Plasma homocysteine concentration is decreased by dietary intervention

High plasma total homocysteine (tHcy) concentration is reported to be a risk factor for vascular diseases. We investigated the extent to which serum folate and plasma tHcy respond to a high intake of natural folate from food. Thirty-seven healthy females volunteered t o participate in a crossover dietary intervention. The study included a baseline period and two 5-week diet periods (low- and high-folate diets) with a 3-week washout in between. The low-folate diet contained one serving of both vegetables and fruit/d, while during the high-folate diet the subjects ate at least seven servings of vegetables, berries, and citrus fruit/d. Serum and erythrocyte (RBC) folate, serum vitamin B (12), and plasma tHcy concentrations were measured at the base-line and at the end of each diet period. The mean concentrations of serum and RBC folate were 11.0 (SD 3.0) nmol/l and 412 (SD 120) nmol/l at the end of the low-folate diet and 78 (95 % CI 62, 94) % and 14 (95 % CI 8, 20) % higher in response to the high-folate diet (P< 0.001). The serum concentration of vitamin B12 remained unchanged during the intervention. The mean plasma tHcy concentration was 8.0 pmol/ at the end of the low-folate diet and decreased by 13 (95% CI 9, 18) % in response to the high-folate diet (P<0.001). In conclusion, a diet high in fresh berries, citrus fruit, and vegetables effectively increases serum and RBC folate and decreases plasma homocysteine.     

VLDL metabolism in rats is affected by the concentration and source of dietary protein

The present study was designed to determine if changes in dietary protein level and source are related to changes in VLDL lipid concentrations and VLDL binding by hepatic membranes and isolated hepatocytes. Male Wistar rats were fed cholesterol-free diets containing 10, 20 or 30 g/100 g casein or highly purified soybean protein for 4 wk. Hepatic, plasma and VLDL lipids, VLDL apo B-100 and VLDL uptake by isolated hepatocytes and VLDL binding to hepatic membrane were determined. Increasing casein or soybean protein level (from 10 to 30 g/100 g) in the diet increased VLDL apo B-100, indicating an increase in the number of VLDL particles. VLDL uptake by isolated hepatocytes and VLDL binding to hepatic membrane increased when the protein level increased from 10 to 20 g/100 g in the diet and decreased with 30 g/100 g protein, regardless of protein type. The dietary protein source did not affect plasma total cholesterol concentrations at any protein level. Feeding 20 g/100 g soybean protein compared with casein lowered plasma triglyceride concentrations and VLDL number as measured by decreased VLDL-protein, -phospholipid, -triglyceride, -cholesterol and -apo B-100. VLDL uptake by isolated hepatocytes and VLDL binding to hepatic membrane were higher in rats fed soybean protein than those fed casein. The higher VLDL uptake could be responsible for the hypotriglyceridemia in rats fed soybean protein.     

Net renal arginine flux in rats is not affected by dietary arginine or dietary protein intake.

Kidneys of adult animals serve as a major biosynthetic source of arginine. Recently, we demonstrated that kidneys of rats infused with citrulline responded to the elevated plasma citrulline concentrations by increasing citrulline uptake and producing greater quantities of arginine. The objective of the present study was to determine the effects of feeding adult male rats different levels of arginine or protein on renal arginine synthesis. Feeding arginine (0, 0.5 and 2.0%) for 1 wk increased circulating plasma concentrations of arginine 2.5-fold (196 mumol/L) in the 2.0% arginine group compared with the 0 and 0.5% arginine groups (73 and 81 mumol/L, respectively). However, the plasma citrulline concentration was unchanged. The renal uptake of citrulline and release of arginine were similar in all the three groups fed different levels of arginine. Feeding diets containing 5, 12 and 50% protein for 1 wk did not alter the circulating plasma concentrations of either citrulline or arginine, and there were no significant differences in the renal release of arginine. These results suggest that renal arginine synthesis is independent of dietary arginine or protein intake.     

Lung eicosanoid synthesis is affected by age, dietary fat and vitamin E.

