UC Davis, in the Sacramento-Davis regional area, several years ago studied green tea's effects on health. Back then, a research group from U.C. Davis discovered how organically and sustainably grown food crops contained significantly higher concentrations of phenolic compounds and vitamin C than the same crops grown conventionally.
Now, October is winding up as Breast Cancer Awareness Month. What studies are focusing on various health effects related to edible plants, and what's the result of the newest study on the effects of green tea on breast cancer risk?
Check out the 2003 article (PDF file) based on the study, "Comparison of the total phenolic and ascorbic acid content of freeze dried and air-dried marionberry, strawberry, and corn grown using conventional, organic, and sustainable agricultural practices," Journal of Agric. Food Chem. 51:1237-1241, 2003. Department of Food Science and Technology, University of California, Davis.
Phenolics are potent antioxidants and are thought to have anti-cancer activity, according to the 1992 study, "Fruit, vegetables, and cancer prevention: A review of the epidemiological evidence," Nutr. Cancer 18:1-29. (Authors are, Block, G, B. Patterson, and A. Subar. 1992.)
Another study focused on the role of vitamin C in cancer prevention. Basically, these studies in nutrition focus on the chemicals called phenolics, which are among the naturally occurring chemicals found in plants that also provide protection to the plant from being eaten by herbivore pests.
What happens is that as a plant grows and a bug eats the plant, the plant sends out a signal to its parts in ways that have the plant changing its own compounds in order to make itself taste ugly to the insect or bird. The taste of the plant is reduced in flavor. How does the plant know the insect bugging it is there for the taste? And so the plant reduces the taste to chase away the pest.
What causes the plant to want to 'change' its taste to the animal or insect world happens only when there is pressure applied to the plant by the insect or animal. Some of the energy of the plant that might otherwise go to growth goes instead to create and design its own defensive compounds that are natural insecticides. They serve a purpose by creating a bad taste in the mouth of the bug or bird when the plant is bothered or bitten.
This change in the plant reduces the plant's energy. It's a trade-off. There are perhaps less crops available when a lot of organic food is grown. But on the other hand, for humans, organic food is better for human health when not sprayed with insecticides designed to kill life forms.
At UC Davis, for example, researchers study what plants give off on their own to chase away pests. It's about taste--bitter, acrid, or tart tastes. Human consumers of plants don't like the bitter tastes given off from the plant that don't want to be eaten.
Scientists also want to find out whether the chemicals that plants give off on their own to repel insects are also toxic to humans. To the suprise of scientists, recent research is revealing that some compounds that are toxic in high concentrations to pests may actually be beneficial at lower levels to humans. The key is lower levels.
What some plant breeders are doing is to find ways to reduce the toxic compounds that plants create on their own to chase away bugs. So what you'd taste in such plants are bland tasting highly bred crop varieties that may not be so good for you.
At the same time, the bland tasting plants also may be less able to ward off attack by plant pests. When that happens, the plants become a lot more dependent upon chemical pesticides to produce edible plants.
So now you have a big loss of beneficial plant chemicals right after crops are harvested. On top of that, the food industry removes more by "de-bittering" agents during food processing. What do some producers of fruits and vegetables add to make their fruit or vegetables sweeter to the human taste?
If you remove bitterness from an edible vegetable or fruit, you may also be removing a lot of nutrition in the plant. Should you be eating more edible wild plants or growing wild, edible food in your yard or planters? The goal is to keep more natural phytochemicals in any given plant.
Why Has Research Rejected Green Tea for Breast Cancer Prevention?
Another study, just published today, October 27, 2010 from another university, reports that green tea isn't helping to prevent breast cancer after all. See the news release, "Research rejects green tea for breast cancer prevention," BioMed Central. According to the new study published in the journal, Breast Cancer Research, green tea does not protect against breast cancer. The study of data from approximately 54,000 women, published in BioMed Central's open access journal Breast Cancer Research, found no association between drinking green tea and breast cancer risk.
Motoki Iwasaki, from the National Cancer Center, Tokyo, worked with a team of researchers to carry out the study. He explained in the October 27, 2010 news release. "Although in vitro and animal-based studies have suggested that green tea may have beneficial protective effects against breast cancer, results from human studies have been inconclusive. Our large-scale, population-based prospective cohort study is one of the first to include a wide range of tea intakes; women who drank green tea less than 1 cup per week to those who drank 10 or more cups per day. It found no overall association between green tea intake and the risk of breast cancer".
Tea intake was assessed by questionnaire, once at the beginning of the study and then again five years later. Cancer incidence was assessed by notification from major local hospitals in the study area and data linkage with population-based cancer registries.
Approximately 12% of women drank green tea less than 1 cup per week while 27% drank 5 or more cups per day. Speaking about the survey, Iwasaki said, according to the Oct. 27, 2010 news release, Research rejects green tea for breast cancer prevention. "The other major strength of the present study was its prospective design, in which information was collected before the subsequent diagnosis of breast cancer, thereby avoiding the exposure recall bias inherent to case-control studies. Drinking green tea as a beverage is unlikely to reduce the risk of breast cancer regardless of green tea type and number of cups."
Nutritionists wonder what other diets or foods were eaten along with the green tea? Perhaps more research should continue on green tea and other similar foods.
Check out the Japanese study, "Green tea drinking and subsequent risk of breast cancer in a population-based cohort of Japanese women," Motoki Iwasaki, Manami Inoue, Shizuka Sasazuki, Norie Sawada, Taiki Yamaji, Taichi Shimazu, Walter C Willett, Shoichiro Tsugane and for the Japan Public Health Center-based Prospective Study Group (JPHC). The study is published in the journal, Breast Cancer Research.
Also see the article, Is Green Tea Drinking Associated With a Later Onset of Breast Cancer? In this other January, 2010 Chinese study, scientists found that tea polyphenols inhibit aromatase. Because of the substantial difference in levels of estrogens between premenopausal and postmenopausal women, the relationship between tea consumption and breast cancer risk may depend on menopausal status. Scientists in the January 2010 study, examined this hypothesis in the Shanghai Women's Health Study, a population-based cohort study of 74,942 Chinese women.
The journal, Breast Cancer Research is an international, peer-reviewed online journal, publishing original research, reviews, commentaries and reports. Research articles of exceptional interest are published in all areas of biology and medicine relevant to breast cancer, including normal mammary gland biology, with special emphasis on the genetic, biochemical, and cellular basis of breast cancer.
BioMed Central is an STM (Science, Technology and Medicine) publisher which has pioneered the open access publishing model. All peer-reviewed research articles published by BioMed Central are made immediately and freely accessible online, and are licensed to allow redistribution and reuse. BioMed Central is part of Springer Science+Business Media, a leading global publisher in the STM sector.
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