Nutrition intervention trials in Linxian, China: multiple vitamin/mineral supplementation, cancer incidence, and disease-specific mortality among adults with esophageal dysplasia

Ecological study on the risks of esophageal cancer in Ci-Xian, China: the importance of nutritional status and the use of well water

Our purpose was to determine the environmental risks in the development of esophageal cancer in Ci-Xian, which has one of the highest incidences of esophageal cancer in China. The subjects included 404, 352 and 400 inhabitants living in high-, medium-, and low-incidence areas of esophageal cancer, as well as 301 esophageal cancer patients. A food intake-frequency survey using a 7-day weighted inventory questionnaire was conducted on these individuals. Questions on occupation, working conditions, income per year, family disease history, medical complaints, and demographic features were also included in the questionnaire. The levels of nitrogen compounds in selected samples of well water were also measured in each of the 3 areas. Clear-cut differences in food intake were seen among inhabitants living in the 3 different areas, suggesting that regional differences in nutritional styles do exist. In both males and females, the intake of potatoes, fruit, vegetables, and meat were significantly lower in inhabitants living in the high-incidence area than in the other inhabitants, much the same as that of cancer patients. A low intake of carotene, and vitamins A and C was also seen in populations living in the high-incidence area of esophageal cancer. The well water polluted with nitrogen compounds was significantly related to the high incidence of esophageal cancer. In contrast, tobacco, alcohol consumption, and the intake of pickled vegetables and moldy foods did not relate to the different incidence rates. Our results suggest that low intake of fruit, vegetables, potatoes and meat, and the quality of well water may be important factors in the development of esophageal cancer in Ci-Xian.

Loss of retinoic acid receptor-beta expression is an early event during esophageal carcinogenesis

We recently observed that growth inhibition of esophageal cancer cells by retinoic acid (RA) was associated with both constitutive expression and RA-induced up-regulation of RA receptor beta (RAR-beta). Cell lines that did not express RAR-beta were also resistant to RA. To explore the expression of RAR-beta mRNA in vivo, we analyzed esophageal tissue specimens from 16 normal mucosae, 30 dysplastic lesions, and 157 esophageal tumors by in situ hybridization. RAR-beta was detected in 88% (14/16) of normal esophageal tissues and in 96% (96/100) of distant normal esophageal mucosa from cancer specimens. In contrast, RAR-beta was expressed in only 57% (17/30) of dysplastic lesions and in 54% (84/157) of carcinomas. Among esophageal carcinomas RAR-beta mRNA was expressed in 62% (26/42) of well-differentiated, 54% (27/50) of moderately differentiated, and only 29% (4/14) of poorly differentiated SCCs. Our data suggest that the loss of RAR-beta expression is an early event associated with esophageal carcinogenesis and the status of squamous differentiation.

Chemopreventive mechanisms of selenium

The element selenium (Se) was recognized only 40 years ago as being essential in the nutrition of animals and humans. It is recognized as being an essential component of a number of enzymes in which it is present as the amino acid selenocysteine (SeCys). Selenium compounds have also been found to inhibit tumorigenesis in a variety of animal models and recent studies indicate that supplemental Se in human diets may reduce cancer risk. Anti-tumorigenic activities have been associated with Se intakes that are more than sufficient to correct nutritionally deficient status; that is, Se appears to be anti-tumorigenic at intakes that are substantially greater than those associated with maximal expression of the known SeCys-containing enzymes. Therefore, while some cancer protection may involve one or more Se-enzymes, it is probable that anti-tumorigenic functions of Se are discharged by certain Se-metabolites produced in significant amounts at relatively high Se intakes. Thus, Se supplementation of individuals with relatively low or frankly deficient natural intakes of the element can be expected to support enhanced anti-oxidant protection due to increased expression of the Se-dependent glutathione peroxidases and thioredoxin reductase. Higher levels of Se-supplementation can be expected to affect other functions related to tumorigenesis: carcinogen metabolism, immune function, cell cycle regulation and apoptosis. Thus, according to this 2-stage model of the roles of Se in cancer prevention, even individuals with nutritionally adequate Se intakes may benefit from Se-supplementation.

Serum antioxidative vitamin levels and lipid peroxidation in gastric carcinoma patients

Serum antioxidative vitamin levels and lipid peroxidation in gastric cancer patients were compared with values for age-matched healthy subjects. Blood samples were collected from the stomach of cancer patients scheduled for surgical removal of their tumor. Serum ascorbic acid, alpha-tocopherol, beta-carotene, and retinol in serum were determined by high-performance liquid chromatography, and malondialdehyde levels were analyzed spectrophotometrically. General health characteristics and taste preference for spicy and/or salty food were assessed by a self-administered questionnaire. Significant decreases in serum ascorbic acid and beta carotene were observed in stomach cancer patient as compared to the control group. The levels of ascorbic acid in patients with gastric carcinoma were less than one-fifth of the control. Beta carotene and alpha-tocopherol levels in the serum of the cancer patients were significantly decreased compared to the control group, but there were no differences in retinol between the groups. Serum malondialdehyde levels were significantly higher in the cancer patients than in controls. The levels of ascorbic acid and alpha-tocopherol tend to be lower in the patient with a preference for spicy and salty food than in others without the preference. Our results demonstrate that a correlation existed between the levels of serum ascorbic acid and beta carotene, alpha-tocopherol and lipid peroxidation in gastric carcinoma.

Expectations about alternative therapies and women with gynecological cancer

Women with gynecological cancers are exploring and using 'alternative medicine(s)', as are other cancer patients and much of Western society. On behalf of their patients, physicians must understand something of its history, terms, types, who uses it and why and where to find answers, as well as being prepared to open and engage in dialogue about alternative medicine with their patients.

