The mighty tomato!
How did a crop from a poisonous plant family pervade our salads, soups, and sauces across numerous cuisines?
Some call them a fruit; some call them a vegetable; I call them juicy, red, and delicious! The weather is perfect now in the Southeast USA for planting our summer tomatoes, and I’ve been busy transplanting different varieties into my garden bed over the last week. Anyone who has tasted a vine-ripened tomato has likely experienced a very different flavor profile than you have with store-bought produce, typically harvested green, to facilitate shipping. So the big question is: What makes the tomato a healthy food ingredient, and how can you capture its best benefits? I explore these questions and more in today’s post.
About the Tomato
The scientific name of the tomato is Solanum lycopersicum of the Solanaceae, or nightshade plant family. Other close relatives in the same genus include potatoes and eggplants. As a genus, Solanum is quite large and diverse, containing somewhere between 13 and 17 hundred species. Botanically speaking, the fruit of this species is a berry, though in cuisine it is often considered a vegetable due to its use in savory flavored dishes.
Some call them tom-ah-tohs, others call them tom-ay-toes! No matter which pronunciation you prefer, I think most can agree that there is just something special about a vine-ripened tomato whether eaten on its own, in a salad, over pasta or rice, or in a variety of sauces. Today, tomatoes are traded in fresh form or processed and sold in soups, as paste, sauce, juice, concentrate, in sun-dried form and in ketchup. In 2016, worldwide tomato production reached 177 million tons, making it the seventh most important crop. China produces 56 tons yearly, almost a third of all commercially cultivated tomatoes globally.
Looking back at the tomato's origins, you might be surprised to see its links to poisonous plants in the deadly nightshade family. However, selective breeding has led to an astonishing array of tomato varieties that come in all sorts of shapes and sizes. Besides its tasty role in the kitchen, this crop has also been linked to numerous health benefits, including antioxidant, anti-inflammatory, and anticancer activities. On the other hand, some people may experience harmful effects from consuming tomatoes or tomato products, ranging from heartburn, allergies, irritable bowel syndrome, to urinary problems.
Origins
Wild tomatoes originated in the western part of South America, and the center of their domestication is still a point of debate. The Peruvian and Mexican hypotheses exist, with a combination of various fields of study needed to solve the question. Tomatoes were introduced to Europe in the 16th century by the Spanish conquistador Cortes, who likely brought a small yellow tomato to Spain. From there, it spread to Italy, and records of its use in gazpacho recipes have been found dating back to the 1600s. By the 1800s, numerous cultivars had emerged, producing various fruits of various shapes, sizes, sweetness, and colors for consumption.
The naming of the tomato has also been the subject of debate. Linnaeus initially classified the tomato plant as Solanum lycopersicum in 1753, but an English botanist named it Lycopersicon esculentum in 1768 and moved it to its own genus. However, new genetic evidence supports Linnaeus's original classification, and Solanum lycopersicum is now the accepted scientific name.
The tomato has come a long way from its origins in South America and its introduction to Europe. It has become a staple in many cuisines worldwide, with numerous cultivars and varieties available for consumption. The debate over its domestication and naming is just one aspect of the fascinating history of this unique fruit.
Pharmacology
Ripe tomatoes are rich in phenolic compounds and carotenoids, which are the primary biologically active compounds that have been identified in the fruits. They are also a rich source of ascorbic acid, also known as Vitamin C. That deep red color that we note in tomato fruits is due to the presence of high levels of the carotenoid compound known as lycopene.
Tomatine is a mildly toxic glycoalkaloid present in the stems, leaves, and unripe tomato fruits. High levels of consumption, particularly from eating tomato leaves, can cause acute tomatine toxicity, resulting in symptoms such as vomiting, diarrhea, abdominal pain, drowsiness, confusion, weakness, and depression. Symptoms are similar to solanine poisoning, a glycoalkaloid found in potato leaves.
About Lycopene
Lycopene, found in tomatoes, is a powerful antioxidant due to its chemical structure, which contains many conjugated double bonds, making it a potent singlet oxygen quencher. Lycopene is the primary health-boosting carotenoid found in tomatoes, with the highest levels found in tomato paste, tomato sauce, and tomato juice.
However, the way a food is prepared can heavily influence the final pharmacology of what is consumed. Cooking tomatoes with onions can enhance this transformation from E to Z isomers, which exhibit better antioxidant activity than the E-isomer. Furthermore, lycopene is fat-soluble, and cooking tomatoes with olive oil aids in the absorption of this molecule in the gut. A study found significantly greater levels of the Z-isomers of lycopene in the blood plasma of healthy volunteers who consumed tomatoes cooked in olive oil compared to those cooked and consumed without olive oil. Cooked tomatoes with onions and olive oil offers a more effective way to obtain lycopene's health benefits.
Clinical Outcomes
Numerous clinical studies have explored the effectiveness of tomatoes against cardiovascular disease and metabolic syndrome, including heart health and obesity. The studies observed a decline in serum triglycerides, total plasma cholesterol, and multiple markers of inflammation, including C-reactive protein, IL-6, IL-8, and TNF-alpha. Additionally, improvements in blood pressure and lower cardiac risks were observed. Tomatoes and their products, such as paste, sauce, and juice, have positively affected biomarkers related to diabetes, obesity, and cardiovascular disease. Tomato consumption in these trials resulted in few adverse effects, with tomatoes being considered a safe and well-tolerated dietary ingredient.
The Takeaway
Tomatoes have a complex origin story and provide various health benefits. Adding companion ingredients like olive oil and onions and heating them can give your final dish an extra antioxidant boost. It is best to store tomatoes out of direct sunlight at room temperature and avoid refrigerating them. If they are not yet fully ripe, store them in a paper bag to capture more of the natural ethylene gas they produce in the ripening process. Tomatoes are easy to process and store for use throughout the year, and they can be canned or sun-dried for a healthy snack.
Yours in health, Dr. Quave
Cassandra L. Quave, Ph.D. is a scientist, author, speaker, podcast host, wife, mother, explorer, and professor at Emory University School of Medicine. She teaches college courses and leads a group of research scientists studying medicinal plants to find new life-saving drugs from nature. She hosts the Foodie Pharmacology podcast and writes the Nature’s Pharmacy newsletter to share the science behind natural medicines. To support her effort, consider a paid or founding subscription, with founding members receiving an autographed 1st edition hardcover copy of her book, The Plant Hunter.