What's New and Beneficial About Tomatoes
- Did you know that tomatoes do not have to be a deep red color to be an outstanding source of lycopene? Lycopene is a carotenoid pigment that has long been associated with the deep red color of many tomatoes. A small preliminary study on healthy men and women has shown that the lycopene from orange- and tangerine-colored tomatoes may actually be better absorbed than the lycopene from red tomatoes. That's because the lycopene in deep red tomatoes is mostly trans-lycopene, and the lycopene in orange/tangerine tomatoes is mostly tetra-cis-lycopene. In a recent study, this tetra-cis form of lycopene turned out to be more efficiently absorbed by the study participants. While more research is needed in this area, we're encouraged to find that tomatoes may not have to be deep red in order for us to get great lycopene-related benefits.
- Tomatoes are widely known for their outstanding antioxidant content, including, of course, their oftentimes-rich concentration of lycopene. Researchers have recently found an important connection between lycopene, its antioxidant properties, and bone health. A study was designed in which tomato and other dietary sources of lycopene were removed from the diets of postmenopausal women for a period of 4 weeks, to see what effect lycopene restriction would have on bone health. At the end of 4 weeks, women in the study started to show increased signs of oxidative stress in their bones and unwanted changes in their bone tissue. The study investigators concluded that removal of lycopene-containing foods (including tomatoes) from the diet was likely to put women at increased risk of osteoporosis. They also argued for the importance of tomatoes and other lycopene-containing foods in the diet. We don't always think about antioxidant protection as being important for bone health, but it is, and tomato lycopene (and other tomato antioxidants) may have a special role to play in this area.
- There are literally hundreds of different tomato varieties. We usually choose our favorite varieties by some combination of flavor, texture, and appearance. But a recent study has shown that we may also want to include antioxidant capacity as a factor when we are choosing among tomato varieties. Surprisingly, researchers who compared conventionally grown versus organically grown tomatoes found that growing method (conventional versus organic) made less of an overall difference than variety of tomato. While all tomatoes showed good antioxidant capacity, and while the differences were not huge, the following four varieties of tomatoes turned out to have a higher average antioxidant capacity regardless of whether they were grown conventionally or organically: New Girl, Jet Star, Fantastic, and First Lady. It's only one study, of course, and we're definitely not ready to recommend these four varieties at the exclusion of all others. But these findings are fascinating to us, and they suggest that specific types of nutrient benefits may be provided by specific varieties of tomatoes. Also, if you're seeking good antioxidant protection and you're in the grocery standing in front of a New Girl, Jet Star, Fantastic, or First Lady tomato, you would probably be well-served to place it in your shopping cart.
- Intake of tomatoes has long been linked to heart health. Fresh tomatoes and tomato extracts have been shown to help lower total cholesterol, LDL cholesterol, and triglycerides. In addition, tomato extracts have been shown to help prevent unwanted clumping together (aggregation) of platelet cells in the blood - a factor that is especially important in lowering risk of heart problems like atherosclerosis. (In a recent South American study of 26 vegetables, tomatoes and green beans came out best in their anti-aggregation properties.) But only recently are researchers beginning to identify some of the more unusual phytonutrients in tomatoes that help provide us with these heart-protective benefits. One of these phytonutrients is a glycoside called esculeoside A; another is flavonoid called chalconaringenin; and yet another is a fatty-acid type molecule called 9-oxo-octadecadienoic acid. As our knowledge of unique tomato phytonutrients expands, we are likely to learn more about the unique role played by tomatoes in support of heart health. Tomatoes are also likely to rise further and further toward the top of the list as heart healthy foods.
Tomatoes are a treasure of riches when it comes to their antioxidant benefits. In terms of conventional antioxidants, tomatoes provide an excellent amount of vitamin C and beta-carotene; a very good amount of the mineral manganese; and a good amount of vitamin E. In terms of phytonutrients, tomatoes are basically off the chart, and include:
- Hydroxycinnamic acids
- caffeic acid
- ferulic acid
- coumaric acid
- esculeoside A
- Fatty acid derivatives
- 9-oxo-octadecadienoic acid
Specific antioxidant nutrients found in tomatoes, whole tomato extracts, and overall dietary intake of tomatoes have all been associated with antioxidant protection. Sometimes this protection comes in the form of reduced lipid peroxidation (oxygen damage to fats in cell membranes or in the bloodstream). Sometimes this protection comes in the form of better antioxidant enzyme function (for example, better function of the enzymes catalase or superoxide dismustase). Better antioxidant protection has also been shown using broad measurements of oxidative stress in different body systems. We've seen studies involving tomato and specific antioxidant protection of the bones, liver, kidneys, and bloodstream.