The effect of age, dietary fat type and all-rac-alpha-tocopheryl acetate (vitamin E) supplementation on ex vivo synthesis of lung eicosanoids was measured in C57BL/6NIA mice using a 2 (age) x 3 (fat) x 3 (vitamin E) factorial design. Young (3-mo-old) and old (24-mo-old) mice were fed a semipurified diet containing 5% (by wt) corn oil, coconut oil or fish oil supplemented with 30, 100 or 500 mg vitamin E/kg for 4 wk. Ex vivo synthesis of thromboxane B2 (TXB2) and 6-keto-prostaglandin F1 alpha (PGI2) were measured by RIA in lung homogenates. Old mice had significantly higher concentrations of TXB2 and PGI2 than did young mice, resulting in a significant increase in the TXB2:PGI2 ratio with aging. Young and old mice fed fish oil had significantly lower concentrations of PGI2 and TXB2 than those fed corn oil or coconut oil. The degree of reduction varied according to age and vitamin E status. Old mice fed fish oil and 30 mg vitamin E/kg diet had the lowest plasma vitamin E concentration and the highest TXB2:PGI2 ratio. The TXB2:PGI2 ratio was significantly reduced in old mice fed coconut oil or fish oil by vitamin E supplementation. Vitamin E supplementation (100 mg/kg) significantly increased PGI2 concentration in young mice fed coconut oil. Thus, significant changes in the capacity of lung to synthesize eicosanoids occur with age and are influenced by dietary fat type and vitamin E. J. Nutr.     

Depressed prostanoid-induced contractility of the gut in spontaneously hypertensive rats (SHR) is not affected by the level of dietary fat

Dietary saturated fat (SF) has adverse effects on cardiac and vascular smooth muscle (VSM) contractility. Furthermore, VSM of spontaneously hypertensive rats (SHR) is overreactive to various biological stimuli. The aim of this study was to investigate the effects of increasing dietary fat as lard on gut contractility in SHR. Control Wistar-Kyoto (WKY) rats and SHR (13 wk old) were fed for 12 wk a diet containing 3% sunflower oil [low fat (LF), 3% total fat] or diets supplemented with 7% lard [medium fat (MF), 10% total fat] or 27% lard [high fat (HF), 30% total fat]. For ileal and colonic tissues (WKY and SHR), there was a lower total phospholipid PUFA (n-6)/(n-3) ratio with increased dietary SF (P < 0.003). For WKY, increasing SF led to lower levels of the major SCFA and lower total SCFA levels in cecal digesta (P < 0.01). This trend was evident in SHR but significant only for butyrate (P < 0.01). Contractility responses were unaltered in ileum. In colon, there was a change of sensitivity (50% effective concentration) to angiotensin II in WKY (P < 0.05) due to increased SF and a change of sensitivity to prostaglandin (PG)E(2) and carbachol in SHR (P < 0.05). When the 3 dietary groups were combined, there was lower sensitivity (P < 0.01) and lower maximal contraction (P < 0.05) in ileum and lower maximal contraction in colon of SHR in response to PGF(2alpha) (P < 0.05) and PGE(2) (P < 0.01) compared with WKY. Unlike (n-3) PUFA, dietary SF had little overall effect on gut contractility. However, this is the first report of a defect in PG responsiveness from gut tissue from hypertensive rats.     

Effect of dietary cholesterol in normolipidemic subjects is not modified by nature and amount of dietary fat

A double-blind, cross-over study of the effects of adding cholesterol to the diet, equal to about two egg yolks daily, was carried out in 25 men with an average plasma cholesterol of 5.3 mmol/L. There were no significant elevations in the mean plasma concentrations of cholesterol, low-density-lipoprotein cholesterol, or apolipoprotein B. The absence of an effect was seen against two background diets, one high in saturated fatty acids and the other modified in fat content and in fatty acid composition. Although the mean high-density-lipoprotein (HDL) cholesterol concentration did not change, the proportion of HDL2 particles (radius greater than 4.4 nm) increased significantly, especially in subjects who did not show a rise in plasma cholesterol; this may represent a means of clearing dietary cholesterol. The results suggest that reducing dietary cholesterol might be emphasized for hypercholesterolemic subjects rather than for the population generally.     

Promoting dietary change: demonstrating reduction of dietary fat

This short demonstration accomplishes several goals. People see where fat comes from and learn amounts needed to be removed. They practice substituting complex carbohydrate foods for fat. Most important, they learn that changing is not an "all-or-nothing" proposition. They can reduce dietary fat and still eat many of their favorite foods. This demonstration is a useful tool for nutrition educators who want to promote dietary change.     

Are dietary recommendations for dietary fat reduction achievable?

Despite several sets of dietary guidelines aimed at reducing fat intakes in the UK populations the actual fat intake in the UK has remained remarkably constant over the last decade. It is therefore of utmost importance to understand why the advice of the 1980s was not taken on board by the nation, to enable the achievement of current nutritional targets for dietary fat set for 2005. The nature of the diets of those individuals in the UK who have low fat intakes in line with the dietary goals are considered here, with the aim to increase our understanding of how the goals can be achieved in the free-living population. This paper postulates that a low fat diet will be easier to achieve, more palatable and hence more acceptable to the consumer if the dietary fat is replaced with a mixture of energy from sugar and starch. Further research is required to gain a greater understanding of what type of dietary composition will enable the free-living population to achieve a reduction in their dietary fat intake. This in turn will allow the dissemination of appropriate nutritional advice in the future and inform product development initiatives in the food industry.     

