Effects of vitamin E and alpha-lipoic acid on skeletal muscle contractile properties

Initial experiments were conducted using an in situ rat tibialis anterior (TA) muscle preparation to assess the influence of dietary antioxidants on muscle contractile properties. Adult Sprague-Dawley rats were divided into two dietary groups: 1) control diet (Con) and 2) supplemented with vitamin E (VE) and alpha -lipoic acid (alpha -LA) (Antiox). Antiox rats were fed the Con rats' diet (AIN-93M) with an additional 10,000 IU VE/kg diet and 1.65 g/kg alpha -LA. After an 8-wk feeding period, no differences existed (P > 0.05) between the two dietary groups in maximum specific tension before or after a fatigue protocol or in force production during the fatigue protocol. However, in unfatigued muscle, maximal twitch tension and tetanic force production at stimulation frequencies less than or equal to 40 Hz were less (P < 0.05) in Antiox animals compared with Con. To investigate which antioxidant was responsible for the depressed force production, a second experiment was conducted using an in vitro rat diaphragm preparation. Varying concentrations of VE and dihydrolipoic acid, the reduced form of -LA, were added either individually or in combination to baths containing diaphragm muscle strips. The results from these experiments indicate that high levels of VE depress skeletal muscle force production at low stimulation frequencies.

Kidney dysfunction and hypertension: Role for cadmium, P450 and heme oxygenases?

Cadmium (Cd) is a metal toxin of continuing worldwide concern. Daily intake of Cd, albeit in small quantities, is associated with a number of adverse health effects which are attributable to distinct pathological changes in a variety of tissues and organs. In the present review, we focus on its renal tubular effects in people who have been exposed environmentally to Cd at levels below the provisional tolerable intake level set for the toxin. We highlight the data linking such low-level Cd intake with tubular injury, altered abundance of cytochromes P450 (CYPs) in the kidney and an expression of a hypertensive phenotype. We provide updated knowledge on renal and vascular effects of the eicosanoids 20-hydroxyeicosatetraenoic acid (20-HETE) and eicosatrienoic acids (EETs), which are biologically active metabolites from arachidonate metabolism mediated by certain CYPs in the kidney. We note the ability of Cd to elicit oxidative stress and to alter metal homeostasis notably of zinc which may lead to augmentation of the defense mechanisms involving induction of the antioxidant enzyme heme oxygenase-1 (HO-1) and the metal binding protein metallothionein (MT) in the kidney. We hypothesize that renal Cd accumulation triggers the host responses mediated by HO-I and MT in an attempt to protect the kidney against injurious oxidative stress and to resist a rise in blood pressure levels. This hypothesis predicts that individuals with less active HO-1 (caused by the HO-1 genetic polymorphisms) are more likely to have renal injury and express a hypertensive phenotype following chronic ingestion of low-level Cd, compared with those having more active HO-1. Future analytical and molecular epidemiologic research should pave the way to the utility of induction of heme oxygenases together with dietary antioxidants in reducing the risk of kidney injury and hypertension in susceptible people.

Evaluation of brief dietary questions to estimate vegetable and fruit consumption - using serum carotenoids and red-cell folate

Objective: To evaluate responses to self-administered brief questions regarding consumption of vegetables and fruit by comparison with blood levels of serum carotenoids and red-cell folate. Design: A cross-sectional study in which participants reported their usual intake of fruit and vegetables in servings per day, and serum levels of five carotenoids (alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein/zeaxanthin and lycopene) and red-cell folate were measured. Serum carotenoid levels were determined by high-performance liquid chromatography, and red-cell folate by an automated immunoassay system. Settings and subjects: Between October and December 2000, a sample of 1598 adults aged 25 years and over, from six randomly selected urban centres in Queensland, Australia, were examined as part of a national study conducted to determine the prevalence of diabetes and associated cardiovascular risk factors. Results: Statistically significant (P < 0.01) associations with vegetable and fruit intake ( categorised into groups: = 4 servings per day) were observed for alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein/zeaxanthin and red-cell folate. The mean level of these carotenoids and of red-cell folate increased with increasing frequency of reported servings of vegetables and fruit, both before and after adjusting for potential confounding factors. A significant association with lycopene was observed only for vegetable intake before adjusting for confounders. Conclusions: These data indicate that brief questions may be a simple and valuable tool for monitoring vegetable and fruit intake in this population.