Reduced risk of heart disease is an area of health benefits in which tomatoes truly excel. There are two basic lines of research that have repeatedly linked tomatoes to heart health. The first line of research involves antioxidant support, and the second line of research involves regulation of fats in the bloodstream.
No body system has a greater need for antioxidant protection than the cardiovascular system. The heart and bloodstream are responsible for taking oxygen breathed in through the lungs and circulating it around throughout the body. In order to keep this oxygen in check, antioxidant nutrients are needed in an ample supply. Earlier in this Health Benefits section, we gave you a close-up look at some of the best-researched antioxidants in tomatoes. It's worth noting here that conventional vitamin antioxidants like vitamin E and vitamin C are sometimes overlooked in tomatoes because of their unique phytonutrient composition. Yet vitamin E and vitamin C provide critical antioxidant support in the cardiovascular system, and they are an important part of the contribution made by tomatoes to our heart health. It's the carotenoid lycopene, however, that has gotten the most attention as tomatoes' premier antioxidant and heart-supportive nutrient. Lycopene (and a related group of nutrients) has the ability to help lower the risk of lipid peroxidation in the bloodstream. Lipid peroxidation is a process in which fats that are located in the membranes of cells lining the bloodstream, or fats that are being carried around in the blood, get damaged by oxygen. This damage can be repaired if it is kept at manageable levels. However, chronic and/or excessive lipid peroxidation in the bloodstream leads to trouble. Overly damaged fat components sound an alarm to the body's immune and inflammatory systems, and the result is a series of processes that can lead to a gradual blocking of blood vessels (atherosclerosis) or other problems.
The second line of research linking tomatoes with heart health involves regulation of fats in the blood. Dietary intake of tomatoes, consumption of tomato extracts, and supplementation with tomato phytonutrients (like lycopene) have all been shown to improve the profile of fats in our bloodstream. Specifically, tomato intake has been shown to result in decreased total cholesterol, decreased LDL cholesterol, and decreased triglyceride levels. It's also been shown to decrease accumulation of cholesterol molecules inside of macrophage cells. (Macrophage cells are a type of white blood cell that gets called into action when oxidative stress in the bloodstream gets too high, and the activity of macrophages—including their accumulation of cholesterol—is a prerequisite for development of atherosclerosis.) Many phytonutrients in tomatoes are likely to be involved with the improvement of our blood fat levels. Two little-known phytonutrients—one called esculeoside A and the other called 9-oxo-octadecadienoic acid—are currently under active investigation by researchers as tomato phytonutrients especially important in blood fat regulation.
Yet another area of increasing interest in tomatoes and heart health involves blood cells called platelets. The excessive clumping together of platelet cells can cause problems for our bloodstream in terms of blockage and unwanted clotting, and prevention of this excessive clumping is important for maintaining heart health. Numerous phytonutrients in tomatoes have been shown to help prevent excessive clumping of our platelet cells. (This ability is usually referred to as an "antiaggregatory effect.") In combination with the other heart benefits described above, this platelet-regulating impact of tomatoes puts them in a unique position to help us optimize our cardiovascular health.
Supports Bone Health
Bone health is another area of growing interest in tomato research. Interestingly, the connection of tomato intake to bone health involves the rich supply of antioxidant in tomatoes. We don't always think about antioxidant protection as being important for bone health, but it is; and tomato lycopene (and other tomato antioxidants) may have a special role to play in this area. In a recent study, tomato and other dietary sources of lycopene were removed from the diets of postmenopausal women for a period of 4 weeks to see what effect lycopene restriction would have on bone health. At the end of 4 weeks, women in the study started to show increased signs of oxidative stress in their bones and unwanted changes in their bone tissue. We expect to see follow-up studies in this area that will hopefully determine exactly what levels of tomato intake are most helpful in protecting bone tissue.
While not well researched for all cancer types, tomatoes have repeatedly been show to provide us with anti-cancer benefits. The track record for tomatoes as a cancer-protective food should not be surprising, since there is a very large amount of research on tomato antioxidants and a more limited but still important amount of research on tomato anti-inflammatory nutrients. Risk for many cancer types starts out with chronic oxidative stress and chronic unwanted inflammation. For this reason, foods that provide us with strong antioxidant and anti-inflammatory support are often foods that show cancer prevention properties.
