The Japanese and Lung Cancer

The Japanese smoker’s paradox has been recognised by medical authorities for some time. Although cigarette smoking rates are higher amongst the Japanese population than in many Western nations, their incidence of lung cancer is much lower. In fact it has been estimated that as many as 90% of lung cancers in the US are, directly or indirectly, caused by smoking whilst in Japan this statistic may be as low as 10%. But it is not just Japanese smokers that enjoy lower cancer rates, Japanese society as a whole, is blessed with a low cancer incidence. Why is this case? Could it be the possession of favourable genes or are there environmental forces at work? Perhaps it’s a combination of both.

Genetics or Environment?

At the individual level, genetic factors are known to influence a person’s susceptibility to contracting cancer. Perhaps genetically close knit individuals within a population share ‘cancer protection genes’. However, research indicates, that for the Japanese population, genetic factors are not mainly responsible for low lung cancer rates. Second generation Japanese immigrants to the US show levels of smoking associated lung cancer similar to that of the general US population. Diet may have an influence. The traditional Japanese diet is rich in fish oils and vegetables and low in dairy products. Fish oils and vegetables are known health promoters and dairy products are full of the ‘wrong’ type of fats.

Are Filters Responsible?

Seventy percent of cigarettes sold in Japan contain filters with activated charcoal. In contrast, only one percent of cigarettes sold in America have similar filters. Charcoal filters are efficient absorbers of a number of harmful chemicals including hydrogen cyanide, ammonia and formaldehyde. It may be that the charcoal also removes cancer causing chemicals as well. Charcoal filtered cigarettes have never been popular in the US as the filter also changes the taste of the inhaled tobacco stream.

Lung Cancer and Time

Although smoking prevalence amongst the current Japanese population is relatively high, this has not always been the case. Smoking only really became popular following the decade after the Second World War, while smoking popularity in many Western nations can be traced back 40 years earlier to the First World War. It is possible that the Japanese smoker’s paradox could be explained away by simple ‘catch up’. It is known that the lag between lung cancer and smoking, in many instances, is about 30 years. What we may be seeing, in the Japanese smoking population, is a delay in the rise cancer incidence due to the fact that the Japanese are relatively late comers to the smoking habit. If this is indeed the case then we should see a rise in lung cancer rates over the next few years as the cumulative damage due to smoking becomes manifest.

In the final analysis it may be a host of cumulative environmental factors that explain the Japanese smoker’s paradox. It will be interesting to see whether lung cancer rates in Japanese smokers increases within the next few decades due to the Japanese young increasingly embracing Western habits and lifestyle.