The effect on the blood-sugar and blood-phosphate of ingested creatine

Creatine supplementation and glycemic control: a systematic review

The focus of this review is the effects of creatine supplementation with or without exercise on glucose metabolism. A comprehensive examination of the past 16 years of study within the field provided a distillation of key data. Both in animal and human studies, creatine supplementation together with exercise training demonstrated greater beneficial effects on glucose metabolism; creatine supplementation itself demonstrated positive results in only a few of the studies. In the animal studies, the effects of creatine supplementation on glucose metabolism were even more distinct, and caution is needed in extrapolating these data to different species, especially to humans. Regarding human studies, considering the samples characteristics, the findings cannot be extrapolated to patients who have poorer glycemic control, are older, are on a different pharmacological treatment (e.g., exogenous insulin therapy) or are physically inactive. Thus, creatine supplementation is a possible nutritional therapy adjuvant with hypoglycemic effects, particularly when used in conjunction with exercise.

Creatine feeding does not enhance intramyocellular glycogen concentration during carbohydrate loading: an in vivo study by 31P- and 13C-MRS

The main aim of this study was to examine the hypothesis that creatine (Cr) feeding enhances myocellular glycogen storage in humans undergoing carbohydrate loading. Twenty trained male subjects were randomly assigned to have their diets supplemented daily with 252 g of glucose polymer (GP) and either 21 g of Cr (CR-GP, n = 10) or placebo (PL-GP, n = 10) for 5 days. Changes in resting myocellular glycogen and phosphocreatine (PCr) were determined with Magnetic Resonance Spectroscopy (13C- and 31P-MRS, respectively). After CR-GP, the levels of intramyocellular glycogen increased from 147 +/- 13 (standard error) mmol x (kg wet weight(-1)) to 172 +/- 13 m mol x (kg wet weight)(-1), while it increased from 134 +/- 17 mmol x (kg wet weight)(-) to 182 +/- 17 mmol x (kg wet weight)(-1) after PL-GP; the increments in intramyocellular glycogen concentrations were not statistically different. The increment in the PCr/ATP ratio after CR-GP (+ 0.20 +/- 0.12) was significantly different compared to PL-GP (- 0.34 +/- 0.16) (p < 0.05). The present results do not support the hypothesis that Cr loading increases muscle glycogen storage.

Effect of creatine ingestion on glucose tolerance and insulin sensitivity in men

PURPOSE

This study investigated whether acute (5 d) and/or short-term (28 d) creatine (Cr) ingestion altered glucose tolerance or insulin action in healthy, untrained men (aged 26.9 +/- 5.7 yr; SD).

METHODS

Subjects were randomly allocated to either a Cr ( N= 8) or placebo group (N = 9) and were tested in the control condition (presupplementation), and after 5 and a further 28 d of supplementation. The Cr group ingested 20 g and 3 g.d (-1) of Cr for the first 5 and following 28 d, respectively. The placebo group ingested similar amounts of glucose over the same time period. During each testing period, subjects underwent an oral glucose tolerance test (OGTT) to determine insulin sensitivity, and six subjects from each group underwent a muscle biopsy before each OGTT.

RESULTS

Cr supplementation resulted in an increased (P< 0.05) muscle TCr content after both the acute and short-term loading phase compared with placebo. Neither acute nor short-term Cr supplementation influenced skeletal muscle glycogen content, glucose tolerance, or measures of insulin sensitivity.

CONCLUSIONS

These findings demonstrated that acute Cr supplementation (20 g.d(-1) for 5 d) followed by short-term Cr supplementation (3 g.d(-1) for 28 d) did not alter insulin action in healthy, active untrained men.