Last update on 6 May 2013 by Dr Cécile Loï

Muscle loss : the main causes


 

Throughout life, the muscles are constantly renewed: Every day, the muscle cells are destroyed and replaced by new.

Whith age, our body loses its complete ability to renew its muscles, and they are less sensitive to various stimuli such as food, sports, nervous or hormonal stimulation. Every day, at a certain age, the destroyed cells are more than replacement cells and this explains the age-related muscle loss, which can lead to sarcopenia.

 


The protein imbalance

Proteins are molecules composed of amino acids that can be produced naturally by the body or provided by food.

Our body uses protein provided by food to maintain, repair and grow muscles. Imagine a chain is a protein. The links in this chain are amino acids. Several associated chains represent a muscle fiber. A muscle consists of muscle fibers.

With age, an imbalance between protein synthesis and degradation sets in, in favour of degradation. This phenomenon is due to a lower production of muscle proteins after each meal. In addition, protein balance is dependent on other parameters such as less muscle response to hormones or decrease physical activity.

This imbalance of protein metabolism contributes to the phenomenon of muscle loss.



Appetite

With age, hunger decreases and our diet may become insufficient and inadequate with our daily needs. Thus, according to studies, 2-20% of elderly people living at home and 38% of older people living in institutions are malnourished.



Decrease in the avaibility of ingested amino acids

With age, some of the nutrients provided by our food isn’t redistributed to all muscles.

This physiological and natural restriction, two-fold higher in the elderly than in young adults, occurs in our digestive system, and is scientifically known as “the splanchnic sequestration.”

However, there are an amino acid able to escape this phenomenon : the L-citrulline.



Physical activities

The onset of muscle pain and fatigue are the first signs of aging, leading to the gradual cessation of physical activities. This inactivity is also responsible for age-related muscle loss.



Genetic factors

Each of us, from our parents, has a unique genetic heritage. The genes that composed are expressed differently according to age. Thus, during aging, genes involved in the synthesis of muscle proteins are more weakly expressed.


The main consequences

The consequences of muscle loss appear very late. In fact, losing muscle doesn’t cause pain. At first it’s difficil to detect. However, it can lead to a pathology : sarcopenia

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