Tomatoes

Health Benefits
(Source: World's Healthiest Foods, George Mateljan)

Outstanding Antioxidant and Anti-Inflammatory Benefits from Tomatoes

We realize that it is easy to find websites that describe tomatoes as a cause of inflammation and a food that can increase risk of unwanted inflammation rather than reducing it. Research studies on tomatoes consistently show a very different relationship in which tomato intake is associated with decreased risk of unwanted inflammation and decreased risk of oxidative stress as well. These research studies should not be surprising, given the wealth of antioxidant and anti-inflammatory phytonutrients provided to us by tomatoes. While carotenoids have been key area of research focus in this regard, tomatoes actually offer an extensive list of health-supportive phytonutrients. This list includes flavonoids, carotenoids, saponins, and fatty acid derivatives. Some of the best-studied phytonutrients in tomatoes are listed below.

  • Flavones

    • fisetin

  • Flavonones

    • naringenin

    • chalconaringenin

  • Flavonols

    • rutin

    • kaempferol

    • quercetin

  • Hydroxycinnamic acids

    • caffeic acid

    • ferulic acid

    • coumaric acid

  • Carotenoids

    • lycopene

    • lutein

    • photofluene

    • neurosporine

    • zeaxanthin

    • beta-carotene

  • Saponins

    • esculeoside A

  • Fatty acid derivatives

    • 9-oxo-octadecadienoic acid

While not typically considered phytonutrients, one unusual category of compounds found in tomatoes may also provide us with health benefits. Members of this category are called alkaloids (and in tomatoes, they are also sometimes called solanaceous alkaloids, since they are found almost exclusively among plants in the nightshade or Solanaceae family). Tomato alkaloids include tomatine and tomatidine. The reason that these alkaloids are not currently considered to be phytonutrients involves the risk that they can pose when consumed in large amounts or by individuals with a special sensitivity to them. (And to be fair, we should note that some observers believe tomato alkaloids can pose a certain level of risk even when consumed in smaller amounts, despite lack of evidence for this conclusion in large-scale research studies.) Another piece of information that is helpful to know in this regard involves the way that alkaloids are distributed within the tomato plant. Tomato alkaloids are far more concentrated in the leaves and stems of the plant than in the fruit portion that we commonly enjoy.

In addition to the phytonutrient antioxidants listed above, tomatoes also provide us with a good number of conventional antioxidants, including excellent amounts of vitamin C; very good amounts of vitamin E, vitamin A (in the form of carotenoids), and manganese; and good amounts of zinc and chromium.

If you combine all studies on the antioxidant and anti-inflammatory benefits of tomatoes, you will find these benefits extending to many different body systems, including the cardiovascular system, musculoskeletal system, renal system (kidneys), hepatic system (liver), and integumentary system (skin).

It's also worth noting the level of detail that has come into play with research studies on the anti-inflammatory benefits of tomatoes. Multiple studies have documented these anti-inflammatory benefits at the level of cell signaling in our body. This research has centered on biomarkers of inflammation including interleukin-6 (IL-6), vascular cell adhesion molecule-1 (VCAM-1), and lymphocyte function-associated antigen-1 (LFA-1).

Cardiovascular Benefits from Tomatoes

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 has the ability to help lower the risk of lipid peroxidation in our 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 can lead to trouble. Overly damaged fat components can sound an alarm to the body's immune and inflammatory systems, and the result is a series of events 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 (a saponin) and the other called 9-oxo-octadecadienoic acid (a fatty acid derivative)—are currently under active investigation by researchers as tomato phytonutrients that can provide us with special benefits for regulation of fats in our bloodstream.

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 "anti-aggregatory effect.") In combination with the other heart benefits described above, this platelet-regulating impact of tomatoes puts them in a great position to help us optimize our cardiovascular health.

Other Potential Health Benefits from Tomatoes

In addition to the areas of health support described above, the single largest area of potential health benefits from tomatoes involves cancer risk. Prostate cancer is the best-researched type of cancer in relationship to tomato intake, and here the verdict is pretty clear: tomato intake helps lower risk of prostate cancer in men. One key tomato nutrient that has received special attention in this regard is alpha-tomatine. Alpha-tomatine is a saponin phytonutrient and it has demonstrated an ability to alter metabolic activity in developing prostate cancer cells. It has 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 have been examined in relationship to tomato intake. Research on tomatoes and breast cancer has largely focused on the carotenoid lycopene, however, rather than tomato intake per se. In association with lycopene intake (in supplemental form), there is reasonably consistent research showing risk reduction for breast cancer. However, we have not seen a large-scale study that expanded this risk reduction to intake of fresh tomatoes in a weekly meal plan.

The area of skin health has also sparked the interest of tomato researchers. Tomato and tomato products—especially tomato paste—have been shown to provide health benefits following unprotected sun exposure in humans. Specifically, researchers have found tomato consumption to result in less skin redness after UV exposure from sunlight. In addition, they have found that food forms of tomato (like tomato paste ) do a better job of lessening the impact of sunburn than purified tomato-based nutrients like lycopene (which are taken in the form of dietary supplements).

The ability of tomato intake to help protect our skin comes as no surprise since carotenoids like beta-carotene have long been known for their ability to get deposited in our skin cells. And we know that they can play a protective role there in fending off the unwanted consequences of excessive UW light. Animal studies have extended the skin-support role of tomato intake to risk reduction for certain types of skin cancer. In one recent study, mice were given whole tomato powder from two different varieties of tomato—one red-colored variety and one tangerine-colored variety. Consumption of both tomato powders was determined to affect skin cell metabolism and to lower risk of skin cancer development. Specifically, the researchers measured a form of skin cancer called keratinocyte carcinoma (sometimes more loosely referred to as nonmelanoma skin cancer) and found the occurrence to be reduced in the mice consuming the tomato powder. It's only the carotenoids in tomato that were likely associated with this reduced risk, but also certain tomato alkaloids, including tomatine and tomatidine. We expect to see follow-up studies on tomato intake and reduced risk of skin cancer in humans that analyze routine intake of fresh tomatoes in an everyday meal plan.

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