Chronic obstructive pulmonary disease (COPD) is characterized by chronic lung inflammation, which causes damage to the airways and lung parenchyma and leads to an irreversible restriction of airflow. According to the Global Initiative for Chronic Obstructive Pulmonary Disease, COPD is now the fourth leading cause of death worldwide and will become the third leading cause by 2020. The dominant risk factor for COPD is smoking and approximately 15-20% of smokers have COPD. Smokers tend to consume high amounts of beverages such as soda, coffee and green tea due to increased thirst after smoking. Like smoking, these drinks also have an effect on lung function. A study conducted in Australia suggested that the intake of sugary drinks increases the prevalence of asthma; and a different study showed that coffee intake increases the risk of lung cancer. Additionally, green tea consumption has been shown to be associated with an increase in lung function.
Previous studies have shown evidence of the individual effects of consuming different beverages and smoking on lung function; however, only a few studies have examined simultaneous exposure to smoking and drinking during COPD. The latest studies conducted indicate that the consumption of carbonated drinks reduces lung function over time, as does cigarette smoking. Conversely, the consumption of at least two cups of green tea a day improves lung compliance. But how do fizzy drinks negatively affect lung health? Carbonated beverage consumption is a modern marker of overweight and obesity, with an increase in body mass index (BMI). There are findings that BMI affects lung function. Although the mechanism of these findings is still unclear, respiratory muscle weakness, gas exchange disturbance, and inhibition of immune response are some potential mechanisms that have been suggested.
Additionally, studies have shown that continuously drinking alcohol causes inflammation of the airways and aggravates lung function. The effects of alcohol are both direct and indirect. Among the direct effects there is the variability of the transport of sodium and magnesium ions in the bronchial muscle, therefore a tendency to bronchial constriction similar to asthma. Furthermore, alcohol induces oxidative stress and damages the intestinal bacterial composition; the same effect is thought to have on the airway microbiota. The interaction between coffee and cigarettes was not seen to be significant, possibly because coffee intake affects COPD prevalence through a different mechanism. Most of the studies on caffeine provide evidence of a mechanism affecting the lungs with the spread of adenocarcinoma cells through some enzymatic reactions. One study showed that caffeine affects COPD and bronchial cancer and increases the risk of neonatal apnea in newborns.
The mechanism by which green tea has a protective effect on lung function is thought to have no interaction with smoking, which has a negative effect on lung function. Catechin, the major polyphenol found in green tea, has a major antioxidant effect via a direct mechanism by scavenging free radicals (ROS) and chelating metal ions. But it also acts through indirect mechanisms, acting as an inducer of antioxidant enzymes, through stress-producing cellular pathways. Characterized by this antioxidant activity, catechins are effective in the prevention of pathologies mediated by oxidative stress. In addition to other organs, catechins can also reduce inflammation in lung tissue. Tea consumption has been positively associated with a lower risk of diabetes and this is interesting information, because the latest studies suggest that among COPD patients who have never smoked or had occupational exposure, the prevalence of diabetes mellitus is higher than the norm.
There are no definitive data, but if the consumption of green tea can reduce the incidence of diabetes and respiratory diseases, it is hoped that science will find the rational basis for such an application, considering that the WHO has stated that lung diseases will outnumber heart disease itself in the next thirty years. As proof of the above, an article published just a couple years ago on the in vitro blocking effects of green tea and pomegranate extracts on the replication of the SARS-CoV2 virus of the current pandemic.
- edited by Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.