Tomato Leaves: The Toxic Myth

Edible tomato leaves

Maybe it was my Asian upbringing that taught me never to waste food, as my family used and ate every part of the vegetable, fish, chicken, pig or cow that we brought home. Or maybe it’s my ever-growing curiosity when it comes to food from the land… but when I walk around the garden, looking at all my lovely plants, I always think, Can I eat that part?

And by “part,” I mean the unconventional parts of the plant that you typically don’t think to eat. This was how I came to love artichoke stems, leek greens, and cucumber leaves, parts that are normally discarded or composted, but are in fact quite tasty.

So one day, when I was walking by my tomato plants, I started wondering whether the leaves were edible or not. With vines that sometimes grow to 10 feet long, it seemed like such a waste that the leaves weren’t used when the amount of fruit seemed so small in proportion. It got me to thinking… Why don’t we eat tomato leaves?

Tomato vines

Popular culture has taught us that tomato leaves are part of the “deadly nightshade” family and thus, they must be toxic. But I bet that more than a few people, if asked, would have no idea what that even means. It’s just what’s known. No questions asked — but we need to ask. What is a nightshade, why are the leaves toxic but not the fruit, and why don’t we see bunches of leaves in the supermarket if they aren’t toxic?

Let’s take a look at all the myths surrounding the Solanaceae family and explore the science that says otherwise.

Tomato leaves are edible

Myth #1: Nightshades are highly poisonous.
When referring to the Solanaceae family of plants, many people call it by its more common moniker, the nightshade family. Within this family are the vegetables we know and love, like tomatoes, tomatillos, potatoes, eggplants, and sweet and hot peppers.

But also within this family is the ominous “deadly nightshade,” also known as belladonna (Atropa belladonna). This herbaceous perennial has historical use in herbal medicine as a pain reliever and muscle relaxer, and even as a beauty aid. In fact, the name “bella donna” means beautiful lady in Italian. It comes from the outdated practice of women putting drops of belladonna berry juice in their eyes to dilate their pupils; the look was considered attractive in the day. But rest assured that though tomatoes are distantly related to belladonna, they do not contain the chemical compounds that make belladonna (especially its berries) so poisonous.

The tomato (Solanum lycopersicum) does have an interesting history however, as its scientific name, lycopersicum, is Latin for “wolf peach” and derives from German folklore. When the tomato was brought to Europe in the 16th century, people believed it to be poisonous like other members of the Solanaceae family, including belladonna, henbane and mandrake. Legend had it that witches used these hallucinogenic plants in potions to conjure werewolves. Since the tomato’s fruit looked so similar to that of belladonna, it was dubbed the wolf peach.

These days, we know that while tomatoes belong to the (very large and diverse) nightshade family, they definitely aren’t of the deadly nightshade variety.

Tomato leaves

Myth #2: Tomato leaves contain toxic compounds called alkaloids.
As mentioned in my previous post on carrot tops, all vegetables contain alkaloids. Alkaloids are part of a plant’s defense mechanisms (existing in all parts of the plant to protect against certain animals, insects, fungi, viruses, and bacteria) and we consume them on a daily basis in various amounts.

That locally-grown heirloom bean and kale salad you had for lunch? Alkaloids. Those antioxidant-rich organic green smoothies you make every week? Major alkaloids.

While it’s true that some alkaloids are not good for you (like nicotine and cocaine), others can be good or bad, depending on your view (like theobromine, the stimulant found in chocolate, or caffeine, that Monday-morning life-giver). Even though alkaloids are present in your everyday veggies, you could never eat enough of them in one sitting for the alkaloids to be harmful.

The major glycoalkaloid in the tomato plant is tomatine. (To put it simply, a glycoalkaloid is an alkaloid bonded with a sugar.)

Tomatine exists in all green parts of the plant, including the stems, leaves, and green tomatoes. (For the sake of clarity, whenever I mention “green tomatoes” in this post, I’m referring to the immature, unripened green tomatoes — and not the varieties of naturally green tomatoes.) A study published in the Journal of Agricultural and Food Chemistry found that the highest concentrations of tomatine were found in senescent leaves, followed by the stems, fresh leaves, calyxes, green fruits, and finally, roots (which had the lowest concentrations).

