Carotenoids are plant pigments with antioxidant properties responsible for many bright red, yellow and orange pigments found in the produce aisle.
These include compound lycopene, which is found in abundance in tomatoes and also colors watermelon and pink grapefruit.
Scientists have identified several potential anti-cancer benefits of lycopene, including in prostate, lung and skin cancers.
But in a recent study from Ohio State University, researchers found eating tomato sauce with meatballs piled on top could have a surprising downside.
This is because some of the anti-cancer benefits of tomatoes, specifically those from lycopene, could disappear when they’re eaten with iron-rich foods.
Iron is essential in our diet, performing such critical functions as allowing our bodies to produce energy and get rid of waste.
The study is published in Molecular Nutrition & Food Research. The lead author is Rachel Kopec, an assistant professor of human nutrition at Ohio State.
In the study, the team analyzed the blood and digestive fluid of a small group of medical students after they consumed either a tomato extract-based shake with iron or one without iron.
They found lycopene levels in digestive fluid and in the blood were much lower when the people drank the liquid meal mixed with an iron supplement, meaning there was less for the body to use in potentially beneficial ways.
It’s unclear precisely what is happening that is changing the uptake of lycopene, but it could be that the meal with iron oxidizes the lycopene, creating different products of metabolism than those followed in the study.
It’s also possible that iron interrupts the nice emulsified mix of tomato and fats that is critical for cells to absorb the lycopene.
It could turn it into a substance like separated salad dressing—oil on top and vinegar on the bottom—that won’t ever mix properly.
This finding 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.
People are probably only getting half as much lycopene from this as they would without the iron.
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