BCAAs can protect smokers’ muscle mass

Smoking is bad for pretty much everything, and that includes your muscles. Researchers at Nara Medical University in Japan made an interesting discovery for bodybuilders and other strength athletes who still smoke: supplementation with BCAAs can help counteract the negative effects that smoking has on muscles.

Smoking boosts myostatin activity in muscle cells, causing muscle degeneration. Smoking also encourages the formation of advanced glycation end products [AGEs] in the muscles, thus reducing muscle strength.

The Japanese were curious as to whether the muscle-shrinking effects of smoking were in any way related to BCAAs [structural formulas shown below]. Did smokers’ muscles absorb fewer BCAAs perhaps? And if so, could smokers maintain muscle strength by taking a supplement containing BCAAs?


To answer these questions the researchers devised an animal experiment in which one group of young rats was exposed to cigarette smoke for four weeks, and one group was not.

Of both groups, half was given standard food and the other half was given food to which BCAAs had been added. The BCAA-enriched food contained approximately the same amount of amino acids as the standard food.


The rats that inhaled cigarette smoke grew less fast. That was partly because they ate less.


The BCAA supplementation did not normalise the growth rate of the smoking rats, but it did counteract the negative effects of smoking on muscle mass. The figure below shows the weight of the gastrocnemius [calf muscle] in the four groups.


The Japanese discovered that smoking reduces the concentration of BCAAs in the blood. BCAA supplementation can negate the effect of smoking and restore the quantity of BCAAs in the bloodstream.


The muscles of the animals that inhaled smoke also contained lower amounts of BCAAs. That’s why their muscles were smaller than those of the other lab rats. BCAA supplementation also normalised the amount of BCAAs in the rats’ muscles.


In 2011 the researchers published the results of another animal experiment in which they had studied the effects of cigarette smoke. [J Toxicol Sci. 2011 Jun;36(3):261-6.] In that experiment they observed that exposure to tobacco smoke caused the immune cells in the intestines to use more glutamine. That might explain why the amount of BCAAs goes down as a result of exposure to cigarette smoke: smokers’ bodies use larger amounts of BCAAs to synthesise glutamine.

Branched-chain amino acid-rich diet improves skeletal muscle wasting caused by cigarette smoke in rats.


Cigarette smoke induces skeletal muscle wasting by a mechanism not yet fully elucidated. Branched-chain amino acids (BCAA) in the skeletal muscles are useful energy sources during exercise or systemic stresses. We investigated the relationship between skeletal muscle wasting caused by cigarette smoke and changes in BCAA levels in the plasma and skeletal muscles of rats. Furthermore, the effects of BCAA-rich diet on muscle wasting caused by cigarette smoke were also investigated. Wistar Kyoto (WKY) rats that were fed with a control or a BCAA-rich diet were exposed to cigarette smoke for four weeks. After the exposure, the skeletal muscle weight and BCAA levels in plasma and the skeletal muscles were measured. Cigarette smoke significantly decreased the skeletal muscle weight and BCAA levels in both plasma and skeletal muscles, while a BCAA-rich diet increased the skeletal muscle weight and BCAA levels in both plasma and skeletal muscles that had decreased by cigarette smoke exposure. In conclusion, skeletal muscle wasting caused by cigarette smoke was related to the decrease of BCAA levels in the skeletal muscles, while a BCAA-rich diet may improve cases of cigarette smoke-induced skeletal muscle wasting.

PMID: 24646715 [PubMed – in process]

Source: http://www.ncbi.nlm.nih.gov/pubmed/24646715