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Efficacité de l’acide guanidinoacétique pour remplacer la créatine?

28/11/2014 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

Je n’ai pas encore compris pourquoi certains prenaient ça mais j’ai renoncé à essayer de tout comprendre

Dose–response effects of oral guanidinoacetic acid on serum creatine, homocysteine and B vitamins levels
European Journal of Nutrition December 2014, Volume 53, Issue 8, pp 1637-1643     Sergej M. Ostojic

Guanidinoacetic acid (GAA) is an intermediate in the biosynthesis of creatine (Cr), yet its use in human nutrition is limited due to a lack of a clear understanding of its’ dose–response effect. Thus, the purpose of this study was to investigate the effect of three different dosages of GAA (1.2, 2.4 and 4.8 g/day) administered for 6 weeks on serum and urinary variables related to GAA metabolism.

Methods

Forty-eight healthy volunteers participated in the randomized, placebo-controlled, double-blind, repeated-measure study. At baseline, after 1, 2, 4 and 6 weeks, participants provided both fasting blood samples and 24-h urine.

Results

GAA intervention significantly increased serum and urinary GAA, Cr and creatinine as compared to placebo (P < 0.05). Differences were found for serum GAA and Cr responses between the three GAA dosages, with high-dose GAA resulting in a greater increase (P < 0.05) in the plasma concentration of both variables as compared to other GAA dosages. In GAA groups, fasting plasma total homocysteine (T-Hcy) increased by 3.5 μmol/L on average at post-administration, yet no dose–response differences were found between trials. Serum B vitamins were not affected by either placebo or GAA intervention (P > 0.05).

Conclusion

Results indicate that low-to-high dosages of exogenous GAA can increase serum concentrations of Cr and T-Hcy while not depleting the B vitamins pool available for remethylation of homocysteine.

Creatine metabolism and safety profiles after six-week oral guanidinoacetic acid administration in healthy humans.

Int J Med Sci. 2013;10(2):141-7.      Ostojic SM

Guanidinoacetic acid (GAA) is a natural precursor of creatine, yet the potential use of GAA as a nutritional additive for restoring creatine availability in humans has been limited by unclear efficacy and safety after exogenous GAA administration. The present study evaluated the effects of orally administered GAA on serum and urinary GAA, creatine and creatinine concentration, and on the occurrence of adverse events in healthy humans.
METHODS AND RESULTS:
Twenty-four healthy volunteers were randomized in a double-blind design to receive either GAA (2.4 grams daily) or placebo (PLA) by oral administration for 6 weeks.

CONCLUSION:
Exogenous GAA is metabolized to creatine, resulting in a significant increase of fasting serum creatine after intervention. GAA had an acceptable side-effects profile with a low incidence of biochemical abnormalities.

Co-administration of methyl donors along with guanidinoacetic acid reduces the incidence of hyperhomocysteinaemia compared with guanidinoacetic acid administration alone.

Ostojic SM     Br J Nutr. 2013 Sep 14;110(5):865-70.
Guanidinoacetic acid (GAA) is the natural biosynthetic precursor of creatine, in a metabolic reaction that requires only a methyl group transfer. The use of GAA as a food additive for restoring creatine load in human tissues is rather unexplored and data on efficacy and safety are limited. In particular, an increase in serum homocysteine after GAA administration can be regarded as critical and should be prevented. The present study evaluated the effects of orally administered GAA with and without methyl group donors on serum and urine creatine concentrations, and the occurrence of adverse events during an intervention in healthy human subjects. A total of twenty male and female volunteers were randomised in a double-blind design to receive either GAA (2.4 g/d) or GAA with methyl donors (2.4 g/d of GAA and 1.6 g/d of betaine HCl, 5 μg/d of vitamin B12, 10 mg/d of vitamin B6 and 600 μg/d of folic acid) by oral administration for 8 weeks. Serum and urine creatine increased significantly from before to after administration in both groups (P< 0.001). The proportion of participants who reported minor adverse events was 33.3 % in the GAA group, and 10.0 % in the GAA with methyl donors group (P= 0.30). Hyperhomocysteinaemia was found in 55.6 % of participants supplemented with GAA, while no participant experienced hyperhomocysteinaemia in the group supplemented with GAA and methyl donors (P= 0.01). In summary, both interventions strongly influenced creatine metabolism, resulting in a significant increase in fasting serum creatine. The concomitant supplementation of methyl donors along with GAA largely precluded the elevation of serum homocysteine caused by GAA administration alone.

Le cardio à jeun est-il plus efficace chez les femmes?

