Health effects of vegetables and fruit: assessing mechanisms of action in human experimental studies.

Epidemiologic data support the association between high intake of vegetables and fruits and low risk of chronic disease. There are several biologically plausible reasons why consumption of vegetables and fruit might slow or prevent the onset of chronic diseases. Vegetables and fruit are rich sources of a variety of nutrients, including vitamins, trace minerals, and dietary fiber, and many other classes of biologically active compounds. These phytochemicals can have complementary and overlapping mechanisms of action, including modulation of detoxification enzymes, stimulation of the immune system, reduction of platelet aggregation, modulation of cholesterol synthesis and hormone metabolism, reduction of blood pressure, and antioxidant, antibacterial, and antiviral effects. Although these effects have been examined primarily in animal and cell-culture models, experimental dietary studies in humans have also shown the capacity of vegetables and fruit and their constituents to modulate some of these potential disease-preventive mechanisms. The human studies have relied on intermediate endpoints related to disease risk. Design methodologies used include multiple-arm trials, randomized crossover studies, and more compromised designs such as nonrandomized crossovers and pre- and posttreatment analyses. Length of treatment ranged from a single dose to years depending on the mechanism of interest. Stringency of dietary control varied from addition of supplements to a habitual diet to provision of all food for the duration of a treatment. Rigorously conducted experimental dietary studies in humans are an important link between population- and laboratory-based research.

Carotenoids and colon cancer.

BACKGROUND: Carotenoids have numerous biological properties that may underpin a role for them as chemopreventive agents. However, except for beta-carotene, little is known about how dietary carotenoids are associated with common cancers, including colon cancer. OBJECTIVE: The objective of this study was to evaluate associations between dietary alpha-carotene, beta-carotene, lycopene, lutein, zeaxanthin, and beta-cryptoxanthin and the risk of colon cancer. DESIGN: Data were collected from 1993 case subjects with first primary incident adenocarcinoma of the colon and from 2410 population-based control subjects. Dietary data were collected from a detailed diet-history questionnaire and nutrient values for dietary carotenoids were obtained from the US Department of Agriculture-Nutrition Coordinating Center carotenoid database (1998 updated version). RESULTS: Lutein was inversely associated with colon cancer in both men and women [odds ratio (OR) for upper quintile of intake relative to lowest quintile of intake: 0.83; 95% CI: 0.66, 1.04; P = 0.04 for linear trend]. The greatest inverse association was observed among subjects in whom colon cancer was diagnosed when they were young (OR: 0.66; 95% CI: 0.48, 0.92; P = 0.02 for linear trend) and among those with tumors located in the proximal segment of the colon (OR: 0.65; 95% CI: 0.51, 0.91; P < 0.01 for linear trend). The associations with other carotenoids were unremarkable. CONCLUSION: The major dietary sources of lutein in subjects with colon cancer and in control subjects were spinach, broccoli, lettuce, tomatoes, oranges and orange juice, carrots, celery, and greens. These data suggest that incorporating these foods into the diet may help reduce the risk of developing colon cancer.

Vegetables, fruits, legumes and prostate cancer: a multiethnic case-control study.

The evidence for a protective effect of vegetables, fruits, and legumes against prostate cancer is weak and inconsistent. We examined the relationship of these food groups and their constituent foods to prostate cancer risk in a multicenter case-control study of African-American, white, Japanese, and Chinese men. Cases (n = 1619) with histologically confirmed prostate cancer were identified through the population-based tumor registries of Hawaii, San Francisco, and Los Angeles in the United States and British Columbia and Ontario in Canada. Controls (n = 1618) were frequency-matched to cases on ethnicity, age, and region of residence of the case, in a ratio of approximately 1:1. Dietary and other information was collected by in-person home interview; a blood sample was obtained from control subjects for prostate-specific antigen determination. Odds ratios (OR) were estimated using logistic regression, adjusting for age, geographic location, education, calories, and when indicated, ethnicity. Intake of legumes (whether total legumes, soyfoods specifically, or other legumes) was inversely related to prostate cancer (OR for highest relative to lowest quintile for total legumes = 0.62; P for trend = 0.0002); results were similar when restricted to prostate-specific antigen-normal controls or to advanced cases. Intakes of yellow-orange and cruciferous vegetables were also inversely related to prostate cancer, especially for advanced cases, among whom the highest quintile OR for yellow-orange vegetables = 0.67 (P for trend = 0.01) and the highest quintile OR for cruciferous vegetables = 0.61 (P for trend = 0.006). Intake of tomatoes and of fruits was not related to risk. Findings were generally consistent across ethnic groups. These results suggest that legumes (not limited to soy products) and certain categories of vegetables may protect against prostate cancer.

Diet and lung cancer: a new approach.