Health benefits of dietary fat reduction by a novel fat replacer: Mimix

The primary goals of this study were to identify any health benefits of the replacement of dietary fat with a novel fat replacer, Mimix, and to assure that the consumption of this fat replacer did not convey any deleterious health effects. Male, weanling, Fischer 344 rats were fed one of six diets containing between 5 and 20% w/w as fat for 8 weeks. These diets included two high fat diets (safflower oil or lard), a low fat diet and three diets where 15% of the fat in the high fat diets was replaced with various amounts of Mimix. When animals were fed a diet rich in saturated fat they consumed significantly more energy than other diet groups. When 15% saturated fat (lard) was replaced with safflower oil animals adjusted their food intake so that no difference in energy intake was observed between the high safflower diet and the low fat and Mimix diets. When the various Mimix fat replacements were compared to animals fed a high fat lard diet there was incomplete compensation of energy intake. Animals fed the high fat lard diet also had higher glucose and total serum cholesterol than their low fat and fat replacement counterparts. Feeding a high fat safflower oil diet to rats resulted in a significantly lower total serum cholesterol and serum triglyceride than all other diets. Replacement of dietary fat with Mimix demonstrated no deleterious effects on the heart, liver and intestinal tract that were all of normal weight, morphology and colour compared to other diet groups. Body composition analysis demonstrated that animals fed high fat diets had higher body fat mass at the expense of lean body mass. This was most obvious for animals fed high fat lard diets who had heavier epididymal fat pads. These data demonstrate that the replacement of dietary fat with the novel fat replacer Mimix can convey a number of health benefits in the absence of any deleterious effects.     

Health benefits of dietary fat reduction by a novel fat replacer: Mimix

The primary goals of this study were to identify any health benefits of the replacement of dietary fat with a novel fat replacer, Mimix, and to assure that the consumption of this fat replacer did not convey any deleterious health effects. Male, weanling, Fischer 344 rats were fed one of six diets containing between 5 and 20% w/w as fat for 8 weeks. These diets included two high fat diets (safflower oil or lard), a low fat diet and three diets where 15% of the fat in the high fat diets was replaced with various amounts of Mimix. When animals were fed a diet rich in saturated fat they consumed significantly more energy than other diet groups. When 15% saturated fat (lard) was replaced with safflower oil animals adjusted their food intake so that no difference in energy intake was observed between the high safflower diet and the low fat and Mimix diets. When the various Mimix fat replacements were compared to animals fed a high fat lard diet there was incomplete compensation of energy intake. Animals fed the high fat lard diet also had higher glucose and total serum cholesterol than their low fat and fat replacement counterparts. Feeding a high fat safflower oil diet to rats resulted in a significantly lower total serum cholesterol and serum triglyceride than all other diets. Replacement of dietary fat with Mimix demonstrated no deleterious effects on the heart, liver and intestinal tract that were all of normal weight, morphology and colour compared to other diet groups. Body composition analysis demonstrated that animals fed high fat diets had higher body fat mass at the expense of lean body mass. This was most obvious for animals fed high fat lard diets who had heavier epididymal fat pads. These data demonstrate that the replacement of dietary fat with the novel fat replacer Mimix can convey a number of health benefits in the absence of any deleterious effects.     

Level of dietary iron,not type of dietary fat,is hyperlipidemic in copper-deficient rats

OBJECTIVE: This study was conducted to determine whether high dietary iron will negate the protective effect of unsaturated fat against hyperlipidemia. METHODS: Forty-eight weanling, male Sprague Dawley rats were randomly assigned to eight dietary groups differing in the levels of copper and iron and type of dietary fat (saturated or unsaturated). The diets were either deficient (0.6 microg Cu/g) or adequate (6.8 microg Cu/g) copper and either adequate (53 microg Fe/g) or high (506 microg Fe/g) iron. All diets contained starch as the sole source of dietary carbohydrate. RESULTS: Regardless of the type of dietary fat, three copper-deficient rats fed the high levels of dietary iron died prematurely due to ruptured hearts. Surviving rats belonging to the copper deficiency and high-dietary iron regimen developed severe anemia, enlarged hearts and livers, and exhibited the highest levels of liver iron. These rats also developed hypercholesterolemia. Triglycerides were elevated by the consumption of high iron diets. CONCLUSION: Data show that levels of dietary iron, not the type of dietary fat, are potential inducers of hypertriglyceridemia. Data also show that the combination of high iron intake and dietary copper deficiency is responsible for elevating blood cholesterol.     