Beta - caroteno e câncer

Há mais de vinte anos tem-se pesquisado sobre a relação entre β-caroteno e câncer. Inúmeros trabalhos têm tentado esclarecer a hipótese, formulada a partir de achados epidemiológicos e experimentais, de que o carotenóide poderia agir como anticarcinogênico de origem alimentar. Estudos epidemiológicos observacionais, tipo caso-controle e coorte, sugerem que o consumo elevado de frutas e vegetais ricos em β-caroteno reduz o risco de câncer, especialmente de pulmão. Estudos de intervenção em humanos, administrando doses farmacológicas crônicas a milhares de indivíduos, têm demonstrado resultados contraditórios. Pesquisas em animais experimentais e em cultura de células apontam o carotenóide como quimiopreventivo, agindo sobretudo como retinóides, através de conversão metabólica extra-intestinal e como antioxidante de membrana. Conclui-se que o β-caroteno pode proteger contra o câncer, quando suplementado em doses fisiológicas, isto é, cerca de 4 a 6mg/dia. Doses farmacológicas crônicas não estão recomendadas para indivíduos saudáveis e particularmente para tabagistas.

Influence of diet, vitamins and chemotherapeutic agents on gastrointestinal cancer

Dietary influences play a major role in the pathogenesis of most gastrointestinal malignancies. However, it has been difficult to define which dietary components will be most significant for any given individual. In this article we discuss the methodological challenges to research in this field as well as recent observations that have been made on the role of dietary factors in specific digestive tract neoplasms.

Epidemiology of gastric cancer in relation to diet and Helicobacter pylori infection

Gastric cancer is the second most common fatal malignancy in the world. In China, gastric cancer is now the second most common malignancy, while in Hong Kong, the mortality rate ranked fourth among all cancers in 1995. Dietary factors in gastric carcinogenesis came mostly from case-control studies. N-Nitroso compounds from dietary sources such as preserved, smoked and salted foods were found to be associated with gastric cancer. ß-Carotene, selenium and α-tocopherol have been shown in an intervention study to be favourable in the reduction of stomach cancer mortality. Fruits and vegetables showed the most consistent results of inverse association with gastric cancer. Dietary salt intake in preserved or salted foods is also shown to be associated with gastric cancer. Tea drinking, especially green tea, has a protective effect against gastric cancer as shown in some studies. Prospective case-control studies of the association between Helicobacter pylori infection and the subsequent development of gastric cancer showed that the odds ratio ranged from 2.8 to 6.0. However, results of similar case-control studies in countries with a high frequency of gastric cancer are controversial. Infection with H. pylori leads to changes in the vitamin C content of gastric juice, reactive oxygen metabolites, epithelial cell proliferation and apoptosis. Recently, CagA-positive strains were found to be associated with gastric cancer and also duodenal ulcers. The exact role of H. pylori in gastric carcinogenesis is still under investigation. Large-scale intervention studies are underway to examine dietary supplementation, H. pylori infection and gastric cancer. Helicobacter pylori eradication for gastric cancer prevention is being conducted in China and other parts of the world. In high-risk areas, for example in China, a combination approach including H. pylori eradication and dietary supplementation may be necessary.

Chemopreventive agents: selenium

The element selenium (Se) was recognized only 40 years ago as being essential in the nutrition of animals and humans. It is recognized as being an essential component of a number of enzymes, in which it is present as the amino acid selenocysteine. Se compounds have also been found to inhibit tumorigenesis in a variety of animal models, and recent studies indicate that supplemental Se in human diets may reduce cancer risk. The antitumorigenic activities have been associated with Se intakes that correct nutritionally deficient status in animals, as well as higher intakes that are substantially greater than those associated with maximal expression of the selenocysteine-containing enzymes. Therefore, it is proposed that while some cancer protection, particularly that involving antioxidant protection, involves selenoenzymes, specific Se metabolites, which are produced in significant amounts at relatively high Se intakes, also discharge antitumorigenic functions. According to this two-stage model of the roles of Se in cancer prevention, individuals with nutritionally adequate Se intakes may benefit from Se supplementation. Evidence for chemoprevention by Se and for the apparent mechanisms underlying these effects is reviewed to the end of facilitating the development of the potential of Se compounds as cancer chemopreventive agents.

Alcohol-stimulated promotion of tumors in the gastrointestinal tract

Alcohol is a major risk factor for cancers of the upper gastrointestinal tract but the association with cancers of the large bowel is not as clearly established. In recent studies, we have provided experimental support for the associations in the esophagus and oral cavity. Our studies also indicate that the tumor promotion ability of ethanol is related to its ability to generate oxygen free radicals as measured by an increase in indices of lipid peroxidation. This increase in lipid peroxidation was evident in the liver as well as the tissues targeted by the site-specific carcinogens and promoted by ethanol. Studies in mice showed that the increased lipid peroxidation as well as tumor incidence was inhibited by the administration of vitamin E, the potent antioxidant. Determination of fatty acid profiles showed significant alterations when ethanol was used as a tumor promoter after treatment with the carcinogen. Ethanol as a promoter caused an increase in esophageal polyunsaturated fatty acids (PUFA). Ethanol promotion was also evident in increased arachidonate and an exaggeration in PUFA that are involved in eicosanoid production. Thus, these results suggest that ethanol-related promotion may be the result of excessive cell proliferation induced by disordered lipid and eicosanoid metabolism that may cause a selective outgrowth of the carcinogen-initiated cells. Supporting evidence for ethanol-induced hyper-regeneration is also reviewed.

