Colorless Tomato Compound Sharply Cuts Fatty Liver Disease in Mice

Researchers at Tufts University have found that phytoene, a colorless compound in tomatoes, sharply reduced fatty liver disease in mice — a discovery that could help explain why whole tomato powder has sometimes protected the liver better than purified lycopene alone. The study, published in Molecular Nutrition & Food Research, focused on metabolic dysfunction-associated steatotic liver disease, in which fat builds up in liver cells and can eventually cause inflammation, tissue damage and cirrhosis. The disease is estimated to affect up to 38% of U.S. adults, rising to 75% among those with obesity or diabetes.

Phytoene is a colorless precursor that plants use to make lycopene, the red pigment that draws most attention in tomatoes. Lead author Na Youn Lee, a PhD candidate at Tufts' Friedman School of Nutrition Science and Policy, said phytoene is more readily absorbed by the body than lycopene. For the study, researchers fed mice a diet rich in refined carbohydrates for six months, giving half of them phytoene at a dose comparable to a person eating three to four medium raw tomatoes a day.

Mice given phytoene developed far less severe fatty liver disease on the same diet, though changes in gut bacteria did not explain the protection. Instead, phytoene activated proteins that control liver metabolism, shifting the liver toward burning fat rather than storing it. Mice lacking two enzymes that process carotenoids accumulated more phytoene yet got no protection, suggesting it must first break down into smaller metabolites. Female mice also accumulated more phytoene than males, though its effect on protection is unclear.

Senior author Xiang-Dong Wang, a scientist at Tufts' Jean Mayer USDA Human Nutrition Research Center on Aging, said phytoene is also found in carrots, red peppers, pink grapefruit, watermelon and apricots, giving the findings broad implications. He said that, if further research confirms the results, encouraging people to eat more phytoene-rich foods could help prevent or slow metabolic liver disease in high-risk people.