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11 Common Foods That Can Turn Toxic During Cooking

SheKnows logo SheKnows 9/2/2019 Heather Barnett
11 Common Foods That Can Turn Toxic During Cooking: Believe it or not, these foods can become toxic if you don't cook them correctly © Getty Images/Design: Ashley Britton/SheKnows Believe it or not, these foods can become toxic if you don't cook them correctly

It can be easy to take for granted that foods we're accustomed to cooking with (especially healthy ones) are safe, but it turns out that's not always true. While most of these foods won't make you keel over within minutes of ingestion, they could make you feel sick temporarily or the negative effects can build up in your system over time like a cancer — quite literally in some cases, actually.

The good news is that you don't necessarily need to flip out if you've cooked with and eaten these foods. The bad news is that some of them are really, really tasty — but for your health's sake, now that you know their toxic potential, you should limit your intake.

I know what you're thinking. "Prithee tell, what are these dastardly delights?" Here are the 11 you should know about:

1. Microwave popcorn

Say it ain't so! Microwave popcorn bags are lined with perfluorooctanoic acid. This nonstick lining, when heated, might cause cancer with consistent exposure over time. Instead, make your own DIY microwave popcorn using paper lunch bags or buy a microwave air popper (Walmart, $15.97).

2. Burned toast (and burned food in general)

The European Union's health advisors give us all a good excuse to chuck that burned toast — the chemical reaction that occurs when it's burned results in the production of acrylamide, which might cause severe nerve damage and cancer over time.

Sadly, while the chemical reactions may be slightly different, the risk of cancer also applies to burned meats and even beloved campfire staple the humble marshmallow. So if you burn your din-din, it might be best to throw it out — with zero guilt thanks to those unnamed EU experts.

3. High-nitrate veggies

The minute you chomp down on a hummus-dipped baby carrot, special bacteria ninjas in your mouth go straight to work turning those nitrates into nitrites, and what a difference a letter makes. Nitrites are a natural anti-inflammatory your body stores to increase your blood flow when it's needed. This is good for your heart, of course, but some experts believe nitrites (or at least too much of them) can be carcinogenic. So what may be good for your heart could build up to levels high enough to eventually cause cancer.

The thing is, if you cook high-nitrate veggies first, that conversion happens before you eat them, and again each time you reheat them, so it might be best to stick to eating these veggies raw or at least limiting the number of times they're heated (make only what you can eat and if you do have leftovers, reheat them only once).

Other high-nitrate veggies include celery, turnips, beets, leafy greens, leeks, endive, cabbage, fennel and more.

4. Egg-free cookie dough

A lot of people, myself included, have long been on the hunt for the perfect egg-free cookie dough recipe so we can indulge without fear of salmonella. Bad news, guys. Flour is also at high risk of salmonella contamination, so egg-free doesn't equal salmonella-free. Flour can also be contaminated with E. coli. If you're going to indulge in raw dough, know that you're always doing it at your own risk.

5. Lobster

Bet you didn't realize there's a very good reason why you generally buy chicken that's slaughtered and lobsters that are still alive. The moment lobsters die, the naturally occurring bacteria they contain throw a house party, and the toxins that bacteria releases while doing so isn't always destroyed during cooking. The most humane cooking method is to put lobsters on ice for 15 minutes to anesthetize them before dropping them into boiling water. Or, you know… there's always veganism.

6. Rice

If you have a tendency to let cooked rice hang out at room temp after it's done thinking it's totally fine (it needs to cool off, right?), you might be in for a surprise. Cooked rice can actually be susceptible to rapid bacterial spore development, which can cause anything from mild digestive issues to poisoning. So make sure you store that leftover rice in an airtight container and refrigerate it quickly after eating.

7. Oils

As long as you don't exceed an oil's smoke point, it's safe, right? Not so fast. While this isn't likely to happen at home unless you use (and reuse) less delicate oils like grapeseed or flaxseed, constantly reheating oils can make them turn rancid, increasing the toxin 4-hydroxy-trans-2-nonenal. That may sound like it was invented by an uncreative sci-fi writer, but it's actually a chemical that has been linked to heart disease, stroke, Parkinson's disease and cancer.

Why should you care? Because when you eat fried food at restaurants, the oils they use are typically being used over and over to cook a succession of meals throughout the day. Yet another reason grilled foods are a better option when you're eating out.

8. Potatoes

Cooked potatoes left at room temperature for too long, reheated incorrectly or stored for more than a couple of days can cause a form of food poisoning called botulism. Not only that, but raw potatoes can develop solanine, a naturally occurring poison that can develop when they're exposed to sunlight. When this happens, potatoes can develop a green color just under the skin. Eating those green parts can cause issues including nausea, headache and fatigue. The good news is you can just cut off the green parts and everything should be fine — or you could just store your potatoes in a cool, dark, dry place and avoid it altogether.

9. Chicken

You already know consuming raw or undercooked chicken is dangerous because of salmonella, but did you know that cooked chicken can cause issues too? Chicken has more protein than red meat, and that's not always a good thing. When you go through the cook-refrigerate-reheat cycle with chicken, it breaks down the protein and might wreak havoc on your digestive system (think tummy aches, nausea, etc.). The best way to use leftover chicken is in a cold preparation like chicken salad, but if you do reheat it, only reheat what you'll eat immediately, make sure it's totally heated through and don't reheat it after more than two days. The good news here is that if you properly defrost, cook (to the correct temperature) and immediately cool your chicken, then follow proper reheating instructions, as well, one reheating should be perfectly safe.

10. High-protein foods (like eggs and mushrooms)

Eggs were bound to make an appearance on this list, and this time, it doesn't come from their salmonella potential. Beyond that, cooked eggs are a breeding ground for microorganisms, so only make what you can eat and store and reheat them similarly to chicken.

Surprisingly, mushrooms fall into this category as well. They have a very complex protein structure (so complex you only need to add broccoli and corn to make a complete protein), which may account for their meatiness and ready substitutability for animal proteins, but it also makes them susceptible to develop microorganisms similar to those eggs do. And don't even get me started on "wild" mushrooms, which can easily be toxic if not cooked or prepared properly (or even if they are for some). For example, the ink cap mushroom is poisonous when it it's cooked or consumed with alcohol.

Ketamine and Other Drugs Were Found in All-Natural Chicken

11. Cassava

To most Americans, it's known as tapioca (which is made from a starchy tuberous root called cassava). But cassava can be more deadly than people realize. While it won't kill you immediately, long-term exposure to improperly cooked cassava is already causing health disorders and death in countries where people consume it regularly. Cassava should always be dried, soaked, rinsed and cooked soon after being harvested. Fortunately, that's exactly how mass-produced tapioca is handled in the U.S. But... maybe don't try to make your own tapioca from raw cassava.

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