Iron deficiency presents medicine with a frustrating problem. Iron itself is inexpensive and easy to put into a tablet. Getting enough of that iron from the digestive system into the bloodstream is considerably more difficult. That helps explain why iron deficiency remains one of the world's most common nutritional problems despite the widespread availability of supplements. Oral iron can be poorly absorbed, food can interfere with its absorption and traditional supplements frequently cause gastrointestinal problems that make them difficult to tolerate.
Researchers at ETH Zurich believe they may have found a better way to deliver it. In a study published in Nature Food, scientists developed a new iron compound using microscopic structures made from oat protein coated with iron particles. In a clinical study involving 52 women with iron deficiency, the most effective version delivered substantially more absorbed iron than ferrous sulfate, one of the most commonly used forms of supplemental iron.
The difference was striking: participants absorbed an average of 46.2% of the iron from the new compound, compared with 26.3% from ferrous sulfate — roughly 76% more. The finding raises an intriguing possibility: perhaps improving iron treatment isn't simply a matter of giving people more iron. It may be about helping the body absorb more of what it is already given.
A supplement label may tell you how many milligrams of iron are in a tablet, but that number does not tell you how much will ultimately enter your bloodstream.
Iron absorption depends on its chemical form and on what else is being eaten at the same time. Compounds naturally present in foods — including polyphenols in tea and coffee and phytates found in grains, legumes, nuts and seeds — can significantly reduce the absorption of non-heme iron. That creates an obvious problem for supplements: a substantial portion of the iron someone swallows may never be absorbed. It also helps explain why researchers are interested in new ways of delivering the mineral.
The ETH team used oat globulin, one of the major proteins in oats, to create extremely small protein fibers called nanofibrils. Iron particles were attached to these structures, effectively creating a microscopic carrier for the mineral. One version was particularly successful because most of its iron remained in the ferrous, or Fe²⁺, form, which is more readily absorbed. But laboratory chemistry can only tell researchers so much. The real question was whether the human body would actually absorb it.
The clinical study included 52 women between 18 and 45 years old with iron deficiency.
Researchers used stable iron isotopes — non-radioactive forms of iron that can be tracked inside the body — to determine how much iron from each preparation was incorporated into red blood cells after consumption. Each dose contained 4 milligrams of elemental iron. When consumed in water, the oat-based formulation achieved an average iron absorption of 46.2%, compared with 26.3% for ferrous sulfate.
Researchers then made the test more difficult by giving the iron with an açai-and-honey mixture rich in polyphenols, compounds known to inhibit iron absorption.
The new formulation still performed better, producing approximately 65% greater absorption than ferrous sulfate under those conditions. That could be important in the real world, where iron is rarely consumed under perfectly controlled laboratory conditions.
Could better absorption mean fewer side effects?
Potentially — but we don't know yet. Traditional oral iron is notorious for gastrointestinal side effects, including nausea, abdominal discomfort, constipation and diarrhea. One reason is that much of the iron isn't absorbed and continues through the digestive tract.
If a greater proportion of a dose can be absorbed, it is reasonable to ask whether smaller amounts could eventually achieve the same effect while leaving less iron behind in the intestine. But this study did not prove that.
It was designed to measure iron absorption, not long-term tolerability. Researchers did not demonstrate that the new formulation causes less constipation, corrects anemia faster or raises ferritin more effectively over several months.
Those questions will require larger and longer clinical trials. Still, the study points toward an interesting change in strategy. The new approach asks a different question: What if we could simply make the iron easier for the body to use?
If larger clinical trials confirm these early results, the future of iron supplementation may depend less on increasing the dose and more on improving its delivery.
Study: Zhou J, et al. Oat protein nanofibril–iron hybrids offer a stable, high-absorption iron delivery platform for iron fortification. Nature Food. 2025;6:1164–1175. DOI: 10.1038/s43016-025-01260-6.
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