Is Starfruit Toxic? (Averrhoa carambola)

General Fruit Growing
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If I understood this correctly, Starfruit (Averrhoa carambola) is poisonous because it contains 2 toxins, the Neurotoxin Caramboxin (which Damages Brain) & the Toxin Oxalic Acid (which Damages Kidney).
It’s been recomended to not eat starfruit in large quantities (Especially on an empty stomach) because of these toxins, but at the same time lots of people eat starfruit making this very concerning. Aparently in Brazil Starfruit is sold with a warning label about these toxins but in the U.S., no such label is found (At least from my experience).
Normally Caramboxin is filtered thru healthy Kidneys but this can be compromised by Oxalic acid & thus together they interact & worsen the problem. This is especially why starfruit should be avoided entirely if suffering from any kidney issues, but the same could be said about Woodsorrel (which belongs to the Same family as starfruit), Garden Sorrel, Rhubarb, Spinach, Beets, Amaranth (Which all contain Oxalic Acid also).

Any information about how the ripeness of starfruit affects the toxicity? I’ve read the more riper yellow with brown edges a starfruit is, the less oxalic acid it contains (A typical trend of many ripe fruits having reduced/no toxins left after ripening. For example : Tomato, Figs, Avocados, ect). Most grocery stores sell Starfruit greenish as it ships better that way.
Here’s an Unripe vs Ripe starfruit I found at my grocery strore. Last photo on right shows a mix of ripe & unripe fruit at grocery store (which is typical because starfruit ripen off the tree).

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I’ve also heard cutting off the edges of star fruit significantly reduces the oxalic acid content.

So if we reduce the content of oxalic acid by trimming the edges & eating starfruit at peak ripeness, we can also better process the Neurotoxin Caramboxin to filter it out thru our urine? However does the amount of Caramboxin also get reduced when the fruit ripens, or does this only apply to the Oxalic acid?

In other countries, unripe fruits are eaten cooked or in pickles, is this a safe thing to do? Maybe the cooking or pickling process reduces/breaks down the oxalic acid making it not a problem (Just like with Spinach, Sorrel & Beets)? But what happens to the Caramboxin?

I found this study on Starfruit toxicity, however no info about how ripeness affect toxicity. Has anyone found a study on how ripeness of starfruit affects toxicity or what we can do to safely eat startfruit?
https://sci-hub.box/https://doi.org/10.1016/j.toxicon.2020.09.010

The flowers of Starfruit are also edible raw or cooked just like wood sorrel (Oxalis spp.), both part of the same family, both contain Oxalic acid, both edible in small quantities. They add an acidic flavor in salads. Do the Flowers also contain the Neurotoxin Caramboxin, or is that only found in the fruit?

The leaves of Starfruit are also edible raw or cooked & used as a sorrel substitute. What are the health risks here beside oxalic acid? Should we eat small quantities of Starfruit leaves raw & boil larger quantities or just avoid starfruit leaves entirely? Do the leaves also contain the Neurotoxin Caramboxin, or is that only found in the fruit?

What about the other species of Startfruit (Averrhoa spp.), are they also toxic? Such as Bilimbi (Averrhoa bilimbi)?

I found this study on Bilimbi fruits toxicity : https://casereports.bmj.com/content/bmjcr/14/7/e242325.full.pdf

Apparently the toxin Caramboxin is water soluable. Hmm… how can we out-smart this toxin? Lectins in beans are also water soluble hence why pre-soaking is so important prior to cooking them. Should we be pre-soaking our starfruits too? How does that work practically :sweat_smile:?

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Tomatoes, Peppers and other Fruiting Nightshades 2026
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It is indeed mildly toxic to most and very toxic to a few Star fruit 2/$1

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Bilimbi also contains the same toxins.

If its water soluble, then wouldn’t making juice (not concentrate) alliviate some of the toxins? I also know that oxalic acid in like spinach is heat soluble, so cooking with it (I’ve used bilimbi like limes before) should help as well. I didn’t see anything about the other toxin being heat soluble though.

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I don’t care. I love it. Caffeine is toxic too and I dink coffee very day. I have a cmp done every year and My kidney’s are fine. I might reconsider if my kidneys were in decline.

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hmm… and how do we solve the toxicity issue? So we can eat it safely?
I’ve eaten fully ripe fruits + bit off the edges to not eat them.

hmm… than we should be able to solve their toxicity issue with the same methods of starfruit? like cut off the edges, cook fruit, pick fully ripe fruits?

Caffeine is toxic? Perhaps only in large doses? I don’t drink coffee cuz it never tastes like chocolate, so it’s always been a turn off for me.

How many star fruits have you eaten? How do you eat them?

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@Professor_Porcupine @sharq @ribs1

All food is toxic in large quantity. There is a little arsenic and cyanide in most fruits. I accept toxicity as part of life. I eat prunus besseyi at times which are more toxic than star fruit, poke greens after boiling at least 2x, mushrooms, not to mention think about many peoples food allergies to strawberry , shrimp,wheat, milk etc. Food is life and death and i expect nothing different from starfruit.

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Yes caffeine is toxic. You can google it. I’ve eaten a lot of star fruit. I slice them and eat them or put in fruit salad. I’m not worried about it.

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Agreed! The Dosage is what determines the toxin, but for some foods there is pretty much no safe dosage. Cyanide in small amounts can be beneficial, but cyanide is also destroyed by cooking.

I’ve never tried pokeweed, it’s something I want to try eventually but I don’t understand it’s toxicity enough, I’m afraid.

However the key question is how to process the toxins in Starfruit to make it safe to eat in reasonable quantities. I’ve eaten 1 fruit a week for this very reason, I know it’s edible yet why does it have this problem???

