The review, published open access on 3 October 2026, set out to bring order to a literature that has produced stubbornly inconsistent results. Rather than running a new experiment, the authors conducted a comprehensive search of three major bibliographic databases, PubMed, Scopus, and Web of Science, hunting for quantitative studies published between 2000 and November 2024 that measured diet quality in adult immigrants and compared it against a meaningful reference group. That comparison could take one of three forms: immigrants versus the native-born population of the destination country, immigrants versus the native-born population of their country of origin, or the same individuals measured before and after migration. Only studies meeting these criteria, framed by the authors in a Population, Exposure, Comparator, Outcome, Study design, or PECOS, structure, were eligible.

Nineteen studies survived the screening process. That number may sound modest for a field as globally significant as migration and health, but it reflects how demanding the inclusion criteria were: the studies had to use validated quantitative indices of diet quality rather than loose proxies such as single food items or self-reported general eating habits, and they had to include an explicit non-migrant comparison group. Fifteen of the nineteen studies compared immigrants with the native-born population of their destination country. Within that group, seven studies found immigrants had higher diet quality, two found lower diet quality, and the remaining six reported mixed results, with outcomes differing either between immigrant groups or between the different diet quality indices used to score the same diets.

The second comparison strategy yielded a similarly nuanced picture. Five studies compared immigrants with the native-born residents of their countries of origin, effectively asking whether moving to a wealthier country improved the quality of what people ate relative to those who stayed behind. Three of those studies found immigrants eating better, one found them eating worse, and one found no significant difference at all. Finally, a single study took the most direct approach of all, tracking diets before and after immigration, and observed a decline in diet quality following the move. That lone longitudinal data point is a reminder that the aggregate statistics can conceal real individual trajectories of dietary deterioration.

Why would immigrants so often out-eat their new neighbors? The authors point to a cluster of mechanisms that researchers have been refining for decades. Many migrants arrive from food cultures built around home-cooked meals, fresh produce, legumes, and traditional dietary patterns that happen to align well with modern healthy eating indices such as the Alternative Healthy Eating Index, the Alternate Mediterranean Diet score, or the Healthy Eating Index. Compared with the highly processed, convenience-driven diets common in high-income destination countries, those inherited patterns can look remarkably protective. The review’s finding that most immigrant groups showed higher diet quality than non-migrants is consistent with this interpretation: the baseline diet a person brings with them can be better than the one waiting for them at the destination.

But the same review shows how quickly that advantage can erode, and for whom. The studies that reported poorer diet quality among immigrants concentrated in socioeconomically underprivileged groups, where the forces that shape eating are less about cultural heritage and more about budget, time, and access. The authors identify length of residence in the destination country as a key variable, reflecting the well-documented process of dietary acculturation: as migrants spend more years in a new food environment, their diets tend to converge toward local norms, and not always in a healthy direction. Educational attainment, financial status, and occupational conditions also emerged as contributing factors, as did food culture itself, the shared expectations and practices that determine what a family considers a proper meal.

Methodology matters too, and the review is unusually candid about this source of heterogeneity. Diet quality is not a single measurable quantity like blood pressure; it is a constructed score, and different indices weight different things. The studies included in the review used a wide array of instruments, among them the Healthy Eating Index, the Alternative Healthy Eating Index, the Alternate Mediterranean Diet score, the Diet Quality Index and its international variant DQI-I, the Dietary Diversity Score, the Food Variety Score, the Dietary Guidelines Index-2013, the Healthful Plant-based Diet Index, and the Pyramid-based Mediterranean Diet Score. A diet that scores well on a Mediterranean-style index might score only modestly on a diversity-based measure, and vice versa. Six of the fifteen destination-country comparisons reported mixed results precisely because different indices or different migrant subgroups produced different verdicts within the same study.

The practical implications reach well beyond academic taxonomy. Public health agencies in immigrant-receiving countries often design nutrition interventions on the assumption that migrants are a uniformly vulnerable population, and this review complicates that assumption in a useful way. If most immigrant groups eat better than their non-migrant neighbors, blanket dietary warnings aimed at migrant communities may miss the mark. The groups that genuinely need support are identifiable and specific: those facing economic precarity, those who have lived in the destination country long enough for dietary acculturation to take hold, and those whose food culture has been disrupted without being replaced by an equally healthy alternative. Targeted interventions grounded in socioeconomic status and length of residence, the review suggests, would be far more efficient than one-size-fits-all messaging.

