Role of pfkA and general carbohydrate catabolism in seed colonization by Enterobacter cloacae.
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Enterobacter cloacae A-11 is a transposon mutant of strain 501R3 that was deficient in cucumber spermosphere colonization and in the utilization of certain carbohydrates (D. P. Roberts, C. J. Sheets, and J. S. Hartung, Can. J. Microbiol. 38:1128-1134, 1992). In vitro growth of strain A-11 was reduced or deficient on most carbohydrates that supported growth of strain 501R3 but was unaffected on fructose, glycerol, and all amino acids and organic acids tested. Colonization by strain A-11 was significantly reduced (P +info)
Antimicrobial susceptibility of Enterobacteriaceae isolated from vegetables.
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There is potential for the normal faecal flora of humans to be augmented by resistant strains of bacteria, acquired from food. The frequency of resistance in the aerobic Gram-negative faecal flora is often very high. The purpose of this study was to find out whether food strains contribute to this resistance. One hundred and thirty-seven vegetable samples were studied, 48 of Finnish origin, and 89 imported. From these samples, 535 different strains of bacteria belonging to the family Enterobacteriaceae were isolated. Enterobacter spp. were most frequent, Escherichia coli was rare. Sensitivity testing was undertaken only for isolates with different biotypes and antibiograms. No resistance was found to cefotaxime, aztreonam, imipenem, gentamicin, nalidixic acid or ciprofloxacin. The frequency of trimethoprim resistance was 0.2%, sulphamethoxazole resistance 1.3%, and tetracycline resistance 5.5%. These frequencies were much lower than those found in faecal flora. Chloramphenicol and cefuroxime resistance was found in 12% and 14% of isolates, respectively. The only statistically significant differences between the Finnish and imported strains were for these two; the Finnish isolates were more resistant to cefuroxime, whereas the imported ones were more resistant to chloramphenicol. Consequently, bacteria from vegetables are not responsible for the high prevalence of resistant Enterobacteriaceae in faecal flora in Finland; they are in fact unusually susceptible to the antibiotics studied. Multiresistance profiles, typical of strains associated with human activities, were not identified in these isolates. (+info)
Conversion of glucosinolates to isothiocyanates in humans after ingestion of cooked watercress.
(19/2539)
Isothiocyanates (ITCs), major constituents of cruciferous vegetables, can inhibit tumorigenesis in rodents by modulating the metabolism of carcinogens. ITCs that occur as glucosinolates are released by myrosinase-mediated hydrolysis when raw vegetables are chopped or chewed. However, because cruciferous vegetables are commonly consumed by humans after being cooked, it is important to examine whether dietary glucosinolates are converted to ITCs after cooked cruciferous vegetables in which myrosinase is deactivated have been consumed. This information is useful for evaluating the potential role of ITCs in cruciferous vegetables in the protection against human cancers. A urinary marker, based on a cyclocondensation product formed by the reaction of ITCs and their conjugates with 1,2-benzenedithiol, was used to quantify the uptake of dietary ITCs in humans. At breakfast and lunch, nine volunteers consumed a total of 350 g of cooked watercress in which the myrosinase activity was completely deactivated. On the basis of the analysis of ITCs in the cooked watercress upon adding exogenous myrosinase, the amount of glucosinolates ingested by each subject was estimated to be 475 micromol. The 24-h urine samples showed that the total urinary excretion of ITC conjugates in the subjects ranged from 5.6 to 34.8 micromol, corresponding to 1.2-7.3% of the total amount ingested. On the basis of our previous results that approximately 50% of dietary ITCs were excreted in the urine as conjugates, these values represent the minimal in vivo conversion of glucosinolates to ITCs. For purposes of comparison, we carried out a second experiment in which 150 g of uncooked watercress were consumed. The percentage of urinary ITC conjugates excreted in this study ranged from 17.2 to 77.7% of the total ingested ITCs. These results indicate that glucosinolates are converted to ITCs in humans after ingestion of cooked watercress, in which the myrosinase has been completely inactivated. The extent of conversion, however, is considerably less than that after ingesting uncooked vegetables. Furthermore, upon incubation of the cooked watercress juice with fresh human feces under anaerobic conditions, approximately 18% of glucosinolates was hydrolyzed to ITCs in 2 h. These results suggest that the microflora in the intestinal tract are a likely source for the hydrolysis of glucosinolates to ITCs in humans. (+info)
Dietary folate from vegetables and citrus fruit decreases plasma homocysteine concentrations in humans in a dietary controlled trial.
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Elevated total plasma homocysteine (tHcy) concentrations are considered a risk factor for neural tube defects (NTD) and cardiovascular disease. Supplementation with folic acid decreases the risk of women having children with NTD. In both sexes, it decreases tHcy levels. We investigated the efficacy of natural dietary folate in improving folate and homocysteine status. We performed a 4-wk dietary controlled, parallel design intervention trial with 66 healthy subjects (18-45 y) divided into 3 treatment groups: the dietary folate group, the folic acid group and the placebo group. Each day each group was fed a different diet. The dietary folate group received a diet high in vegetables and citrus fruit (total folate content approximately 560 microgram) plus a placebo tablet. The folic acid group received a diet naturally low in folate (approximately 210 microgram) plus 500 microgram folic acid and placebo tablet on alternate days, i.e., 250 microgram folic acid/d. And the placebo group received the same low-folate diet as the folic acid group plus a placebo tablet. After 4 wk of intervention, folate status improved, and tHcy concentrations decreased in both the dietary folate and the folic acid groups. From the amount of additional folate (350 microgram/d) and folic acid (250 microgram/d) consumed, the relative bioavailability of dietary folate compared to folic acid was calculated to be 60-98%, depending on the endpoint used. In conclusion, increasing the consumption of vegetables and citrus fruit, both good sources of folate, will improve folate status and decrease tHcy concentrations. This may contribute to the prevention of cardiovascular disease and NTD in the general population (+info)
Comparison of phylloquinone bioavailability from food sources or a supplement in human subjects.