Prostate cancer is by far the best-researched type of cancer in relationship to tomato intake. The jury verdict here is clear: tomatoes can definitely help lower risk of prostate cancer in men. One key tomato nutrient that has received special focus in prostate cancer prevention is alpha-tomatine. Alpha-tomatine is a saponin phytonutrient and it's shown the ability to alter metabolic activity in developing prostate cancer cells. It's also been shown to trigger programmed cell death (apoptosis) in prostate cancer cells that have already been fully formed. Research on alpha-tomatine has also been conducted for non-small cell lung cancer, with similar findings.
Along with prostate cancer and non-small cell lung cancer, pancreatic cancer and breast cancer are the two best-studied areas involving tomatoes and cancer risk. Research on tomatoes and breast cancer risk has largely focused on the carotenoid lycopene, and there is fairly well documented risk reduction for breast cancer in association with lycopene intake.
Other Health Benefits
While not as thoroughly researched as these other areas of antioxidant support, cardiovascular support, and anti-cancer benefits, several other health benefit areas are important to mention with respect to tomatoes. Diets that include tomatoes have been linked with reduced risk of some neurological diseases (including Alzheimer's disease) in multiple studies. Tomato-containing diets have also been linked in a few studies with reduced risk of obesity.
The tomato is the fruit of the plant Lycopersicon esculentum. (Botanically speaking, tomato is not only a fruit, but also a berry since it is formed from a single ovary.) Originally, tomato was named after the food family to which it belongs - the Solanaceae (sometimes called "solanoid" or "nightshade") family. The botanical name Solanum lycopersicum for tomatoes has now largely been replaced by the name Lycopersicon esculentum. (The genus/species name Lycopersicon esculentum is also sometimes used to refer to tomatoes.)
The French sometimes refer to the tomato as pomme d'amour, meaning "love apple," and in Italy, tomato is sometimes referred to as "pomodoro" or "golden apple," probably referring to tomato varieties that were yellow/orange/tangerine in color.
Regardless of its name, the tomato is a wonderfully popular and versatile food that comes in over a thousand different varieties that vary in shape, size, and color. There are small cherry tomatoes, bright yellow tomatoes, Italian pear-shaped tomatoes, and the green tomato, famous for its fried preparation in Southern American cuisine.
Only the fruits of this plant are eaten since the leaves often contain potentially problematic concentrations of certain alkaloids (see Individual Concerns section below). Tomatoes have fleshy internal segments filled with slippery seeds surrounded by a watery matrix. They can be red, pink, yellow, orange/tangerine, green, purple, brown, or black in color.
Beefsteak and beef master tomatoes are among the largest-sized varieties. Roma tomatoes are more of an intermediate size, while cherry and grape tomatoes are small and rounded. The term "heirloom tomatoes" has become somewhat confusing as it can have a variety of different meanings. In the most traditional sense, "heirloom" refers to seeds from tomato cultivars that get handed down over time from family to family. Obviously, seeds handed down in this way do not make it possible for tomato production on a very large commercial scale. Yet there are definitely "commercial heirloom" tomatoes in the marketplace (sometimes produced from cross-breeding and sometimes produced through open pollination.)
Although tomatoes are fruits in a botanical sense, they don't have the dessert quality sweetness of other fruits. Instead they have a subtle sweetness that is complemented by a slightly bitter and acidic taste. They are prepared and served like other vegetables, which is why they are often categorized as such, including in our A-Z List of the World's Healthiest Foods. Cooking tempers the acid and bitter qualities in tomatoes and brings out their warm, rich sweetness.
There are few food sensations that better mark the summer and early fall months than the sweet juiciness of a vine-ripened tomato. Although tomatoes are available year-round across the U.S., some of the most delicious tomato flavors come from fresh tomatoes that have been planted in late spring or early summer and ripen from July through September.
Although tomatoes are often closely associated with Italian cuisine, they are actually originally native to the western side of South America, in the region occupied by Columbia, Ecuador, Peru, Chile, and the western half of Bolivia. The Galapagos Islands off the coast of Ecuador are also believed to be part of tomatoes' native area. The first type of tomato grown is thought to have more resembled the smaller-sized cherry tomato than the larger varieties.
The tomato does not appear to have been first cultivated in South America, however, but rather in Mexico, most likely in Aztec civilizations and probably in the form of small yellow fruits. The word "tomato" may actually originate from the Nahautl (Aztecan) word "tomatl " meaning "the swelling fruit." It wasn't until the 1500's that Spanish explorers and colonizers brought tomato seeds from Mexico back to Spain and introduced this food to European populations.
