King Grub
2014-06-09, 11:36
Detrimental effects of acute and chronic alcohol (ethanol) consumption on human physiology are well documented in the literature. These adversely influence neural, metabolic, cardiovascular, and thermoregulatory functions. However, the side effects of ethanol consumption on hormonal fluctuations and subsequent related skeletal muscle alterations have received less attention and as such are not entirely understood. The focus of this review is to identify the side effects of ethanol consumption on the major hormones related to muscle metabolism and clarify how the hormonal profiles are altered by such consumption.
Research results confirm the detrimental effects of ethanol ingestion on a multitude of physiological levels. Protein synthesis and resulting muscle hypertrophy appears to be directly affected by ethanol. Ethanol and its metabolic sub-products selectively impair IGF-I signalling via S6K1 that directly affects the transcription of genes involved in muscle hypertrophy especially in type IIx fibers, those more responsive to hypertrophy. A direct linkbetween ethanol consumption and hormonal profiles is evident. These links indicate that ethanol reduces GH plasmatic levels and alters the pituitary axes by decreasing LH release, which consequently, depending on the dose consumed could induce a decrease in the level of testosterone. Furthermore ethanol and its metabolic sub-products, inhibit testosterone but also increase cortisol levels, an opposite trend on muscle hypertrophy achievement. Though, the findings seem to be contradictive; the role of ethanol on cortisol and testosterone secretion is still not entirely understood but the stressful effects of ethanol onto the human body may be responsible for the increase in cortisol serum levels in a number of studies. Moreover, alterations in testosterone levels appear to be gender specific. A decrease in secreted testosterone has been shown in males whilst an increase due to the activation of the adrenal axes has been shown in females. Interestingly in 100% of analysed studies, an ethanol dose administration greater than 1.5 g/kg showed a decrease in testosterone serum levels. This underlines a dose dependent physiological mechanism related to ethanol consumption (Assuming that a glass of beer is around 12 oz (355 ml) and on average it’s alcohol content is between 4.5 and 6%, for a 70Kg man this dose would correspond to 5–6 glasses of beer). No differences between adolescents and adults were identified. If a reduced level of blood testosterone is present, a reduced protein synthesis should occur in males and this would lead to atrophy. This review has identified a lack of information about the specific and direct interaction between ethanol and muscle hypertrophy. Furthermore, the majority of studies related to the topic are often dated with conflicting results being evident. Ethical considerations to ethanol consumption and/or intoxication in in vivo studies might be the cause of low publication numbers. This study underlines to scientist involved in the field of exercise nutrition the need to inform athletes and sport professionals on the possible effects and implications that the consumption of this substance could cause.
Alcohol consumption and hormonal alterations related to muscle hypertrophy: a review. Nutrition & Metabolism 2014, 11:26. 6 June 2014
Research results confirm the detrimental effects of ethanol ingestion on a multitude of physiological levels. Protein synthesis and resulting muscle hypertrophy appears to be directly affected by ethanol. Ethanol and its metabolic sub-products selectively impair IGF-I signalling via S6K1 that directly affects the transcription of genes involved in muscle hypertrophy especially in type IIx fibers, those more responsive to hypertrophy. A direct linkbetween ethanol consumption and hormonal profiles is evident. These links indicate that ethanol reduces GH plasmatic levels and alters the pituitary axes by decreasing LH release, which consequently, depending on the dose consumed could induce a decrease in the level of testosterone. Furthermore ethanol and its metabolic sub-products, inhibit testosterone but also increase cortisol levels, an opposite trend on muscle hypertrophy achievement. Though, the findings seem to be contradictive; the role of ethanol on cortisol and testosterone secretion is still not entirely understood but the stressful effects of ethanol onto the human body may be responsible for the increase in cortisol serum levels in a number of studies. Moreover, alterations in testosterone levels appear to be gender specific. A decrease in secreted testosterone has been shown in males whilst an increase due to the activation of the adrenal axes has been shown in females. Interestingly in 100% of analysed studies, an ethanol dose administration greater than 1.5 g/kg showed a decrease in testosterone serum levels. This underlines a dose dependent physiological mechanism related to ethanol consumption (Assuming that a glass of beer is around 12 oz (355 ml) and on average it’s alcohol content is between 4.5 and 6%, for a 70Kg man this dose would correspond to 5–6 glasses of beer). No differences between adolescents and adults were identified. If a reduced level of blood testosterone is present, a reduced protein synthesis should occur in males and this would lead to atrophy. This review has identified a lack of information about the specific and direct interaction between ethanol and muscle hypertrophy. Furthermore, the majority of studies related to the topic are often dated with conflicting results being evident. Ethical considerations to ethanol consumption and/or intoxication in in vivo studies might be the cause of low publication numbers. This study underlines to scientist involved in the field of exercise nutrition the need to inform athletes and sport professionals on the possible effects and implications that the consumption of this substance could cause.
Alcohol consumption and hormonal alterations related to muscle hypertrophy: a review. Nutrition & Metabolism 2014, 11:26. 6 June 2014