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Phylloquinone (K) absorption was assessed in 22- to 30-y-old human subjects consuming a standard test meal [402 kcal (1682 kJ), 27% energy from fat]. The absorption of phylloquinone, measured over a 9-h period as the area under the curve (AUC), was higher (P < 0.01) after the consumption of a 500- microgram phylloquinone tablet [27.55 +/- 10.08 nmol/(L. h), n = 8] than after the ingestion of 495 microgram phylloquinone as 150 g of raw spinach [4.79 +/- 1.11 nmol/(L. h), n = 3]. Less phylloquinone (P < 0.05) was absorbed from 50 g of spinach (AUC = 2.49 +/- 1.11 nmol/(L. h) than from 150 g of spinach. Absorption of phylloquinone from fresh spinach (165 microgram K), fresh broccoli (184 microgram K) and fresh romaine lettuce (179 microgram K) did not differ. There was no difference in phylloquinone absorption from fresh or cooked broccoli or from fresh romaine lettuce consumed with a meal containing 30 or 45% energy as fat. (+info)
Beta-carotene and lung cancer: a case study.
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The conflicting evidence of the relation between beta-carotene and lung cancer in humans serves as a poignant case study with respect to what types of evidence are sufficient to support or change a nutrition recommendation. This article is a review of the available evidence of the relation between beta-carotene and lung cancer, including data regarding beta-carotene intake (from diet and supplements), beta-carotene biochemical status, and vegetable and fruit consumption, and a discussion of the role of this evidence in making nutrition recommendations. More than 30 case-control and cohort studies were conducted over many years in various populations and indicated that people who eat more vegetables and fruit, foods rich in carotenoids, and carotenoids (beta-carotene in particular), as well as those with higher blood beta-carotene concentrations, have a lower risk of lung cancer than those who eat fewer such foods or have lower beta-carotene concentrations. In contrast, the intervention results from large, controlled trials of beta-carotene supplementation do not support the observed beneficial associations or a role for supplemental beta-carotene in lung cancer prevention; instead, they provide striking evidence for adverse effects (ie, excess lung cancer incidence and overall mortality) in smokers. The findings require that caution be exercised in recommending supplemental beta-carotene, particularly for smokers, and argue against changing the vegetable-fruit recommendations in the direction of greater nutrient specificity. This case study of beta-carotene and lung cancer stresses the importance of having results from at least one, and preferably more, large, randomized intervention trial before public health recommendations concerning micronutrient supplementation are considered. (+info)
Fresh fruit intake and asthma symptoms in young British adults: confounding or effect modification by smoking?
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Antioxidant vitamins have been postulated as a protective factor in asthma. The associations between the frequency of fresh fruit consumption in summer, and the prevalence of self-reported asthma symptoms were investigated. The analysis was based on 5,582 males and 5,770 females, born in England, Wales and Scotland between March 3-9, 1958 and aged 33 yrs at the time of survey. The 12-month period prevalence of wheeze and frequent wheeze were inversely associated with frequent intakes of fresh fruit and salad/raw vegetables and positively associated with smoking and lower social class. After adjustment for mutual confounding and sex, associations with smoking persisted, but those with social class and salad/raw vegetable consumption lost significance. The frequency of fresh fruit intake was no longer associated with wheeze after adjustment, but was inversely associated with frequent wheeze and speech-limiting attacks. The association with frequent wheeze differed significantly between smoking groups (never, former, current) and appeared to be confined to exsmokers and current smokers. These findings support postulated associations between infrequent fresh fruit consumption and the prevalence of frequent or severe asthma symptoms in adults. Associations appeared to be restricted to smokers, with effect modification as a more likely explanation of this pattern than residual confounding by smoking. (+info)
The Health Education Authority's health and lifestyle survey 1993: who are the low fruit and vegetable consumers?
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STUDY OBJECTIVE: Firstly, to determine the demographic and behavioural characteristics of low fruit and vegetable consumers. Secondly, to investigate whether knowledge and attitudes are barriers to consumption of fruit and vegetables. DESIGN: Cross sectional survey: an interviewer administrated questionnaire was used to assess the demographic, knowledge, attitude, and behavioural characteristics of the respondents. SETTING: England. PARTICIPANTS: Random sample of 5553 men and women aged between 16 and 74 years. Response rate 70%. MAIN RESULTS: The main demographic characteristics of the respondents identified as low consumers of fruit and vegetables (less than daily consumption of either fruit or vegetables) were age, sex, and smoking status. The adjusted odds ratios were 2.59 for those aged 16-24 years compared with those aged 45-74 years, 2.17 for men compared with women, and 1.77 for current smokers compared with never smokers. The most important knowledge and attitude statements after adjusting for the demographic variables were disagreeing with the statement "healthy foods are enjoyable" (odds ratio 1.90) and agreeing with the statement "I don't really care what I eat" (odds ratio 1.76). The impact of knowledge seemed less important than attitudes about a healthy diet in characterising a low fruit and vegetable consumer. CONCLUSIONS: These findings are relevant to future strategies for improving intake of fruit and vegetables, but demonstrate the complexity of interventions required, and the dangers inherent in assuming simplistic relations between psychosocial factors and behaviour. (+info)