Serving vegetables first: A strategy to increase vegetable consumption in elementary school cafeterias.

Vegetable consumption in the United States is low despite the wealth of evidence that vegetables play an important role in reducing risk of various chronic diseases. Because eating patterns developed in childhood continue through adulthood, we need to form healthy eating habits in children. The objective of this study was to determine if offering vegetables before other meal components would increase the overall consumption of vegetables at school lunch. We served kindergarten through fifth-grade students a small portion (26-33 g) of a raw vegetable (red and yellow bell peppers) while they waited in line to receive the rest of their lunch meal. They then had the options to take more of the bell peppers, a different vegetable, or no vegetable from the lunch line. We measured the amount of each vegetable consumed by each child. Serving vegetables first greatly increased the number of students eating vegetables. On intervention days most of the vegetables consumed came from the vegetables-first portions. Total vegetable intake per student eating lunch was low because most students chose to not eat vegetables, but the intervention significantly increased this value. Serving vegetables first is a viable strategy to increase vegetable consumption in elementary schools. Long-term implementation of this strategy may have an important impact on healthy eating habits, vegetable consumption, and the health consequences of vegetable intake.

Soy induces phase II enzymes but does not inhibit dimethylbenz[a]anthracene-induced carcinogenesis in female rats.

Isoflavones in soy may play a role in the prevention of cancer through their capacity to affect antioxidant or protective phase II enzyme activities. This study evaluated the effects of dietary isoflavone levels on the induction of antioxidant and phase II enzyme activities and inhibition of breast carcinogenesis. Female Sprague-Dawley rats (36 d) were fed one of four purified diets with casein, or with soy containing three levels of isoflavonoids (0.03, 0.4 or 0.81 mg/g diet; low, middle and high level of isoflavones, respectively). After 2 wk, enzyme activity was determined of rats (n = 6-7) from each diet group. Liver glutathione peroxidase and glutathione reductase activities, blood glutathione levels, kidney glutathione S-transferase and colon quinone reductase (QR) activities were greater in rats consuming the high isoflavone diet compared to rats consuming the casein diet. Kidney QR and liver, kidney, small intestine, and colon UDP-glucuronosyltransferase activities were greater in rats fed the high isoflavone diet compared to rats fed the casein and low-isoflavone diets. Liver and blood oxidized glutathione were lower in rats fed the high-isoflavone diet compared to those fed the low-isoflavone diet. A subset of rats (n = 86) was fed the purified diets for 2 wk and intubated with dimethylbenz[a]anthracene or peanut oil and palpated weekly for tumors. At 13 wk, there was an inverse relationship (R(2) = 0.911, P < 0.09) between tumor incidence and increasing isoflavone intake. These data support the mechanism of soy and soy isoflavones as antioxidant and phase II enzyme inducers, but not as tumor inhibitors.

Soy feeding induces phase II enzymes in rat tissues.

The ability of soy to induce phase II detoxification enzymes was evaluated in male Sprague-Dawley rats. Soybeans contain biologically active compounds that are known inducers of phase II enzyme activity. Rats were fed soy flour (SF) or soy protein isolate (SPI) to provide 75% of total protein as soy. Rats were given free access to food for one- and two-week periods before enzyme activity was compared with that of casein control groups (AIN-93G). Hepatic glutathione S-transferase (GST) activity was significantly greater in rats fed SF for one and two weeks and in rats fed SPI for two weeks than in controls. Quinone reductase activity was significantly greater (12- to 14-fold) in the colon of rats fed SF and SPI for two weeks and in serum (1.8- to 2-fold) in the SF group at one and two weeks. Liver, kidney, and small intestine uridine 5'-diphosphate-glucuronosyl transferase activity was significantly increased in the SPI and SF groups at two weeks. A time dependence in induction of phase II enzymes was observed in several tissues. There was no significant difference in total liver glutathione in either diet group compared with controls. The data indicate that dietary soy enhances phase II enzyme activity, especially quinone reductase and uridine 5'-diphosphate-glucuronosyl transferase, which could lead to protection from potentially harmful xenobiotics.

