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Propriétés anti-oxydantes de la stévia

29/08/2015 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

Propriétés anti-oxydantes de la stévia

Comparative Study of the Antioxidant Properties of Stevia rebaudiana using cellular approaches

Cecilia Bender   Free Radical Biology and Medicine Volume 86, Supplement 1, September 2015, Pages S39

In recent years, Stevia rebaudiana is gaining popularity in Europe, especially in weight control and among diabetics since it has a high sweetening power without calories. More recently, its antioxidant properties have been studied with different chemical methods; all authors have agreed that stevia has antioxidant activity.

Our study aims to better examine its antioxidant properties using a relevant model to assess the antioxidant capability of stevia extracts within human cells, to determine its efficiency of protection against free radicals under physiological conditions. To this end, stevia leaf and stem samples were subjected to water extraction, chemically characterized and subsequently the antioxidant potentials were determined in vitro through the ORAC assay and in vivo in a cell-based assay (CAA). The CAA assay measures ROS levels in the presence or absence of stevia extracts using 2′,7′-dichlorofluorescein diacetate dye, a molecule that becomes a highly fluorescent probe in the presence of oxidants. In addition, purified steviol glycosides were analyzed.

Our results showed that stevia extracts decreased the intracellular oxidation in a dose-dependent manner when compared to control cells, indicating its antioxidant action within the cell. Despite, its purified steviolglycosides showed a low ORAC value compared with crude extracts and do not elicit any cellular antioxidant activity. This study provides evidence that stevia is certainly a potential source of antioxidative agents for the food and dietary supplements companies, that apart its natural sweetness has a cellular antioxidant potential. Moreover, the antioxidant capacity both in vitro as well as in the cell-based assay is higher for crude leaves extracts than for purified steviol glycosides, thus suggesting that the polyphenols present in the crude extracts are responsible for the antioxidant activity of stevia. Thus, stevia leaves or crude extracts thereof might be considered as a food ingredient.

La curcumine est-elle efficace?

29/08/2015 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

Peut-être que ça ne marche pas ou qu’il fallait en prendre plus?

Six-week supplementation with highly bioavailable curcuminoids is safe but does not alter blood lipids and inflammation markers in humans
Free Radical Biology and Medicine Volume 86, Supplement 1, September 2015, Pages S38     Alexa Kocher

Cardiovascular diseases (CVD) are one of the leading risk factors for morbidity and mortality in the Western world. Due to the fact that conventional medications possess side effects, there is large interest to find alternatives.

Curcuminoids are lipophilic phytochemicals from the plant curcuma longa. Besides their reported antioxidant, anticancer and anti-inflammatory activities, they may also be able to decrease blood cholesterol when regularly consumed.

Therefore, we investigated, in a randomized, double-blind, crossover study, the effects of curcuminoids, in form of a bioavailability-improved formulation (micelle), on lipid and inflammation markers. Subjects (25 women, 17 men) with moderately elevated concentrations of total cholesterol, LDL-cholesterol and C-reactive protein (CRP) consumed 240 mg curcuminoids/d as micelles or placebo for six weeks, respectively, interrupted by a four week washout phase. Blood was collected at the beginning, after three and six weeks of each intervention and concentrations of curcuminoids, triacylglycerols, total, HDL- and LDL-cholesterol, CRP, interleukine-6 and liver and kidney function markers were determined. In spite of detectable plasma curcuminoid concentrations, lipid and inflammation parameters were not altered by curcuminoid supplementation and safety markers remained in the reference ranges. Thus, daily supplementation of otherwise healthy subjects with slightly elevated blood lipids and inflammation markers with highly bioavailable curcuminoids is safe, but does not alter blood lipids and inflammatory status.

L’art de la nutrition est plus complexe que beaucoup tentent de le faire croire!

29/08/2015 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

La science de la nutrition est plus complexe que beaucoup tentent de le faire croire!

Natural antioxidants accelerate cachexia development in colon cancer
Free Radical Biology and Medicine Volume 86, Supplement 1, September 2015, Pages S9–S10         Mohamad Assi

Cancer cachexia is a multifactorial syndrome and a complex metabolic disorder, characterized by a continuous loss of muscle mass with or without depletion of adipose tissue. It manifests mainly in patients with advanced stages of colon cancer and accounts for more than 20% of mortality in total cancer patients. Muscle atrophy is one of the most relevant clinical events in cancer cachexia that negatively impact patient’s quality of life. Currently, it is well established and recognized that cachexia-induced muscle atrophy is intimately linked to oxidative stress (OS), since oxidative damages were increased in the skeletal muscle of cachectic patients and were positively correlated with muscle proteolysis.

