MONDAY, Jan. 9 (HealthDay News) -- Tomato juice prevented emphysema in mice exposed to cigarette smoke, a known cause of the lung-destroying disease, Japanese researchers report.
They attributed the protective effect to lycopene, an antioxidant with a somewhat checkered history as a supplement to protect against various diseases.
The Japanese report, in the February issue of the American Journal of Physiology-Lung Cellular and Molecular Physiology, appears to be the first to link tomato consumption to emphysema prevention.
The researchers are cautious about applying the findings to humans. "We can't simply accept that these results go beyond the mouse model," Kuniaki Seyama, a leader of the research team at Juntendo University School of Medicine in Tokyo, said in a statement. "They are not so smoothly applied to human beings."
But they said they would like to test the effect of tomato juice on people with chronic obstructive lung disease (COPD).
The U. S. Food and Drug Administration recently ruled that lycopene, found in red fruits such as tomatoes and watermelon, is not likely to reduce the risk of cancer. A highly publicized report that it might have such an effect briefly increased sales of ketchup.
On the other hand, Harvard University researchers have said their dietary studies indicate that one serving a day of tomato-based foods could reduce the risk of heart disease by as much as 30 percent.
The Japanese researchers used two breeds of mice, one normal and one bred to age quickly; emphysema would show up quicker in those mice, they explained.
They found that after eight weeks of exposure to cigarette smoke, the fast-aging mice did develop emphysema, while the normal mice did not. But when they had the mice drink a 50 percent tomato juice mixture, emphysema did not develop.
Lycopene was probably responsible for the protective effect, they wrote, because tobacco smoke is full of tissue-destroying oxidant molecules and lycopene is a powerful antioxidant.
"We expect that lycopene modulates the oxidant-antioxidant balance perturbed by our experimental condition of tobacco smoke exposure," they wrote.
But a different explanation was proposed by Richard C. Baybutt, an associate professor of human nutrition at Kansas State University, who has done research along the same lines.
Tomato juice is rich in beta-carotene, which is easily converted to vitamin A, Baybutt said. And his experiments with rats showed that "animals on a vitamin A-deficient diet without any exposure to smoke developed emphysema," he added.
In addition, one notorious component of cigarette smoke, benzopyrene, induces vitamin A deficiency, another connection between lack of that vitamin and emphysema, Baybutt said.
Comprehensive information on emphysema is available from the National Library of Medicine.