Chemoprevention of lung cancer: the rise and demise of beta-carotene

Beta-carotene and retinoids were the most promising agents against common cancers when the National Cancer Institute mounted a substantial program of population-based trials in the early 1980s. Both major lung cancer chemoprevention trials not only showed no benefit, but had significant increases in lung cancer incidence and in cardiovascular and total mortality. A new generation of laboratory research has been stimulated. Rational public health recommendations at this time include: 1. Five-A-Day servings of fruits and vegetables, a doubling of current mean intake; 2. systematic investigation of the covariates of extremes of fruit and vegetable intake; 3. discouragement of beta-carotene supplement use, due to adverse effects in smokers and no evidence of benefit in non-smokers; 4. multilevel research to develop and evaluate candidate chemoprevention agents to prevent lung and other common cancers; and 5. continued priority for smoking prevention, smoking cessation, and avoidance of known carcinogens in the environment.

Diet, nutrients, and gastrointestinal cancer

Tobacco and alcohol use are strong risk factors for cancer of the upper gastrointestinal tract. Saturated fat and red meat intake also appear to increase the risk of colorectal cancer. The strongest and most consistent dietary protective factors for gastrointestinal cancer are vegetables and fruits. Some micronutrients show beneficial effects, but the degree of protection is less than that observed from whole plant foods. Substantial decreases in the morbidity and mortality from gastrointestinal cancer could occur with more widespread adoption of dietary guidelines designed for cancer prevention.

Correlation between the levels of certain carcinogenic and anticarcinogenic trace elements and esophageal cancer in northern Iran

Levels of four carcinogenic (Ni, Fe, Cu, Pb) and four anticarcinogenic (Zn, Se, Mn, Mg) trace elements were measured in hair samples from esophageal cancer patients, their unaffected family members, and members of families with no history of cancer. Measurements were also made in non-esophageal cancer patients, using atomic absorption spectroscopy, inductively coupled plasma-emission spectroscopy, and neutron activation analysis. The results showed that Ni and Cu concentrations were significantly higher and Mg and Mn concentrations were significantly lower in all cancer cases. Levels of Zn, Fe, Se, and Pb were not significantly different in the above-mentioned groups. In addition, the serum albumin fraction, which is reported to have antioxidant activity, was found to be significantly lower among esophageal cancer patients.

Gastric cancer and premalignant lesions in atrophic gastritis: a controlled trial on the effect of supplementation with alpha-tocopherol and beta-carotene. The Helsinki Gastritis Study Group

BACKGROUND

Vitamin E and beta-carotene are considered to decrease the risk of gastric cancer both in humans and in laboratory animals. We studied the effect of dietary supplementation with alpha-tocopherol and beta-carotene on the end-of-trial prevalence of premalignant and malignant lesions of the stomach in older men with atrophic gastritis.

METHODS

The study was carried out within the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study (ATBC study) in Finland, in which 29,133 male smokers aged 50-69 years were randomly assigned to receive daily 50 mg alpha-tocopherol, 20 mg beta-carotene, both of these agents, or placebo, for 5-8 years. Serum pepsinogen was determined at base line and after 3 years' supplementation to find men with atrophic gastritis. A low serum pepsinogen I level, indicating atrophic gastritis of the corpus area of the stomach, was found in 2132 men. These men were invited to have upper gastrointestinal endoscopy (gastroscopy), which was performed on 1344 subjects after a median supplementation time of 5.1 years.

RESULTS

Neoplastic alterations were found in 63 of the men (4.7%): 42 with definite dysplasias of low grade (moderate dysplasia), 7 with definite dysplasias of high grade (severe dysplasia), 11 with carcinomas (of which 7 were 'early' cancers), and 3 with carcinoid tumors. Neither alpha-tocopherol (relative risk, 0.98; 95% confidence interval, 0.57-1.69) nor beta-carotene (relative risk, 1.13; 95% confidence interval, 0.65-1.95) supplementation had any association with end-of-trial prevalence of gastric neoplasias after adjustment for other possible risk factors. The effect was not modified by base-line serum level or dietary intake of vitamins, prevalence of Helicobacter pylori infection, or other covariates.

CONCLUSIONS

We thus conclude that supplementation with alpha-tocopherol or beta-carotene for 5 years has no major impact on the occurrence of neoplastic changes of the stomach in older male smokers with atrophic gastritis.

Vitamins E plus C and interacting conutrients required for optimal health. A critical and constructive review of epidemiology and supplementation data regarding cardiovascular disease and cancer

Antioxidants are crucial components of fruit/vegetable rich diets preventing cardiovascular disease (CVD) and cancer: plasma vitamins C, E, carotenoids from diet correlate prevalence of CVD and cancer inversely, low levels predict an increased risk of individuals which is potentiated by combined inadequacy (e.g., vitamins C + E, C + carotene, A + carotene); self-prescribed rectification of vitamins C and E at adequacy of other micronutrients reduce forthcoming CVD, of vitamins A, C, E, carotene and conutrients also cancer; randomized exclusive supplementation of beta-carotene +/- vitamin A or E lack benefits except prostate cancer reduction by vitamin E, and overall cancer reduction by selenium; randomized intervention with synchronous rectification of vitamins A + C + E + B + minerals reduces CVD and counteracts precancerous lesions; high vitamin E supplements reveal potentials in secondary CVD prevention. Plasma values desirable for primary prevention: > or = 30 mumol/l lipid-standardized vitamin E (alpha-tocopherol/cholesterol > or = 5.0 mumol/mmol); > or = 50 mumol/l vitamin C aiming at vitamin C/vitamin E ratio > 1.3-1.5; > or = 0.4 mumol/l beta- (> or = 0.5 mumol/l alpha+ beta-) carotene.

CONCLUSIONS

In CVD vitamin E acts as first risk discriminator, vitamin C as second one; optimal health requires synchronously optimized vitamins C + E, A, carotenoids and vegetable conutrients.

