Effect of texture preference on food texture perception: Exploring the role of matching food texture and preference.

This study aimed to investigate the influence of smooth texture preference on smoothness perception. An online questionnaire (Study 1, n = 464) and a sensory evaluation test (Study 2, n = 65) were administered to Japanese elderly participants (65-74 years), with common Japanese confectionery (Daifuku) as test foods. Through the online questionnaire, four distinct texture preference groups were formed based on the factors of preference for smoothness and firmness of the inner bean paste layer. Analysis of the food preference scale for imbalanced diet (FPSID) revealed that smooth-texture likers were more likely to be picky eaters than firm-texture likers. Furthermore, high (HiSm) and low smoothness preference groups (LoSm) were selected for the food sensory evaluation test to compare perceived textures (smoothness and firmness). Only the HiSm group exhibited a positive association between perceived smoothness and overall texture liking, perceiving smoothness significantly more intense than the LoSm group in situations where overall texture liking was high. This finding indicates that smooth texture preference does not act independently but rather interacts with food texture matching to affect perception. Our findings suggest that when food texture aligns with individuals' preferences, it elicits hedonic emotions and dynamically enhances food texture perception. This preference-involved perceptual process may contribute to the development of more explicit texture preferences.

Effects of Branched-Chain Amino Acids on Skeletal Muscle, Glycemic Control, and Neuropsychological Performance in Elderly Persons with Type 2 Diabetes Mellitus: An Exploratory Randomized Controlled Trial.

Although branched-chain amino acids (BCAA) are known to stimulate myofibrillar protein synthesis and affect insulin signaling and kynurenine metabolism (the latter being a metabolite of tryptophan associated with depression and dementia), the effects of BCAA supplementation on type 2 diabetes (T2D) are not clear. Therefore, a 24-week, prospective randomized open blinded-endpoint trial was conducted to evaluate the effects of supplementation of 8 g of BCAA or 7.5 g of soy protein on skeletal muscle and glycemic control as well as adverse events in elderly individuals with T2D. Thirty-six participants were randomly assigned to the BCAA group (n = 21) and the soy protein group (n = 15). Skeletal muscle mass and HbA1c, which were primary endpoints, did not change over time or differ between groups. However, knee extension muscle strength was significantly increased in the soy protein group and showed a tendency to increase in the BCAA group. Homeostasis model assessment for insulin resistance did not significantly change during the trial. Depressive symptoms were significantly improved in the BCAA group but the difference between groups was not significant. Results suggested that BCAA supplementation may not affect skeletal muscle mass and glycemic control and may improve depressive symptoms in elderly individuals with T2D.

Effects of a high-γ-polyglutamic acid-containing natto diet on liver lipids and cecal microbiota of adult female mice.

Natto is a traditional Japanese fermented soy product high in γ-polyglutamic acid (γ-PGA), whose beneficial effects have been reported. We prepared high-γ-PGA natto and compared the dietary influence on liver lipids and cecal microbiota in mice fed a diet containing it or a standard diet. The mice were served a 30% high-γ-PGA natto diet (PGA group) or standard diet (Con group) for 28 days. Liver lipids, fecal lipids, and fecal bile acids were quantified. Cecal microbiota were analyzed by PCR amplification of the V3 and V4 regions of 16S rRNA genes and sequenced using a MiSeq System. Additionally, the cecal short-chain fatty acid profile was assessed. The results revealed that the liver lipid and triglyceride contents were significantly lower (p<0.01) and amounts of bile acids and lipids in the feces were significantly higher in the PGA group than in the Con group. The cecal butyric acid concentration was observed to be significantly higher in the PGA group than in the Con group. Principal component analysis of the cecal microbiota revealed that the PGA and Con groups were distinct. The ratio of Firmicutes/Bacteroidetes was found to be significantly low in the PGA mice. The results revealed a significantly higher relative abundance of Lachnospiraceae (p<0.05) and significantly lower relative abundance of Coriobacteriaceae (p<0.01) in the PGA group. Analysis of the correlation between bacterial abundance and liver lipids, cecal short-chain fatty acids, fecal lipids, and fecal bile acids suggested that intestinal microbiota can be categorized into different types based on lipid metabolism. Hepatic lipid accumulation typically facilitates the onset of nonalcoholic fatty liver disease (NAFLD). Our findings suggest that high-γ-PGA natto is a beneficial dietary component for the prevention of NAFLD.

