Iron-rich foods may cancel out tomatoes' anticancer benefits

New research finds that iron halves the absorption of lycopene. Lycopene is a carotenoid full of antioxidants that is present in tomatoes.

Adding iron-rich meat to tomato sauce might counter tomatoes' health benefits.

Tomatoes offer a rich variety of health benefits.
These range from protecting against cancer and hypertension to maintaining the health of our heart, skin, and eyes.
Regarding cancer, previous studies have found a link between lycopene — which is a plant compound present in tomatoes — and a lower risk of prostate cancer, colon cancer, and lung cancer, among others.
Although consuming lycopene-rich foods is good for health, other nutrients that we combine them with may help or hinder their cancer fighting properties.
For instance, a small new study now suggests that consuming foods or supplements rich in iron may halve the benefits of lycopene.
Rachel Kopec, an assistant professor of human nutrition at Ohio State University in Columbus, was the lead author of the new study. The findings appear in the journal Molecular Nutrition & Food Research.

Why we may only get half the lycopene

Kopec and colleagues set out to examine the "formation and absorption of lycopene metabolites" in seven males who consumed test meals, both with and without iron. The test meals consisted of a shake with tomato extract.
The participants drank the shake either with ferrous sulfate as an iron supplement or without. The researchers analyzed the participants' blood and digestive fluids.
"When people had iron with their meal, we saw almost a twofold drop in lycopene uptake over time," explains Kopec.

"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."

Rachel Kopec

"Nutrition can play an important role in disease prevention, but it's important for us to gather the details about precisely how what we eat is contributing to our health so that we can give people reliable, science based recommendations," emphasizes the researcher.

How does iron counter lycopene's benefits?

Kopec explains the strength of the research, saying that it adds to our knowledge of iron's cellular disruption.
"We know that if you mix iron with certain compounds it will destroy them, but we didn't know if it would impair potentially beneficial carotenoids, like lycopene, found in fruits and vegetables," she says.
Carotenoids are "yellow, orange, and red pigments synthesized by plants." Alpha-carotene, beta-carotene, lutein, and lycopene are some of the most prevalent carotenoids in the Western diet.
These plant pigments have antioxidant properties, but researchers do not yet know with certainty whether these phytochemicals owe their potential cancer fighting properties to the antioxidants they contain or to other compounds, which may have nothing to do with antioxidants.
In the case of the recent research, the mechanisms behind the lycopene "diluting" effects of iron also remain a mystery. One possibility, however, is that the iron oxidizes the lycopene, creating metabolites other than apo‐lycopenoids, which were the only ones the team studied this time around.
"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," Kopec explains.
The study authors note that using only male participants in their tests, as well as focusing exclusively on apo‐lycopenoids, limits the study findings.