Impairment of cognitive performance in dietary restrained women when imagining eating is not affected by anticipated consumption

Dietary restraint is associated with impairments on tasks requiring concurrent processing of food-related information and performance of a secondary cognitive task. The aim of the present study was to investigate whether manipulating information about post-task consumption of food enhances the cognitive impairments observed in restrained eaters when they are required to think about food at the same time as performing a simple reaction time task. On separate trials within the same session, restrained (n=29) and unrestrained eaters (n=29) were asked to imagine eating a slice of chocolate cake and drinking glass of water while performing a simple reaction time task. Half the participants were told that they would not be able to consume the cues following the task, while the other half were told that they would be required to eat the cake and drink the water. The reaction time performance of restrained eaters was slowed when imagining eating the cake, relative to imagining drinking the water in both the consumption and no consumption conditions. No effects of cue exposure on reaction time were found for unrestrained eaters. The results suggest that dietary restrained eaters are more reactive to food cues but that this effect is not modulated by information about post-task consumption of the food.     

Association between dietary arginine and C-reactive protein

OBJECTIVE: We investigated whether a dietary intake of arginine is associated with risk for cardiovascular disease as determined by levels of C-reactive protein (CRP). METHODS: We analyzed the Third National Health Nutrition and Examination Survey, a national public-use dataset collected between 1988 and 1994. Arginine intake was calculated from the 24-h dietary recall using the nutrient composition database of the University of Minnesota Nutrition Coordinating Center. A logistic regression model was used to evaluate the relation between arginine intake and serum levels of CRP while controlling for age, sex, race, exercise, total caloric intake, body mass index, smoking status, diabetes, hypertension, and fiber intake. RESULTS: In the unadjusted model, the likelihoods of having a high level of CRP (>3.0 mg/L), from the lowest to the highest level of arginine intake, were 34.8%, 31.0%, 27.7%, and 18.4% respectively. Arginine intake below the median range was associated with higher levels of CRP (P < 0.05), and arginine intake above the median range was associated with lower levels of CRP (P < 0.05). In the adjusted regression, subjects in the highest level (90th percentile) of arginine intake were 30% less likely to have a CRP above 3.0 mg/L than were subjects with a median arginine intake (odds ratio= 0.70, 95% confidence interval = 0.56 to 0.88). CONCLUSIONS: The results of this study show a relation between arginine intake and CRP level that persisted after controlling for factors associated with CRP. Individuals may be able to lower their risk for cardiovascular disease by consuming more arginine-rich foods such as nuts and fish.     

The human cholesteryl ester transfer protein I405V polymorphism is associated with plasma cholesterol concentration and its reduction by dietary phytosterol esters

We examined the relationships of I405V cholesteryl ester transfer protein (CETP), Taq1B CETP and apolipoprotein (apo)E polymorphisms with the pattern of response to dietary plant sterol ester (PSE) by plasma lipids and CETP concentrations as well as lecithin-cholesterol acyltransferase (LCAT) activity. Subjects with moderate primary hypercholesterolemia (20-60 y old; 50 women; 10 men) consumed margarine (20 g/d) without (placebo) or with PSE (2.8 g/d = 1.68 g/d phytosterols) for 4 wk each period, in a crossover, double-blind study. Plasma CETP concentration was measured by ELISA; endogenous LCAT activity was expressed as the percentage of esterification (30 min incubation) of the subjects' (14)C-unesterified cholesterol HDL. PSE reduced concentrations of plasma total cholesterol (TC) (10%) and LDL cholesterol (LDL-C) (12%). In relation to the I405V CETP polymorphism, the percentage reductions in TC with consumption of PSE for the II, IV and VV phenotypes were 7.2, 4.2 and not significant, respectively, whereas LDL-C significant reductions occurred only for II (9.5%). However, the CETP concentration diminished only in the II phenotype.     

