The results suggest smokers and non-smokers exposed to second-hand smoke could benefit from daily intake of tomato juice although expert advice is clearly to avoid tobacco smoke altogether.
Smoking causes most cases of emphysema, a progressive and incurable disease. The alveoli in the lungs gradually lose their elasticity, making it more and more difficult for sufferers to force air in and out of their lungs.
There are over 1 billion smokers worldwide with 80 per cent of these people living in low and middle-income countries. Ten million people are diagnosed with emphysema in the US alone, with an estimated 14 million people not aware they have the disease.
The researchers, from the Juntendo University School of Medicine in Tokyo, exposed the mice models to short periods of tobacco smoke to induce emphysema over an eight-week period. A group of mice also had its water supply replaced by tomato juice (5 mg lycopene, 52.6 mg vitamin A).
Significant destruction of the alveoli in the lungs of the mice not given tomato juice indicated the development of emphysema. The ingestion of tomato juice produced convincing results.
"Smoke-induced emphysema was completely prevented by concomitant ingestion of lycopene given as tomato juice," wrote lead author Satoshi Kasagi in the American Journal of Physiology - Lung Cellular and Molecular Physiology (published online October 2005).
Lycopene, a potent antioxidant, can be extracted from tomatoes and is considered to the most efficient natural carotenoid for stopping reactive oxygen.
The balance between oxidant stress and antioxidant defences in the lungs is proposed to be a possible process that leads to emphysema. Therefore, intake lycopene could restore the natural oxidant-antioxidant balance.
Lycopene was detected in both serum and lung tissue samples of the test group, leading the researchers to propose, "lycopene modulates the oxidant-antioxidant balance perturbed by chronic tobacco smoke exposure."
However the researchers were unable to specify if the antioxidant effects were due solely to lycopene or from a combination of compounds found naturally in tomatoes.
"Since mice were given tomato juice instead of pure lycopene preparation, we cannot exclude a possibility that other ingredients contained in tomato juice affected the results," wrote Kasagi.