Development of a dietary supplement database

Data describing the composition of dietary supplements are not readily available to the public health community. As a result, intake from dietary supplements is generally not considered in most dietary surveys and, hence, little is known about the significance of supplement intake in relation to total diet or disease risk. To enable a more comprehensive analysis of dietary data, a database of the composition of various dietary supplements has been compiled. Active ingredients of all dietary supplements sold in Australia are included in the Australian Register of Therapeutic Goods (ARTG), maintained by the Therapeutic Goods Administration. Products included in the database were restricted to those vitamin, mineral and other supplements identified in dietary data collected from studies conducted in southeast Queensland and New South Wales (850 supplements). Conversion factors from ingredients compounds to active elements were compiled from standard sources. No account has been made for bioavailability, consistent with current practice for food composition databases. The database can be queried by ARTG identification number, brand, product title, or a variety of other fields. Expected future developments include development of standard formulations for use when supplements are incompletely specified, and expansion of products included for more widespread use.

Effect of combined supplementation with vitamin E and alpha-lipoic acid on myocardial performance during in vivo ischaemia-reperfusion

Reactive oxygen species (ROS) contribute significantly to myocardial ischaemia-reperfusion (I-R) injury. Recently the combination of the antioxidants vitamin E (VE) and alpha-lipoic acid (alpha-LA) has been reported to improve cardiac performance and reduce myocardial lipid peroxidation during in vitro I-R. The purpose of these experiments was to investigate the effects of VE and alpha-LA supplementation on cardiac performance, incidence of dysrhythmias and biochemical alterations during an in vivo myocardial I-R insult. Female Sprague-Dawley rats (4-months old) were assigned to one of the two dietary treatments: (1) control diet (CON) or (2) VE and alpha-LA supplementation (ANTIOXID). The CON diet was prepared to meet AIN-93M standards, which contains 75 IU VE kg(-1) diet. The ANTIOXID diet contained 10 000 IU VE kg(-1) diet and 1.65 g alpha-LA kg(-1) diet. After the 14-week feeding period, significant differences (P < 0.05) existed in mean myocardial VE levels between dietary groups. Animals in each experimental group were subjected to an in vivo I-R protocol which included 25 min of left anterior coronary artery occlusion followed by 10 min of reperfusion. No group differences (P > 0.05) existed in cardiac performance (e.g. peak arterial pressure or ventricular work) or the incidence of ventricular dysrhythmias during the I-R protocol. Following I-R, two markers of lipid peroxidation were lower (P < 0.05) in the ANTIOXID animals compared with CON. These data indicate that dietary supplementation of the antioxidants, VE and alpha-LA do not influence cardiac performance or the incidence of dysrhythmias but do decrease lipid peroxidation during in viva I-R in young adult rats.

Dietary trends: Estimates from food supply and survey data

Objective: To illustrate methodological issues involved in estimating dietary trends in populations using data obtained from various sources in Australia in the 1980s and 1990s. Methods: Estimates of absolute and relative change in consumption of selected food items were calculated using national data published annually on the national food supply for 1982-83 to 1992-93 and responses to food frequency questions in two population based risk factor surveys in 1983 and 1994 in the Hunter Region of New South Wales, Australia. The validity of estimated food quantities obtained from these inexpensive sources at the beginning of the period was assessed by comparison with data from a national dietary survey conducted in 1983 using 24 h recall. Results: Trend estimates from the food supply data and risk factor survey data were in good agreement for increases in consumption of fresh fruit, vegetables and breakfast food and decreases in butter, margarine, sugar and alcohol. Estimates for trends in milk, eggs and bread consumption, however, were inconsistent. Conclusions: Both data sources can be used for monitoring progress towards national nutrition goals based on selected food items provided that some limitations are recognized. While data collection methods should be consistent over time they also need to allow for changes in the food supply (for example the introduction of new varieties such as low-fat dairy products). From time to time the trends derived from these inexpensive data sources should be compared with data derived from more detailed and quantitative estimates of dietary intake.