Differences in the Effects of Anthocyanin Supplementation on Glucose and Lipid Metabolism According to the Structure of the Main Anthocyanin: A Meta-Analysis of Randomized Controlled Trials.

The effectiveness of anthocyanins may differ according to their chemical structures; however, randomized clinical controlled trials (RCTs) or meta-analyses that examine the consequences of these structural differences have not been reported yet. In this meta-analysis, anthocyanins in test foods of 18 selected RCTs were categorized into three types: cyanidin-, delphinidin-, and malvidin-based. Delphinidin-based anthocyanins demonstrated significant effects on triglycerides (mean difference (MD): -0.24, p < 0.01), low-density lipoprotein cholesterol (LDL-C) (MD: -0.28, p < 0.001), and high-density lipoprotein cholesterol (HDL-C) (MD: 0.11, p < 0.01), whereas no significant effects were observed for cyanidin- and malvidin-based anthocyanins. Although non-significant, favorable effects on total cholesterol (TC) and HDL-C were observed for cyanidin- and malvidin-based anthocyanins, respectively (both p < 0.1). The ascending order of effectiveness on TC and LDL-C was delphinidin-, cyanidin-, and malvidin-based anthocyanins, and the differences among the three groups were significant (both p < 0.05). We could not confirm the significant effects of each main anthocyanin on glucose metabolism; however, insulin resistance index changed positively and negatively with cyanidin- and delphinidin-based anthocyanins, respectively. Therefore, foods containing mainly unmethylated anthocyanins, especially with large numbers of OH groups, may improve glucose and lipid metabolism more effectively than those containing methylated anthocyanins.

Effects of Continuous Intake of Rosemary Extracts on Mental Health in Working Generation Healthy Japanese Men: Post-Hoc Testing of a Randomized Controlled Trial.

We previously performed a 4 week interventional trial that suggested that continuous intake of rosemary extract improves the mood states, fatigue, and cognitive function of working generation healthy adult Japanese men. However, the severity of depression in participants in our previous study was relatively mild. Therefore, in the present study, a post-hoc analysis of our previous study was conducted, limited to participants whose total mood disturbance (TMD) scores, which indicate greater mood disturbance, were above the median at baseline, to evaluate whether rosemary extract was effective for individuals with poor mental health. Following the intervention, the scores of TMD and "Confusion-Bewilderment" were significantly decreased (both p < 0.05), and scores of "Vigor-Activity" were significantly increased in the rosemary group (n = 8) compared with those in the control group (n = 13; p < 0.01). When comparing the scores from pre- and post-intervention, significant improvements in "Tension-Anxiety", "Vigor-Activity", "Fatigue on awakening", "Daytime sleepiness", and "Psychomotor speed" were observed in the rosemary group only (all p < 0.05). Based on these results, it was expected that rosemary extracts were effective for improving the mental energy and sleep quality of work-age men with poor mental health.

Gamma-Polyglutamic Acid-Rich Natto Suppresses Postprandial Blood Glucose Response in the Early Phase after Meals: A Randomized Crossover Study.

