The Multiethnic Cohort, established in 1993–1996 in Hawaii and Los Angeles, was designed precisely to overcome a weakness that has plagued nutritional epidemiology: study populations dominated by White, well-educated participants whose habits and biology may not generalize. Colorectal cancer is the third most common cancer worldwide and the second leading cause of cancer death in the United States, and the burden is unevenly distributed. Black men and women in the US experience roughly 40 percent and 24 percent higher colorectal cancer mortality than their White counterparts, while disaggregated data show elevated rates among Japanese and Native Hawaiian populations. At the same time, national dietary surveys show that coffee consumption itself varies sharply by group, with non-Hispanic White individuals averaging about 1.5 cups per day, Hispanic individuals about one cup, and Black individuals about half a cup. Any study that hopes to draw honest conclusions about coffee and cancer survival must therefore contend with the fact that who drinks coffee, how much, and in what form differs profoundly across communities.

The new analysis capitalized on the cohort’s structure. Participants completed a validated food frequency questionnaire at enrollment and again a decade later, between 2003 and 2008. The researchers identified 1,098 individuals who were free of colorectal cancer at baseline, were diagnosed with the disease before the follow-up survey, and survived long enough to complete that second questionnaire, which captured post-diagnosis intake of regular coffee, decaffeinated coffee, and cappuccino-style drinks across nine frequency categories ranging from never to four or more times daily. Mortality was tracked through linkage with SEER cancer registries, state vital records, and the National Death Index through December 31, 2019, yielding 628 deaths, of which 107 were attributable to colorectal cancer. The median time from diagnosis to the post-diagnosis survey was nearly five years, and the average follow-up after that survey exceeded ten years, giving the analysis unusual depth.

Methodologically, the team used multivariable Cox proportional hazards regression, the workhorse of survival analysis, to estimate hazard ratios adjusted for a carefully assembled battery of confounders. The fully adjusted models accounted for age, sex, race and ethnicity, body mass index, time from diagnosis to the dietary assessment, tumor site and SEER stage, educational attainment, marital status, smoking status, physical activity, a comorbidity index spanning conditions from diabetes to Parkinson’s disease, history of another cancer, alcohol intake, and omega-3 fatty acid consumption. A third model mutually adjusted caffeinated and decaffeinated coffee against each other to disentangle their independent effects. Sensitivity analyses excluding participants who died within one or two years of the survey, those with distant-stage disease, those who did not undergo surgical resection, and records with missing data all left the core results intact, addressing the ever-present specter of reverse causation, in which sicker patients simply drink less coffee.

The central result was a null that speaks volumes. Total and caffeinated coffee intake showed no statistically significant association with all-cause or colorectal cancer-specific mortality in the overall cohort, although the association for total coffee and all-cause mortality hovered at the edge of significance, with a hazard ratio of 0.92 per additional cup per day and a p-value of 0.057. Decaffeinated coffee, by contrast, was clearly associated with survival: each additional cup per day carried a hazard ratio of 0.82 for all-cause mortality, and participants drinking at least one cup daily had a 29 percent lower risk compared with non-drinkers. The finding persisted even after controlling for caffeinated coffee consumption, suggesting that compounds other than caffeine, or the behaviors of people who choose decaf, may be at work.

The caffeine analysis added a twist that cuts against a simple decaf story. When the researchers aggregated caffeine from every source, including coffee, black tea, green tea, regular soda, and diet soda, participants in the top quartile of intake had a 22 percent lower risk of all-cause mortality and a 52 percent lower risk of colorectal cancer-specific mortality compared with those in the bottom quartile. The authors suggest that measuring caffeine across all dietary sources may have captured a wider range of exposure than coffee alone, where the cohort’s relatively modest consumption levels, topping out well below the four or more cups per day examined in prior studies, may have limited the ability to detect an effect.

The stratified results are arguably the study’s most consequential contribution. Among White participants, who reported the highest coffee and caffeine intake in the cohort, both total and caffeinated coffee were associated with lower colorectal cancer-specific mortality, with hazard ratios of 0.48 and 0.45 per additional daily cup, and decaffeinated coffee was again linked to lower all-cause mortality. Among Native Hawaiian participants, total and caffeinated coffee were associated with lower all-cause mortality, with hazard ratios of 0.62 and 0.55 per cup per day, an observation never before reported for this group. No statistically significant associations emerged among Black, Japanese American, or Latino participants. Formal tests for interaction did not reach significance, meaning the differences between groups could reflect chance, but the pattern is biologically and culturally plausible. Coffee strength, preparation methods, and additives such as sugar and cream vary across cultures, and coffee interacts with diet-dependent gut microbiome compositions and insulin dynamics in ways that could differ across populations.