Modulation of rat hepatic cytochrome P-450 activity by garlic organosulfur compounds.

Garlic organosulfur compounds exert chemopreventive effects at several organ sites in rodents after administration of chemical carcinogens, possibly by inhibiting carcinogen activation via cytochrome P-450-mediated oxidative metabolism. It has been suggested that the variability in potency of tumor inhibition by garlic sulfur compounds is due to structural differences, such as the number of allyl and sulfur groups. In this study, diallyl sulfide (DAS), diallyl disulfide (DADS), and allyl methyl sulfide (AMS) were administered to acetone-treated adult male Sprague-Dawley rats by gastric gavage at a dose of 1.75 mmol/kg in cottonseed oil. After 15 hours, hepatic microsomal cytochrome P-450 activity and content were examined. The activity of p-nitrophenol (pNP) hydroxylase (E.C. 1.14.13.29) was significantly decreased by all garlic compounds, whereas benzphetamine N-demethylase and ethoxyresorufin O-deethylase activities were not changed. The activity of pNP hydroxylase was decreased to 31%, 54%, and 65% of control activity, and immunodetectable CYP2E1 protein levels were decreased in a similar manner by DAS, DADS, and AMS, respectively. Additional acetone-treated rats were given 4-methyl pyrazole, a ligand specific for CYP2E1, intraperitoneally five hours after garlic compound administration. Ten hours later, pNP hydroxylase activity was decreased to 73%, 78%, and 67% of control levels by DAS, DADS, and AMS, respectively. Further studies are needed to determine whether the variable potency of inhibition of CYP2E1 enzyme activity is related to chemopreventive efficacy of garlic sulfur compounds.

Effects of D-limonene on hepatic microsomal monooxygenase activity and paracetamol-induced glutathione depletion in mouse.

1. D-Limonene, a monoterpenoid constituent of citrus fruit oil, blocks tumour induction by chemical carcinogens in laboratory animals, apparently by preventing bioactivation of procarcinogens and by enhancing conjugation of proximal carcinogenic metabolites. 2. Inhibitory effects of D-limonene were measured in vitro using cytochrome P450 isoform-specific substrates. D-Limonene inhibited p-nitrophenol hydroxylase (pNP) activity in vitro in liver microsomes from acetone-, phenobarbital (PB)- and beta-naphthoflavone (BNF)-treated mouse, and 7-ethoxyresorufin O-deethylase (EROD) activity in microsomes from PB- and BNF-treated mouse. p-Nitrophenol and ethoxyresorufin are substrates for cytochromes P2E1 and P1A1, respectively. No inhibition of benzphetamine (BNZP) or aminopyrine (AP) demethylases by D-limonene was observed. 3. EROD, BNZP and AP activities in liver microsomes were increased 18 h after i.p. administration of D-limonene to acetone-induced mouse, while pNP activity was unchanged. The immunodetectable protein level of cytochrome P2B1 in non-acetone treated mouse was increased 18 h after D-limonene, with no differences in P2E1 or P1A1. 4. Acute D-limonene did not protect against paracetamol (acetaminophen)-induced depletion of liver reduced glutathione (GSH). A prolonged paracetamol challenge (0.6% diet for 10 days) elevated liver cytosolic GSH-S-transferase activity (GST) two-fold and decreased liver GSH to 46% of control values. Dietary D-limonene (1.0% diet for 10 days) maintained liver GSH concentrations at 92% of control values in the paracetamol-challenged mouse without altering GST activity. D-Limonene also increased liver GSH concentration (23%) in mouse fed 1.0% D-limonene alone.

Prolonged acetaminophen ingestion by mice fed a methionine-limited diet does not affect iron-induced liver lipid peroxidation or S-adenosylmethionine.