Lung cancer is one of major public health problems facing the world today, owing to the high incidence of the disease and its poor prognosis. Although the principal cause of lung cancer is tobacco use, smokers find it extremely difficult to quit the habit. Hence, there is a need to take action targeted at other risk factors for this disease. One such factor is diet, which is known to be able to raise or lower the risk of lung cancer. This paper seeks to complement other reviews in the field and to shed more light both on the influence that dietary factors may have upon the occurrence of this neoplasm and on the causes of this possible effect.

Eggplant (Solanum melongena) infusion has a modest and transitory effect on hypercholesterolemic subjects.

Eggplant (Solanum melongena) is consumed extensively in Brazil. It has been believed that infusion of a powdered preparation of the fruit may reduce serum cholesterol. However, there are few documented reports on its effects on cholesterol metabolism and its possible hypocholesterolemic effect has not been proved by well-controlled studies. The aim of the present study was to observe the effects of S. melongena on the serum cholesterol and triglycerides of 38 hypercholesterolemic human volunteers ingesting S. melongena infusion for five weeks. Thirty-eight hypercholesterolemic subjects receiving either S. melongena infusion (N = 19) or placebo (N = 19) participated in two clinical experiments in which the effect of S. melongena infusion was studied with (N = 16) or without (N = 38) dietary orientation. Total cholesterol and its fractions, triglycerides, and apolipoproteins A and B were measured in blood at the beginning of the experiment and three and five weeks thereafter. No differences were observed compared to control. Intraindividual analysis showed that S. melongena infusion significantly reduced the blood levels of total and LDL cholesterol and of apolipoprotein B. After dietary orientation, no intra- or intergroup differences were seen for any of the parameters analyzed. The results suggest that S. melongena infusion had a modest and transitory effect, which was not different from that obtained with standard orientation for dyslipidemia patients (diet and physical activities).

Arrowroot as a treatment for diarrhoea in irritable bowel syndrome patients: a pilot study.

OBJECTIVES: Arrowroot is an old-fashioned remedy for diarrhoea, but no clinical studies have been done to evaluate its effectiveness. The aim of this pilot study was to assess its efficacy as a treatment for diarrhoea in 11 patients, all of whom had irritable bowel syndrome with diarrhoea as a feature. METHODS: The patients were interviewed and a questionnaire completed on entry into the trial. They then took 10 mL arrowroot powder three times a day for one month and discontinued the treatment for the subsequent month. Questionnaires were completed after one month on treatment and at the end of the trial after one month off treatment. RESULTS: Arrowroot reduced diarrhoea and had a long-term effect on constipation. It also eased abdominal pain. CONCLUSION: Arrowroot is an effective treatment for diarrhoea. Its action could be explained by several theories which relate to an increase in faecal bulk and thus a more efficient bowel action. The number of patients was small, and further studies are needed to substantiate preliminary results.

Effect of Momordica charantia (Karolla) extracts on fasting and postprandial serum glucose levels in NIDDM patients.

Effect of Momordica charantia, a bitter vegetable popularly known as Karolla, on fasting and post prandial (2 hours after 75 gm oral glucose intake) serum glucose levels were studied in 100 cases of moderate non-insulin dependent diabetic subjects. Drinking of the aqueous homogenized suspension of the vegetable pulp led to significant reduction (p < 0.001) of both fasting and post-prandial serum glucose levels. This hypoglycaemic action was observed in 86 (86%) cases. Five cases (5%) showed lowering of fasting serum glucose only.

Evaluation of the evidence on the role of tomato products in disease prevention.

During the last 30 years, research in the field of nutrition and chronic disease causation has led to exciting, significant progress in providing an understanding of specific risk factors and chemopreventive agents. The major health problems considered are cardiovascular diseases and the nutritionally linked cancers, including those in the stomach, colon, breast, prostate, ovary, and endometrium. The major elements considered were salt, type and amount of fat, and heterocyclic amines formed during cooking. Bran cereal fiber, as well as vegetables, fruits, and tea have been shown to inhibit the complex processes of initiation and development of these diseases. One aspect involved in initiation and development of both cardiovascular diseases and the cancers noted are abnormal oxidative processes leading to the generation of hydroxy radicals and peroxy compounds. In part, the protective role of vegetables, fruits, and tea is to provide antioxidant vitamins and specific polyphenols that display a powerful inhibition in oxidative reactions. Epidemiological studies as well as laboratory experimentation have yielded sound data and evidence in support of the fact that vegetables, fruits, and tea and specific antioxidants therein account mechanistically for inhibition. Geographic pathology has provided important data that populations with a regular intake of tomato products, such as in the Mediterranean region, have a lower incidence of the chronic diseases noted. The current Symposium is considering the varied mechanisms of action of tomato products in general, and one of the active principles, lycopene. Cooking is a factor in releasing the desirable antioxidants from tomatoes. Cooked tomato products may be preferable to the raw vegetable or juices derived from tomatoes bearing on absorption of the active principles. Optimally, absorption of lycopene, a highly lipid-soluble chemical, is improved in the presence of a small, but essential amount of oil or fat. Research in the field of nutrition and health has shown that monounsaturated oils such as olive oil or canola oil are most desirable, since such oils do not increase the risk of atherosclerosis, coronary heart disease, or the nutritionally linked cancers. The International Symposium on tea conducted in 1991 has provided worldwide interest in research on the beneficial effects of tea. It is now hoped that the present Symposium, dealing with another inexpensive and readily available food, tomatoes, will enhance interest in and funding for additional research, to underwrite future recommendations for possibly enhanced production and use of tomato-derived nutritional elements, with the goal of application to the prevention of major chronic diseases, the treatment of which is costly and often ineffective.

