Fruits and Vegetables You Should Never Put in a Juicer

It takes roughly 200 crushed apple seeds to seriously poison a grown adult. A juicer can pulverize that many before your coffee finishes brewing.

That’s the thing nobody tells you when you buy the machine. You start feeding it whatever’s in the produce drawer, because juice is healthy and fruit is fruit, right? Mostly, sure. But a few things in there will either taste terrible, turn to paste, quietly wreck a $150 motor, or release a compound you’d rather leave alone.

None of this is a reason to fear your kitchen. It’s just a reason to know which items to skip, which parts to pull off first, and which ones belong in a blender instead. Here are the fruits and vegetables to keep out of your juicer, sorted by whether they’re a threat to you, your machine, or just your taste buds.

1. Apple seeds

Apples are fine. The seeds are the catch.

Apple seeds contain amygdalin, a compound that breaks down into hydrogen cyanide when the seed is crushed. Whole seeds are harmless. You could swallow a handful and they’d pass right through you, shell intact. The danger only shows up when something grinds them open, and grinding is exactly what a juicer does.

Now, the actual math is reassuring. Each seed holds only about 1 to 4 milligrams of amygdalin, and you’d need to thoroughly crush somewhere north of 200 of them to reach a lethal dose. Nobody cores that many apples by accident.

So this isn’t a “your morning juice will kill you” warning. It’s a “there’s zero upside to blending the seeds, so core the apple first” nudge. Two seconds of prep, and you never have to think about it.

2. Cherry pits and other stone-fruit pits

Same compound, more famous fruit. Cherry, plum, peach, and apricot pits all carry amygdalin too, and all of them release cyanide when they’re cracked open.

You’ve probably swallowed a cherry pit at some point and lived to tell about it. That’s normal. Whole pits do nothing. But a juicer or high-powered blender cracks them, and a cracked pit is a different story.

Pit your stone fruit before it goes anywhere near the machine. This one’s easy to forget because we think of the pit as the trash you spit out, not something you’d ever process on purpose.

3. Rhubarb leaves

The pink stalks are a classic in spring juices and totally safe. The big leafy tops are genuinely poisonous, and this is one of the few items on this list where “poisonous” isn’t an exaggeration.

Rhubarb leaves are loaded with oxalic acid, which is hard on the kidneys, plus a few other rough compounds. Eating them can cause a burning mouth and throat, nausea, and vomiting, and in extreme quantities they can damage the kidneys. You’d have to work at it to reach real danger, but there’s no reason to test the ceiling. Buy rhubarb, cut the leaves off, juice the stalks.

Worth one honest note here: juicing concentrates oxalates in general, and rhubarb stalks, spinach, and beets all carry them. If you’ve dealt with kidney stones, that’s worth asking your doctor about before you go on a green-juice bender. For everyone else it’s a non-issue.

4. Green or sprouted potatoes

Raw potato juice is having a wellness moment, which is a good time to mention that green potatoes shouldn’t be part of it.

When a potato greens up, sprouts, or gets bruised, it builds up solanine, a natural defense compound that causes nausea, vomiting, and diarrhea in high enough amounts. The green tint is your visual cue that levels are climbing. Skip raw potatoes in the juicer as a general rule, and absolutely skip any that have gone green or grown little eyes.

5. Raw elderberries

Elderberries are the health-store darling that comes with an asterisk. Raw, they’ve been behind more than one reported case of poisoning, with the classic nausea-cramps-and-worse lineup.

They have to be fully ripe and cooked before you extract anything from them. Raw elderberry juice straight through the machine is a hard no. If you want the syrup, make the syrup, on the stove, the way it’s meant to be made.

6. Bananas

Here’s where we leave the danger zone and enter the disappointment zone. Bananas won’t hurt you. They just won’t juice.

A banana is about 75% water, which sounds perfect until you learn that water is trapped inside dense, starchy cells a juicer can’t rupture. Instead of liquid, you get a gummy beige paste that smears across the filter screen and gums up the works. I’ve watched a friend try it “just to see,” and the answer was a machine that needed a full teardown to clean.

Bananas are blender food. Toss one in a smoothie and it does exactly what you wanted.

7. Avocado

Avocado is the one that doesn’t just fail, it retaliates.

Run one through a juicer and you get oily green sludge. Worse, that fat oxidizes and coats the inside of the machine in a film that’s a nightmare to scrub out, and it can leave a faint rancid smell in the housing that outlasts several washes. There’s no world where a juicer gives you avocado juice, because there’s basically no free liquid in there to extract.

It’s a fat, not a fountain. Blend it, mash it, spread it on toast. Leave the juicer out of it.

8. Mango and coconut

Two more that promise juice and deliver frustration.

