit it, it’s on your radar.) Oxalates are the reason rhubarb leaves are poisonous (the old wives’ tale is true!), and if you ever eat the green leafy tops from a bunch of beets, they’re loaded with ‘em, too. That’s the bad news. The good news is, cooking to the rescue again. Cooking reduces the mineral blocking effects of oxalates, which is good, because raw chard is as hard to chew as shoe leather, and tastes about as good.
There are other antinutrients, but you’re probably already sufficiently scared. So now that we know what these things do, the question is, how much worrying do they warrant? The answer is, not a whole lot. Yes, these substances can be problematic, but let’s not throw the baby out with the bathwater. Most of these foods—dark green leafy vegetables, berries, and nuts—are nutritional powerhouses and shouldn’t be avoided because of antinutrients that can be neutralized pretty easily anyway. It would be a shame to miss out on the good things because of overblown fear of antinutrients.
When you’re first starting out with a shift away from the grain-heavy, fat-phobic modern western diet, it can be a heck of a shock to your system. The psychological shift can be even more daunting than the physical one. All of a sudden, you’ve stopped eating the vast majority of foods that got you through the day. Once you’ve adapted, though, you’re feeling great, you’re looking better, and you’ve got a spring in your step. And then, WHAM. You find out that the new foods that sustain you are full of these antinutrients. Can’t eat spinach anymore. Can’t eat kale, and you won’t go near cabbage without a hazmat suit. And yet, you can’t live on air alone. What’s a person to do?
Step 1: Relax. Remember, most of these bad boys are taken care of by cooking or fermentation. (In the case of cabbage, it’s a great reason to make some homemade sauerkraut or kimchi!)
Step 2: Relax more. In terms of worry-inducing issues, there are much bigger fish to fry. A couple of spinach salads and a little dark chocolate aren’t going to cause mineral deficiencies in a matter of days. Our bodies are surprisingly robust. We have multiple feedback loops and checks and balances to make sure nothing gets too far out of whack. These foods are only troublesome when eaten in excess. What is excess? It’s partly in the eye of the beholder, and partly in the homemade cole slaw you love and have been eating six cups of every day for eight months. Even eating antinutrient-rich foods for several days in a row won’t do much harm. It’s when these foods are eaten in large quantities over long periods of time, in the absence of other foods, that they can turn on you.
Step 3: Eat a varied diet. Eating a wide variety of plant and animal foods is practically a guarantee that you won’t overdose on any particular antinutrient. It’s also a good way to make sure you get the full complement of vitamins, minerals, and phytonutrients you’d miss out on by limiting yourself to a handful of beloved foods. How do you eat a varied diet? One simple way is to take a look at the colors in your shopping cart or farmer’s market bags. Is green all you see? How about tossing in some red peppers, carrots, or blueberries? The more “colors” you eat, the more phytonutrients you’ll get—most of which scientists are only scratching the surface of in terms of health benefits. Another way is to buy what’s on sale. If zucchini’s on sale this week, chances are, something else will be marked down next week. Eggplant, maybe, or asparagus. What a good way to try something outside your culinary norm. (And if it sucks, well, okay, dump it and go back to the zucchini!)
But the best way to make sure you’re eating a good variety of plant foods is to stick with the seasons. It is only thanks to the wacky hijinks of our modern global food economy that you can go to a supermarket in Michigan in January and buy a papaya. Certain foods are symbolic of certain times of year: asparagus in spring, peaches and tomatoes in summer, butternut squash in fall. Even when you can get them at other times, they just don’t taste as good. Eating what’s in season makes it difficult to eat the same limited foods all year long. Granted, this isn’t always possible. Not everyone lives in places with year-round growing seasons or farmer’s markets, and maybe in the middle of December, you’re jonesing for some blueberries with your coconut milk. Not a big deal. Canned tomatoes and frozen berries can be lifesavers some days!
Remember, these are general guidelines. Eating the same things a couple days in a row won’t kill you. The overall picture, over time, should include a wide variety of animal and plant foods. The poison is in the dose. Most good things can enter not-good territory in massive quantities: exercise, fish oil, and yes, raw cauliflower. But don’t stress out. The cortisol from overwhelming anxiety in the produce aisle will do you more damage than anything from the broccoli boogeyman.