We evaluated the suppressive effects of high-gamma-polyglutamic acid (γ-PGA) natto on postprandial blood glucose level and insulin response. After confirming the eligibility of candidates using a pre-selective test with packaged white rice, a meal loading test including low- or high-γ-PGA natto (with 57.6 mg (LPGA) and 439.6 mg (HPGA) of γ-PGA, respectively) was conducted in men aged 20 to 70 years (n = 29) and postmenopausal women aged ≤70 years (n = 7). On each examination day, blood samples were obtained after they fasted overnight and for 120 min after test meal loading. The primary outcome of this study was the difference between the measurements of the incremental area under the curve (IAUC) for blood glucose 0 to 30 min after loading of LPGA and HPGA meals. The IAUCs for blood glucose and insulin after the HPGA meal were lower than those after the LPGA meal within 45 min (0 to 15 and 0 to 30 min: p < 0.001, 0 to 45 min: p < 0.01) and 1 h (all p < 0.001) of loading, respectively. The suppressive effects of HPGA natto on postprandial glucose response in the early phase, which possibly relates to the risk of dysglycemia and cardiovascular disease, were clarified.

The Possibility of Suppression of Increased Postprandial Blood Glucose Levels by Gamma-Polyglutamic Acid-Rich Natto in the Early Phase after Eating: A Randomized Crossover Pilot Study.

The natto containing high levels of gamma-polyglutamic acid (γ-PGA) was recently developed. We investigated the effect of γ-PGA-rich natto consumption on postprandial glycemic excursion in humans. A randomized crossover meal test study was performed on healthy volunteers aged 20-64 years using the following test meals: (1) white rice (WR), (2) low-γ-PGA natto meal (WR + low-γ-PGA natto), and (3) high-γ-PGA natto meal (WR + high-γ-PGA natto). Blood samples were obtained at each visit before and for 120 min after loading. The incremental area under the curve (IAUC) of blood glucose and insulin levels was calculated and compared among the test meals. The blood glucose's IAUC at 0-120 min, the primary endpoint, was 20.1% and 15.4% lower for the high- and low-γ-PGA natto meal than for the WR, with a significant difference only between the high-γ-PGA natto meal and WR (p < 0.05). The blood glucose's IAUC at 0-15, 0-30, and 0-45 min was lower for the high-γ-PGA natto meal than for the low-γ-PGA natto meal (all p < 0.05). The possibility that high-γ-PGA natto might suppress blood glucose elevations in the early phase after eating is indicated.

Prescription of potentially inappropriate medications in elderly outpatients: a survey using 2015 Japanese Guidelines.

Background In recent years, rapid increase of elderly population has become a major social problem in developed countries. They tend to receive an increasing number of prescibed drugs due to multiple illnesses, which might include inappropriate medications, in turn leading to health hazards and rising healthcare cost. Objective To evaluate the current status of potentially inappropriate medications prescribed for elderly outpatients and filled by dispensing pharmacies using the recent Japanese Guidelines, and to determine factors that are related to prescribing potentially inappropriate medications. Setting A cross-sectional study of older patients (≥ 75 years) who visited dispensing pharmacies in the Ibaraki Prefecture, Japan. Method We identified patients prescribed potentially inappropriate medications using the "List of Medications that Require Particularly Careful Administration" in the Guidelines (Guideline List). We explored patient's factors related to polypharmacy (≥ 5 medications) and prescription of inappropriate medications through multivariate analysis, and a cutoff value for predicting potentially inappropriate medications through receiver operating characteristic curve analysis. Main outcome measure Prevalence of polypharmacy and potentially inappropriate medications, and patient's factors associated with them. Results Of 8080 patients (39,252 medications) who visited pharmacies during the study period, 43.1% (3481) were prescribed ≥ 5 medications. In total, 2157 patients (26.7%) were prescribed at least one potentially inappropriate medication. The most prescribed inappropriate medication class was (benzodiazepine) sedatives and hypnotics. Potentially inappropriate medications were 7.11 times (95% CI 6.29-8.03) and 1.51 times (1.34-1.71) more likely to be prescribed for patients with ≥ 5 medications and those prescribed by multiple physicians, respectively. A cutoff value for potentially inappropriate medications was found to be five for the total number of medications and four for the number of chronic medications with a systemic effect. Conclusion Prescription of potentially inappropriate medications was increased among patients with ≥ 5 medications and those chronically prescribed ≥ 4 medications with a systemic effect. The Guideline List should be actively used to screen such patients, and to carefully examine prescriptions. Particular care should be exercised when patients are visiting multiple physicians.