Evaluation of short dietary questions from the 1995 National Nutrition Survey

Six of the short dietary questions used in the 1995 National Nutrition Survey (see box below) were evaluated for relative validity both directly and indirectly and for consistency, by documenting the differences in mean intakes of foods and nutrients as measured on the 24-hour recall, between groups with different responses to the short questions. 1. Including snacks, how many times do you usually have something to eat in a day including evenings? 2. How many days per week do you usually have something to eat for breakfast? 3. In the last 12 months, were there any times that you ran out of food and couldn’t afford to buy more? 4. What type of milk do you usually consume? 5. How many serves of vegetables do you usually eat each day? (a serve = 1/2 cup cooked vegetables or 1 cup of salad vegetables) 6. How many serves of fruit do you usually eat each day? (a serve = 1 medium piece or 2 small pieces of fruit or 1 cup of diced pieces) These comparisons were made for males and females overall and for population sub-groups of interest including: age, socio-economic disadvantage, region of residence, country of birth, and BMI category. Several limitations to this evaluation of the short questions, as discussed in the report, need to be kept in mind including: · The method for comparison available (24-hour recall) was not ideal (gold standard); as it measures yesterday’s intake. This limitation was overcome by examining only mean differences between groups of respondents, since mean intake for a group can provide a reasonable approximation for ‘usual’ intake. · The need to define and identify, post-hoc, from the 24-hour recall the number of eating occasions, and occasions identified by the respondents as breakfast. · Predetermined response categories for some of the questions effectively limited the number of categories available for evaluation. · Other foods and nutrients, not selected for this evaluation, may have an indirect relationship with the question, and might have shown stronger and more consistent responses. · The number of responses in some categories of the short questions eg for food security may have been too small to detect significant differences between population sub-groups. · No information was available to examine the validity of these questions for detecting differences over time (establishing trends) in food habits and indicators of selected nutrient intakes. By contrast, the strength of this evaluation was its very large sample size, (atypical of most validation studies of dietary assessment) and thus, the opportunity to investigate question performance in a range of broad population sub-groups compared with a well-conducted, quantified survey of intakes. The results of the evaluation are summarised below for each of the questions and specific recommendations for future testing, modifications and use provided for each question. The report concludes with some general recommendations for the further development and evaluation of short dietary questions.

Dietary fat intake and risk of type 2 diabetes in women

Background: The long-term relations between specific types of dietary fat and risk of type 2 diabetes remain unclear. Objective: Our objective was to examine the relations between dietary fat intakes and the risk of type 2 diabetes. Design: We prospectively followed 84204 women aged 34–59 y with no diabetes, cardiovascular disease, or cancer in 1980. Detailed dietary information was assessed at baseline and updated in 1984, 1986, and 1990 by using validated questionnaires. Relative risks of type 2 diabetes were obtained from pooled logistic models adjusted for nondietary and dietary covariates. Results: During 14 y of follow-up, 2507 incident cases of type 2 diabetes were documented. Total fat intake, compared with equivalent energy intake from carbohydrates, was not associated with risk of type 2 diabetes; for a 5% increase in total energy from fat, the relative risk (RR) was 0.98 (95% CI: 0.94, 1.02). Intakes of saturated or monounsaturated fatty acids were also not significantly associated with the risk of diabetes. However, for a 5% increase in energy from polyunsaturated fat, the RR was 0.63 (0.53, 0.76; P < 0.0001) and for a 2% increase in energy from trans fatty acids the RR was 1.39 (1.15, 1.67; P = 0.0006). We estimated that replacing 2% of energy from trans fatty acids isoenergetically with polyunsaturated fat would lead to a 40% lower risk (RR: 0.60; 95% CI: 0.48, 0.75). Conclusions: These data suggest that total fat and saturated and monounsaturated fatty acid intakes are not associated with risk of type 2 diabetes in women, but that trans fatty acids increase and polyunsaturated fatty acids reduce risk. Substituting nonhydrogenated polyunsaturated fatty acids for trans fatty acids would likely reduce the risk of type 2 diabetes substantially.

Dietary and supplement treatment of iron deficiency results in improvements in general health and fatigue in Australian women of childbearing age

Objective: To examine the effects of iron deficiency and its treatment by iron supplementation or a high iron diet on fatigue and general health measures in women of childbearing age. Design: Randomised controlled trial to compare supplement and dietary treatment of iron deficiency. Subjects: 44 iron deficient (serum ferritin < 15 mug/L or serum ferritin 15-20 mug/L, plus two of the following: serum iron < 10 mu mol/L, total iron binding capacity > 68 mu mol/L or transferrin saturation < 15%) and 22 iron replete (hemoglobin greater than or equal to 120 g/L and serum ferritin > 20 mug/L) women 18 to 50 years of age were matched for age and parity. Interventions: Iron deficient women were randomly allocated to either iron supplementation or a high iron diet for 12 weeks. Measures of Outcome: Iron deficient and iron replete participants had iron studies performed and completed the Piper Fatigue Scale (PFS) and the SF-36 general health and well-being questionnaire at baseline (TO), following the 12 week intervention (TI) and again after a six-month non-intervention phase (T2). The SF-36 includes measures of physical (PCS) and mental (MCS) health and vitality (VT). Results: MCS and VT scores were lower and PFS scores were higher for iron deficient women (diet and supplement groups) than iron replete women at baseline. Both intervention groups showed similar improvements in MCS, VT and PFS scores during the intervention phase, but mean increases in serum ferritin were greater in the supplement than the diet group. PCS scores were not related to iron status. Conclusions: Treatment of iron deficiency with either supplementation or a high iron diet results in improved mental health and decreased fatigue among women of childbearing age.