Alcohol is commonly known as one of many foods and beverages having empty calories because it contains 7 calories per gram of the drink but without macro- and micronutrients. However, even with this knowledge, many individuals do not consider alcohol consumption to negatively impact fitness goals as long as there is a combination of proper nutrition, exercise, and recovery.
Researchers have reported that alcohol consumption has negative effects on muscle growth, repair, and recovery due to various factors. Alcohol alters hormone production, impairs myofibrillar protein synthesis, and increases stress and inflammation in the body. Thus, alcohol consumption should be limited to moderate amounts in order to avoid its detrimental effects.
Because excessive alcohol consumption has been reported to commonly occur in athletes especially after training, understanding how alcohol affects muscle development is necessary in attaining an individual’s fitness goals.
How to Achieve Muscle Growth
Muscle growth or hypertrophy is the increase in the size of muscle cells. In a healthy individual, hypertrophy is achieved through exercise and is usually associated with weight lifting. However, muscle growth only occurs with exercise if protein synthesis exceeds muscle protein breakdown.
A positive muscle protein balance must be achieved for optimal muscle growth which is improved by resistance exercises; but, without sufficient food intake, the balance turns negative as in a catabolic state. Furthermore, a number of factors affect muscle growth in response to resistance exercises including mechanical tension, muscle damage and metabolic stress among others.
Force generation and stretch produces mechanically induced tension which is essential to muscle growth. The integrity of skeletal muscles is thought to be disturbed by the tension associated with resistance training, which in turn causes mechano-chemically converted molecular and chemical responses in muscle fibers and satellite cells.
Passive muscular tension is developed upon eccentric contraction of skeletal muscles due to the lengthening of non contractile units of the muscle. This increases the active tension from the contractile elements, thus augmenting the hypertrophic response.
Exercise training causes damage to the skeletal muscles such as microtears which are theorized to elicit hypertrophy. When the body experiences microtrauma from exercise, it responds by recruiting more fibers to replace the damaged ones. It is believed that this overcompensation response occurs to reduce the risk of repeat damage.
Damage caused by exercise has been theorized to be the cause of delayed onset muscle soreness. This is why progressive overload is necessary for the development of the muscle as it adapts and becomes more resistant to stress.
Exercise that relies on anaerobic glycolysis for ATP production induces a physiological response called metabolic stress which manifests with the subsequent accumulation of metabolites such as lactate, inorganic phosphate, hydrogen ions, and so on. It is believed that the accumulation of metabolites trigger anabolic signaling cascades which contribute to muscle growth.
Effects of Alcohol on the Muscle
Moderate alcohol consumption has been associated with positive effects on the body. However, chronic intake or acute heavy consumption has negative impacts on muscle development due to its effects on factors such as protein synthesis, hormone production, and inflammation.
In order to achieve muscle growth, proteins must be synthesized by the body. The synthesis of proteins in skeletal muscles is particularly referred to as myofibrillar protein synthesis. Myofibrillar proteins are the proteins that make up the contractile units of the skeletal muscles.
A study by Parr et al. (2014) reported that consuming large amounts of alcohol, around 1.5 g/kg of body mass, impairs the rate of myofibrillar protein synthesis. The study noted a 37% decrease in myofibrillar protein synthesis rate when alcohol was ingested without intake of post-exercise protein. However, even with the intake of a post-exercise protein, the rate of myofibrillar protein synthesis was still reduced by around 24%.
Another study mentioned that it is the secondary metabolites of alcohol that cause direct effects on protein synthesis, mainly affecting type II muscle fibers with preference for type IIx. The type IIx muscle fiber is known to be more responsive to hypertrophy, thus its affectation by alcohol clearly leads to an impairment in muscle growth.
Mechanisms involving muscle growth are largely hormone mediated. Hormones dictate whether the outcome is protein synthesis or breakdown. Studies have shown that a direct link between alcohol consumption and hormonal profiles is evident.