Olive leaf tea is beneficial for lipid metabolism in adults with prediabetes: an exploratory randomized controlled trial.

Olive leaves are rich in oleuropein, which has been shown to have beneficial effects on dyslipidemia, type 2 diabetes, and obesity. However, we previously found no significant health benefits of olive leaf tea (OLT) on nonobese and nondiabetic individuals. Thus, we performed this study to further explore the health benefits of OLT in individuals with prediabetes and compare the health benefits between low-concentration OLT (LOLT) and OLT. We hypothesized that OLT will have a more pronounced effect on abdominal obesity as well as glucose and lipid metabolism in prediabetic individuals. Individuals between 40 and 70 years of age with a body mass index of 23.0-29.9 kg/m2 and prediabetes status were recruited and randomly assigned to the OLT or the LOLT group. The intervention, which was the consumption of 330 mL of the test beverage 3 times daily during mealtime, lasted for 12 weeks. After the intervention, serum levels of log-transformed triglycerides (P < .05) and low-density lipoprotein cholesterol (P < .01) decreased significantly in the OLT group (n = 28), with the reductions higher in the OLT group than those in the LOLT group (n = 29, log-transformed triglycerides: P = .079, low-density lipoprotein cholesterol: P < .05). Whereas body weight, waist circumference, and insulin levels were not significantly changed in both groups, fasting plasma glucose levels in the OLT group were significantly decreased compared to those in the LOLT group (P < .05). In conclusion, although the effect of OLT on abdominal obesity and glucose metabolism remains unclear, OLT has been found to have lipid-lowering effects.

[Analysis of Nedaplatin Dose in Patients with Impaired Renal Function].

Nedaplatin(NDP)is a platinum derivative anticancer drug.An NDP dose of 100mg/m2 every 4 weeks is recommended in non-elderly Japanese patient because a higher dose may lead to myelosuppression, such as thrombocytopenia.In a pharmacokinetic analysis, thrombocytopenia was significantly correlated with renal function.However, the correct dose in patients with impaired renal function remains unclear.To evaluate the usefulness of dose reduction in patients with renal dysfunction, we conducted a retrospective study.This study included Japanese solid cancer patients who received NDP monotherapy in Nagoya University Hospital between April 2011 and March 2014. Eighty three patients were evaluated and divided into 2 groups based on renal function: a creatinine clearance(Ccr; mL/min)≥60 group and a Ccr<60 group.The frequency of B Grade 3 thrombocytopenia and neutropenia was significantly higher in the Ccr<60 group than that in the Ccr≥60 group (3.4% vs 32.0%; p=0.001 and 6.8% vs 32.0%; p=0.005, respectively).In the Ccr<60 group, the frequency of BGrade 3 thrombocytopenia and neutropenia was lower in the reduced dose group than that in standard dose(100mg/m2)group (41.7% vs 23.1%; p=0.410 and 41.7% vs 23.1%; p=0.410, respectively).A multiple logistic regression analysis revealed that NDP dose and serum creatinine were risk factors for the incidence of BGrade 3 thrombocytopenia and neutropenia.These results suggest that NDP dose should be reduced to achieve safe drug treatment in patients with Ccr<60.

Incidence of and risk factors associated with nedaplatin-related hypersensitivity reactions.