There is also a broader scientific lesson in the paper’s structure. By explicitly separating the three comparison frames, destination-country natives, origin-country natives, and pre-migration baselines, the authors show that the question “do immigrants eat better or worse?” is not one question but three, and answers to one frame do not transfer to the others. An immigrant may eat better than a stay-at-home compatriot while eating worse than their new next-door neighbor, and both facts can be true simultaneously because the reference points measure different things: the effect of leaving versus the effect of arriving. The single before-and-after study, showing a decline in diet quality after migration, hints that the transition itself, with its stress, changed schedules, and unfamiliar food markets, may push diets downward even when the destination country offers greater abundance.

The review’s conclusion distills all of this into a single framing that is likely to shape future research: diet quality among immigrants is a function of multiple social, cultural, and economic factors, with socioeconomic status standing out as especially decisive. That is a more sophisticated picture than the simple narrative of migration as either dietary rescue or dietary ruin, and it sets a clear agenda. Future studies, the authors imply, should stop asking whether migrants eat well and start asking which migrants, under which conditions, measured with which instruments, and at what point in their migration journey. With international migration continuing to reshape the demographics of nearly every high-income country, the answer to that refined question will help determine whether the food systems of destination countries become a source of health for newcomers or another axis along which inequality is written into the body.

Subject of Research: Comparative diet quality of adult immigrants versus non-migrant populations

Article Title: Diet quality of adult immigrants compared with non-migrants: a systematic review of quantitative studies

Article References: Kohanmoo, A., & Mirfardi, A. (2026). Diet quality of adult immigrants compared with non-migrants: a systematic review of quantitative studies. BMC Public Health. https://doi.org/10.1186/s12889-026-29748-1

Image Credits: AI Generated

DOI: 10.1186/s12889-026-29748-1

Keywords: diet quality, immigrants, migration, systematic review, public health, nutrition, dietary acculturation, socioeconomic status, Healthy Eating Index, Mediterranean diet, food culture, BMC Public Health

The study, published in the journal Cancer Causes & Control, drew on the Multiethnic Cohort Study, a prospective population-based investigation that enrolled more than 215,000 residents of Hawaii and California between 1993 and 1996. Participants aged 45 to 75 completed detailed baseline questionnaires covering diet, medications, occupation, physical activity, family history of cancer, and immigration history. The research team, led by Haejin In of the Rutgers Cancer Institute together with Meira Epplein of Duke University, restricted their analysis to individuals who identified as Japanese or non-Hispanic White, ultimately following 94,232 participants for a median of just over 20 years. During that time, 716 primary gastric cancer cases were identified through statewide SEER cancer registries in Hawaii and California.

The central innovation of the study was its use of generational immigration status, a classification built from the birthplaces of the participants and their parents. Japanese descendants were divided into four groups: those born in Japan themselves, US-born individuals with both parents born in Japan, US-born individuals with one parent born in Japan, and US-born individuals whose parents were both born in the United States. Non-Hispanic White participants served as the reference group. The researchers then used Cox proportional hazards models, with age as the time scale, to estimate how gastric cancer risk varied across these groups while adjusting for a wide range of demographic, dietary, and lifestyle variables, including education, body mass index, smoking, alcohol consumption, fruit and sodium intake, diabetes history, and family history of the disease.

The results were unambiguous. Japan-born participants had a 4.62-fold higher hazard of developing gastric cancer compared with non-Hispanic Whites. Among US-born participants, the risk declined in a clear gradient: those with both parents born in Japan had a 3.66-fold higher hazard, those with one Japan-born parent had a 3.39-fold higher hazard, and those whose parents were both born in the United States had a 2.57-fold higher hazard. The trend across generations was highly statistically significant, with a p-value for trend below 0.0001. When the two second-generation groups were combined, their pooled risk was 3.59 times that of non-Hispanic Whites, confirming a progressive attenuation of risk across generations rather than a sharp drop confined to the transition from the first to the second generation.

Perhaps the most striking finding emerged when the researchers broke the results down by anatomical subsite. The generational association was driven almost entirely by non-cardia gastric cancer, the type that arises in the lower portions of the stomach and is most strongly linked to chronic infection with the bacterium Helicobacter pylori. First-generation Japanese descendants had a nearly six-fold increased risk of non-cardia cancer compared with non-Hispanic Whites, second-generation descendants a 4.5-fold increased risk, and third-generation descendants roughly a three-fold increased risk. When the analysis was restricted to precisely defined non-cardia subsites, the associations grew even stronger, with the first-generation hazard ratio reaching 7.13. In contrast, the associations for cardia cancer, the type arising near the junction with the esophagus, were weaker and showed no statistically significant linear trend across generations.

