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.
Health Benefits
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:
Flavonones
- naringenin
- chalconaringenin
Flavonols
- rutin
- kaempferol
- quercetin
Hydroxycinnamic acids
- caffeic acid
- ferulic acid
- coumaric acid
Carotenoids
- lycopene
- lutein
- zeaxanthin
- beta-carotene
Glycosides
- 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.
Cardiovascular Support
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.
Anti-Cancer Benefits
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.
Individual Concerns: Tomatoes Belong to the Nightshade Family
Tomatoes are one of the vegetables in the nightshade (Solanaceae) family, which includes eggplant, bell peppers, and potatoes (although not sweet potatoes and yams). Anecdotal case histories link improvement in arthritis symptoms with removal of these foods; however, no case-controlled scientific studies confirm these observations.
Note: Many members of the
nightshade family are used by humans, and are important sources of food, spice and medicine. However,
nightshade species are often rich in alkaloids whose toxicity to humans and animals ranges from mildly irritating to fatal in small quantities.
Reference: www.whfoods.com
No comments:
Post a Comment