Cell density and antioxidant vitamins determine the effects of hyperoxia on proliferation and death of MDCK epithelial cells

Epithelial cells are prone to oxidant injury, which could change epithelial cell homeostasis and lead to degenerative diseases. We examined the effects of hyperoxia on death and proliferation off Madin-Darby canine kidney (MDCK) epithelial cells and antioxidant vitamin protection. Subconfluent and near-confluent MDCK cells were cultured under normoxia or hyperoxia for two days. We measured cell number and viability, mitochondria enzymatic activity, thymidine incorporation, necrosis [lactate dehydrogenase (LDH) release], and apoptosis (DNA fragmentation and morphological changes). When the cells were subconfluent, hyperoxia decreased the number of adherent cells, mitochondrial enzymatic activity, and thymidine incorporation, but neither LDH release nor apoptotic changes increased compared with normoxic controls. In normoxia, near-confluent cells had lower nonadherent cell numbers, mitochondrial enzymatic activity, and thymidine incorporation than subconfluent cells; hyperoxia further decreased the latter two parameters and increased apoptotic changes and LDH release in near-confluent cells. Vitamin E protected mitochondrial enzymatic activity, apoptotic changes, and LDH release against hyperoxic injury but did not affect changes in thymidine incorporation with hyperoxia. Vitamin C partially protected the mitochondrial enzymatic activity and thymidine incorporation in subconfluence, but not in near confluence. These results indicate that cell density is a major determinant of the effects of hyperoxic injury and the profile of antioxidant vitamin protection.

Reduction of cancer mortality and incidence by selenium supplementation

PATIENTS AND METHOD

In order to test the hypothesis that a dietary supplement of selenium (Se) may reduce cancer risk, 1312 patients with histories of basa/squamous cell carcinomas of the skin were assigned in random, double-blind fashion to daily oral supplements of either Se-enriched yeast (200 micrograms Se/day), or a low-Se yeast placebo. Patients were recruited in 1983 to 1990 and were followed with regular dermatologic examinations through, 1993 for a total of 8269 person-years of observation. Skin cancer diagnoses were confirmed histologically and plasma Se concentration was determined at 6 to 12 months intervals. All deaths and patient-reported illnesses were confirmed and documented by consultation with the patient medical care providers.

RESULTS

Results showed that Se-supplementation did not significantly affect the incidences of recurrent basal/squamous cell carcinomas of the skin. However, Se-treatment was associated with reductions in total cancer mortality and in the incidences of lung, colorectal, prostate and total cancers. These effects were consistent over time and between study clinics.

CONCLUSION

The results strongly suggest benefits of Se-supplementation for this cohort of patients and support the hypothesis that supplemental Se can reduce risks to at least some types of cancer.

Cigarette smoke radicals and the role of free radicals in chemical carcinogenicity

This article consists of two parts: a brief overview of the ways in which free radicals can be involved in chemical carcinogenesis, and a review of cigarette smoke chemistry. Carcinogenesis is generally agreed to involve at least three stages: initiation, promotion, and progression. It is suggested that radicals sometimes are involved in the initiation step, either in the oxidative activation of a procarcinogen (such as benzo[a]pyrene) to its carcinogenic form or in the binding of the carcinogenic species to DNA, or both. The fraction of initiation events that involve radicals, as opposed to two-electron steps, is not known, but radicals probably are involved in a substantial number, although probably not a majority, of cancer initiation reactions. Promotion always involves radicals, at least to some extent. Progression probably does not normally involve radicals. The second part of this article reviews the molecular mechanisms involved in cigarette-induced tumors, particularly by aqueous cigarette tar (ACT) extracts and by a model of these solutions, aged solutions of catechol. ACT solutions as well as aged solutions of catechol contain a quinone-hydroquinone-semiquinone system that can reduce oxygen to produce superoxide and hence hydrogen peroxide and the hydroxyl radical. Both the cigarette tar radical and the catechol-derived radical can penetrate viable cells, bind to DNA, and cause nicks.

Association of serum vitamin levels, LDL susceptibility to oxidation, and autoantibodies against MDA-LDL with carotid atherosclerosis. A case-control study. The ARIC Study Investigators. Atherosclerosis Risk in Communities

Oxidative modification of LDL is believed to be a crucial step in atherosclerosis. Thus, antioxidant vitamins may have a role in the prevention of coronary disease. We examined the cross-sectional association of serum vitamin levels, the susceptibility of LDL to hemin-induced oxidation (lag phase to conjugated diene formation), and the malondialdehyde-LDL (MDA-LDL) to native LDL radioactivity binding ratio with carotid intima-media thickness (IMT), a measure of asymptomatic early atherosclerosis. The participants in this observational study were 231 asymptomatic age-, sex-, race-, and field center-matched case-control pairs selected from the Atherosclerosis Risk in Communities (ARIC) study cohort on the basis of B-mode carotid artery ultrasonograms obtained from 1986 through 1989. Cases exceeded the 90th percentile of IMT, and control subjects were below the 75th percentile of IMT for all arterial segments. Biochemical analyses were performed on fasting frozen (-70 degrees C) serum specimens collected from 1990 through 1992. In conditional logistic regression adjusting for age, blood storage time, total cholesterol, and log-triglyceride concentrations, serum beta-cryptoxanthin and lutein plus zeaxanthin levels were inversely related to the extent of atherosclerosis (odds ratio [OR] per 1-SD increase: 0.75, 95% confidence interval [CI]: 0.59-0.94; and OR per 1-SD increase: 0.76, 95% CI: 0.59-0.95, respectively). Increases in alpha-carotene and lycopene were associated with nonsignificantly lower odds of being a case, whereas beta-carotene, retinol, and alpha-tocopherol were unrelated to IMT. Although not reaching statistical significance, the lag phase and autoantibodies against MDA-LDL were positively associated with asymptomatic atherosclerosis. After adjustment for potential confounders, only the inverse association of lutein plus zeaxanthin with asymptomatic atherosclerosis was maintained. This study supports a modest inverse association between circulating levels of some carotenoids, particularly lutein plus zeaxanthin, and carotid IMT. These findings suggest that these carotenoid compounds (regarded as biomarkers of fruit and vegetable intake) may be important in early stages of atherosclerosis.