Thus, supplementation with natural antioxidants could be a valuable strategy to prevent the deterioration of patient’s quality of life and/or alleviate cachexia-related symptoms, like muscle atrophy. Herein, we tested the effectiveness of this strategy in a model of C26-tumor bearing mice. Five-week old Balb/c mice have received a subcutaneous injection of PBS or C26 cancer cells with or without daily supplementation with a cocktail of natural antioxidants. Venous blood and skeletal muscles were removed at 20-22 days after injection.

We found that supplemented mice started to lose weight faster and died prematurely compared to no supplemented mice. Muscle atrophy occurred earlier in supplemented mice as evidenced by the decrease in fibers diameter, skeletal muscle weights and muscle endurance. These events were concomitant with an increase in systemic and muscular oxidative stress (e.g. carbonyls proteins, 4-HNE). Surprisingly, oxidative damage markers were decreased only in tumor of antioxidants-supplemented mice and were associated with a decrease in cell cycle inhibitors expression (e.g. p21), leading to tumor proliferation and progression. In line with recently published reports, our study support the evidence that antioxidants supplementation, if there is no need, could have deleterious consequences on health and well-being.

Du jus de raisin pour courir plus vite?

27/08/2015 | Etudes cardio et Etudes Compléments alimentaires et Etudes Anti-âge

 

Potential ergogenic activity of grape juice in runners
Lydiane Tavares Toscano       Physiologie appliquée, nutrition et métabolisme, 2015, 40(9): 899-906,

Selon des études récentes, certains produits alimentaires auraient un potentiel ergogène analogue à celui des suppléments pour sportifs. Cette étude se propose d’examiner l’effet ergogène potentiel du jus de raisin pourpre intégral sur la performance de coureurs par loisir.

On répartit aléatoirement 28 volontaires des deux sexes (âgé de 39,8 ± 8,5 ans, consommation d’oxygène de pointe : 43,2 ± 8,5 mL/(kg·min)) en deux groupes, l’un recevant du jus de raison (GJG, n = 15; 10 mL/(kg·min) durant 28 jours) et l’autre, une boisson de contrôle isoénergétique, isoglycémique et isovolumétrique (CG, n = 13). Au début et 48 h après le protocole de supplémentation, on administre un test de temps d’effort jusqu’à épuisement, un test du seuil anaérobie et un test de capacité aérobie et on évalue les marqueurs du stress oxydatif, de l’inflammation, de la réponse immunitaire et de lésion musculaire.

Le GJG présente une augmentation significative (15,3 %) au test de temps d’effort jusqu’à épuisement (p = 0,002) sans une amélioration significative du seuil anaérobie (3,6 %; p = 0,511) et de la capacité aérobie (2,2 %; p = 0,605). En outre, le GJG présente une augmentation significative de la capacité antioxydante totale (38,7 %; p = 0,009), de la vitamine A (11,8 %; p = 0,016) et de l’acide urique (28,2 %; p = 0,005) et une diminution significative de l’α-1-glycoprotéine acide (20,2 %; p = 0,006) et aucune variation de la protéine C-réactive de grande sensibilité. Par contre, le CG ne présente aucune modification significative de ces variables.

En conclusion, la supplémentation en jus de raisin pourpre comporte un effet ergogène chez des coureurs par loisir en accroissant la durée de l’effort jusqu’à épuisement accompagné d’une augmentation de l’activité antioxydante et une diminution possible des marqueurs de l’inflammation.

La pub, ça ne marche pas toujours!

26/08/2015 | Etudes Perte de poids et Etudes Anti-âge

 

Consumption Patterns of Fruit and Vegetable Juices and Dietary Nutrient Density among French Children and Adults
Nutrients 2015, 7(8), 6073-6087       Aurée Francou

Background: Fruit and vegetable consumption is a marker of higher-quality diets; less is known about the contribution of 100% fruit and vegetable juices (FVJ) to diet quality.

Objective: To explore FVJ consumption patterns in relation to dietary nutrient density among French children (aged 3–14 years old) and adults (≥21 years old).
Methods: Analyses were based on the nationally representative 2013 CCAF (Comportements et Consommations Alimentaires en France) survey of 1930 respondents, stratified by age group, FVJ consumption, and socioeconomic status (SES). Dietary nutrient density was based on the Nutrient Rich Food (NRF9.3) index, adjusted for gender and age.