26/11/2014 | Etudes cardio et Etudes Perte de poids et Etudes Anti-âge

 

Body composition changes associated with fasted versus non-fasted aerobic exercise
Brad Jon Schoenfeld             Journal of the International Society of Sports Nutrition 2014, 11:54

It has been hypothesized that performing aerobic exercise after an overnight fast accelerates the loss of body fat. The purpose of this study was to investigate changes in fat mass and fat-free mass following four weeks of volume-equated fasted versus fed aerobic exercise in young women adhering to a hypocaloric diet. Twenty healthy young female volunteers were randomly assigned to 1 of 2 experimental groups: a fasted training (FASTED) group that performed exercise after an overnight fast (n = 10) or a post-prandial training (FED) group that consumed a meal prior to exercise (n = 10). Training consisted of 1 hour of steady-state aerobic exercise performed 3 days per week. Subjects were provided with customized dietary plans designed to induce a caloric deficit. Nutritional counseling was provided throughout the study period to help ensure dietary adherence and self-reported food intake was monitored on a regular basis. A meal replacement shake was provided either immediately prior to exercise for the FED group or immediately following exercise for the FASTED group, with this nutritional provision carried out under the supervision of a research assistant. Both groups showed a significant loss of weight (P = 0.0005) and fat mass (P = 0.02) from baseline, but no significant between-group differences were noted in any outcome measure. These findings indicate that body composition changes associated with aerobic exercise in conjunction with a hypocaloric diet are similar regardless whether or not an individual is fasted prior to training.

Importance santé du silicium

24/11/2014 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

Update on the possible nutritional importance of silicon
Forrest H. Nielsen   Journal of Trace Elements in Medicine and Biology Volume 28, Issue 4, October 2014, Pages 379–382

Convincing evidence that silicon is a bioactive beneficial trace element continues to accumulate. The evidence, which has come from human, animal, and in vitro studies performed by several laboratories, indicate that silicon in nutritional and supra nutritional amounts promotes bone and connective tissue health, may have a modulating effect on the immune or inflammatory response, and has been associated with mental health.

A plausible mechanism of action for the beneficial effects of silicon is the binding of hydroxyl groups of polyols such that it influences the formation and/or utilization of glycosaminoglycans, mucopolysaccharides, and collagen in connective tissue and bone
. In addition, silicon may affect the absorption, retention or action of other mineral elements (e.g., aluminum, copper, magnesium). Based on findings from both animal and human experiments, an intake of silicon of near 25 mg/d would be a reasonable suggestion for an adequate intake that would assure its nutritional benefits. Increased intakes of silicon through consuming unrefined grains, certain vegetables, and beverages and cereals made from grains should be recognized as a reasonable dietary recommendation.

Plus de klotho

21/11/2014 | Etudes sur les hormones et Etudes Anti-âge et Etudes sur les boosters sexuels et la sexualité

 

Testosterone increases renal anti-aging klotho gene expression via the androgen receptor-mediated pathway
Shih‑Che Hsu           Biochem. J. (2014) 464 (221–229)

Gender is known to be associated with longevity and oestrogen administration induced longevity-associated gene expression is one of the potential mechanisms underlying the benefits of oestrogen on lifespan, whereas the role of testosterone in the regulation of longevity-associated gene expressions remains largely unclear. The klotho gene, predominantly expressed in the kidney, has recently been discovered to be an aging suppressor gene. In the present study, we investigated the regulatory effects of testosterone on renal klotho gene expression in vivo and in vitro. In testosterone-administered mouse kidney and NRK-52E cells, increased klotho expression was accompanied by the up-regulation of the nuclear androgen receptor (AR). Overexpression of AR enhanced the expression of klotho mRNA and protein. Conversely, testosterone-induced klotho expression was attenuated in the presence of flutamide, an AR antagonist. A reporter assay and a chromatin immunoprecipitation (ChIP) assay demonstrated that AR directly binds to the klotho promoter via androgen response elements (AREs) which reconfirmed its importance for AR binding via the element mutation. In summary, our study demonstrates that testosterone up-regulates anti-aging klotho together with AR expression in the kidney in vivo and in vitro by recruiting AR on to the AREs of the klotho promoter.

La musculation contre les effets toxiques des méga-doses de créatine

20/11/2014 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge et Etudes sur les boosters sexuels et la sexualité

 

Equivalent à 24 g par jour pour un culturo de 80 kg et 30 g pour un de 100 kg

Effects of creatine supplementation along with resistance training on urinary formaldehyde and serum enzymes in wrestlers
Nasseri A., Jafari A.          The Journal of Sports Medicine and Physical Fitness 2014 Oct 06 [EPUB ahead of print]

AIM: Formaldehyde is a cytotoxic agent produced from creatine through a metabolic pathway, and in this regard, it has been claimed that creatine supplementation could be cytotoxic. Even though the cytotoxic effects of creatine supplementation have been widely studied, yet little is known about how resistance training can alter these toxic effects. This study aimed to determine the effects of short-­term creatine supplementation plus resistance training on the level of urinary formaldehyde and concentrations of serum enzymes in young male wrestlers.