Chemoprevention of respiratory tract cancer

Lung cancer is the leading cause of cancer death in the United States, and advances in therapy have accounted for an improvement in five-year survival in this disease from 9% to 13% over the last three decades. Molecular genetic evidence has confirmed the epidemiologic link between tobacco and lung cancer causation, and has clarified the etiology of the persistent risk of lung cancer development in former smokers. Retinoids have shown promise in aerodigestive cancer chemoprevention, both in the reversal of preneoplastic lesions and in the prevention of second primary cancers. After initial epidemiologic and dietary studies had linked beta-Carotene with cancer risk reduction, large randomized phase III studies of this compound have shown no evidence of benefit and some evidence of heightened lung cancer risk in active smokers on high dose supplemental beta-Carotene. Therefore, careful clinical, epidemiologic, and basic studies of retinoids using intermediate end point markers are necessary to determine the definitive role of these compounds in the chemoprevention of respiratory tract cancer, with a particular focus on former smokers.

Cancer Prevention: The Roles of Diet and Chemoprevention

BACKGROUND: Reduction of cancer risk by either preventing carcinogenesis or stopping carcinogenesis in its early stages is a logical approach for reducing the cancer burden, both for high-risk individuals and for the general population. The areas of dietary modification and chemoprevention show considerable promise as effective approaches for cancer prevention and are a focus of research efforts. RESULTS: Diet and cancer studies show that, generally, vegetables and fruits, dietary fiber, and certain nutrients seem to be protective against cancer, whereas fat, excessive calories, and alcohol seem to increase cancer risk. Chemoprevention research is closely linked to diet and cancer research and represents a logical research progression. CONCLUSIONS: Dietary epidemiologic studies have helped to identify many naturally occurring chemopreventive agents. Currently, randomized clinical prevention trials sponsored by the NCI include dietary interventions (eg, low-fat and/or high-fiber vegetables and fruits) targeting breast and colorectal cancer, chemoprevention trials using micronutrients (eg, vitamin E, calcium, vitamin D) aimed at lung and colorectal cancer, and chemoprevention trials testing the effectiveness of pharmaceutical agents (eg, tamoxifen, finasteride, aspirin) for breast, prostate, and colorectal cancer.

Nutrition chemoprevention of gastrointestinal cancers: a critical review

Various strategies utilizing specific dietary factors have been investigated for their ability to modulate the development of several cancers of the gastrointestinal tract. The effects of fat, red meat, fiber, fruits and vegetables, and alcohol on colorectal carcinogenesis have been reasonably well defined. Folate, selenium, and omega-3 fatty acids are rapidly emerging as important agents in nutrition chemoprevention, while the role of antioxidant vitamins and calcium is less certain. Although recent intervention studies from China have suggested a protective role of certain vitamins and minerals for esophageal and gastric cancers, further data from prospective randomized intervention studies are needed. Until more firm data are available, the dietary recommendations provided by the American Cancer Society and the National Cancer Institute are appropriate guidelines.

Prediction of male cancer mortality by plasma levels of interacting vitamins: 17-year follow-up of the prospective Basel study

Plasma vitamins C, E, retinol and carotene were measured in 1971-1973 in 2,974 men working in Basel Switzerland. In 1990, the vital status of all participants was assessed. A total of 290 men had died from cancer during the 17 years of follow-up, including 87 with lung cancer, 30 with prostate cancer, 28 with stomach cancer and 22 with colon cancer. Overall mortality from cancer was associated with low mean plasma levels of carotene (adjusted for cholesterol) and of vitamin C. Lung and stomach cancers were associated with low mean plasma carotene level. After calculation of the relative risk, using the Cox model, with exclusion of mortality during the first 2 years of follow-up, simultaneously low levels of plasma carotene (below quartile I) and lipid-adjusted retinol were related to a significantly increased mortality risk for all cancers and for lung cancer. Simultaneously, low levels of plasma vitamin C and lipid-adjusted vitamin E also were associated with a significantly increased risk for lung cancer. Additionally, low vitamin E levels in smokers were related to an increased risk for prostate cancer. It is concluded that low plasma levels of the vitamins C, E, retinol and carotene are related to increased risk of subsequent overall and lung-cancer mortality and that low levels of vitamin E in smokers are related to an increased risk of prostate-cancer mortality.

A computer program for sample size and power calculations in the design of multi-arm and factorial clinical trials with survival time endpoints

This paper presents a computer program for use in the design of long-term clinical trials with multiple treatment arms in which the primary outcome variables are censored survival times. The treatment arms may be structured as a one-way or multi-way factorial design. It is assumed that patients are entered and randomized to a treatment arm during an accrual period. The patients are then followed for a fixed period during which there may be dropouts. Various distributional assumptions can be used to model the survival times. These include an option in which there is an effect of treatment duly after a lag or delay time. The program then computes the power of various statistical tests of hypotheses concerning treatment differences, interactions and trends. The power computations are "exact" in that they use the Monte Carlo method to obtain Type I and II error probabilities. However the program also outputs the normal approximations for comparison, although they are typically not accurate in these situations. Fisher's LSD method is used to adjust for the multiple comparisons. By comparing the power for various sets of design parameters, such as sample size, numbers of factor levels, patient accrual rate, and length of follow-up, an appropriate design can be constructed. Two examples are provided. The first is a simple one-way layout with multiple treatment arms; the second a two-way factorial design for a proposed large scale cancer chemoprevention trial.

