Explore the Timeless Appeal and Health Benefits of Tomatoes, the Quintessential Taste of Summer.
An average tomato contains a gram each of protein and fiber, no fat, and only a small amount of carbohydrate, most of which is sugar. Tomatoes are a reliable source of vitamin C, vitamin A, folate, vitamin K, and potassium. They are also high in carotenoid phytochemicals including beta-carotene, lycopene, and lutein.
Culinary Medicine
by Lori A Smolin, PhD and
Nothing says summer like ripe, juicy home-grown tomatoes. With 10,000 varieties to choose from, they are among America’s top vegetable choices. [1,2] They come in a rainbow of colors from golden to purple and range in size from tiny ones the size of a marble to giant ones bigger than your fist. Tomatoes are technically fruit – an edible berry – but we generally eat them as a vegetable in salads and on sandwiches. We also eat them canned and processed; 60 percent of the tomatoes we eat are consumed in foods such as sauces, beverages, soups, ketchup, pizza, and spaghetti sauce. Whether fresh or cooked, they provide flavor, nutrition, and health benefits.
How Tomatoes Went Global
Tomatoes were grown in South America as early as 700 BCE. [3] The plant eventually made it north into Mexico and then to Europe in the 1500s. Along their journey, tomatoes were known by many different names ranging from golden apple and love apple to wolf peach and poison apple. [2] Although tomatoes were eaten by indigenous peoples in the Americas, in Europe they were initially grown as an ornamental plant because people thought the fruit was poisonous. Tomatoes are a member of the nightshade family of plants, which contain potentially harmful chemicals called alkaloids. Belladonna, for example, is a nightshade that was used by the ancients as a poison, and by fortune tellers and witches to cause hallucinations. [4] Tomatoes, however, do not contain enough of these alkaloids to be harmful. [5,6] Nonetheless, the myth of poison tomatoes was perpetuated into the 18th century, in part because some European aristocrats died after consuming them. These deaths were not actually due to the tomatoes, but rather to the pewter plates they were served on. Pewter is high in lead and the acidity of the tomatoes leached lead from the dinnerware, causing lead poisoning among the diners. [1,2]
The consumption of tomatoes was eventually bolstered in Europe by the invention of pizza in Naples, Italy in 1880. [3] Tomatoes made their way back to the Americas with colonists in the early 1700s, but popularity there did not become widespread until the early 1900s. [1,2] Today, tomatoes are the most popular homegrown vegetable; annual consumption in the United States is over thirty-one pounds per person. [1,7]
Nutrients and Phytochemicals
Tomatoes have been called a superfood because of their nutritional benefits. They are low in calories; an entire large tomato has only about 20 Calories. An average tomato (2.6 inches) contains a gram each of protein and fiber, no fat, and a small amount of carbohydrate, most of which is sugar. Tomatoes are a reliable source of vitamin C, vitamin A, folate, vitamin K, and potassium. They are also high in carotenoid phytochemicals including beta-carotene, lycopene, and lutein. Beta-carotene is a red-orange pigment that functions as an antioxidant and can be converted into vitamin A in the body. Lycopene is a red pigment that is an even more potent antioxidant than beta-carotene and has anti-inflammatory effects. [8] Lutein is best known for its ability to protect the eye from light-induced damage. Lutein also provides color to food ranging from yellow to red depending on its concentration.
Tomatoes and Health
Many of the health benefits of tomatoes and tomato products are attributed to their antioxidant content. Antioxidants protect us from conditions associated with oxidative stress and chronic inflammation such as macular degeneration, neurological and skin disorders, diabetes, cardiovascular disease, and cancer. A diet high in antioxidants can help reduce the risks of these conditions.
