Gut Bacteria Turn Diet Into a Heart-Protecting Molecule, Study Finds

Every time you eat a plate of spinach or a beet salad, your gut bacteria may be quietly manufacturing a molecule that protects your heart and liver – at least if you are a mouse. A study published in Cell found that gut microbes convert dietary nitrate and iron into compounds called dinitrosyl iron complexes (DNICs), and that boosting these compounds improved blood pressure, blood sugar control, and fatty liver in mice fed a Western-style diet. For anyone tracking a gut-health link to heart disease, high blood pressure, or fatty liver, this is one of the more concrete mechanistic explanations yet offered for why a vegetable-heavy diet keeps showing up in better cardiometabolic outcomes.

Key takeaways:

• Gut bacteria convert dietary nitrate (from spinach, beets, and other vegetables) and iron into dinitrosyl iron complexes (DNICs), and these compounds are completely absent in mice with no gut bacteria at all.
• In mice with diet-induced cardiometabolic dysfunction, raising DNIC levels – either through diet or a synthetic version of the compound – lowered blood pressure, improved glucose tolerance, and reduced liver fat.
• The mechanism runs through a cell-signaling pathway (cGMP) that relaxes blood vessels and a separate pathway that dials down fat-storage signals in the liver.
• The catch: every benefit was shown in mice and human cells in a dish, not in people – there's no human clinical trial data yet.

Gut Bacteria Manufacture Dinitrosyl Iron Complexes From Diet

Researchers at Karolinska Institutet found that gut bacteria transform dietary nitrate and non-heme iron (the form of iron found in plant foods, as opposed to the heme iron in meat) into dinitrosyl iron complexes, or DNICs – molecules built around an iron atom bound to nitric oxide. Using electron paramagnetic resonance (EPR, a technique that detects specific iron-nitrogen structures), the team measured DNICs in the liver and kidneys of normal mice and found none in germ-free mice, which lack gut bacteria entirely. That absence is the key evidence: without gut microbes, the body doesn't make these compounds on its own, no matter how much nitrate and iron are in the diet. The team traced the chemistry further, showing that mouse and human feces, along with lab-grown E. coli, generate DNICs from nitrate and iron – and that an E. coli strain engineered to lack the nitrate-reducing enzyme could not, tying the effect to a specific bacterial process rather than a coincidence of gut chemistry.

Blood Pressure and Fatty Liver Are the Conditions to Watch

This matters most for readers already worried about high blood pressure, prediabetes, or non-alcoholic fatty liver disease, since all three showed up as endpoints in the study, and all three are conditions repeatedly linked to gut health in ways that have been hard to pin down mechanistically. Gut microbiome research has connected microbial imbalance to metabolic disease for years, but a specific molecule the microbiome produces – one that a reader can trace to a specific vegetable and mineral in their own diet – is a rarer and more useful kind of finding. If DNICs hold up as a real driver of the diet-microbiome-heart connection in humans, it would help explain a pattern nutrition researchers have observed for over a decade: that nitrate-rich vegetables like beets and leafy greens are consistently associated with lower blood pressure.

Germ-Free Mice and Gene-Knockout Bacteria Built the Causal Case

The strength of this study is in how it ruled out coincidence. Beyond the germ-free comparison, the researchers fed mice a Western-style diet to induce cardiometabolic dysfunction, then gave separate groups either dietary nitrate plus iron or a synthetic DNIC supplement, with groups of 10 to 20 mice repeated across multiple independent experiments. Both interventions lowered blood pressure, improved glucose tolerance, and reduced hepatic steatosis (fatty liver) compared to untreated Western-diet mice. The researchers then worked out the biology underneath the effect: DNICs activate a signaling pathway called soluble guanylate cyclase (sGC)-cGMp, which relaxes blood vessels, and separately suppress a growth-signaling pathway (mTORC1-SREBP1) that drives fat storage and buildup in the liver – and they showed this happens independently of free nitric oxide release, meaning DNICs aren't just a slow-release form of a mechanism already well understood.

What This Means If You're Watching Your Own Heart or Liver Health

None of this is a green light to load up on iron supplements or treat beets as medicine. The blood pressure, blood sugar, and liver improvements were demonstrated in mice, not people, and the study's human data is limited to confirming that human feces and gut bacteria can also generate DNICs – not that doing so changes a person's blood pressure or liver fat. What it does support, cautiously, is a mechanistic reason behind existing advice: eating plenty of nitrate-rich vegetables (spinach, beets, arugula) alongside plant sources of iron (beans, whole grains) gives your gut bacteria the raw material to make a compound your body appears built to use. If you already have high blood pressure, prediabetes, or fatty liver and are researching dietary changes, this is a study to mention to a doctor as context, not a supplement or protocol to start on your own – synthetic DNIC compounds used in the study are not an available consumer product.

Open Questions Before This Reaches the Clinic

The researchers themselves flagged the obvious next step: this is an animal and cell-line study, and how directly it translates to humans is unknown. It's not established how much dietary nitrate and iron a person would need to eat, in what form or combination, to meaningfully raise their own DNIC levels, or whether gut bacterial composition varies enough between people to make this work reliably for everyone. There's also no human trial yet testing whether raising DNICs changes blood pressure or liver fat in people the way it did in mice. The study authors reported no competing financial interests, and the work was funded by the Swedish Research Council, the Swedish Heart and Lung Foundation, and Karolinska Institutet.

What Comes Next for DNIC Research

The researchers describe this as groundwork for future human studies rather than a finished story. DNICs have separately been studied in lab settings for their protective effects on human heart cells, which lends some independent support to the idea that these compounds do something biologically real rather than being an artifact of the mouse model. The logical next step – not yet undertaken, per the researchers – is testing whether nitrate-and-iron intake or a DNIC-based intervention changes blood pressure, blood sugar, or liver fat in human volunteers, and whether gut microbiome composition predicts who benefits most.

Common Questions

What are dinitrosyl iron complexes (DNICs)? They're molecules made of an iron atom bound to nitric oxide, produced when gut bacteria process dietary nitrate (from vegetables like beets and spinach) together with non-heme iron (from plant foods like beans and whole grains).

Do I need to take an iron supplement to get this benefit? No. The study didn't test iron supplements in isolation, and there's no established dose or product shown to raise DNIC levels in humans – the finding supports eating nitrate- and iron-rich vegetables generally, not supplementing with iron.

Does this mean beets or spinach lower blood pressure in people? Separately from this study, nitrate-rich vegetables like beets have long been linked to modest blood pressure reductions in human research; this new study adds a possible bacterial mechanism behind that link, but the specific DNIC-driven benefits were shown only in mice.

Is this relevant if I don't have high blood pressure or liver problems? The findings are most directly relevant to people managing or researching high blood pressure, prediabetes, or fatty liver, since those were the conditions tested – but the underlying diet-microbiome mechanism could plausibly matter for general cardiometabolic health as more human research emerges.

References

1. Andrei L. Kleschyov, Miho Shimari, Ariela Maína Boeder, et al. (2026). Gut microbiota generate dinitrosyl iron complexes with cardiometabolic benefits. Cell. https://doi.org/10.1016/j.cell.2026.07.055
2. Natalia Pavlovna Akentieva, Natalia Alekseevna Sanina, Artur Rasimovich Gizatullin, et al. (2019). Cytoprotective Effects of Dinitrosyl Iron Complexes on Viability of Human Fibroblasts and Cardiomyocytes. Frontiers in Pharmacology. https://doi.org/10.3389/fphar.2019.01277