METHODS:In a double-­blind design twenty-­one subjects were randomized into creatine supplementation (Cr), creatine supplementation plus resistance training (Cr + T) and placebo plus resistance training (Pl + T) groups. Participants ingested creatine (0.3 g∙kg-­1∙d-­1) or placebo for 7 days. The training protocol consisted of 3 sessions in 1 week, each session including three sets of 6-­9 repetitions at 80-­85% of 1-­RM for whole body exercise. Urine and blood samples were collected at baseline and at the end of the supplementation.

RESULTS: Creatine supplementation significantly increased the excretion rate of urinary formaldehyde in the Cr and Cr + T groups by 63.4% and 30.4%, respectively (P

< 0.05), indicating that

resistance training could partially lower this rate by 17.7%. No significant differences were detected in the levels of serum enzymes across time and groups (P > 0.05).

CONCLUSION: These findings indicate that resistance training may lower the increase of urinary formaldehyde excretion induced by creatine supplementation, suggesting that creatine consumption could be relatively less toxic when combined with resistance training.

anciennes études sur le sujet

Effect of oral creatine supplementation on urinary methylamine, formaldehyde, and formate.

Poortmans JR               Med Sci Sports Exerc. 2005 Oct;37(10):1717-20.

It has been claimed that oral creatine supplementation might have potential cytotoxic effects on healthy consumers by increasing the production of methylamine and formaldehyde. Despite this allegation, there has been no scientific evidence obtained in humans to sustain or disprove such a detrimental effect of this widely used ergogenic substance.
METHODS:
Twenty young healthy men ingested 21 g of creatine monohydrate daily for 14 consecutive days. Venous blood samples and 24-h urine were collected before and after the 14th day of supplementation. Creatine and creatinine were analyzed in plasma and urine, and methylamine, formaldehyde, and formate were determined in 24-h urine samples.
RESULTS:
Oral creatine supplementation increased plasma creatine content 7.2-fold (P < 0.001) and urine output 141-fold (P < 0.001) with no effect on creatinine levels. Twenty-four-hour urine excretion of methylamine and formaldehyde increased, respectively, 9.2-fold (P = 0.001) and 4.5-fold (P = 0.002) after creatine feeding, with no increase in urinary albumin output (9.78 +/- 1.93 mg x 24 h(-1) before, 6.97 +/- 1.15 mg x 24 h(-1) creatine feeding).
CONCLUSION:
This investigation shows that short-term, high-dose oral creatine supplementation enhances the excretion of potential cytotoxic compounds, but does not have any detrimental effects on kidney permeability. This provides indirect evidence of the absence of microangiopathy in renal glomeruli.

Potential cytotoxic effect of chronic administration of creatine, a nutrition supplement to augment athletic performance.

Med Hypotheses. 2000 May;54(5):726-8.    Yu PH

Creatine is alleged to be an ergogenic aid to enhance sports performance and recently became a popular sports nutrition supplement. Although short-term supplementation of creatine has not been associated with major health risks, the safety of prolonged use has caused some concern. The present study demonstrates that creatine is metabolized to methylamine, which is further converted to formaldehyde by semicarbazide-sensitive amine oxidase (SSAO). Formaldehyde is well known to cross-link proteins and DNAs, and known to be a major environmental risk factor. SSAO-mediated production of toxic aldehydes has been recently proposed to be related to pathological conditions such as vascular damage, diabetic complications, nephropathy, etc. Chronic administration of a large quantity of creatine can increase the production of formaldehyde, which may potentially cause serious unwanted side-effects.

Low-dose creatine combined with protein during resistance training in older men.
Med Sci Sports Exerc. 2008 Sep;40(9):1645-52   Candow DG