Although the use of tomatoes spread throughout Europe (including Italy) over the course of the 1500's, tomatoes did not enjoy full popularity then and were seen by many people as unfit to eat. Part of this "food inappropriateness" was associated with the status of the tomato plant as a nightshade plant and its potential poisonousness in this regard. (It's true, of course, that tomatoes belong to the Solanaceae or nightshade family of plants, along with potatoes, sweet and hot peppers, eggplant, tomatillos, tamarios, pepinos, pimentos, paprika, and cayenne. It's also true that tomatoes contain alkaloids —substances that even in small doses can be associated with adverse reactions in sensitive individuals. But it's also true that the levels of alkaloids found in nightshade foods are well-tolerated by many individuals in diets worldwide. For more on nightshades, please see our article "What are nightshades and in which foods are they found?")
Today tomatoes are enjoyed worldwide—to the tune of about 130 million tons per year. The largest tomato-producing country is China (with approximately 34 million tons of production), followed by the United States, Turkey, India, and Italy.
In the U.S., cultivation of tomato varieties is usually determined by their final destination: (1) consumption in fresh form by consumers or (2) use in processing by manufacturers of tomato products. Tomato processors need varieties that have a greater proportion of soluble solids in order to make products like tomato paste more efficiently. Between 80-90% of all commercial tomato cultivation in the U.S. is cultivation for eventual use in processing. (Processing tomatoes are needed for the manufacturing of pasta sauces, pizza sauces, and tomato pastes. Both processing and fresh market tomatoes may be used in the production of salsa—although fresh market tomato salsas or homemade salsas—like our Fresh Tomato Salsa—are the salsas that we like best on account of their minimal processing.) California and Florida produce about two-thirds of all commercially grown fresh market tomatoes in the U.S. During the winter months, because Florida tomatoes are generally shipped to other states along the east coast of the U.S., imported Mexican tomatoes make up a high percentage of commercially grown fresh tomatoes along the west coast.
How to Select and Store
Choose tomatoes that have rich colors. Deep reds are a great choice, but so are vibrant oranges/tangerines, brilliant yellows, and rich purples. Tomatoes of all colors provide outstanding nutrient benefits. Tomatoes should be well shaped and smooth skinned with no wrinkles, cracks, bruises, or soft spots. They should not have a puffy appearance since that characteristic is often associated with inferior flavor and may also result in excess waste during preparation. Ripe tomatoes will yield to slight pressure and will have a noticeably sweet fragrance.
When buying canned tomatoes, it is often better to buy those that are produced in the United States as many foreign countries do not have as strict standards for lead content in containers. This is especially important with a fruit such as tomatoes, whose high acid content can cause corrosion to, and subsequent migration into the foods of, the metals with which it is in contact.
While on the topic of canning, you may also be interested in some of the most recent information about canned tomato products and BPA (bisphenol A). BPA is an added component in the vinyl lining of numerous canned foods, and it's also known to be problematic from a health standpoint because of its impact on estrogen metabolism. (For more extensive information about BPA, click here.) A recent study of canned foods in Canada has shown an average of about 1 ppb of BPA in canned tomato paste products (with a maximum amount of about 2 ppb), and an average of 9 ppb in pure tomato products liked diced, sliced, or whole peeled tomatoes (with a maximum amount of about 23 ppm). While the U.S. Food and Drug Administration has not set a limit on the amount of BPA allowed in canned tomatoes, the European Commission Directive for BPA has set a limit of 600 ppb. While any amount of BPA in canned tomatoes seems undesirable, we are glad to see that the BPA levels were fairly low in this recent study, especially in canned tomato paste products. You'll need to look for a claim of "BPA-Free" on the label of your canned tomato products (or call the manufacturer) if you want to be sure that your canned tomatoes contain no BPA, since even some certified organic canned tomato products may contain—and are allowed to contain—BPA (through migration from the can).
Since tomatoes are sensitive to cold, and it will impede their ripening process, store them at room temperature and out of direct exposure to sunlight. They will keep for up to a week, depending upon how ripe they are when purchased. To hasten the ripening process, place them in a paper bag with a banana or apple since the ethylene gas that these fruits emit will help speed up the tomato's maturation. If the tomatoes begin to become overripe, but you are not yet ready to eat them, place them in the refrigerator (if possible, in the butter compartment which is a warmer area), where they will keep for one or two more days. Removing them from the refrigerator about 30 minutes before using will help them to regain their maximum flavor and juiciness. Whole tomatoes, chopped tomatoes and tomato sauce freeze well for future use in cooked dishes. Sun-dried tomatoes should be stored in an airtight container, with or without olive oil, in a cool dry place.