The difference in concentration between the fresh leaves and green fruits is negligible, so one isn’t necessarily “safer” to consume than the other. While tomatoes do show a decline in tomatine content as they mature and ripen, no one has ever thought twice about devouring a heaping of fried green tomatoes or pickled green tomatoes!

Glycoalkaloids are also poorly absorbed by the gastrointestinal tract of mammals, and will pass through quickly to the urine or feces. In people who are sensitive to these compounds, stomach irritation may occur but they would have to ingest an unrealistic amount of green tomatoes or tomato leaves to experience ill effects.

So what’s the deal? Are tomato leaves toxic or not? According to this food safety study (which compared the potential toxicity of glycoalkaloids found in tomatoes, potatoes, and eggplants), tomatine is a relatively benign glycoalkaloid. It resulted in no significant changes to liver weight or body weight when fed to mice, and is not considered adverse to human health.

What’s most surprising is the discovery of tomatine as a cancer inhibitor. The glycoalkaloid has been found to effectively kill or suppress the growth of human breast, colon, liver, and stomach cancer cells. This study suggests that consumers could benefit from eating high-tomatine green tomatoes, and that there may be a “need” to develop high-tomatine red tomatoes as well (for the treatment of cancer and/or the study of tomatine as an anti-carcinogenic and anti-viral agent).

Judging from these studies, and the lack of evidence that tomato leaves are toxic in any way, I’ll have to give Myth #2 a miss.

Potato-shaped tomato leaves

Myth #3: Organic gardeners make tomato-leaf sprays to kill pests, so that must mean tomato leaves can kill us too.
Tomato-leaf sprays are made by chopping and soaking tomato leaves in water, then using the sprays on various plants to control aphids. Since tomatine, a glycoalkaloid, has fungicidal properties and is part of the tomato’s natural defenses, it makes sense that the compound could potentially protect against pests when extracted into a solution.

But theoretically, you could make a spray with any green part of the plant, like the stem (which contains even higher amounts of tomatine). Unless you’re allergic to tomatoes, the tomatine in tomato-leaf sprays won’t harm you — and that’s why it’s used as an organic method of pest control.

Tomato leaves

Myth #4: Tomato leaves aren’t sold commercially and no one has ever cooked with them, so that’s a sign they’re not meant to be eaten.
True, if you tried to Google recipes for tomato leaves, you aren’t likely to find any. Former Chez Panisse chef Paul Bertolli is known to infuse his tomato sauces with tomato leaves, but aside from that, not many people have stepped up and ‘fessed up to their culinary use.

But — and a big but — that does not mean they aren’t edible. Until I started cooking from my garden, I never knew all the possibilities of the plants I was growing. An adventurous appetite has led me to discover how delicious broccoli greens are (you won’t find many recipes for those either), as well as carrot tops, nasturtium pods, radish pods, radish greens, and pea shoots (which are actually an Asian grocery staple). The fact that tomato leaves aren’t part of the mainstream American diet doesn’t make them toxic by any means. People just don’t know what to do with them… yet. (Hopefully this will change in my generation.)

You know what is toxic though? The amount of food we waste in this country.

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August 20 2013      107 comments     Linda Ly
Jardín   Verduras

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  • James Duncan

    Great article!!!! These are the types of arguments that I use all of the time concerning foods and gardening. My favorite term, but not the most accurate I feel, is ‘cultural brainwashing.’ Culture has brainwashed people into doing and believing so that it becomes habit. So much so that to challenge those beliefs/actions is incredibly disruptive and generates backlash, even though they don’t really know why they are doing/believing whatever it is. I’m half Japanese, and you should see the responses when people see the heads still on the fish when we cook them. As you are well aware, they can’t see it, because they’ve been raised to believe that one is supposed to cut the heads off. What a waste.

    • http://www.gardenbetty.com/ Linda Ly

      LOL love your mention of fish heads. I grew up eating in Asian restaurants and eating the entire fish (along with spitting out bones as needed), so imagine my surprise one day when I was 14, ordering in a nice American restaurant with my friends, and they served me a salmon filet… small, perfectly cut, no bones, no skin… and I wondered where the rest of it went?!