Splanchnic amino acid balance is affected by moderate variations of dietary protein in the developing Zucker rat

This study attempted to determine the influence of moderate chronic variations in dietary protein intake, on splanchnic amino acid balances. Two series of 30-day-old male lean (Fa/?) Zucker rats were fed ad libitum for 30 days with either a standard diet (reference diet: RD), a high-protein diet (HP) (35%) or a low-protein diet (LP) (9%). After 30 days of dietary treatment, blood was withdrawn from hepatic vein, portal vein and arterial aorta in one set of rats. In another series the splanchnic organ blood flows were determined using fluorescent microspheres. From the individual amino acid concentration in each sample and the blood flows, we calculated the intestinal and hepatic balances. There were no significant differences in the hepatic arterial, portal or supra-hepatic flows induced by dietary protein content. The RD group showed a marked intestinal uptake of Gln and Cit and a net release of Pro, Ala and Gly. The LP group showed the same pattern, with increased release of Ala and Gly. In contrast to this limited amino acid release, the HP group showed a generalized net release of amino acids from the intestine. The RD group only show a net Gln release from the liver. Conversely, the HP group showed net uptake of Gln, Pro, Ala, Tyr and Lys, and the LP group took up Gly and Ala and released Asn, Gln and Cit. Our results indicate that growing Zucker rats respond to long-term moderate changes in the protein intake, diminishing the growth pattern only in the LP group, but not in the HP group. In spite of the limited amino acid supply, the LP group followed a similar pattern of intestinal balance for Ala, Gln, Pro, Gly and Cit, as showed by the RD group. On the other hand, excess of dietary amino acids in the HP group seems to promote a lower utilization of Gln by intestine probably due to an increased release of Ala instead of Gln from peripheral tissues.     

Splanchnic amino acid balance is affected by moderate variations of dietary protein in the developing Zucker rat

This study attempted to determine the influence of moderate chronic variations in dietary protein intake, on splanchnic amino acid balances. Two series of 30-day-old male lean (Fa/?) Zucker rats were fed ad libitum for 30 days with either a standard diet (reference diet: RD), a high-protein diet (HP) (35%) or a low-protein diet (LP) (9%). After 30 days of dietary treatment, blood was withdrawn from hepatic vein, portal vein and arterial aorta in one set of rats. In another series the splanchnic organ blood flows were determined using fluorescent microspheres. From the individual amino acid concentration in each sample and the blood flows, we calculated the intestinal and hepatic balances. There were no significant differences in the hepatic arterial, portal or supra-hepatic flows induced by dietary protein content. The RD group showed a marked intestinal uptake of Gln and Cit and a net release of Pro, Ala and Gly. The LP group showed the same pattern, with increased release of Ala and Gly. In contrast to this limited amino acid release, the HP group showed a generalized net release of amino acids from the intestine. The RD group only show a net Gln release from the liver. Conversely, the HP group showed net uptake of Gln, Pro, Ala, Tyr and Lys, and the LP group took up Gly and Ala and released Asn, Gln and Cit. Our results indicate that growing Zucker rats respond to long-term moderate changes in the protein intake, diminishing the growth pattern only in the LP group, but not in the HP group. In spite of the limited amino acid supply, the LP group followed a similar pattern of intestinal balance for Ala, Gln, Pro, Gly and Cit, as showed by the RD group. On the other hand, excess of dietary amino acids in the HP group seems to promote a lower utilization of Gln by intestine probably due to an increased release of Ala instead of Gln from peripheral tissues.     

Association between dietary fiber and serum C-reactive protein

BACKGROUND: High sensitivity C-reactive protein (CRP) is a marker of acute inflammation recently recognized as an independent predictor of future cardiovascular disease and diabetes. The identification of modifiable factors, such as diet, that influence serum CRP concentrations may provide the means for reducing the risk of these diseases. Data on longitudinal associations between dietary fiber intake and CRP are currently lacking. OBJECTIVE: The purpose of this study was to examine longitudinal associations between dietary fiber intake and CRP. DESIGN: Data collection took place at baseline and quarterly (every 13 wk) thereafter for a total of 5 visits, each including measurements of body composition, CRP, diet, and physical activity. Relations between serum CRP and dietary fiber were assessed by using linear mixed models and logistic regression, adjusted for covariates. RESULTS: A total of 524 subjects had multiple measurements of CRP and dietary factors. The average total dietary fiber intake was 16.11 g/d. Average serum CRP was 1.78 mg/L. We observed an inverse association between intake of total dietary fiber (separately for soluble and insoluble fiber) and CRP concentrations in both cross-sectional and longitudinal analyses. The likelihood of elevated CRP concentrations was 63% lower (OR: 0.37; 95% CI: 0.16, 0.87) in participants in the highest quartile of total fiber intake than in participants in the lowest quartile. CONCLUSIONS: Our results suggest that dietary fiber is protective against high CRP, which supports current recommendations for a diet high in fiber.