Green tea does not lower the risk of lung cancer

By Dr. Chinta SidharthanReviewed by Lily Ramsey, LLMFeb 22 2024

In a recent study published in Frontiers in Nutrition, researchers from China conducted a Mendelian randomization-based analysis to understand whether green tea consumption was associated with a lower risk of lung cancer.

Study: Investigating the potential causal association between consumption of green tea and risk of lung cancer: a study utilizing Mendelian randomization. Image Credit: 5secondStudio/Shutterstock.com

Background

Although tobacco smoking has been established as the leading cause of lung cancer, studies have found that environmental and other lifestyle factors may also play a role in the etiology of lung cancer.

The high prevalence and morbidity of lung cancer have generated significant interest in and prioritized the identification of other modifiable risk factors.

Diet has been proposed as one of the potential areas of investigation to identify modifiable risk factors for lung cancer.

Tea is a beverage that is consumed across the world and is known to have numerous health benefits. Polyphenolic compounds such as epigallocatechin-3-gallate, which is a catechin, have been found to have anti-inflammatory, anti-carcinogenic, and anti-oxidant properties.

The regular consumption of various kinds of tea, such as green tea, is thought to confer protection from various diseases, including cancer.

However, the findings on the protective effects of green tea against cancer, especially lung cancer, have been largely inconclusive, with some studies on non-smoking populations indicating protective effects while others show no associations.

About the study

In the present study, the researchers re-examined the association between the consumption of green tea and the risk of lung cancer using a Mendelian randomization approach, which is a tool that allows the evaluation of epidemiological underpinnings using genetic variants as leverage, eliminating the bias that results from observational studies.

The researchers examined the potential association between the consumption of green tea and the risk of two types of lung cancer, namely small cell lung cancer and non-small cell lung cancer, using genome-wide association data on volunteers from the United Kingdom Biobank.

Given that genetic variants are considered instrumental variables in Mendelian randomization analysis, the low-penetrance genome-wide association data was optimal for examining the association between genetic variants and phenotypes, such as the different subtypes of lung cancer.

The Biobank dataset contained information on the regular green tea intake of the participants, which was the exposure of interest.

The genome-wide association data was used to detect single-nucleotide polymorphisms associated with the consumption of green tea and its potential impact in lowering the risk of lung cancer.

The identified single-nucleotide polymorphisms were used as the instrumental variables for the consumption of green tea, and the researchers carried out further linkage disequilibrium pruning to ensure the absence of any bias due to genetic variants being co-inherited.

The instrumental variables were refined further, resulting in a set of single-nucleotide polymorphisms that had robust and independent associations with the intake of green tea.

Multiple datasets were used for the genetic association data on small cell lung cancer and non-small cell lung cancer. Data on non-small cell lung cancer was further split based on the subtypes squamous cell carcinoma and adenocarcinoma.

The data from these sources provided summary statistics on single-nucleotide polymorphism-wise association with cancer cases, which was used to explore potential causal relationships through Mendelian randomization analysis.

Results

The study found that the consumption of green tea does not exhibit any protective effects against lung cancer at the population level.

No associations were observed between green tea intake and the risk of non-small cell lung cancer or small cell lung cancer despite the Mendelian randomization approach.

Furthermore, the sensitivity analyses also did not reveal any significant association between the consumption of green tea and lung cancer risk.

The results of this study were in contrast to various observational studies that reported that the consumption of green tea potentially lowered the risk of lung cancer, although these studies were largely in non-smoking populations.

Furthermore, in previous studies, the protective effect of green tea was found to be especially notable in Asian populations, among whom the consumption of green tea is more prevalent, indicating the potential role of lifestyle factors.

However, the researchers believe that this contrast between their results and previous studies could be due to reverse causation, confounding bias, and other limitations of observational studies.

Individuals who regularly consume green tea could also be making healthier choices in other lifestyle aspects, such as following a healthy diet, exercising regularly, and avoiding smoking.

These findings highlight the importance of the Mendelian randomization approach, which eliminates the bias introduced by confounders such as lifestyle factors.

Conclusions

Overall, the study found that the intake of green tea was not associated with a lowered risk of the two subtypes of lung cancer, non-small cell lung cancer and small cell lung cancer.

However, the findings also showed that Mendelian randomization studies effectively teased apart the bias due to potential confounders while examining the causal relationships between lifestyle factors and diseases.