      These days, my non-Asian friends have all learned to appreciate those tasty fish cheeks! Still no takers on the eyeballs, though. ;-)

      And if you’re a fan of radish pods, try pickling them! It’s my favorite way to eat them: http://www.gardenbetty.com/2013/04/radish-seed-pods-and-some-pickles/

      • James Duncan

        No skin?! What a waste. I LOVE grilled salmon skin. That’s where all of the flavor is hiding. I didn’t have enough radish pods to pickle, maybe next season. But I did fill TWO one-gallon jars with four different types of cucumbers mixed with vinegar. SO good. My favorite is to layer the cukes on a pulled pork sandwhich; FYI, I AM in NC, the BBQ south.

        I’m always amazed at how many people have never even seen a whole fish ready to be cooked. They would leave if they saw a traditional Asian dinner being prepared, which is too bad because of the wasted nutrion in American preparation. I saw on a survival show in which a guy on a life raft survived by eating all of the organs. At first, he only ate the meat, but started suffering vitamin deficiencies. In a delirium, he started eating everything, heart, lungs, brain, eyes – all raw – and literally ate his way back to health.

        About the radish pods again, I have to wonder if eating the pods is similar to eating sprouts in terms of nutritional volume.

      • tomaf

        In Indonesia in 2001, I watched my Chinese-Indonesian friend break open the skull of a cooked
        dove and suck its brain out. He was polite and offered it to me first, but my stomach was still uneasy after trying the slimy chicken feet and the baked chicken blood pudding. Being a white man with an Asian soul, I’m not afraid to try new things, but I do have my limits. Why are chicken feet so hard when uncooked, but so soft and slimy when cooked?

        • http://www.gardenbetty.com/ Linda Ly

          Chicken foot bones have a lot of gelatin in them. When cooked down, they become a gooey gelatinous mess. Personally, I don’t really enjoy eating them (too much work for too little meat) but chicken feet do make an amazing broth.

  • Thai

    Thanks for the tips regarding the organic pesticide. Just add it to my garden book for next season.
    You’re great by the way!

    • http://www.gardenbetty.com/ Linda Ly

      Thank you!

  • Pingback: Spicy Minty Tomato Sauce Infused With Tomato Leaves | Garden Betty

  • life on bonita

    awesome article!

  • growntocook

    I very much appreciate your inquisitive approach to “well known truths”. So much in the gardening books is just repeated without anybody testing the validity of the statement!

  • Hanna

    I really appreciate your evidence based approach for this article! Those studies aren’t always easy to read, but you translated them well. Thanks!

    • http://www.gardenbetty.com/ Linda Ly

      You’re welcome! It’s something I’ve always been meaning to research, especially now that my tomato plants are at their peak!

  • Margo, Thrift at Home

    Fascinating. I’m interested in the sauce recipe.
    I save all carrot and radish tops for the stock pot. I freeze them until I make big pots of stock in the winter. Works great.

    • http://www.gardenbetty.com/ Linda Ly

      I wonder if adding tomato leaves to a stock pot would impart a tomato-y flavor to the stock… hmm.

      • Anomy8

        Tomato leaves are used in the process of making Estratto

        • http://www.gardenbetty.com/ Linda Ly

          I might have to try estratto sometime! Currently I make a tomato sauce with the leaves, and I’ve recently used them in a basil pesto.

  • Xochi Navarro

    How would you cook and eat tomato leaves? AND I didn’t know you could eat cucumber leaves! How do you cook and eat those?

    • http://www.gardenbetty.com/ Linda Ly

      I’ll be posting a tomato sauce recipe this week that uses tomato leaves. As for cucumber leaves, I don’t cook them (only because I don’t want to strip my vines of all the leaves) but I do put them in salads and wraps. If you thin out cucumber seedlings, you can eat those microgreens too.

  • dave

    In case I missed it, did you eat any?

    • http://www.gardenbetty.com/ Linda Ly

      Yes. I’ve cooked with tomato leaves (adding them to omelets and such) but am experimenting with other recipes where I can bring out their flavor more. (Since now, all I taste are the garlic, onions etc that I cook them with.) I’ll post recipes as I try them and like them. :-)

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