I really just want to enjoy starfruit safely & not worry about this (Especially I want to breed starfruit which means I’m gonna be taste testing those species with “rough around the edges” fruit traits that could contain even more toxins.

So you eat them raw??? Do they taste good cooked?
What level of ripeness are you eating them at? Green unripe, Yellow ripe, Orange-Yellow with brown spots ripe?

and by slice, are you slicing off the edges before eating them?

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I thought it was just the seeds that are really toxic :thinking:

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Actually… I don’t know if the seeds is actually toxic (Or what toxins it contains)?
I’ve read some people just eat the seeds no problem, perhaps it’s less toxic than the actual fruit?

There are very limited studies addressing this issue.
There needs to be a study testing & comparing toxicity of ripe/overripe vs unripe fruits, edges removed/sliced, toxicity in seeds, ect.

I know how to solve the Oxalate problem, it’s the Neurotoxin Caramboxin that concerns me, which I have no idea how to solve.
For example does cooking reduce Caramboxin? What about the state of ripeness of the fruits? Is it concentrated in the winged edges or around the seeds? Is the toxin simply in the seeds which we can easily spit out???

Also is Caramboxin only found in the fruit, or do the leaves & flowers also have Caramboxin too? Has anyone tried eating Starfruit flowers & Leaves?

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I eat star fruit raw. I like to get them when they are yellow with brown edges.
All of us breath air full of coal particulates, nitrogen dioxide, sulphur dioxide and carbon monoxide. We breath these every day, all day.
The toxins contained in star fruit are insignificant unless you consume a quart of it’s juice per day. There are other things to worry about. I might reconsider if I had kidney disease.

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I have eaten several star fruit in a sitting. Consider i eat half a dozen pawpaw , drink sassafras, eat cooked poke, eat prunus besseyi, apricot seeds in small quantity etc. . I’m advising others not to do these things. They can all be very dangerous i’m told.

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Worry is even more dangerous.

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Studies I’ve read have shown that the Oxalic Acids is lower as fruit further ripens.
Maybe this is why it taste less sour when compared to less ripe fruit?

You can taste the Oxalic Acid right? I think I can which means I can easily select lower Oxalic Acid Varieties/species to cross hybridize + only eat fully ripe fruits.

But can we taste the Caramboxin? Idk what it taste like or if it’s not detectable by taste alone?

Which toxins? the Oxalic Acid or the Caramboxin? Oxalic Acid can be solved by cooking the juice. How does the Caramboxin get solved? We need to solve it.

:100: Agree!
But I’m a Fatass, I like to eat a lot so I need to figure out a way to reduce the toxin in Starfruit to eat a lot of them safely.

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My point in these responses is that I don’t really care. The toxins are insignificant compared to the much more serious toxins we breath all day. Those will likely kill me before the starfruit, so in the meantime, I’ll eat as much star fruit as I can get my hands on. You worry too much. Do you have stage 2 kidney disease or worse? If not, stop worrying.

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Well that explains why I don’t get answers on the actually toxicity of starfruit :sweat_smile:. If you don’t, you don’t care.

Do you also eat starfruit flowers & tender leaves? I want to explore the other edible parts of starfruit as well.

I want to be proven wrong! I’m researching so I’ve gotta know my shit. It’s why I ask here. I was hoping to find defenders of starfruit, who love the fruit so much & could teach me a way to eat them safely.

But also if I’m serious about Breeding Starfruit with crossing different more wild species, I need to understand the toxicity fully. Especially as a plant breeder, I will be eating more starfruit than usual.

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We all come together with all different perspectives. We are all right about starfruit. i respect your opinions. I will follow this topic closely as i intend to learn something from multiple perspectives. Like i said i intend to eat star fruit regardless. It tastes more or less like oranges if anyone wondered and hasn’t tried it. Naturally i would love to eat it safely. Like poke or sassafras i have no intention of ever not consuming it. I will tell you im very careful with poke and it has killed plenty of people. I only eat it when its small and in early spring. I boil it twice and change the water as raw poke will kill you every time. I say this because people have watched ancient families like mine pick it and they do the same not knowing how to process it. Every year in some part of the country people die from it which it is not that good to die for a greens meal. Stick with lambs quarter people it tastes better.

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Oh yea… kind of altho to me more of a tropical peach. Probably cultivar makes flavor difference.

I’ve never tried poke, I’ve saved seeds so I could grow them for later.
I’ve tried Sassafrass leaves & flowers in spring, Delicious! They taste like Fruity Loops, Sassafrass to me is like a salad tree. Roots I’ve haven’t tried yet.

This is really sad :cry:. I like Lambsquaters altho it too also has Oxalates, it’s my favorite green cooked.

Are Starfruit greens like Woodsorrel Greens?

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here in taiwan we USED TO eat starfruit. back in 1990~2000
but then some kidney dialysis patient get sick after eating starfruit
dr suspect starfruit maybe bad for ur kidney. but only if ur kdney was already bad.
but then it was discovery that starfruit DO actuelly contain Nephrotoxins.
now it;s practally extine and 10 out of 10 Dr. do not recomand eating starfruit .

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I eat pies made out of prunus besseyi that my sister makes. You can taste the poisons in prunus besseyi when fresh, though i doubt it is any different than starfruit in toxicity. Like i said, everything in moderation if you dont know how it affects you, if at all. Morel mushrooms can be harmful if you’re allergic. In the southern US and over the border, vanilla is sold all day long, which is not vanilla. Tonka is sold as vanilla. It Smells and tastes like the real thing. I have consumed a couple of quarts of it in my life.

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