Age-related macular degeneration and cataracts are ophthalmic disorders associated with oxidative stress. [7,9] Lutein, a dietary antioxidant in tomatoes, has been shown to protect against the development of both. The neurodegenerative diseases Alzheimer’s and Parkinson’s are also associated with oxidative stress. Although animal and laboratory studies studies have shown that the pathological changes seen in these are ameliorated with lycopene and tomato extract, few human studies have shown a protective role. [7] The nutrients and phytochemicals in tomatoes may contribute to skin health both by reducing the symptoms of inflammatory skin disorders and by protecting the skin from UV radiation. While tomatoes are a healthy food choice for people with diabetes, there is little evidence supporting a protective effect in diabetes. [7]
The antioxidants in tomatoes have been most extensively studied for their ability to protect against cardiovascular disease and cancer. [7] Lycopene has been shown to reduce the risk of atherosclerosis by inhibiting the oxidation of LDL cholesterol as well as by reducing inflammation, platelet aggregation, and blood pressure. [7,8] High intake and high blood levels of lycopene are associated with a lower risk of cardiovascular disease. [10] One study found that even a single serving of tomatoes, consumed raw, as sauce, or as sauce with olive oil, reduced total cholesterol and triglyceride levels and increased HDL cholesterol levels; the greatest effect occurred when the tomatoes were consumed as sauce with olive oil. [11] Lycopene and other antioxidants in tomatoes have been suggested to guard against cancer by protecting DNA and proteins from oxidative damage. High intakes of tomatoes and lycopene are associated with a lower cancer mortality. [7,12] While lycopene has been studied in a variety of cancers, the greatest benefit was found with prostate cancer. Human observational studies have found lycopene intake to be correlated with a reduced risk of prostate cancer, but more study is needed to recommend a specific amount. [13]
Despite all these benefits, for some individuals tomato consumption can cause significant side effects. The acidic nature of tomatoes may worsen acid reflux or gastroesophageal reflux disease (GERD). The insoluble fiber in tomato skin may be difficult to digest resulting in abdominal pain or diarrhea. Individuals with a sensitivity to nightshades may develop skin irritation, joint pain, and increased inflammation with tomato consumption. Tomatoes can also cause allergic reactions. The most common reaction is irritation of the lips, tongue, pharynx; symptoms can also include irritation of the lower gastrointestinal tract and, in rare cases, anaphylactic reactions. [14] Some individuals with an intolerance to tomatoes only react to fresh tomatoes and can consume processed tomato products. Those allergic to tomatoes should avoid them altogether.
Maximizing Tomato Flavor and Nutrition
Not all tomatoes are the same. Different varieties have different gastronomic traits and nutritional properties. How they are grown and stored also affects their flavor. Tomatoes you buy in the grocery store typically look beautiful but often do not have the juicy sweet flavor of those plucked from a garden. This is because commercial tomatoes have been bred to ripen to a homogeneous color; the unintended consequence of this genetic variant is that they have less sugar and less flavor. [15] Another reason grocery store tomatoes do not taste as good as home grown is they are picked green and ripened artificially with ethylene gas. Tomatoes naturally produce ethylene gas, which causes them to slowly redden and ripen. Gassing green tomatoes forces them to turn red quickly, but not to develop flavor. If you grow them in your garden, you can leave them on the vine until they are completely ripe or harvest them just when they are starting to color – they will ripen on the kitchen counter. For the best flavor, store ripe tomatoes at room temperature. You can refrigerate the unripe ones until you want them to ripen; the refrigeration puts ethylene gas on hold. [16]
The type of tomato also affects its nutrient and phytochemical content. Most tomatoes have similar amounts of potassium and vitamin C; green tomatoes are lower in vitamin A. Because the carotenoids in tomatoes are pigments, different colored tomatoes provide different amounts of certain phytochemicals. Yellow tomatoes, often sought for their sweeter and less acidic flavor, do not contain much lycopene. Orange tomatoes are also sweeter and less acidic but do contain lycopene in a form that is better absorbed than the lycopene in red tomatoes. [17] Purple and black varieties are the best sources of lycopene, lutein, and beta-carotene but are often rejected because consumers are put off by the color. [18]
How tomatoes are prepared affects their nutritional value. The tomato skin is the most concentrated source of lycopene, so you can maximize lycopene by keeping the skin on when eating or cooking tomatoes. Cooking increases the bioavailability of lycopene and concentrates it by cooking off the water. What you eat with your tomatoes also affects how much lycopene you absorb. Like other carotenoids, lycopene is fat soluble, so it is absorbed better when fat is included in the meal. So, drizzle some olive oil on your fresh tomatoes and add it to cooked sauces.
Bottom Line
A diet rich in tomatoes, whether from fresh, cooked, or processed, boosts your vitamin, mineral, and phytochemical intake, and may even reduce your risk of a variety of chronic diseases. Add your favorites to salads, sandwiches, and casseroles. Whether cherry, plum, Campari, Brandywine, beefsteak, Roma, or any of the thousands of varieties, tomatoes will add a sweet tart taste, complexity, color, and a lot of nutrition to your diet, along with the flavor of summer.
Try our Fresh, Flavorful, and Healthy: Marinated Cucumber and Tomato Salad Recipe - A Perfect Summer Salad
References
[1] USDA Economic Research Service. Potatoes and Tomatoes are the Most Commonly Consumed Vegetables. US per capita loss-adjusted vegetable availability, 2019.
https://www.ers.usda.gov/data-products/chart-gallery/gallery/chart-detail/?chartId=58340. Accessed May 10, 2024.