A motivational interviewing intervention to increase fruit and vegetable intake through Black churches: results of the Eat for Life trial.

OBJECTIVES: This study reports on Eat for Life, a multicomponent intervention to increase fruit and vegetable consumption among African Americans that was delivered through Black churches. METHODS: Fourteen churches were randomly assigned to 3 treatment conditions: (1) comparison, (2) self-help intervention with 1 telephone cue call, and (3) self-help with 1 cue call and 3 counseling calls. The telephone counseling in group 3 was based on motivational interviewing. The primary outcome, assessed at baseline and 1-year follow-up, was fruit and vegetable intake as assessed by 3 food frequency questionnaires. RESULTS: Change in fruit and vegetable intake was significantly greater in the motivational interviewing group than in the comparison and self-help groups. The net difference between the motivational interviewing and comparison groups was 1.38, 1.03, and 1.21 servings of fruits and vegetables per day for the 2-item, 7-item, and 36-item food frequency questionnaires, respectively. The net difference between the motivational interviewing and self-help groups was 1.14, 1.10, and 0.97 servings for the 2-item, 7-item, and 36-item food frequency questionnaires, respectively. CONCLUSIONS: Motivational interviewing appears to be a promising strategy for modifying dietary behavior, and Black churches are an excellent setting to implement and evaluate health promotion programs.

Survey of UK dietetic departments: diet in secondary prevention of myocardial infarction.

AIM: To collate information on current British dietetic practice in the area of diet in secondary prevention of myocardial infarction, and to compare this with best evidence. METHODS: A questionnaire was sent to all Chief Dietitians, to be completed by the whole department, asking about current dietary advice and practice, referrals and written dietary information for people following myocardial infarction. RESULTS: Fifty-seven per cent of questionnaires were returned. Dietary fat advice was prioritized by 84% of departments, fruit and vegetables by 49%, oily fish by 45% and fibre by 28%. Most dietitians (81%) felt that this advice would protect from further cardiovascular disease. Percentages of post-myocardial infarction patients given advice by a dietitian varied (median 60%), reasons for non-referral included patients having normal lipids or weight. More were given dietary advice by another health professional (median 90%); however, most dietitians were unsure about the quality of this advice. Diet sheets were felt to reflect advice priorities, but where sheets were sent they were much less likely than departments to prioritize oily fish or fruit and vegetable advice. CONCLUSION: Dietetic practice for people following myocardial infarction is out of line with current best evidence. Almost half of departments correctly prioritize oily fish advice, but often only see patients with raised lipids or weight. This is not the most effective strategy for preventing deaths.

Dietary factors and risk of lung cancer in never-smokers.

We studied dietary risk factors for lung cancer among never-smokers in a population-based case-control study in Stockholm, 1989-1995. Study subjects were older than 30 years of age and had never smoked regularly. A total of 124 cases (35 men, 89 women) and 235 controls (72 men, 163 women) participated. Exposure information was obtained at interview with study subjects. The never-smoking status was validated by interviews with next-of-kin. A protective effect was suggested for vegetables, mediated primarily by carrots (relative risk [RR], 0.7; 95% confidence interval [CI], 0.4-1.3, and 0.6, 0.3-1.1 for intermediate and high consumption of carrots, respectively). Non-citrus fruits appeared to lower the risk as well, with RR 0.6, 95% CI 0.3-1.3 and 0.5, 0.3-1.0 for intermediate and high consumption, respectively. A protective effect with dose-response was also seen for intake of beta-carotene and total carotenoids. Increased risks were seen for cultured milk products in both genders (RR 2.0, 95% CI 1.1-3.9 for intermediate and 1.6, 0.9-2.9 for high consumption), but for milk only among male high consumers. Our results support evidence linking a diet rich in vegetables and non-citrus fruit with decreased lung cancer risk and suggests that among vegetables, carrot consumption is the most important component or marker for this effect in Sweden. The results regarding milk products could be consistent with dietary fat as a risk factor for lung cancer, although a more comprehensive assessment of fat intake is necessary to explore this relation.