Although tomatoes provide a good source of the antioxidant lycopene, new research indicates that iron may half the absorption of the carotenoid.
Studying tomato extract and iron
A team of researchers from Ohio State University had seven men eat meals that consisted of a shake with tomato extract. Some drank the shake with an iron supplement (ferrous sulfate) and some drank the shake without the iron.
The scientists then analyzed the digestive fluids and blood from all the participants.
“When people had iron with their meal, we saw almost a twofold drop in lycopene uptake over time,” says Rachel Kopec, lead author of the study and assistant professor of human nutrition at Ohio State University. “This could have potential implications every time a person is consuming something rich in lycopene and iron—say, a Bolognese sauce, or an iron fortified cereal with a side of tomato juice. You’re probably only getting half as much lycopene from this as you would without the iron.”
How iron might affect lycopene
The brightly colored pigments synthesized by plants are called carotenoids. You probably recognize some of them by name: beta-carotene, lutein and alpha-carotene are just some of them commonly found in Americans’ diets.
But while carotenoids help fight cancer, scientists don’t know if these benefits come from the antioxidants or other compounds in the phytochemicals. There are two theories about why iron “dilutes” lycopene:
- Iron oxidizes lycopene, which, in turn, creates metabolites (other than apo-lycopenoids).
- Iron interrupts the mix of tomato and fats that are needed for cells to absorb the lycopene.
“It could turn it into a substance like separated salad dressing,” explains Kopec, “oil on top and vinegar on the bottom—that won’t ever mix properly.”
It’s worth noting that this study only used men and focused solely on apo-lycopenoids, not other metabolites.