Effects of various carotenoids on cloned, effector-stage T-helper cell activity

Astaxanthin, a carotenoid without provitamin A activity, enhances murine T-helper (Th) cell clone-mediated antibody (Ab) production with suboptimal antigen (Ag) challenges. It also suppresses interferon-gamma (IFN-gamma) production by cloned murine Th1 cells. beta-Carotene is less effective than astaxanthin. This study evaluates the effects of various carotenoids with various relative polarity, provitamin A activity, and antioxidant activity. Carotenoids tested include astaxanthin, cantaxanthin, zeaxanthin, lutein, and lycopene, and their effects were tested at a concentration at which astaxanthin's effect was most potent. A.E7 and CDC35 cells are used as representative type 1 and type 2 Th cell (Th1 and Th2) clones, respectively. In the Th1 clone, astaxanthin, but not other carotenoids, suppressed IFN-gamma production and increased the number of Ab-secreting cells with the use of primed spleen cells. With cultures of Th1 cells and unprimed spleen cells, astaxanthin and zeaxanthin augmented the number of immunoglobulin M Ab-secreting cells. In the cultures of Th2 clone and primed spleen cells, astaxanthin, but not other carotenoids, enhanced the number of Ab-secreting cells. With unprimed spleen cells, lycopene suppressed Th2 clone-mediated Ab production. Interleukin-5 production by the Th2 clone was not significantly altered with the carotenoids tested, irrespective of the use of unprimed or primed spleen cells. Carotenoid actions on Th cells may vary in each carotenoid and do not seem to be closely associated with carotenoid antioxidant activity or relative polarity.

Nutrition and stomach cancer

Epidemiologic evidence on the relation between nutrition and stomach cancer is reviewed. Stomach cancer shows a distinct international variation and dramatic worldwide decline. These descriptive features suggest that dietary factors are important in determining the risk of stomach cancer. The authors assessed relevant data regarding specific dietary hypotheses in the etiology of stomach cancer. A negative association with fresh vegetables and fruits is highly consistent in numerous case-control studies in different populations. Both epidemiologic and experimental data suggest that vitamins C and carotenoids lower risk of stomach cancer. Evidence is sparse and inconsistent as to protective effects of vitamin E and selenium. Epidemiologic studies have not lent, and will not provide, supportive evidence for an etiologic role of nitrate intake. High salt intake has been associated with an increased risk in many case-control studies and limited cohort studies. Taken together with animal data, it is considered that high salt intake is a risk factor for stomach cancer. Both epidemiologic and experimental data are inconclusive as to whether high-starch diets confer an increased risk. Cohort studies using quantitative dietary assessment and biologic measurement of micronutrients are needed for further understanding of etiologic roles of dietary factors in the causation of stomach cancer.

Nutrition and esophageal cancer

Epidemiologic evidence on the relation between nutrition and esophageal cancer is reviewed. Results from ecologic, case-control, cohort, and intervention studies are included. Most of the findings pertain more to squamous cell carcinoma than adenocarcinoma of the esophagus. The protective effect of fruit and vegetable consumption is supported by a large body of evidence, especially from case-control studies. The effects of food groups and nutrients other than fruits and vegetables also have been examined, but the overall evidence is less convincing. Recent intervention studies in high incidence areas in China indicate that micronutrient supplements may have a modest effect in reducing risk, but the generalizability of this result is uncertain. Hot drinks are likely to increase the risk of esophageal cancer. On the other hand, the role of tea drinking, especially the use of green tea, remains to be defined better.

Dietary antioxidants and carotid artery wall thickness. The ARIC Study. Atherosclerosis Risk in Communities Study

BACKGROUND

Evidence that dietary antioxidants may prevent atherosclerotic disease is growing. The relationship between the intake of dietary and supplemental vitamin C, alpha-tocopherol, and provitamin A carotenoids and average carotid artery wall thickness was studied in 6318 female and 4989 male participants 45 to 64 years old int he Atherosclerosis Risk in Communities Study.

METHODS AND RESULTS

Intake was assessed by use of a 66-item semiquantitative food-frequency questionnaire. Carotid artery intima-media wall thickness was measured as an indicator of atherosclerosis at multiple sites with B-mode ultrasound. Among men and women > 55 years old who had not recently begun a special diet, there was a significant inverse relationship between vitamin C intake and average artery wall thickness adjusted for age, body mass index, fasting serum glucose, systolic and diastolic blood pressures, HDL and LDL cholesterol, total caloric intake, cigarette use, race, and education (test for linear trend across quintiles of intake, P = .019 for women and P = .035 for men). An inverse relationship was also seen between wall thickness and alpha-tocopherol intake but was significant only in women (test for linear trend, P = .033 for women and P = .13 for men). There was a significant inverse association between carotene intake and wall thickness in older men (test for linear trend, P = .015), but the association weakened after adjustment for potential confounders. No significant relationships were seen in participants < 55 years old.

CONCLUSIONS

These data provide limited support for the hypothesis that dietary vitamin C and alpha-tocopherol may protect against atherosclerotic disease, especially in individuals > 55 years old.

Distribution of selenium and molybdenum and cancer mortality in Niigata, Japan

Selenium and molybdenum have inhibitory effects on gastrointestinal carcinogenesis. We investigated the levels of selenium and molybdenum in sediments and mortality from cancers at specific sites in 19 areas of Niigata Prefecture, Japan, and compared these factors. The average concentrations of selenium and molybdenum were 0.44 +/- 0.19 ppm (micrograms/g dry weight; mean +/- standard deviation) and 3.82 +/- 1.03 ppm, respectively. Selenium was not associated significantly with cancer mortality. There were inverse correlations between molybdenum levels and female mortality from cancers of the esophagus (r = -.446, .05 < p < .1) and rectum (r = -.529, p < .05). Molybdenum was correlated positively with female mortality from cancer of the pancreas (r = .603, p < .01). Further investigations are needed for causal interpretation of these results.

