Optimizing nutrient absorption: Iron may hinder the benefits of carotenoid-rich foods

18 Sep 2019 --- Some of the anti-cancer benefits of tomatoes, specifically those from a compound called lycopene, could disappear when eaten with iron-rich foods, according to a new study from Ohio State University (OSU). The research sheds light on the importance of understanding the nutritional content of our foods for optimal nutrient absorption. Strategically pairing foods can boost nutrient absorption – such as lycopene in tomatoes and olive oil – but less is known about which pairings inhibit optimal absorption, or even hinder it. The researchers will further investigate lycopene’s role in fighting cancer and its interplay with other compounds and nutrients, to allow for more reliable, science-based dietary recommendations for disease prevention.

Iron is essential in the diet, performing such critical functions as allowing our bodies to produce energy and get rid of waste. But it’s also a nutrient that is known to influence other cellular-level processes. “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,” says Rachel Kopec, Assistant Professor of Human Nutrition at OSU.

In the study, the researchers analyzed the blood and digestive fluid of a small group of medical students after they consumed either a tomato extract-based shake which included iron or one without iron. Lycopene levels in digestive fluid and in the blood were significantly lower when the study subjects drank the liquid meal mixed with an iron supplement, meaning there was less for the body to use in potentially beneficial ways.

When people had iron, the researchers saw almost a twofold drop in lycopene uptake. This could mean dishes such as Bolognese deliver low levels of lycopene.“When people had iron with their meal, we saw almost a twofold drop in lycopene uptake over time,” says Kopec. “This could have potential implications every time a person is consuming something rich in lycopene and iron – for example, 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.”

Carotenoids are plant pigments with antioxidant properties responsible for many bright red, yellow and orange pigments found in the produce aisle. These include 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.

Consuming foods that are high in antioxidants – such as colorful fruit and vegetables – may also lower the risk of age-related cataracts (ARC) and cut restorative eye-sight medical bills by half. 

How does iron influence absorption?
The researchers state that 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 similar to a separated salad dressing – oil on top and vinegar on the bottom – that won't ever mix properly,” she notes.

“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,” Kopec says.

A common food pairing is vitamin E and fat. A recent study on this topic found that vitamin E can still be absorbed if a fat-containing meal is consumed within 12 hours of the nutrient’s ingestion. The findings of the study, published in The American Journal of Clinical Nutrition, offer a fresh look at how we can better adjust dietary recommendations for vitamin E to optimize its absorption. 

Meanwhile, a recent Penn State study found that the antioxidants naturally found in cheese may help protect blood vessels from damage from high levels of salt in the diet. Billie Alba, who led the study, said the findings may help people balance food that tastes good with minimizing the risks that come with eating too much salt.

In the supplement space, ensuring that the body absorbs as much omega as possible has been the focus of research from Evonik. This can be done by improving the bioavailability of the supplement. “At present, if a consumer takes a standard ethyl ester-based omega 3 supplement on an empty stomach, such as before breakfast, research has shown that they will absorb very little omega 3. With the development of [our product] AvailOm, we can improve levels of omega 3 absorption within the gut by three to four times irrespective of whether the consumer has fasted,” Dr. Christopher Studte, Director of New Health Ingredients, explains.

By Laxmi Haigh