Ketchup can be a surprisingly good source of tomato nutrients, including lycopene. But if you are going to purchase tomatoes in the form of ketchup, we recommend that you choose organic ketchup. We make this recommendation not only because you're likely to avoid unwanted pesticide residues and other contaminants if you purchase organic, but also because we've seen a recent study showing higher lycopene content in organic versus non-organic ketchup.
Tips for Preparing and Cooking
Tips for Preparing Tomatoes
Before serving, wash tomatoes under cool running water and pat dry.
If your recipe requires seeded tomatoes, cut the fruit in half horizontally and gently squeeze out the seeds and the juice. However, we encourage you to think about the recipe and consider whether the tomato could be incorporated with seeds intact. There are simply too many valuable nutrients in the seeds that you would not want to lose unnecessarily.
When cooking tomatoes, we recommend avoidance of aluminum cookware since the high acid content of the tomatoes may interact with the metal in the cookware. As a result, there may be migration of aluminum into the food, which may not only impart an unpleasant taste, but more importantly, may have a potentially unwanted impact on your health.
Whenever possible, try to develop recipes that make use of the whole tomato. We've seen research showing higher lycopene content in whole tomato products. For example, when the skins of tomatoes are included in the making of the tomato paste, the lycopene and beta-carotene content of the paste is significant higher according to research studies.
How to Enjoy
A Few Quick Serving Ideas
- To make your own tomato paste, simply Healthy Sauté a couple of cloves of chopped garlic and/or 1 or 2 large chopped onions for a couple of minutes until they are translucent. Add 8 to 10 chopped whole tomatoes and a teaspoon of dried—or several teaspoons of fresh chopped—oregano, basil, and any other herbs you enjoy (such as parsley or rosemary). Simmer for 30-45 minutes. Remove from the heat, drizzle with olive oil, and add sea salt and freshly ground black pepper to taste. For a fancier version, Healthy Sauté chopped olives and/or mushrooms along with the garlic and onions.
- Tomatoes are a great addition to bean and vegetable soups.
- Enjoy a classic Italian salad—sliced onions, tomatoes and mozzarella cheese drizzled with olive oil.
- Combine chopped onions, tomatoes, and chili peppers for an easy-to-make salsa dip.
- Puree tomatoes, cucumbers, bell peppers and scallions together in a food processor and season with herbs and spices of your choice to make the refreshing cold soup, gazpacho.
- Add tomato slices to sandwiches and salads. To keep things colorful, use yellow, green and purple tomatoes in addition to red ones.
Tomatoes Belong to the Nightshade Family
Cherry Tomatoes and Pesticide Residues
Virtually all municipal drinking water in the United States contains pesticide residues, and with the exception of organic foods, so do the majority of foods in the U.S. food supply. Even though pesticides are present in food at very small trace levels, their negative impact on health is well documented. The liver's ability to process other toxins, the cells' ability to produce energy, and the nerves' ability to send messages can all be compromised by pesticide exposure. According to the Environmental Working Group's 2014 report "Shopper's Guide to Pesticides," conventionally grown cherry tomatoes are among the top 12 fruits and vegetables on which pesticide residues have been most frequently found. Therefore, individuals wanting to avoid pesticide-associated health risks may want to avoid consumption of cherry tomatoes unless they are grown organically.
While most often associated with lycopene (a carotenoid phytonutrient widely recognized for its antioxidant properties), tomatoes provide a unique variety of phytonutrients. Included are additional carotenoids (including beta-carotene, lutein, and zeaxanthin); flavonoids (including naringenin, chalconaringenin, rutin, kaempferol, and quercetin); hydroxycinnamic acids (including caffeic, ferulic, and coumaric acid); glycosides (including esculeoside A); and fatty acid derivatives (including 9-oxo-octadecadienoic acid).
Tomatoes are also an excellent source vitamin C, biotin, molybdenum, and vitamin K. They are also a very good source of copper, potassium, manganese, dietary fiber, vitamin A (in the form of beta-carotene), vitamin B6, folate, niacin, vitamin E, and phosphorus. Additionally, they are a good source of chromium, pantothenic acid, protein, choline, zinc, and iron.
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