What could explain such a persistent, generational gradient? The leading hypothesis centers on Helicobacter pylori, the bacterium considered one of the major drivers of gastric cancer development. People who migrate from countries where H. pylori is highly prevalent are more likely to have acquired the infection during childhood, a critical window when chronic gastric inflammation can become established and shape long-term susceptibility to carcinogenesis. Persistent childhood infection is also associated with more virulent bacterial strains, such as those carrying the cagA and vacAs1m1 genes, which may disrupt early-life microbiota and immune regulation. Although H. pylori prevalence is known to decline across generations within immigrant families, the fact that third-generation Japanese descendants still face nearly triple the risk of non-Hispanic Whites suggests the bacterium alone cannot account for the full picture.

The authors point to a constellation of additional mechanisms that may be transmitted across generations or interact with the post-migration environment. Dietary acculturation is one candidate: first-generation immigrants in the cohort consumed the most sodium, a known risk factor for non-cardia gastric cancer, with intake declining in each subsequent generation, while body mass index rose across generations. Prior research has shown that a Westernized diet and lifestyle alter the gut microbiome, causing US-associated microbial communities to replace native Asian ones, with effects that intensify the longer a person lives in the United States. Studies of Japanese descendants have also documented a preference for Japanese food in the second generation giving way to Western foods in the third, alongside microbiome alterations linked to insulin resistance. Epigenetic programming may play a role as well; a cross-sectional study of Italian migrants found differences in DNA methylation compared with non-migrants even after adjusting for diet and lifestyle. Genetic variation adds yet another layer, with certain polymorphisms in inflammatory pathway genes, such as interleukin-1, reported among Japanese individuals to modify gastric cancer risk independently of H. pylori infection or smoking.

Notably, the researchers found no evidence that established risk factors, including family history of gastric cancer, education, body mass index, smoking status, and sodium intake, modified the association between generational status and cancer risk. This suggests that the generational gradient reflects distinct environmental, biological, or early-life influences rather than simple differences in these conventional exposures. The findings echo earlier work, including a landmark study by Kamineni and colleagues showing that first-generation Japanese immigrants to the United States had higher gastric cancer incidence than US Whites but lower rates than people in Japan, and a Hawaiian study by Kolonel and colleagues finding higher incidence among Japan-born than US-born Japanese residents. The new study extends this evidence with individual-level exposure data and more than two decades of prospective follow-up, advantages that registry-based studies could not provide.

The clinical implications are significant. Because the United States does not operate population-wide gastric cancer screening programs, unlike Japan and South Korea, identifying which groups stand to benefit most is essential. The marked differences in risk across immigrant generations, even within a single self-identified ethnic group, suggest that generational status could serve as a practical marker for risk-stratified screening. Prior studies have demonstrated the cost-effectiveness of gastric cancer screening among high-risk US groups, including Asian Americans undergoing upper endoscopy, opportunistic endoscopic examination during routine colonoscopy, and non-invasive biomarker approaches such as serum pepsinogen testing. Concentrating surveillance resources on the most at-risk generations could improve both the effectiveness and the accessibility of gastric cancer prevention for minority populations.

The study has limitations worth noting. Self-reported race and ethnicity may not perfectly reflect genetic ancestry, information on H. pylori infection itself was not available, and the cohort was drawn from Hawaii and California, regions with long-established Japanese American communities whose migration and acculturation patterns may differ from those of Japanese descendants elsewhere in the country. The authors call for replication in geographically diverse cohorts with detailed data on age at migration and duration of US residence. Still, the core message stands: the legacy of where a family came from, and when, is written into cancer risk for at least three generations. Understanding these transgenerational determinants, the authors argue, could reshape how the United States screens, detects, and prevents one of the world’s deadliest cancers.

Subject of Research: Generational immigration status and gastric cancer incidence among Japanese descendants in the Multiethnic Cohort Study

Article Title: Generational immigration status and gastric cancer incidence among Japanese descendants: an analysis of the Multiethnic Cohort (MEC) Study

Article References: In, H., De la Torre-Cisneros, K., Adams, A., Chen, C., Rana, B., Wilkens, L., & Epplein, M. (2026). Generational immigration status and gastric cancer incidence among Japanese descendants: an analysis of the Multiethnic Cohort (MEC) Study. Cancer Causes & Control, 37(10), Article 168. https://doi.org/10.1007/s10552-026-02250-0

Image Credits: AI Generated

DOI: 10.1007/s10552-026-02250-0

Keywords: gastric cancer, Japanese descendants, immigration generation, Multiethnic Cohort Study, Helicobacter pylori, non-cardia gastric cancer, health disparities, cancer screening, epidemiology, dietary acculturation, Cox proportional hazards, cancer risk