BACKGROUND: Nedaplatin (NDP)-related hypersensitivity reactions (HSRs) trigger adverse clinical events. Prediction and prevention of NDP-HSRs are thus essential to minimize the risk and maximize the benefit of NDP therapy. However, the incidence of NDP-HSRs and the associated risk factors remain unclear. METHODS: We retrospectively examined patients who received NDP monotherapy between April 2011 and July 2015 in Nagoya University Hospital. HSRs severity was defined according to the Common Terminology Criteria for Adverse Events version 4 (CTCAE ver.4). Risk factors for NDP-HSRs were determined using multivariate logistic regression. RESULTS: Of 111 patients who received NDP monotherapy, 90 (81%) were female; median age was 59 years (range, 29-78 years). Eighty-eight patients had gynecological cancer and 20 suffered from head and neck cancer. Eight of 111 patients (7.2%) experienced NDP-HSRs, six of which developed in the second NDP cycle. However, all patients with NDP-HSRs were treated with carboplatin (CBDCA) for more than three cycles. Grade 3 and 4 HSRs developed in 2 patients. NDP-HSRs were significantly associated with a history of CBDCA-HSRs (odds ratio 37.5, 95% confidence interval 5.38-262, p < 0.001) and with the interval between NDP administration and the previous platinum treatment (odds ratio 13.9, 95% confidence interval 1.23-158, p = 0.034). CONCLUSION: The risk of NDP-HSRs increases in patients with a history of CBDCA-HSRs and in those administered NDP for more than 6 months after previous platinum treatment. Such individuals must be closely monitored if given NDP, even if they are expected to benefit from the treatment.

Postprandial Paraoxonase 1 Activity Following Consumption of Recommended Amounts of Mixed Meals in Healthy Males.

AIM: Postprandial lipid level increases induce oxidative stress, which is involved in atherogenesis. The antioxidant properties of paraoxonase 1 (PON1) have attracted attention. However, changes in postprandial PON1 levels differ across prior studies, and changes in PON1 lactonase activity, potentially relevant to PON1 physiology, after the consumption of ordinary meals are unknown. Herein we evaluated postprandial serum lipid levels and PON1 changes following mixed-meal consumption of the amounts recommended for ordinary meals. METHODS: Nine healthy male volunteers consumed three different meals in a randomized cross-over design. The test meals were as follows: S, white rice; SMF, S with fat-containing protein-rich main dishes; and SMFV: SMF with vegetable dishes. The serum lipid concentrations and PON1 lactonase and arylesterase activities were determined during a three-hour period after the consumption of these meals. RESULTS: The postprandial triglyceride levels were higher after consuming the SMF and SMFV meals than after consuming the S meal. Despite postprandial high-density lipoprotein cholesterol being unchanged, PON1 lactonase activity was decreased, while PON1 arylesterase activity was increased in the postprandial state after all test meals. Postprandial changes in lactonase and arylesterase activities did not differ among the test meals. CONCLUSIONS: Inverse changes in PON1 lactonase and arylesterase activities were observed after consuming recommended ordinary meals. This observation provides useful information for choosing PON1 species as postprandial markers.

Effects of consumption of main and side dishes with white rice on postprandial glucose, insulin, glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 responses in healthy Japanese men.

The co-ingestion of protein, fat and fibre with carbohydrate reportedly affects postprandial glucose, insulin and incretin (glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1)) responses. However, the effects of combination dishes with carbohydrate-rich foods at typically eaten amounts remain unclear. The objective of the present study was to evaluate the effects of consuming recommended amounts of side dishes with boiled white rice in the same meal on postprandial plasma glucose, insulin and incretin hormone responses. A total of nine healthy male volunteers consumed four different meals in a random order on separate days. The test meals were as follows: S, white rice; SM, addition of protein-rich main dishes to the S meal; SMF, addition of a fat-rich food item to the SM meal; SMFV, addition of vegetables to the SMF meal. Plasma glucose, GIP and GLP-1 and serum insulin concentrations were determined during a 3 h period after consumption of these meals. Postprandial glucose responses were lower after SMFV meal consumption than after consumption of the other meals. The incremental AUC for GIP (0-180 min) were largest after consumption of the SMF and SMFV meals, followed by that after SM meal consumption, and was smallest after S meal consumption (P< 0·05). Furthermore, we found GIP concentrations to be dose dependently increased by the fat content of meals of ordinary size, despite the amount of additional fat being small. In conclusion, the combination of recommended amounts of main and vegetable side dishes with boiled white rice is beneficial for lowering postprandial glucose concentrations, with an increased incretin response, when compared with white rice alone.

Effects of green-leafy vegetable intake on postprandial glycemic and lipidemic responses and α-tocopherol concentration in normal weight and obese men.

