Phytochemicals In Vegetables Research Articles

Phytochemicals in Fruits and Vegetables: Use of Interactive Videoconferencing and the World Wide Web for Teaching a Multidisciplinary Course

ABSTRACT: An evaluation of interactive video conferencing and Web‐assisted instruction to deliver a multidisciplinary course entitled Phytochemicals in Fruits and Vegetables to Improve Human Health was conducted during the spring semesters of 1999 and 2001. This course was taught by 20 instructors from 11 institutions to 49 students during spring 2001, which was an increase of 53% over spring 1999. Weekly 3‐h lectures were delivered by the Trans‐Texas Videoconference Network integrated with PowerPoint® or HTML slides available on the course Web site (http://phytochemicals.tamu.edu). Qualitative and quantitative data were collected through formative and summative methods. Participants expressed their satisfaction with course format and the need for technical support for interactive videoconferencing.

Health benefits of fruit and vegetables are from additive and synergistic combinations of phytochemicals

Cardiovascular disease and cancer are ranked as the first and second leading causes of death in the United States and in most industrialized countries. Regular consumption of fruit and vegetables is associated with reduced risks of cancer, cardiovascular disease, stroke, Alzheimer disease, cataracts, and some of the functional declines associated with aging. Prevention is a more effective strategy than is treatment of chronic diseases. Functional foods that contain significant amounts of bioactive components may provide desirable health benefits beyond basic nutrition and play important roles in the prevention of chronic diseases. The key question is whether a purified phytochemical has the same health benefit as does the whole food or mixture of foods in which the phytochemical is present. Our group found, for example, that the vitamin C in apples with skin accounts for only 0.4% of the total antioxidant activity, suggesting that most of the antioxidant activity of fruit and vegetables may come from phenolics and flavonoids in apples. We propose that the additive and synergistic effects of phytochemicals in fruit and vegetables are responsible for their potent antioxidant and anticancer activities, and that the benefit of a diet rich in fruit and vegetables is attributed to the complex mixture of phytochemicals present in whole foods.

野菜と野菜成分の疾病予防及び生理機能への関与

A large number of studies have shown that a diet rich in vegetables may provide protection against many chronic diseases. We reviewed approximately 560 studies published since 1990, divided into four groups: 1) epidemiological studies on a high intake of vegetables, 2) human studies on vegetable ingredients, 3) animal studies on vegetable ingredients, and 4) physiological studies on each vegetable.Many cohort and case-control studies have reported that a higher consumption of vegetables was inversely related to the risk of chronic diseases. This epidemiological evidence has shown the preventive effect on the incidence of cardiovascular disease and on all types of cancer, specifically of cancer of the lung, stomach and colon. This effect has been suggested to be attributable to the ingestion of micronutrients and numerous phytochemicals in vegetables. Some reports have shown the physiological effects on humans of specific ingredients such as carotenoids and flavonoids. Reports on the physiological effects of vegetable ingredients on experimental animals are increasing, the effects on the liver, cancer, immunization, and nervous and circulatory systems having been well investigated. Some vegetables have been reported to possess such physiological functions as anti-cancer, immune-enhancing and hypolipidemic effects.It would appear that major public health benefits could be achieved by substantially increasing the consumption of vegetables. However, the some studies have also shown null and/or negative effects on health from an increased consumption of vegetables. It is therefore necessary to continue searching for scientific evidence about the role of vegetables.

Anticancer Properties of Fruits and Vegetables

Routine or habitual consumption of fruits and vegetables has been strongly associated with reduced risk for many of the common cancers (Steinmetz and Potter, 1991). The strongest evidence pertains to reduced risk for cancers of the mouth and pharynx, esophagus, lung, stomach, and colon. A moderately strong case can also be made for cancers of the breast, pancreas, and bladder. For other cancers, data are not sufficient to draw a conclusion on the effects of fruits and vegetables (American Institute for Cancer Research, 1997). Available scientific evidence suggests that some components of fruits and vegetables inhibit cancer; therefore, experiments have been conducted to pinpoint which foods provide the most benefit. With the increased ability to isolate and structurally identify phytochemicals in fruits and vegetables, cancer researchers have tested everything from fresh or freeze-dried fruits and vegetables to highly purified agents for cancer prevention. Both cell culture and in vivo studies in animal cancer models have solidly seconded data from human population studies. This paper will review some of the epidemiologic evidence for protection against the development of cancer in populations that consume fruits and vegetables. Also, the four basic mechanisms by which elements in foods can reduce the risk for cancer will be explored using data from animal carcinogenesis models. THE EVIDENCE FOR FRUITS AND VEGETABLES AS CANCER PREVENTIVES IN HUMANS Few studies in humans have evaluated the effect of consuming fruits and vegetables on cancer risk, and most of the available data come from case-control studies where eating patterns in people with cancer were compared with those of control subjects without cancer. One of the problems in assessing the effects of fruit and vegetable intake is the wide variety of these foods available. In a recent report of the expert panel assembled by the American Institute for Cancer Research (1997), a protective role for fruit and vegetable intake was ascribed for four tumor sites: oral-pharynx/esophagus, lung, stomach, and colon. The report inferred that available data are also strong supporting reduced risk for pancreas, breast, and bladder cancer in consumers of fruits and vegetables, and concluded that no increase in cancer risk has been reported for habitual consumers of fruits and vegetables at any tumor site. This is taken in context of concerns that minor contaminants such as fertilizers and pesticides may potentially pose a risk. The available evidence supports claims that fresh fruits and vegetables, when properly harvested, processed, and stored, help reduce risk for certain forms of cancer. MECHANISMS BY WHICH FRUITS AND VEGETABLES