This study determined whether acetaminophen (ACAP)-induced glutathione depletion was associated with liver lipid peroxide formation, or the concentrations of liver S-adenosylmethionine and S-adenosylhomocysteine in mice fed diets with L-methionine below or at the requirement level (0.25 or 0.5%) for 7 wk. Iron dextran (281 mg/kg body wt) or saline was administered for 2 d before measurement of lipid peroxide formation. Chronic dietary ACAP (0.5%) in mice fed 0.25% methionine caused a failure to maintain body weight even though food intake was similar to intake by all other treatment groups. Liver GSH (measured as nonprotein sulfhydryl concentration) and cysteine concentrations were depleted by ACAP and by ACAP plus iron. Liver lipid peroxide formation was increased by iron but was not altered additionally by ACAP ingestion. Liver glutathione peroxidase activity was increased by methionine in controls, whereas glutathione S-transferase activity was increased by ACAP ingestion in mice fed 0.5% methionine compared with controls. Liver S-adenosylmethionine and nuclear 5-methyldeoxycytidine concentrations were not affected by dietary ACAP or methionine. Liver S-adenosylhomocysteine levels were lower in mice fed ACAP and 0.25% methionine compared with mice fed ACAP and 0.5% methionine. In conclusion, chronic ACAP did not increase the susceptibility of mice to liver lipid peroxidation or alter the availability of methyl groups for methylation reactions.

Effects of methionine deficiency and ethanol ingestion on acetaminophen metabolism in mice.

The interaction of the effect of dietary methionine on the availability of hepatic glutathione (GSH) and the effect of chronic ethanol (EtOH) consumption on the activity of the hepatic oxidation system was studied in relation to acetaminophen (ACAP) metabolism in mice. Adult male Swiss-Webster mice were pair-fed for 4 wk an EtOH-containing liquid diet that provided 50 or 100% of the methionine requirement in a 2 X 2 factorial design. Hepatic microsomal protein, relative liver weight and microsomal aniline hydroxylase activity were higher in EtOH-fed groups than in non-EtOH-fed groups. After an ACAP dose of 300 mg/kg body wt i.p., serum inorganic sulfate, endogenous hepatic methionine and GSH concentrations were lower, whereas uridine diphosphoglucuronosyltransferase activity was not changed compared to controls. GSH levels were lowered to a greater extent in the methionine-deficient groups than in methionine-sufficient groups. Incorporation of [35S]methionine into hepatic proteins was lower in all treatment groups after ACAP administration than in controls. The distribution of ACAP into the urinary sulfate conjugates was lower in methionine-deficient than in methionine-sufficient groups, and the percentage of sulfate and mercapturic acid conjugates formed as determined by high-performance liquid chromatographic analysis was higher in mice fed EtOH than in controls. Methionine deficiency compromises the normal pathways of ACAP disposition in the mouse, and chronic EtOH ingestion may potentiate this effect by increasing the amount of activated ACAP formed.

Effects of dietary methionine and ethanol on acetaminophen hepatotoxicity in mice.

The possible interactive relationship between nutritional compromise of acetaminophen detoxification and ethanol enhancement of acetaminophen hepatotoxicity was studied in mice by using a 2-X-2 factorial design. Ethanol was administered to adult male mice at 0 or 15% solution in the drinking water, and dietary methionine levels were at 54 or 100% of the requirement. After 4 weeks, a significant reduction in the median lethal time (LT50) following a high dose of acetaminophen was seen in the methionine-deficient groups. Methionine deficiency also caused a reduction in hepatic glutathione levels in the control group and in mice receiving sublethal doses of acetaminophen. PGOT levels were increased significantly by methionine deficiency but were markedly increased by the interaction of ethanol treatment and methionine deficiency. Glutathione-S-transferase activity was not affected by any treatment combinations, and p-nitroanisole O-demethylase activity and relative liver weights were not increased because of chronic ethanol ingestion. These findings indicate that methionine deficiency causes glutathione reduction, which predisposes the mouse to increased acetaminophen hepatotoxicity. Ethanol consumption did not seem to potentiate the increased hepatotoxic effects caused by methionine deficiency, except as indicated by PGOT activity.