Vegetable consumption has been encouraged as a component of nutritional education for obese and insulin-resistant patients. However, the benefits of vegetable intake in a therapeutic diet on postprandial glycemic and lipidemic responses have not been clarified. We studied the effects of the intake of spinach, a green-leafy vegetable rich in dietary fiber and α-tocopherol, with a fat-rich meal on postprandial glycemic and lipidemic changes. Fourteen normal weight and 10 obese men consumed three test meals of bread, as a control, bread and butter, and bread and butter with boiled spinach. Blood samples were obtained prior to and 30, 60, 120, 180 and 240 min after consuming the test meals. Compared with the bread meal, consumption of the bread and butter meal showed a reduced peak glucose response at 30 min in normal (p<0.05) but not in obese subjects. The increase in triglyceride and decrease in LDL-cholesterol were greater after the butter-containing meal than after the bread meal (p<0.05). The α-tocopherol/lipid level decreased and remained low after the bread and butter meal, but the decrease was smaller with the spinach-containing meal in obese subjects (p<0.05). These results suggest that green-leafy vegetable intake with a fat-rich meal is effective for supplying postprandial α-tocopherol in obese subjects, but consumption of a regular-sized dish cannot be expected to improve abnormal postprandial hyperglycemic or hyperlipidemic responses.

HMW-adiponectin associates with triglyceride concentrations in type 1 diabetic patients.

AIM: The objective of this study was to investigate the relation between serum high molecular weight (HMW)-adiponectin concentration and fasting and postprandial blood glycemic and lipid parameters in type 1 diabetic patients. METHODS: Type 1 diabetic patients treated with short-acting insulin analogs and healthy volunteers were recruited. The subjects were divided into two groups based on the mean HMW-adiponectin value of 12.2 mg/L: low HMW-adiponectin (men/women=7/2) and high HMW-adiponectin (men/women=3/8). Blood samples were collected after an overnight fast, and 30180 min after consuming white bread (B) or white bread with butter (BB). RESULTS: Type 1 diabetic patients with high HMW-adiponectin had lower triglyceride and remnant like particle (RLP)-triglyceride concentrations than those with low HMW-adiponectin (p<0.01), and had a higher lipoprotein lipase mass (p<0.01) than healthy subjects (men/women=8/6). After B and BB meals, type 1 diabetic patients with high HMW-adiponectin consistently had lower triglyceride and RLP-triglyceride concentrations for up to 180 min than those with low HMW-adiponectin (p<0.01); however, apoB48 did not differ between these two groups. Fasting and postprandial plasma glucose were higher in both diabetic groups than in healthy subjects (p<0.001), with no significant difference between patient groups. CONCLUSION: HMW-adiponectin is more strongly associated with very low density lipoprotein remnant metabolism than glucose utilization in type 1 diabetic patients receiving short-acting insulin analogs.

Differences in serum phospholipid fatty acid compositions and estimated desaturase activities between Japanese men with and without metabolic syndrome.

AIM: This study was designed to clarify differences in serum phospholipid fatty acid compositions and estimated desaturase activities between Japanese men with and without metabolic syndrome (MetS). METHODS: From among 227 males, 40 to 59 years of age, excluding those receiving treatment for lipid disorders, 165 subjects (including 27 with MetS) were selected for this study. Serum phospholipid fatty acid compositions were determined, and desaturase activities were estimated. RESULTS: The C15:0 and C17:0 fatty acids associated with hepatic function were lower, while the C20:3n-6 and C20:4n-3 fatty acids were higher, in subjects with than without MetS (p<0.05). The estimated desaturase activity for D5D(n-6) was lower in subjects with than without MetS (p<0.01). Body fat percentage was an independent negative predictor of C17:0, and a positive predictor of log C20:3n-6 and log C20:4n-3 (p<0.01). HDL-C was an independent negative predictor of log C15:0 and of C17:0 (p<0.01). CONCLUSION: Decreases in minor saturated fatty acids, accumulation of C20:3n-6 and C20:4n-3 and low estimated D5D activity were confirmed to be associated with MetS.

