31 October 2004

--- The Confusing Study

In the current issue of the Thorax journal, researchers from the University of Santiago de Compostela in Spain found that drinking a glass of red wine a day reduced the risk of lung cancer by 13 percent compared to non-drinkers.

My friend BatJay, a smoker who recently quit (and happy about it!), asked in his weblog two days ago:

What does this study mean? Does this mean I can smoke again as long as I become an alcoholic?

I must confess that the study has this unwitting and perplexing ability to disconcert readers. It gives the message that consuming large amounts of red wine can protect against lung cancer.

In BatJay's comments page for that post, another blogger friend, Tito Rolly, said:

Hmmm, this is really great news. Imagine, a glass of red wine a day reduces the risk of cancer by 13 percent. You are the engineer, please do the math. How many bottles do we have to drink to reduce our lung cancer risk to 100 percent?

I've read the study in full and I found out that the study was done in order to "estimate the effect of wine consumption, both overall and by type of wine, on the risk of developing lung cancer."

The study in question was actually a case-control study undertaken to find out which among red wine, white wine, beer, and spirits had the characteristic of reducing the risk of developing lung cancer. The authors said that besides the fact that there were few epidemiological studies done in the past which have investigated the effect of wine consumption on lung cancer, most of the studies available did not differentiate between red and white wine, which the authors think is significant because the two wines possess "different composition in terms of potentially antioxidant and anticarcinogenic substances such as tannins and resveratrol."

In their study, the obvious winner among the alcoholic beverages was red wine, which showed an inverse association with the development of lung cancer (odds ratio of 0.87 at 95% confidence interval of 0.77 to 0.99) or simply put --- providing a 13 percent reduced risk of developing lung cancer among those who consumed one glass of red wine daily.

The study also found out that consumption of beer and other spirits did not show any clear effect on the development of lung cancer whether positive or negative.

The full results of the study can be seen here.

As if trying to answer both BatJay's and Tito Rolly's questions, Dr. Alberto Ruano-Ravina, one of the study's authors, cautioned against consuming large amounts of red wine as this will surely bring mostly more harm than benefits. Harm here is defined as increased risks for oral cancers.

What Dr Ruano-Ravina advocates instead is that experimental and clinical studies be conducted in order to isolate and harness the particular components of red wine suspected to be responsible for its ability to decrease cancer risks.

He also admitted several limitations of their study, one of which "exposure is measured retrospectively, so the possibility of a recall bias cannot be excluded." Other limitations of the study cited were the small sample size and that the "subjects were not asked about the number of years during which they had consumed wine or other alcoholic beverages."

Unless documented and verified by a number of studies, we must always approach scientific and medical study claims with a healthy dose of skepticism.

1 reactions:

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