Mechanistically, the plausibility of a coffee-cancer survival link rests on a substantial experimental foundation. In vitro and animal studies have shown that coffee and its constituents are antiproliferative, pro-apoptotic, antioxidant, and anti-inflammatory, capable of slowing the division of cancer cells and promoting their self-destruction. Coffee consumption has also been shown to reshape the gut microbiome and improve insulin sensitivity, both of which are implicated in colorectal carcinogenesis and progression, since hyperinsulinemia fuels tumor growth and inflammation accelerates it. Caffeine specifically may act by enhancing insulin sensitivity and by exerting anti-inflammatory effects that inhibit carcinogenesis. Prior clinical studies lend support: among 953 patients with stage III colon cancer in the CALGB 89803 trial, two or more cups of coffee daily were associated with longer disease-free survival, and among 1,599 patients with stage I–III colorectal cancer in the Nurses’ Health Study and Health Professionals Follow-up Study, four or more cups daily were linked to lower cancer-specific and overall mortality. A 2024 Global Cancer Update Programme meta-analysis graded the evidence as limited-suggestive, and a Dutch study of 1,719 patients reported a U-shaped relationship with the lowest mortality at four cups per day.

The authors are candid about limitations. Coffee consumption in this cohort was modest, few participants drank at the extremes where earlier studies found effects, and the very high consumption seen in some prior cohorts may itself signal healthier, more resilient patients, a bias this more moderate sample partly avoids. Some racial and ethnic subgroups were small, survival bias is unavoidable in a design requiring participants to live long enough to complete a post-diagnosis survey, residual confounding cannot be excluded in any observational study, and the multiplicity of exposures and outcomes examined raises the possibility of chance findings. Coffee recurrence data were unavailable. Still, the study is the first to interrogate the coffee-survival question in a genuinely multiracial population, and its message to patients and clinicians is refreshingly grounded: coffee after a colorectal cancer diagnosis, whether caffeinated or not, does not appear to be harmful, decaffeinated coffee and caffeine may both be associated with survival advantages, and future research should focus less on coffee as a monolith and more on caffeine itself and on how dietary factors interact with the biology of diverse populations.

Subject of Research: Association of post-diagnosis coffee and caffeine intake with mortality among colorectal cancer patients in a racially diverse cohort

Article Title: Association of coffee intake with risk of all-cause and colorectal cancer-specific mortality among individuals with colorectal cancer in the Multiethnic Cohort Study

Article References: Benson, K. R. K., Tolstykh, I., Chan, J. M., Piawah, S., Wilkens, L. R., Park, S.-Y., Kenfield, S. A., Le Marchand, L., Haiman, C. A., Cheng, I., & Van Blarigan, E. L. (2026). Association of coffee intake with risk of all-cause and colorectal cancer-specific mortality among individuals with colorectal cancer in the Multiethnic Cohort Study. Cancer Causes & Control, 37(10), Article 157. https://doi.org/10.1007/s10552-026-02246-w

Image Credits: AI Generated

DOI: 10.1007/s10552-026-02246-w

Keywords: colorectal cancer, coffee, caffeine, decaffeinated coffee, cancer survival, mortality, Multiethnic Cohort Study, nutritional epidemiology, cancer disparities, insulin sensitivity, gut microbiome, prospective cohort

Brazil cultivates coffee across approximately 2.25 million hectares, and the crop’s famously high productivity rests on heavy applications of mineral fertilizers, particularly nitrogen. Nitrogen is the engine of plant metabolism, forming the structural backbone of proteins, nucleic acids, and chlorophyll, and coffee plants grown in full-sun monocultures demand enormous quantities of it during vegetative growth, flowering, and fruit filling. But synthetic nitrogen inputs are notoriously inefficient: a large fraction is lost to leaching, volatilization, and denitrification before the plant can use it, driving up production costs while polluting waterways and warming the atmosphere. That inefficiency has pushed scientists to look beneath their feet for alternatives.

The research team focused on two adjacent coffee-producing areas in the municipality of Araponga, in the state of Minas Gerais, both planted with the Catuaí Vermelho variety at roughly 900 meters altitude and both cultivated for more than fifteen years. One farm followed conventional mineral fertilization, receiving 1,250 kilograms per hectare of NPK fertilizer split into two doses, along with lime. The other practiced organic fertilization, applying 400 kilograms per hectare of urea together with 6,000 kilograms per hectare of composted chicken litter. Soil samples were collected in November 2023 during the flowering stage, with ten composite samples gathered per farm from bulk soil around the tree trunks.

