Although expert advice is clearly to avoid tobacco smoke altogether, the results suggest smokers could benefit from upping their intake of cruciferous vegetables like broccoli and cauliflower that contain the compound indole-3-carbinol (I3C).
Writing in Cancer Prevention Research, scientists from the University of Minnesota report that mice exposed to carcinogens found in tobacco smoke and fed varying doses of I3C had significant reductions in the number of lung tumours.
Indeed, mice fed the highest amount of I3C had 88 per cent fewer tumours than control mice, with the scientists reporting the compound appeared to act on inhibiting cell proliferation, and enhancing programmed cell death (apoptosis).
“These results clearly show the efficacy of I3C in the prevention of tobacco carcinogen-induced lung tumorigenesis in […] mice and provide a basis for future evaluation of this compound in clinical trials as a chemopreventive agent for current and former smokers,” wrote lead author Fekadu Kassie.
One in three Europeans are smokers, while the US figure is one in five. Tobacco smoke contains over 4,000 compounds, of which 60 are known carcinogens. The oxidative stress levels of smokers are significantly greater than non-smokers, and as such there is a bigger drain on the levels of antioxidants in the body.
Kassie and co-workers exposed experimental mice to carcinogenic compounds found in tobacco smoke called 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) plus benzo(a)pyrene (BaP).
This resulted in an average of 21 tumours per mouse after 16 weeks. However, mice fed diets containing 1, 10, 30, 71, and 112 micromoles per gram of I3C were found to have reductions in the number of tumours by 15, 51, 53, 75, and 88 per cent, respectively.
The results need to be repeated in additional studies, and supported by human studies, if the findings are to be applicable to humans.
Previous epidemiological and animal studies have shown that diets high in such vegetables resulted in less instances of certain cancers, while a trial supplementing the diet with I3C reported the prevention of oestrogen-dependent tumours.
Lung cancer is the most common form of cancer worldwide with over 1.2m new cases diagnosed annually, according to the European School of Oncology. It has one of the lowest survival rates with only 25 per cent of patients surviving more than one year after diagnosis (England and Wales).
Source: Cancer Prevention Research December 2008, Volume 1, Issue 568-576, doi: 10.1158/1940-6207.CAPR-08-0064“Dose-Dependent Inhibition of Tobacco Smoke Carcinogen–Induced Lung Tumorigenesis in A/J Mice by Indole-3-Carbinol”Authors: F. Kassie, I. Matise, M. Negia, P. Upadhyaya, S.S. Hecht