Position of the American Dietetic Association: phytochemicals and functional foods

Never before has the focus on the health benefits of commonly available foods been so strong. The philosophy that food can be health promoting beyond its nutritional value is gaining acceptance within the public arena and among the scientific community as mounting research links diet/food components to disease prevention and treatment. Dietitians are uniquely qualified and positioned to translate the available sound scientific evidence into practical dietary applications for the consumer and to provide the food industry and the government with valuable insight and expertise for future research, product development, and regulation of phytochemicals and functional foods. Increasing the availability of healthful foods, including functional foods, in the American diet is critical to ensuring a healthier population. As the nutrition experts, dietetics professionals must be the leaders in this new, exciting, and meaningful field as it evolves.

European School of Oncology Advisory report to the European Commission for the Europe Against Cancer Programme: oral carcinogenesis in Europe

A European School of Oncology Advisory Group has reviewed current knowledge on the epidemiology, treatment and prevention of cancer of the oral cavity. While the major factors in the aetiology of such cancers are thought to be well understood, i.e. tobacco and alcohol consumption, current increases in the occurrence of the disease, especially in young adults throughout Europe, are cause for concern. The reasons for such increases are not clearly evident and the Advisory Group has suggested further work which is required to be carried out to understand the aetiology. In treatment of the disease there have been no major improvements in survival for patients in recent decades and the importance of examining new radiotherapy modalities and defining the role of chemotherapy is emphasized. Primary prevention of oral cancer could be achieved by stopping smoking tobacco, limiting alcohol consumption to a minimum (2-3 drinks per day) and increasing intake of fruits and vegetables. To supplement these actions, while neither population screening programmes nor screening trials could be recommended by the Advisory Group, initial chemoprevention trials have produced some promising results and this represents an interesting area which is the focus of much current research.

Inhibition of skin tumor initiation, promotion, and progression by antioxidants and related compounds

Antioxidants have been shown to inhibit the induction of cancer by a wide variety of chemical carcinogens and radiation at many target sites in mice, rats, hamsters, and man. Evidence is accumulating that suggests that free radicals are important in all stages of chemical carcinogenesis. Both carcinogens and tumor promoters have also been shown to decrease the cellular activity of superoxide dismutase and catalase. A number of antioxidants and related compounds were tested to determine if they would inhibit either skin tumor initiation, promotion, or progression. In terms of skin tumor initiation, compounds such as BHT, vitamins E and C, and CuDIPS have been found to inhibit DMBA skin tumor initiation. The mechanism of action of these compounds appears to be related to their effect on the metabolism of DMBA, as BHT and CuDIPS do not inhibit the initiating activity of BP-diol-epoxide and MNNG. Although several antioxidants do inhibit skin tumor initiation by procarcinogens, antioxidants are in general much more effective inhibitors of skin tumor promotion. BHT, BHA, parahydroxyanisole, disulfiran, and vitamins E and C as well as many other antioxidants are very effective inhibitors of skin tumor promotion. We also determined the effect of free radical scavengers on the progression process. Of the agents tested, glutathione and N-acyl dehydroalamines were the most effective in reducing carcinoma incidence. Diethyl maleate, a chemical that reduces glutathione levels, was effective in enhancing progression. In addition, overexpression of gamma-glutamyltranspeptidase (GGT), which leads to a reduction in cellular glutathione levels, also enhances progression.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of the induction of cancer by antioxidants

Many different antioxidants have been shown to inhibit the induction of cancer by a wide variety of chemical carcinogens and/or radiation at many target sites in mice, rats, and hamsters. Evidence is accumulating that suggests that free radicals are important in all stages of chemical carcinogenesis. Both carcinogens and tumor promoters have also been shown to decrease the cellular activity of superoxide dismutase and catalase. A number of antioxidants and related compounds were tested to determine if they would inhibit either skin tumor initiation, promotion, and/or progression. In terms of skin tumor initiation, BHT, vitamin E and C and CuDIPS have been found to inhibit DMBA skin tumor initiation by approximately 50%. The mechanism of action of these compounds appears to be related to their effect on the metabolism of DMBA, since BHT and CuDIPS do not inhibit the initiating activity of BP-diol-epoxide and MNNG. Although several antioxidants do inhibit skin tumor initiation by procarcinogens, antioxidants are in general much more effective inhibitors of skin tumor promotion. BHT, BHA, parahydroxyanisole, disulfiran, and vitamin E and C inhibit skin tumor promotion by TPA and benzoyl peroxide by greater than 90%. We also determined the effect of free radical scavengers on the progression process. Of the agents tested glutathione and N-acyl dehydroalamines were the most effective in reducing carcinoma incidence. Diethyl maleate, a chemical that reduces glutathione levels, was effective in enhancing progression. In addition overexpression of g-glutamylt-ranspeptidase (GGT) which leads to a reduction in cellular glutathione levels also enhances progression. These results suggest that GGT has a functional role in skin tumor progression, and that a number of antioxidants are either effective inhibitors of skin tumor initiation, promotion, and/or progression.