To determine whether low-dose creatine and protein supplementation during resistance training (RT; 3 d x wk(-1); 10 wk) in older men (59-77 yr) is effective for improving strength and muscle mass without producing potentially cytotoxic metabolites (formaldehyde).
METHODS:
Older men were randomized (double-blind) to receive 0.1 g x kg(-1) creatine + 0.3 g x kg(-1) protein (CP; n = 10), creatine (C; n = 13), or placebo (PLA; n = 12) on training days. Measurements before and after RT included lean tissue mass (air-displacement plethysmography), muscle thickness (ultrasound) of elbow, knee, and ankle flexors and extensors, leg and bench press strength, and urinary indicators of cytotoxicity (formaldehyde), myofibrillar protein degradation [3-methylhistidine (3-MH)],and bone resorption [cross-linked N-telopeptides of type I collagen (NTx)].
RESULTS:
Subjects in C and CP groups combined experienced greater increases in body mass and total muscle thickness than PLA (P < 0.05). Subjects who received CP increased lean tissue mass (+5.6%) more than C (+2.2%) or PLA (+1.0%; P < 0.05) and increased bench press strength (+25%) to a greater extent than C and PLA combined (+12.5%; P < 0.05). CP and C did not differ from PLA for changes in formaldehyde production (+24% each). Subjects receiving creatine (C and CP) experienced a decrease in 3-MH by 40% compared with an increase of 29% for PLA (P < 0.05) and a reduction in NTx (-27%) versus PLA (+13%; P = 0.05).
CONCLUSIONS:
Low-dose creatine combined with protein supplementation increases lean tissue mass and results in a greater relative increase in bench press but not leg press strength. Low-dose creatine reduces muscle protein degradation and bone resorption without increasing formaldehyde production.

Plus de testostérone grâce à la caféine?

20/11/2014 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge et Etudes sur les boosters sexuels et la sexualité

 

Dose effects of caffeine ingestion on acute hormonal responses to resistance exercise
The Journal of Sports Medicine and Physical Fitness 2014 May 27 [EPUB ahead of print]    Wu B.-H.

AIM: The purpose of this study was to examine the dose effects of caffeine on acute hormonal responses to resistance exercise (RE).

METHODS: Twelve university males who regularly performed RE participated in this study. Subjects performed one repetition maximum (1RM) test and four treatments in a counterbalanced order: high dose (HD, 6 mg.kg1), medium dose (MD, 4 mg.kg1), low dose (LD, 2 mg.kg1), and placebo (PLA). Subjects ingested caffeine 1 hour before RE and then performed RE (2 exercises, 3 sets of 10 repetitions at 75% of 1RM). Blood samples were collected before caffeine intake (pre-60), immediately before RE (pre-exe), and 0, 15, 30 min post RE (P0, P15, and P30, respectively) for analysis of serum testosterone, cortisol, insulin, glucose, lactate, and free fatty acid (FFA). Each experiment was separated by 7 days. Statistical analysis of two-way analysis of variance with repeated measures was applied. Statistical significance was set at α = .05.

RESULTS: The concentrations of FFA (pre-exe) were significantly elevated following the HD, MD, and LD ingestions of caffeine. The concentrations of testosterone (P0, P15, and P30) and cortisol (pre-exe, P0, P15, and P30) at HD were significantly increased. However, the responses of insulin (P0 and P15) at HD and MD were significantly decreased.

CONCLUSIONS: The results of this study indicate that high doses of caffeine increase the responses of testosterone and cortisol. Moreover, moderate and high doses of caffeine attenuate the insulin responses.

La caféine diminue le risque de calculs rénaux

19/11/2014 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

Par contre, elle augmente les besoins en potassium et en calcium
Caffeine intake and the risk of kidney stones
Pietro Manuel Ferraro,  Am J Clin Nutr December 2014 vol. 100 no. 6 1596-1603


Background: Although caffeine intake may increase urine calcium excretion, caffeine-containing beverages have been associated with a lower risk of nephrolithiasis.

Objective: We sought to determine the association between caffeine intake and the risk of incident kidney stones in 3 large prospective cohorts.

Design: We prospectively analyzed the association between intake of caffeine and incidence of kidney stones in 3 large ongoing cohort studies, the Health Professionals Follow-Up Study (HPFS) and the Nurses’ Health Studies (NHS) I and II. Information on the consumption of caffeine and the incidence of kidney stones was collected by validated questionnaires.

Results: The analysis included 217,883 participants; over a median follow-up of >8 y, 4982 incident cases occurred. After multivariate adjustment for age, BMI, fluid intake, and other factors, participants in the highest quintile of caffeine intake had a 26% (95% CI: 12%, 38%) lower risk of developing stones in the HPFS cohort, a 29% lower risk (95% CI: 15%, 41%) in the NHS I cohort, and a 31% lower risk (95% CI: 18%, 42%) in the NHS II cohort (P-trend

< 0.001 for all cohorts). The association remained significant in the subgroup of participants with a low or no intake of caffeinated coffee in the HPFS cohort. Among 6033 participants with 24-h urine data, the intake of

caffeine was associated with higher urine volume, calcium, and potassium and with lower urine oxalate and supersaturation for calcium oxalate and uric acid.

Conclusion: Caffeine intake is independently associated with a lower risk of incident kidney stones.

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