[2] Benoit DJ. A History of Tomatoes, The University of Vermont. February 8, 2023: https://www.uvm.edu/news/extension/history-tomatoes#:~:text=Tomato%20seeds%20were%20brought%20from,primarily%20as%20an%20 ornamental%20 plant. Accessed May 10, 2024.
[3] K. Annabelle Smith. Why the Tomato Was Feared in Europe for More Than 200 Years. Smithsonian. Published June 18, 2013. https://www.smithsonianmag.com/arts-culture/why-the-tomato-was-feared-in-europe-for-more-than-200-years-863735/
[4] The Supernatural Side of Plants – CornellBotanicGardens. cornellbotanicgardens.org. https://cornellbotanicgardens.org/the-supernatural-side-of-plants-2/
[5] Zelman K What to Know About Nightshade Vegetables. WebMD. Published April 8, 2021. https://www.webmd.com/diet/what-to-know-about-nightshade-vegetables
[6] Dolan LC, Matulka RA, Burdock GA. Naturally Occurring Food Toxins. Toxins. 2010;2(9):2289-2332. doi:https://doi.org/10.3390/toxins2092289
[7] Collins EJ, Bowyer C, Tsouza A, Chopra M. Tomatoes: An Extensive Review of the Associated Health Impacts of Tomatoes and Factors That Can Affect Their Cultivation. Biology. 2022; 11(2):239. https://doi.org/10.3390/biology11020239
[8] Khan UM, Sevindik M, Zarrabi A, et al. Lycopene: Food Sources, Biological Activities, and Human Health Benefits. Oxidative Medicine and Cellular Longevity. 2021;2021:2713511. doi:https://doi.org/10.1155/2021/2713511
[9] Johra FT, Bepari AK, Bristy AT, Reza HM. A Mechanistic Review of β-Carotene, Lutein, and Zeaxanthin in Eye Health and Disease. Antioxidants. 2020; 9(11):1046. https://doi.org/10.3390/antiox9111046
[10] Cheng HM, Koutsidis G, Lodge JK, Ashor AW, Siervo M, Lara J. Lycopene and tomato and risk of cardiovascular diseases: A systematic review and meta-analysis of epidemiological evidence. Critical Reviews in Food Science and Nutrition. 2017;59(1):141-158. doi:https://doi.org/10.1080/10408398.2017.1362630
[11] Valderas-Martinez P, Chiva-Blanch G, Casas R, et al. Tomato Sauce Enriched with Olive Oil Exerts Greater Effects on Cardiovascular Disease Risk Factors than Raw Tomato and Tomato Sauce: A Randomized Trial. Nutrients. 2016;8(3):170. doi:https://doi.org/10.3390/nu8030170
[12] Mazidi M, Ferns GA, Banach M. A high consumption of tomato and lycopene is associated with a lower risk of cancer mortality: results from a multi-ethnic cohort. Public Health Nutrition. 2020;23(9):1569-1575. doi:https://doi.org/10.1017/S1368980019003227
[13] Kapała A, Szlendak M, Motacka E. The Anti-Cancer Activity of Lycopene: A Systematic Review of Human and Animal Studies. Nutrients. 2022;14(23):5152. doi:https://doi.org/10.3390/nu14235152
[14] Włodarczyk K, Smolińska B, Majak I. Tomato Allergy: The Characterization of the Selected Allergens and Antioxidants of Tomato (Solanum lycopersicum)—A Review. Antioxidants. 2022;11(4):644. doi:https://doi.org/10.3390/antiox11040644
[15] Powell ALT, Nguyen CV, Hill T, et al. Uniform ripening encodes a Golden 2-like transcription factor regulating tomato fruit chloroplast development. Science (New York, NY). 2012;336(6089):1711-1715. doi:https://doi.org/10.1126/science.1222218
[16] Russell A. Pick tomatoes at color break. AgriLife Today. Published June 10, 2022. Accessed June 3, 2024. https://agrilifetoday.tamu.edu/2022/06/10/pick-tomatoes-at-color-break
[17] Robinson J. Lycopene in Orange Tomatoes – Mother Earth News. www.motherearthnews.com. https://www.motherearthnews.com/natural-health/lycopene-in-tomatoes-zmgz16fmzsto/#:~:text=Orange%20tomatoes%20contain%20a%20different
[18] Woodstream W. Which Tomatoes Are the Healthiest to Grow? www.saferbrand.com.
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