Results: Mean total consumption of fruits and vegetables was 2.6 servings/day for children and 3.8 servings/day for adults. Mean population consumption of FVJ was 83 mL/day for children and 54.6 mL/day for adults, equivalent to 0.4 servings/day and 0.3 servings/day respectively. FVJ consumers had higher quality diets than did non-consumers, after adjusting for covariates. The respective NRF9.3 values were 486.4 ± 4.3 vs. 428.7 ± 7.5 for children and 460.7 ± 4.4 vs. 435.4 ± 4.4 for adults. FVJ consumers had similar or higher intakes of fruits and vegetables than did non-consumers. The socioeconomic gradient for FVJ consumption was much weaker (p < 0.046) than for whole fruit (p < 0.01).

Conclusions: In a nationally representative sample of French children and adults, fruit and vegetable consumption fell short of recommended values. Higher FVJ consumption was associated with higher-quality diets and better compliance with the French National Plan for Nutrition and Health (PNNS).

Efficacité d’un supplément de GABA

20/08/2015 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

γ-Aminobutyric acid (GABA) administration improves action selection processes: a randomised controlled trial.
Sci Rep. 2015 Jul 31;5:12770.        Steenbergen L

In order to accomplish a task goal, real-life environments require us to develop different action control strategies in order to rapidly react to fast-moving visual and auditory stimuli. When engaging in complex scenarios, it is essential to prioritise and cascade different actions. Recent studies have pointed to an important role of the gamma-aminobutyric acid (GABA)-ergic system in the neuromodulation of action cascading. In this study we assessed the specific causal role of the GABA-ergic system in modulating the efficiency of action cascading by administering 800 mg of synthetic GABA or 800 mg oral of microcrystalline cellulose (placebo). In a double-blind, randomised, between-group design, 30 healthy adults performed a stop-change paradigm.

Results showed that the administration of GABA, compared to placebo, increased action selection when an interruption (stop) and a change towards an alternative response were required simultaneously, and when such a change had to occur after the completion of the stop process. These findings, involving the systemic administration of synthetic GABA, provide the first evidence for a possible causal role of the GABA-ergic system in modulating performance in action cascading.

La cross-education expliquée à mes muscles

18/08/2015 | Echauffement et blessures et Etudes Musculation

 

Anodal Transcranial Direct Current Stimulation Prolongs the Cross-education of Strength and Corticomotor Plasticity
Medicine & Science in Sports & Exercise: September 2015 - Volume 47 - Issue 9 - p 1788–1797     Hendy, Ashlee M

Purpose: This study aimed to assess the efficacy of applying anodal transcranial direct-current stimulation (a-tDCS) to the ipsilateral motor cortex (iM1) during unilateral strength training to enhance the neurophysiological and functional effects of cross-education.

Methods: Twenty-four healthy volunteers were randomly allocated to perform either of the following: strength training during a-tDCS (ST + a-tDCS), strength training during sham tDCS (ST + sham), or a-tDCS during rest (a-tDCS) across 2 wk. Strength training of the right biceps brachii involved four sets of six repetitions at 80% of one-repetition maximum three times per week. Anodal tDCS was applied to the iM1 at 1.5 mA for 15 min during each strength training session. Outcome measures included one-repetition maximum strength of the untrained biceps brachii, corticomotoneuronal excitability, cross-activation, and short-interval intracortical inhibition (SICI) of the iM1 determined by transcranial magnetic stimulation.

Results: Immediately after the final training session, there was an increase in strength for both the ST + a-tDCS (12.5%, P

< 0.001) and the ST + sham group (9.4%, P = 0.007), which was accompanied by

significant increases in corticomotoneuronal excitability and decreases in SICI for both groups. After a 48-h retention period, strength increase was maintained in the ST + a-tDCS (13.0%, P = 0.001) group, which was significantly greater than the ST + sham group (7.6%, P = 0.039). Similarly, increases in corticomotoneuronal excitability and decreases in SICI were maintained in the ST + a-tDCS group but not in the ST + sham group. No main effects were reported for the a-tDCS group (all P > 0.05).

Conclusions: The addition of a-tDCS to the iM1 during unilateral strength training prolongs the benefits of cross-education, which may have significant implications to enhancement of rehabilitation outcomes after a single-limb injury or impairment.

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