To coax out bacteria capable of living without fixed nitrogen, the team plated soil dilutions onto two nitrogen-free culture media, LGI and JMV, traditionally used to enrich diazotrophic bacteria. In total, thirty-eight morphologically distinct bacterial isolates were purified—nineteen from each farm—and identified by Sanger sequencing of the 16S rRNA gene, the standard molecular barcode for bacteria. The isolates spanned four phyla and fifteen genera, with members of Pseudomonadota and Actinomycetota dominating both farms. Intriguingly, isolates from the phyla Bacillota and Bacteroidota emerged exclusively from the organically fertilized soil, hinting that compost inputs had opened ecological niches that mineral fertilizer alone could not.

Only three genera—Pseudomonas, Streptomyces, and Acinetobacter—were shared between the two management systems. The organic farm exclusively yielded Paraburkholderia, Priestia, Flavobacterium, Curtobacterium, and Dyella, while the conventional farm alone harbored Burkholderia, Ralstonia, Luteibacter, Kosakonia, and Rhizobium. The researchers attribute these management-specific profiles to differences in carbon inputs and nutrient dynamics, noting that organic amendments generally increase soil organic carbon and niche heterogeneity, whereas mineral fertilization favors fast-growing copiotrophic microbes that exploit sudden nutrient pulses. The recovery of Rhizobium and Luteibacter under conventional fertilization was particularly noteworthy, expanding knowledge of these genera’s distribution in coffee agroecosystems.

The functional screening was where the study’s biotechnological promise crystallized. Eleven isolates from the organic farm and nine from the conventional farm grew in nitrogen-free semi-solid NFb medium, forming the subsurface microaerophilic pellicles and alkalinizing the indicator dye that signal a putative diazotrophic phenotype—the ability to convert atmospheric nitrogen into biologically usable forms. Even more striking, every single isolate recovered from the organically fertilized soil could solubilize tricalcium phosphate in vitro, dissolving an otherwise inaccessible mineral pool of phosphorus into forms plants can absorb. Standout performers included Streptomyces, Bacillus, Flavobacterium, and Acinetobacter strains with solubilization indices above 3, the threshold for classification as high-efficiency solubilizers.

Phytohormone production added a third dimension to the isolates’ toolkit. Quantified spectrophotometrically after growth in tryptophan-supplemented medium, indole-3-acetic acid—the principal auxin that stimulates root development—was produced by isolates from both farms, with no statistically significant difference between the two management systems. The most prolific producers included Priestia, Dyella, Paraburkholderia, and Bacillus from the organic soil, and Streptomyces and Luteibacter from the conventional soil. One Streptomyces isolate reached concentrations of up to 68.82 micrograms per milliliter, exceeding values previously reported for well-characterized plant growth-promoting Streptomyces strains, a result the authors describe as reinforcing the biotechnological potential of these genera.

What makes these findings compelling is the convergence of multiple traits within single isolates. A bacterium that simultaneously fixes nitrogen, unlocks phosphorus, and secretes auxins is a candidate for multifunctional microbial inoculants—living fertilizers that could reduce the environmental footprint of coffee cultivation while lowering input costs for farmers. The authors caution that their assays represent an initial in vitro screening. Confirming true diazotrophy will require quantitative nitrogen fixation assays such as acetylene reduction or nitrogen-15 isotope dilution, molecular detection of nitrogenase genes like nifH, and ultimately greenhouse and field inoculation trials to verify agronomic performance under real conditions.

Nevertheless, the study fills an important gap. While culture-independent metagenomic studies have catalogued the vast microbial diversity of coffee plantations across Latin America, cultivable isolates remain indispensable for experimentally validating microbial functions and translating ecological knowledge into practical agricultural products. By demonstrating that both organic and conventionally managed coffee soils harbor a resilient core microbiota alongside management-specific taxa with valuable plant growth-promoting traits, the research establishes a foundation for developing microbial consortia adapted to local edaphoclimatic conditions. For an industry confronting rising fertilizer prices, nitrogen losses, and mounting environmental scrutiny, the humble bacteria of Minas Gerais may prove to be coffee’s most valuable untapped resource.

Subject of Research: Cultivable plant growth-promoting bacteria in Brazilian Coffea arabica soils under organic and conventional mineral fertilization

Article Title: Cultivable diversity and plant growth-promoting traits of free-living bacteria from coffee soils under contrasting fertilization systems

Article References: Guimarães, C. V., Velozo, T. G. R., da Luz, J. M. R., Públio, G. C., da Silva, J. P. T., Pereira, L. L., & de Cássia Soares da Silva, M. (2026). Cultivable diversity and plant growth-promoting traits of free-living bacteria from coffee soils under contrasting fertilization systems. International Microbiology. https://doi.org/10.1007/s10123-026-00893-2

Image Credits: AI Generated

DOI: 10.1007/s10123-026-00893-2

Keywords: coffee, plant growth-promoting bacteria, nitrogen fixation, phosphate solubilization, indole-3-acetic acid, soil microbiome, organic fertilization, mineral fertilization, Coffea arabica, microbial inoculants, Brazil, sustainable agriculture