One hormone affected by alcohol consumption is testosterone which has been proven to increase muscle mass due to numerous factors. Hence, it is ideal for muscle development to have increased testosterone levels as is observed after exercise. However, alcohol consumption of greater than 1.5 g/kg of body mass has been reported to lead to decreased testosterone levels, particularly in men. A point of interest is that ingesting alcohol less than 1.5 g/kg of body mass actually resulted in increased levels of the hormone.
Production of testosterone is stimulated by the luteinizing hormone (LH), which has been shown to have a decrease in serum levels after ingesting alcohol. Luteinizing hormone production is mediated by the gonadotropin releasing hormone (GnRH). Ethanol inhibits the release of GnRH at the hypothalamic level, thus lowering LH levels, which in turn partially lowers testosterone levels as well.
Alcohol Detox Center Bright Future Recovery notes that people with a history of alcohol misuse are at a greater risk for developing low testosterone. More than 90% of men with advanced liver disease also have low testosterone.
Cortisol is a hormone with increased levels following alcohol intake. This hormone functions in response to stress and leads to catabolic events such as protein breakdown and inhibition of protein synthesis. The increase in cortisol level is said to be possibly caused by the stress induced by alcohol on the body.
Along with these, estrogen is another hormone affected by consumption of alcohol in higher doses. Estrogen is responsible for the development and maintenance of the reproductive system and female characteristics, but it also plays a part in increasing muscle strength and force production. Studies have shown no significant difference in estrogen levels after consuming 1.75g/kg of ethanol. However, consuming alcohol in larger amounts resulted in an increase in estrogen levels in females, and a decrease in males.
Most studies analyzing the effect of alcohol consumption on human growth hormone (HGH) levels have shown a decrease in HGH serum levels. Human growth hormone works to increase muscle strength by increasing muscle mass. It stimulates metabolic processes, as well as muscle protein synthesis. Thus, a decrease in HGH as caused by alcohol consumption may lead to decreased muscle mass, strength, and exercise tolerance.
The inflammation known to occur due to alcohol intake is associated with chronic alcohol consumption rather than acute ingestion. Chronic alcohol ingestion encourages an inflammatory setting which may contribute to tissue injury. Increases in inflammation caused by chronic alcohol consumption have been implicated to cause oxidative stress, organ damage, as well as impairments in muscle function.
Cytokines that promote inflammation, particularly the tissue necrosis factor-α (TNF-α), have been shown to have an inverse relationship with lean mass in chronic alcoholics. This is because an increase in TNF-α level occurring in alcohol-related inflammation leads to an increase in protein degradation in cardiac and skeletal muscles.
Ideal Alcohol Consumption
Moderate drinking is considered to be 2 standard alcoholic drinks per day for men and 1 standard alcoholic drink per day for women as stated by the Dietary Guidelines for Americans. According to the Centers for Disease Control and Prevention, a standard drink consists of 14 grams of pure alcohol. This is equivalent to either of the following: 12 ounces of beer with 5% alcohol, 8 ounces of malt liquor with 7% alcohol, 5 ounces of wine with 12% alcohol, and 1.5 ounces of hard drinks with 40% alcohol.
The type of alcoholic beverage does not matter as it is the alcoholic content that should be considered. Although consuming wine is widely assumed to be better than drinking beer, 5 ounces of wine is actually equal to 12 ounces of beer, thus having the same detrimental effects when too much is ingested.
While heavy drinking and chronic alcohol intake have negative impacts on muscle development, moderate consumption still proves to have benefits. Moderate alcohol intake has been shown to improve cardiovascular health, improve insulin sensitivity, and decrease the risk of hypertension. However, drinking less is still considered better for overall health and fitness.
When alcohol is consumed heavily or chronically, it begins to have detrimental effects on muscle growth, recovery, and repair. This is because too much alcohol causes a decrease in protein synthesis, alterations in hormonal balance, and an increase in body inflammation and stress. Thus, alcohol ingestion should be limited to the recommended daily intake in order to maximize potential muscle development.