Article I found from another source. Could be good reading.
4 Reasons Why if You Booze, You Lose Muscle
Written by Michael J. Rudolph, Ph.D.
- Alcohol Impedes Muscle Protein Synthesis
The anabolic response within muscle tissue is due to the difference in muscle protein synthesis and muscle protein breakdown, where higher levels of protein synthesis results in muscle growth. This anabolic response within muscle tissue can be significantly decreased by the consumption of excessive alcohol intake, which inhibits muscle protein synthesis and therefore muscle growth.1-3 In fact, one study by Hong-Brown et al. showed that the exposure of muscle cells to alcohol decreased the ability of either IGF-1 or insulin to stimulate protein synthesis by 30 percent and 60 percent, respectively. In addition, this study also showed that alcohol had no influence on the rate of muscle protein degradation4, demonstrating that alcohol specifically affects muscle protein synthesis.
In addition to alcohol ingestion reducing the ability of IGF-1 and insulin to promote muscle growth, alcohol has also been shown to directly suppress mTOR-driven muscle protein synthesis.5 This effect stems from the ability of alcohol to inhibit the production of phosphatidic acid ¶ by the enzyme phospholipase D within the muscle cell. PA is a signaling molecule that has been shown to directly activate mTOR in response to resistance exercise.6 Consequently, the reduction of PA by alcohol lowers mTOR-activated protein synthesis, leading to reduced muscle growth.
- Alcohol Specifically Reduces Fast-twitch Muscle Fiber Growth
There are basically two types of muscle fiber in the body, known as slow-twitch fiber and fast-twitch fiber. The fibers are called slow and fast due to the relative rate at which they contract with fast-type fiber, contracting roughly four times faster than slow-twitch fiber7, giving the fast-twitch fiber a greater force-producing capacity. In addition, the fast-twitch fiber is considerably larger than the slow-twitch fiber.
Because the fast-twitch fiber is the naturally larger, more powerful fiber type, it imparts the greatest response to weight training, providing superior gains in muscle size and strength. In fact, the fast-twitch fiber is also the primary muscle fiber type negatively influenced by alcohol intake. This outcome was shown in a study by Vary et al.8, where rats given alcohol demonstrated a reduction of muscle protein synthesis in muscle tissue comprised primarily of fast-twitch fibers. These results strongly indicate that alcohol consumption will likely decrease muscle size and strength, based on the negative influence that alcohol consumption has on fast-twitch fiber growth.
3) Alcohol Further Depletes Muscle Growth by Increasing Myostatin Levels
In addition to alcohol reducing muscle growth by inhibiting muscle protein synthesis, studies indicate that alcohol exposure also increases the amount of the potent muscle-depleting molecule myostatin in muscle cells, which likely decreases muscle growth even further.9 Myostatin is a member of the transforming growth factor-beta (TGF-beta) super family of growth factors where, despite being a growth factor, it actually reduces muscle growth by inhibiting the formation of new muscle fibers10 while decreasing mTOR-driven muscle protein synthesis.11 The negative impact of myostatin on muscle growth from alcohol consumption was demonstrated in a study by Lang et al.9, where they showed that long-term consumption of alcohol for 16 weeks in rats increased myostatin levels in muscle tissue. Furthermore, the greater amount of myostatin led to a considerable loss of muscle protein mass in the alcohol-fed rats.
4) Excessive Alcohol Intake Creates a Catabolic Hormonal Mixture That Favors Muscle Loss
The consumption of alcohol can alter the quantity of the anabolic hormone testosterone, providing a considerable influence on muscle growth. This effect is apparently dose-dependent with relatively low levels of alcohol increasing testosterone production, while higher levels of alcohol cause a considerable drop in testosterone.
In one study showing the positive impact of low amounts of alcohol on testosterone, subjects consumed roughly two alcoholic drinks, resulting in an increase in circulating testosterone of 17 percent.12 The authors suggest that this boost in testosterone may be due to the increase in NADH, which is produced from the metabolism of the ingested alcohol. NADH (nicotinamide adenine dinucleotide) is a coenzyme that occurs naturally in the body and plays a role in the chemical process that generates energy. The increase in NADH enhances the activity of the enzyme 17-hydroxysteroid dehydrogenase (17 beta-HSD), which catalyzes the production of testosterone.13 As a result of the increased activity of 17 beta-HSD, more testosterone is produced.
In addition to the higher amounts of alcohol decreasing testosterone, higher levels of alcohol also trigger a spike in the muscle-depleting hormone cortisol. In one study by Valimaki et al., they showed that the consumption of six to seven drinks of alcohol caused an increase in cortisol of 152 percent, four hours after alcohol consumption.16
Taken together, the depletion of testosterone combined with a spike in cortisol from excessive alcohol ingestion conceivably increases muscle protein degradation, contributing to the negative influence of alcohol on muscle size and strength.
For most of Michael Rudolph’s career he has been engrossed in the exercise world as either an athlete (he played college football at Hofstra University), personal trainer or as a research scientist (he earned a B.Sc. in Exercise Science at Hofstra University and a Ph.D. in Biochemistry and Molecular Biology from Stony Brook University). After earning his Ph.D., Michael investigated the molecular biology of exercise as a fellow at Harvard Medical School and Columbia University for over eight years. That research contributed seminally to understanding the function of the incredibly important cellular energy sensor AMPK leading to numerous publications in peer-reviewed journals including the journal Nature. Michael is currently a scientist working at the New York Structural Biology Center doing contract work for the Department of Defense on a project involving national security.
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