A study from Karolinska Institutet in Sweden, published in Cell on August 19, 2026, identifies a specific molecule that gut microbes build from ingredients in vegetables. The compound is called a dinitrosyl iron complex, or DNIC, and raising its levels was tied to lower blood pressure, improved vascular function, better blood sugar control and less fat accumulation in the liver in the animal model tested.
The raw materials are two things vegetables happen to deliver together. One is nitrate, concentrated in beetroot and leafy greens such as spinach, arugula and lettuce. The other is non-heme iron, the plant form of iron found in beans, whole grains and green vegetables. Gut bacteria appear to combine the two into DNICs, which are then absorbed into the bloodstream and reach organs, primarily the liver and the kidneys.
Why the microbiome is doing the work
Researchers compared conventional mice with germ-free mice raised without any gut microbes. DNICs were present in the tissues of the first group and completely absent in the second, pointing to bacteria as the necessary step. The study drew on experiments in mice, cells, bacteria and human samples, using advanced analytical methods to detect DNIC in tissue.
Andrei L. Kleschyov, senior researcher at the Department of Physiology and Pharmacology at Karolinska Institutet, said in the university's press release that "gut bacteria can convert components in food into biologically active molecules that influence important bodily functions."
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DNICs also function as a storage form of nitric oxide, a short-lived molecule that helps blood vessels relax. That is one plausible route to the lower blood pressure seen when DNIC levels were raised in the study.
What it adds to what we already knew
Nutrition science has long linked vegetable-heavy diets to lower cardiovascular risk, and part of the accepted mechanism runs through bacteria in the mouth that reduce nitrate to nitrite, which the body then converts to nitric oxide. A 2024 review in Nutrition Research Reviews laid out that oral pathway in detail. The new work does not replace it. It adds a second, gut-based route that also depends on microbes for the conversion to happen.
Mattias Carlström, professor of cardiorenal physiology at Karolinska Institutet and one of the study's shared last authors, said the findings help explain "why a diet rich in vegetables, which contain both nitrate and iron, is linked to a lower risk of several diseases."
What it means for your plate, cautiously
The practical read is familiar advice with a new reason behind it. Meals that pair nitrate-rich leafy greens or beets with plant sources of iron give the microbes the substrate they seem to need. A systematic review of beetroot juice trials already found modest reductions in blood pressure in people with hypertension, consistent with the broader nitrate story.
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The caveats matter. The Karolinska team measured DNICs in mice, cells, bacteria and human samples, not in a clinical trial. The researchers say they now need to develop methods to detect DNICs directly in humans and to study how the compound behaves in the body. Anyone with high blood pressure or on medication should keep working with their doctor rather than making changes based on a single early study.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.