Micronutrients and cancer aetiology: the epidemiological evidence

Micronutrient deficiencies occur most commonly in poor countries and, therefore, are most likely to be associated with cancers common in these countries. Epidemiological studies are hampered by inaccurate measurement of micronutrient intake and by the correlations between intakes of many nutrients. The strongest evidence for a protective effect of micronutrients is for oesophageal cancer. The identity of the micronutrients is not certain, but may include retinol, riboflavin, ascorbic acid and Zn; alcohol, smoking and dietary nitrosamines increase the risk for oesophageal cancer. For stomach cancer there is good evidence that fruit and vegetables are protective. The protective effect of these foods might be largely due to ascorbic acid, but other nutrients and non-nutrients may also be important; the risk for stomach cancer is increased by salt, some types of preserved foods, and by infection of the stomach with the bacterium Helicobacter pylori. The risk for lung cancer appears to be reduced by a high intake of fruit and vegetables, but it is not clear which agents are responsible and the major cause of lung cancer is cigarette smoking. Diet is probably the major determinant of the risk for colo-rectal cancer; there is evidence that fruit and vegetables and fibre reduce risk and that meat and animal fat increase risk, but there is no convincing evidence that these relationships are mediated by micronutrients. The risk for cervical cancer is inversely related to fruit and vegetable consumption and, therefore, to consumption of carotenoids and ascorbic acid, but the major cause of this cancer is human papillomavirus and it is not yet clear whether the dietary associations indicate a true protective effect or whether they are due to confounding by other variables. The evidence that micronutrients are important in the aetiology of either breast cancer or prostate cancer is weak, but the possible roles of 1,25-dihydroxycholecalciferol and alpha-tocopherol in prostate cancer require further study.

Squamous esophageal histology and subsequent risk of squamous cell carcinoma of the esophagus. A prospective follow-up study from Linxian, China

BACKGROUND

Linxian, China, has some of the highest rates of esophageal cancer in the world. Previous authors have proposed that esophagitis, atrophy, and dysplasia may be precursor lesions of esophageal cancer in such high risk populations.

METHODS

To examine the relationship between squamous esophageal histology and subsequent esophageal cancer in Linxian, the authors prospectively followed 682 participants of a 1987 endoscopic survey for 3.5 years and compared their initial biopsy diagnoses with the occurrence of squamous cell carcinoma during this follow-up period.

RESULTS

Squamous cell carcinoma of the esophagus was identified in 52 (7.6%) of the participants during the follow-up period. After adjusting for potential confounding factors, relative risks (95% confidence intervals) for squamous cell carcinoma incidence by initial histologic diagnoses were as follows: normal, 1.0 (reference); basal cell hyperplasia, 2.1 (0.4-9.8); mild dysplasia, 2.2 (0.7-7.5); moderate dysplasia, 15.8 (5.9-42.2); severe dysplasia, 72.6 (29.8-176.9); dysplasia not otherwise specified, 22.9 (6.7-78.0); and carcinoma in situ, 62.5 (24.1-161.9).

CONCLUSION

In this study, moderate dysplasia, severe dysplasia, and carcinoma in situ were the only histologic lesions associated with a significantly increased risk of developing squamous cell carcinoma of the esophagus within 3.5 years after endoscopy. Increasing grades of dysplasia were associated with increasing risk, but severe dysplasia were associated with increasing risk, but severe dysplasia and carcinoma in situ had similar degrees of risk, findings that suggest a continuous spectrum of esophageal intraepithelial neoplasia, without morphologically distinguishable dysplasia and in situ carcinoma. A longer follow-up will be necessary to fully evaluate the less severe diagnostic categories, which may take more than 3.5 years to affect the occurrence of squamous cell carcinoma in this high risk population.

Role of chemopreventers in human diet

Recent research has confirmed that many common foods contain nonnutritive components that may provide protection against chronic disease including some forms of cancer. These naturally occurring compounds, which possess anticarcinogenic and other beneficial properties, are referred to as chemopreventers. The predominant mechanism of their protective action is due to their antioxidant activity and the capacity to scavenge free radicals. Among the most investigated chemopreventers are some vitamins, plant polyphenols, flavonoids, catechins, and some components in spices. The majority of chemopreventers are available in and consumed from vegetables, fruits, grains, and tea. Various naturally occurring chemicals in garlic, soybeans, tea, and red wine appear to be responsible for the beneficial effect of these commodities on several chronic diseases. This article will review some recent studies in the search for the beneficial effects of dietary chemopreventers on human health.

Squamous esophageal histology and subsequent risk of squamous cell carcinoma of the esophagus. A prospective follow-up study from Linxian, China

BACKGROUND

Linxian, China, has some of the highest rates of esophageal cancer in the world. Previous authors have proposed that esophagitis, atrophy, and dysplasia may be precursor lesions of esophageal cancer in such high risk populations.

METHODS

To examine the relationship between squamous esophageal histology and subsequent esophageal cancer in Linxian, the authors prospectively followed 682 participants of a 1987 endoscopic survey for 3.5 years and compared their initial biopsy diagnoses with the occurrence of squamous cell carcinoma during this follow-up period.

RESULTS

Squamous cell carcinoma of the esophagus was identified in 52 (7.6%) of the participants during the follow-up period. After adjusting for potential confounding factors, relative risks (95% confidence intervals) for squamous cell carcinoma incidence by initial histologic diagnoses were as follows: normal, 1.0 (reference); basal cell hyperplasia, 2.1 (0.4-9.8); mild dysplasia, 2.2 (0.7-7.5); moderate dysplasia, 15.8 (5.9-42.2); severe dysplasia, 72.6 (29.8-176.9); dysplasia not otherwise specified, 22.9 (6.7-78.0); and carcinoma in situ, 62.5 (24.1-161.9).

CONCLUSION

In this study, moderate dysplasia, severe dysplasia, and carcinoma in situ were the only histologic lesions associated with a significantly increased risk of developing squamous cell carcinoma of the esophagus within 3.5 years after endoscopy. Increasing grades of dysplasia were associated with increasing risk, but severe dysplasia were associated with increasing risk, but severe dysplasia and carcinoma in situ had similar degrees of risk, findings that suggest a continuous spectrum of esophageal intraepithelial neoplasia, without morphologically distinguishable dysplasia and in situ carcinoma. A longer follow-up will be necessary to fully evaluate the less severe diagnostic categories, which may take more than 3.5 years to affect the occurrence of squamous cell carcinoma in this high risk population.