Antioxidant Phytochemicals in Fruits and Vegetables: Diet and Health Implications

Received for publication 26 May 1999. Accepted for publication 10 Aug. 1999. Mention of a trade name, proprietary product ,or specific equipment does not constitute a guarantee by the U.S. Dept. of Agriculture and does not imply its approval to the exclusion of other products that may be suitable.The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact. To whom reprint requests should be addressed (phone: (617) 556-3311; fax: (617) 556-3299; e-mail: prior@hnrc.tufts.edu). Increased consumption of fruits and vegetables has been associated with protection against various age-related diseases (Ames et al., 1993; Steinberg, 1991). What dietary constituents are responsible for this association is not known, but well-characterized antioxidants, including vitamins C and E, or β-carotene, are often assumed to contribute to the observed protection (Ames et al., 1993; Buring and Hennekens, 1997; Gey et al., 1991; Stahelin et al., 1991; Steinberg, 1991; Willett, 1994). However, the results from intervention trials have not been conclusive regarding the protection following supplementation with such antioxidants (Hennekens et al., 1996; Omenn et al., 1996; Prieme et al., 1997; Van Poppel et al., 1995). Recent epidemiological evidence indicates that the putative beneficial effects of a high intake of fruits and vegetables on the risk of diseases of aging may not be exclusively due to these antioxidants (Hertog et al., 1992; Knekt et al., 1997), but other antioxidant phytochemicals contained in fruits and vegetables may be equally important. To critically evaluate the potential roles of these phytochemicals in prevention of agerelated diseases, we will discuss the free radical or oxidative stress theory of aging and present data on the antioxidant capacities of fruits, vegetables, and their phytochemical components, mainly flavonoids. Reports on the absorption of these flavonoids and the effects of fruit and vegetable intake on the antioxidant status in humans will be reviewed.

Cytotoxicity, genotoxicity and oxidative reactions in cell-culture models: modulatory effects of phytochemicals.

Much research effort has focused on the identification of phytochemicals in fruit and vegetables which exert beneficial effects. Our research examines modulatory effects of phytochemicals on cytotoxicity, genotoxicity and oxidative reactions in cell systems. Two examples of our studies are discussed. First, the potential beneficial effects of flavonoids are demonstrated. Flavonoids are reported to exhibit a wide variety of biological effects, including antioxidant and free-radical-scavenging activities. The aim of the study was to determine if flavonoids could protect against H2O2-induced DNA damage, as measured by the comet assay, in Caco-2 and HepG2 cells. Both cell lines were supplemented with increasing concentrations of myricetin, quercetin and rutin for 24 h followed by exposure to H2O2 (50 microM) for 30 min. Exposure to H2O2 for 30 min at 37 degrees C resulted in significant DNA damage and pre-incubation with the flavonoids before H2O2 exposure significantly (P <0.05) protected Caco-2 and HepG2 cells against H2O2-induced DNA damage. Secondly, we illustrate the use of cellular models to study oxysterol-induced toxicity. Oxysterols are generated during the cooking and processing of foods and may be produced endogenously by the oxidation of membrane lipids. Recent findings suggest that oxysterols may modulate cytotoxicity by exerting effects on the induction of apoptosis. 7beta-Hydroxycholesterol (7beta-OHC) and 25-hydroxycholesterol, both of which are commonly found in foods, were investigated for their abilities to induce apoptosis in a human monocytic blood cell line, U937, and in the human hepatoma cell line, HepG2 cells. U937 and HepG2 cells were incubated for up to 48 h with 30 microM oxysterol. 7beta-OHC induced apoptosis in U937 cells as measured by non-random DNA fragmentation, condensed and fragmented nuclei, and the generation of hypodiploid cells. In contrast, oxysterols may induce cell death by a different mechanism in the hepatoma cells, possibly by necrosis.