Research: KOO, Department of Commun

Listed in Issue 25


KOO, Department of Community Medicine, University of Hong Kong. writes that a critical review (82 references) of epidemiological studies regarding diet and lung cancer over the past 20 years has not provided overwhelming evidence that higher consumption of vegetables, fruit, low-fat/low-cholesterol foods or micronutrients such as carotenoids, selenium and vitamins A, C or E is associated with reduced lung cancer risk.




Results from case-control studies have been more positive; about half the studies show fruit and vegetables or their associated micronutrients to be associated with reduced risk. However, most results from cohort and micronutrient studies which avoid the problems of inaccurate accounting of diet and recall bias, were statistically insignificant. Moreover, although the majority of studies were conducted with white North American and European male smokers, the few studies which determined significant contrary trends were with people of different backgrounds, such as black American males and Chinese women in China. As male smokers vs nonsmokers in Europe, North America and Japan have been shown in studies to be lower consumers of fruit/vegetables and less likely to pursue perceived healthier lifestyles, the possibility must be considered that some epidemiological findings regarding diet and lung cancer are artifactually due to inadequate adjustment for behavioural correlates of smoking and health seekers within a particular society. This is especially true with recent chemoprevention trials showing higher lung cancer incidence and deaths in the beta-carotene supplement group compared to the control group.



Koo LC. Diet and lung cancer 20+ years later: more questions than answers? Int J Cancer Supp 10: 22-9. 1997 .


At the risk of sounding like a broken record, I must reiterate that conducting long-term epidemiological studies regarding diet is fraught with logistical obstacles. Short of imprisoning people for long periods and subjecting them to a controlled diet, analysis of peoples lifetime diet and exposure to environmental carcinogens is short of impossible. And, in view of the molecular biology of cancer and its long incubation period, establishing whether certain foods or dietary micronutrients can negate the effects of decades of smoking, for example, will be an unenviable assignment. In this case, in my opinion, better to look at the cellular, animal and case-control research, despite their flaws.

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