Such research is significant because iron deficiency remains the leading nutrient deficiency in both developed as well as developing countries. It affects around one in five women in the UK.
Many women are encouraged to take supplements but research suggests that these are not always very effective as the body has trouble taking up the form of iron provided.
This problem is compounded when coffee or tea are drunk during mealtimes, because the beverages have been shown to reduce iron absorption in the gut.
The new study, by Maria García-Casal from the Venezuelan Institute of Scientific Investigations, reports that consumption of 3.6 milligrams of lycopene, or 1.8 milligrams of lutein and/or zeaxanthin, improved iron absorption (in the form ferrous fumarate) and were also "capable of overcoming coffee-mediated inhibition of iron absorption."
García-Casal recruited 128 volunteers (average age 32, 89 women) and assigned them to one of five study groups. Each group contained about 20 volunteers. Each group was given four different breakfasts during the course of the study, containing precooked white corn flour (donated by Alimentos POLAR Commercial) or white wheat flour (donated by Cargill), both of which were enriched with ferrous fumarate (5 milligrams).
The fist meal was the simple iron-enriched breakfast. Meal 2 was fortified with lycopene (either 1.8 or 3.6 mg), meal 3 with lutein (0.9 or .8 mg), and meal 4 with zeaxanthin (0.9 or 1.8 mg). Some of the groups were also given coffee to drink with the breakfast.
"The highest amount of carotenoid used (3.6 mg) was chosen as a result of previous experiences with beta-carotene, because it achieved a significant increase in iron absorption capable of counteracting coffee-mediated inhibition," explained García-Casal in the journal Nutrition Research (Vol. 26, pp. 340-344).
Absorption of iron from the wheat-based breakfast was found to significantly increase in the presence of the carotenoids, with no significant difference between the individual carotenoids, compared to the simple iron-enriched breakfast.
Similar results were observed for the corn bread groups, although absorption was lower from the corn breakfasts compared to the wheat breakfast.
The lower doses did not appear to affect iron absorption, but the higher doses did significantly improve the absorption and were not inhibited by coffee.
"To my knowledge, there is no report on carotenoids increasing iron absorption from food and the mechanism responsible for the effect needs to be addressed," said García-Casal.
One potential mechanism, said the author, could be due to an association between the carotenoid and the iron molecule, which changes the solubility of the iron form and improves the absorption in the gut. This remains to be demonstrated scientifically, said García-Casal, "but there are some other evidence besides solubility changes that seem to indicate direct iron-carotenoid binding."
The research could lead to improved bioavailability of iron from supplements that would help tackle iron deficiency and related diseases like anaemia. It is well established that absorption of iron from animal tissue (haem iron) is better absorbed that synthetic forms of the mineral.
Haem iron is absorbed around five times more efficiently than the inorganic iron from plant sources and is therefore better at preventing deficiency.