For four weeks, 12 adults with obesity drank a specially formulated tomato-soy juice every day. By the end, their blood showed lower levels of inflammatory markers tied to metabolic disease, and their urine revealed shifts in metabolites linked to lipid oxidation and amino acid processing. When those same people switched to a control juice without soy or significant carotenoids, the changes faded.
The results, published in May 2026 in Molecular Nutrition and Food Research, come from a randomized crossover trial run by researchers at the USDA-ARS Beltsville Human Nutrition Research Center and Ohio State University. The study is small, but its design and federal research backing make it one of the more rigorous tests of whether a targeted food formulation can dial down the chronic, low-grade inflammation that accompanies obesity.
What the juice contained and how the trial worked
The fortified beverage was engineered to deliver high concentrations of two plant compounds: lycopene, the red pigment in tomatoes and a potent antioxidant, and soy isoflavones, a class of phytoestrogens found in soybeans. The control juice was a low-carotenoid tomato drink with no soy component.
Each participant consumed both beverages in separate four-week periods, with a washout phase in between. Because every person served as their own control, the crossover structure helps neutralize confounding variables like age, sex, baseline body fat, and medication use. The trial was pre-registered on ClinicalTrials.gov before enrollment began, allowing independent verification of its planned endpoints.
Compliance was tracked through self-reported intake and confirmed by the presence of lycopene-related metabolites in biological samples. No serious adverse events were attributed to the juice.
What the researchers found
Compared with the control period, the tomato-soy juice phase was associated with reductions in selected inflammatory cytokines and chemokines. The published findings also documented shifts in urinary metabolites, particularly those connected to oxidized lipid species and amino acid metabolism, suggesting the bioactive compounds were not just absorbed but were influencing downstream metabolic pathways.
“This crossover design allowed us to see consistent within-person changes in inflammatory markers that would be difficult to detect in a parallel-group study of this size,” said lead investigator Janet Novotny of the USDA-ARS Beltsville Human Nutrition Research Center, as reported in the published paper.
The pairing of lycopene with soy isoflavones was deliberate. The authors cite earlier human trials showing that plain tomato juice reduced systemic inflammation in overweight and obese women, with measurable drops in C-reactive protein, though the current paper does not provide direct citation links to those specific studies. Separate prior work found that trans-lycopene from tomato juice attenuated inflammatory biomarkers in plasma. And in preclinical research, a soy-tomato enriched diet lowered inflammation and disease severity in a chronic pancreatitis model, hinting that the two compound classes might work better together than alone. These supporting references are discussed in the paper’s introduction but are not independently linkable here.
A prior bioavailability study on a closely related soy-fortified, lycopene-rich tomato juice, also referenced by the authors, had confirmed that the phytochemicals reach measurable levels in the bloodstream and urine rather than simply passing through the gut unabsorbed. That pharmacokinetic groundwork gave the team confidence to focus the new trial on functional outcomes rather than absorption questions.
Why 12 participants is both a strength and a limitation
Crossover trials squeeze more statistical power from fewer people because each participant generates data under both conditions. That makes 12 participants more informative here than it would be in a parallel-group design. Still, the sample is far too small to capture the full range of human variability in gut microbiome composition, baseline diet, and genetic differences in lycopene metabolism, all of which could influence individual responses.
Kevin Maki, a clinical trialist and president of the Midwest Biomedical Research Center who was not involved in the study, has noted in prior commentary on similar nutrition trials that crossover designs with fewer than 20 participants can reliably detect large biomarker shifts but are poorly suited to identifying modest effects or subgroup differences. That general caution applies here: the inflammatory marker reductions may be real, but their magnitude and consistency across a broader population remain unproven.
No larger follow-up trial or long-term data appear in the published record or the trial registration as of June 2026. That means the durability of the observed changes remains unknown. A four-week window can show that something is happening biologically, but it cannot tell us whether the effect persists, plateaus, or reverses over months.
The trial also did not include a head-to-head comparison isolating the contribution of soy isoflavones from that of lycopene. The control juice differed from the fortified version in multiple ways, so it is impossible to say from this data alone whether the soy component added a distinct anti-inflammatory benefit or whether lycopene did most of the heavy lifting. Answering that question would require a factorial design with four arms: lycopene alone, soy isoflavones alone, the combination, and a matched placebo.
Open questions the study does not answer
Dose-response is a blank spot. The juice was formulated with relatively high amounts of both compounds, but the study did not test lower or higher doses, nor did it examine whether splitting intake across the day matters compared with a single serving.
It is also unclear whether eating whole tomatoes alongside soy foods, such as tofu or edamame, would produce similar results. Whole foods differ from a formulated juice in fiber content, food matrix effects, and the presence of other bioactive compounds that could either amplify or blunt the response.
Full individual participant data and detailed results tables for pre-specified secondary endpoints have not been deposited in a public repository. That limits the ability of outside researchers to run independent statistical analyses or pool this trial with earlier work in meta-analyses.
One intriguing thread in the urinary metabolome data is the possibility that lycopene and soy isoflavones undergo co-metabolism, producing oxidized lipid species that neither compound would generate on its own. Confirming that hypothesis would require targeted lipidomics in a larger cohort.
How a formulated juice fits into the broader inflammation picture
The trial offers proof-of-concept, not a prescription. It demonstrates that a carefully formulated plant-based beverage can shift inflammatory and metabolic biomarkers in adults with obesity over a matter of weeks. That is a meaningful step beyond animal studies and observational data.
But the findings do not establish that this approach reduces hard clinical outcomes like cardiovascular events, type 2 diabetes progression, or liver disease. They also do not clarify how a tomato-soy juice stacks up against established anti-inflammatory strategies: sustained weight loss, regular physical activity, or medications like metformin or statins.
For anyone considering adding tomato-soy products to their diet, the practical reality is that no commercially available juice has been shown to replicate this trial’s specific formulation or results. The beverage used in the study was purpose-built for research, with controlled concentrations of lycopene and isoflavones that off-the-shelf products may not match.
The study’s most lasting contribution may be methodological. It shows that food-based interventions can be tested with the same rigor applied to pharmaceutical trials, using pre-registration, crossover designs, and metabolomic profiling. That framework could shape a new wave of nutrition research focused not on single nutrients in isolation but on combinations designed to work together, tested in the populations most likely to benefit.
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*This article was researched with the help of AI, with human editors creating the final content.