Azuki bean juice lowers serum triglyceride concentrations in healthy young women.

Effects of azuki bean juice supplementation, prescribed according to a Kanpo medicine regimen, on serum lipid concentrations were studied. Healthy young Japanese women were recruited and were randomly assigned to one of the three groups using a parallel-group design. Control (n = 10), azuki (n = 11) and Concentrated azuki (CA) (n = 12) juice groups consumed 150 g daily of the isocaloric assigned juice for one menstrual cycle with their usual diet. Triglyceride concentrations were decreased in the azuki juice group (p<0.05) and tended to be decreased in the CA juice group (p = 0.055). Triglyceride concentrations in the azuki and CA juice groups decreased by 0.170 mmol/liter (15.4%) and 0.159 mmol/liter (17.9%), respectively (p<0.05). The azuki and CA juice used in this study inhibited pancreatic lipase activity 29.2% and 56.9%, respectively, in vitro. Lipid peroxide changes, based on ANCOVA with the initial level and alpha-tocopherol changes as covariates, did not differ among the three groups. Serum low density lipoprotein-cholesterol and high density lipoprotein-cholesterol (HDL) cholesterol concentrations did not change. Thus, azuki bean juice intake, as a traditional Kampo prescription, might be beneficial for preventing hypertriglyceridemia.

Low folate status increases chromosomal damage by X-ray irradiation.

PURPOSE: To examine how folate status influences chromosomal damage following X-ray irradiation. MATERIAL AND METHODS: In an animal study, mice were fed either a low, basal, or high folic acid diet (0, 2, or 40 mg/kg diet, respectively) for 4 weeks, and then given total body irradiation (TBI) at 0.5 Gy. In a human study, subjects were supplemented with folic acid (800 microg/day) for 2 weeks and their peripheral blood was irradiated at 0.5 Gy in vitro. Chromosomal damage was determined by micronucleus assay. RESULTS: In an animal study, TBI-induced chromosomal damage was higher and folate concentration was lower in the bone marrow of the low folic acid group compared to the other two diet groups. The chromosomal damage and folate concentration were comparable between the basal and high folic acid groups. TBI administered to mice decreased folate in the plasma, erythrocyte and bone marrow. In a human study, supplementation with folic acid increased plasma folate, but did not influence either plasma homocysteine or X-ray-induced chromosomal damage in lymphocytes. CONCLUSION: Low folate status increases susceptibility to X-ray-induced chromosomal damage, but excessive folic acid supplementation under normal conditions yields no further protection due to folate saturation in the target tissue.

Relationships of nutrient intake and lifestyle-related factors to serum folate and plasma homocysteine concentrations in 30-69 year-old Japanese.

We studied non-hospitalized 30-69 y-old Japanese subjects to ascertain the influences of a 677C-T methylene-tetrahydrofolate reductase (MTHFR) genotype, nutritional intake and lifestyle-related factors on plasma homocysteine (Hcys) and serum folate concentrations. Hcys was higher and serum folate was lower in males than in females (p < .01). The Hcys concentration was higher in the VV group than in the AA and AV groups for both males and females. However, a relatively low serum folate concentration of 18 +/- 7 nmol/L was found in the entire male group as compared with 22 +/- 10 nmol/L in all females. In the female subjects, serum folate concentrations differed among MTHFR genotypes, being lowest in the VV group. In all male subjects, log folate intake per 1,000 kcal was a significant positive predictor of log serum folate concentration (p < 0.01), while in females the log vitamin C intake per standard body weight was a significant positive variable (p < 0.001) predicting the log serum folate concentration. Smokers had significantly lower serum folate concentrations, regardless of dietary folate intake. High folate and vitamin C consumptions, appears to be beneficial to normal and heterozygous MTHFR genotype subjects for maintaining serum folate concentrations. Even a 400 microg daily intake of folate might be less than what is needed, especially for homozygous MTHFR subjects and smokers, to maintain an adequate serum folate concentration.