Mango is all soft, clingy flesh and very little loose liquid, so you get low yield and a lot of pulp packed against the screen. Coconut meat is worse for the machine itself, dense and fibrous and fatty enough that it can bog the motor down and heat it up. Both are fantastic in a blender and stubborn in a juicer. The rule that saves you every time: if it’s creamy, starchy, or low on free water, it’s a smoothie ingredient, not a juice one.

9. Figs and dates

Sugar is sticky, and figs and dates are basically sugar with a peel.

Under the pressure of the machine, all that concentrated sugar caramelizes into a tacky mass that welds itself to every internal surface and can block the pulp chute in seconds. It’s less “juice” and more “candy-coating the inside of your appliance.” If you want their sweetness in a drink, blend them into it. Your juicer will thank you.

10. Pineapple core

The soft pineapple flesh is great to juice. The core is the problem.

That dense central column is tough and stringy enough to strain or even damage juicer parts if you keep shoving it through. Cut it out, or at least chop it small and feed it slowly. This is one of those cases where a little knife work up front saves you a repair bill later.

11. Frozen produce

Grabbing a bag of frozen berries and dumping it straight into the juicer feels efficient. It’s a good way to break something.

Frozen fruit is rock-hard, and most machines, especially cold-press ones, aren’t built to chew through ice. You risk cracking the auger or blades. Let it thaw first, then juice it like normal produce. Same fruit, same juice, minus the sound of your machine cracking.

12. Big loads of fibrous greens and hard roots

Kale, celery, cabbage, broccoli, wheatgrass, whole raw beets, fat carrots. None of these are off-limits, but jamming a huge load through at once is how you clog the screen and strain the motor. Long stringy pulp wraps and packs, and hard roots make the machine work overtime. Cut everything smaller and feed it in reasonable amounts.

There’s a real catch here, though, and it’s about your specific machine. A masticating juicer, the slow kind that grinds at 40 to 100 RPM, chews through leafy greens and wheatgrass beautifully. A centrifugal juicer spinning at 14,000 RPM more or less flings them around and hands you back wet, barely-juiced pulp.

So “never juice greens” is often really “don’t juice greens in that juicer.” If leafy greens are your whole reason for owning one, the type matters more than the technique. Either way, check your own manual for what it’s rated to handle.

13. Citrus peel

The peel smells incredible. That’s exactly the problem.

Orange, grapefruit, and tangerine peels are packed with essential oil that’s over 90% d-limonene, the same aromatic compound that makes orange oil smell like sunshine. In your mouth, in quantity, it’s intensely bitter and can unsettle your stomach.

A curl of zest as flavoring is lovely. A whole rind fed through the juicer turns your glass sharp and medicinal. Peel your citrus first and keep the bitterness out.

The carrot-top and tomato-leaf myths

Two things get called “toxic” constantly that deserve a closer look, because repeating it doesn’t make it true.

Carrot tops are not poisonous. The claim shows up all over the internet and traces back to a single 2009 blog post that offered no real evidence, and it’s been echoed ever since. Like most leafy greens they contain trace alkaloids, which are harmless in any amount you’d ever eat.

The honest reason to leave them out of your juice is that they taste bitter, not that they’ll hurt you. If you like the flavor, they’re fine.

Tomato leaves and stems are the genuinely debated one. Some sources say the green parts hold tomatine and should be removed. Others, including USDA researchers, argue tomatine is relatively benign and that true solanine is a potato compound, not a tomato one.

The reasonable move is to pull off the greens and juice the fruit, without losing sleep over it. Remove them to be safe, but you don’t need to panic if a leaf sneaks in.

One last thing that applies to this whole list: none of it is medical advice, and if you ever think someone has actually been poisoned, skip the internet and call Poison Control at 1-800-222-1222.

Quick questions people actually ask

Can I juice a whole apple, seeds and all? You can, and in normal amounts the risk is genuinely tiny. But the juicer pulverizes the seeds, and there’s no benefit to leaving them in, so core it and move on.

Why did my banana or avocado turn to paste? Wrong machine. Those are blender foods with almost no free liquid to extract. A juicer can’t do anything with them but make a mess.

Do I really have to peel citrus? For taste and for your stomach, yes. The rind is bitter and oily. A little zest for flavor is fine.

Can I juice frozen fruit straight from the freezer? Thaw it first. Ice-hard produce can crack the moving parts on a lot of machines.

The Bottom Line

Your juicer is a specialist, not a garbage disposal. It’s built to pull liquid out of things that are mostly liquid, and it politely falls apart when you ask it to do more. Pull the seeds, pits, and leaves that don’t belong, send the creamy and starchy stuff to the blender, and cut the hard fibrous loads down to size. Do that and the only surprise left in your morning juice is how good it tastes.