Previous reports have demonstrated that risk for stroke mortality varies among ethnic groups , and that dietary patterns also differ by ethnicity [8, 9]. To date, there is a lack of research on ethnic specific effects of adherence to the recommended daily servings of fruits and vegetables and risk for fatal stroke. African Americans and Latinos were included in the Continuing Surveys of Food Intakes by Individuals (CSFII) 1994–96, but the samples of these ethnic groups were relatively small . The 3rd National Health and Nutrition Examination Survey (NHANES III) included a large sample of African Americans and Latinos born in Mexico, but the results on adherence to recommendations have not yet been published . Furthermore, no national survey has yet investigated these associations among Asians or Pacific Islanders, who are estimated to comprise 5% of the U.S. population . Neither NHANES nor CSFII sampled populations in Hawaii, a state with a clustering of Japanese Americans [22, 23]. Thus, the MEC study provided a unique opportunity to explore the associations between risk for stroke mortality and dietary intake among a very large sample representing these ethnic groups in the United States.
In the current study, statistically significant associations were observed between adherence to dietary recommendations for fruit intake and risk for fatal stroke among Japanese American women. These effects were not observed in Japanese American men, nor any other ethnic-sex group. The apparent stronger association among a specific ethnic group could be attributable to differences in the specific types of fruit and vegetables consumed among the ethnic-sex groups. For example, chili and olives were identified among the top vegetable sources only for Latino-Mexico men and Latino-US men and women, while mangos and papaya are were among the top 10 fruit sources for Japanese Americans and Native Hawaiians only [Sharma, publication under review]. Many fruits are high in vitamin C, which has been shown to lower levels of uric acid, which may in turn decrease blood pressure, and subsequently, risk for stroke [25, 26]. Potassium, which plays a role in vasodilation , and antioxidants which have been demonstrated to have antiatherosclerotic effects , have also been shown to reduce risk for stroke [29, 30]. Although analysis of sub-groups was outside the scope of the current study, this factor should be considered in future work.
The current observations also suggest that vegetable intake may be a preventive factor for the risk of fatal stroke in all women, although the results were not statistically significant. Similar results regarding the preventive effects of fruits and vegetables for risk of stroke have been reported previously. A meta-analysis published in 2005 found that the risk of stroke decreased by 5% for each additional serving of fruit and vegetables consumed per day . More recently, the results from a large prospective study found that high intake of raw fruits and vegetables were associated with a preventive effect against stroke, while no associations were observed for processed fruits and vegetables . Unfortunately, information on food preparation was not available for this analysis, but this factor may have accounted for the relatively weak associations observed in this study.
There was also a statistically significant increase in risk for stroke mortality among African American men who had vegetable intake in the second quintile of adherence, compared to the lowest. Given that there was no apparent trend effect, this observation is likely attributable to a chance finding resulting from the number of statistical comparisons.
Although some weak associations were observed among women, the current findings do not provide evidence that associations between fruit and vegetable intake and risk for stroke mortality differ between men and women. However, there did appear to be stronger protective associations between dietary intake and risk for stroke mortality among women, as compared to the results for men. The variation in strength of associations between diet and stroke mortality could be due to differences in physiologic and biochemical characteristics (e.g., percent body fat, serum cholesterol level, blood glucose, hormonal effects in women, or insulin resistance), genetic differences , or differences in type and amount of foods consumed and food preparation methods  used. Positive or inverse interactions for several nutrients within the diet could also have affected the association between fruit and vegetable intake and risk of death from stroke differently in men and women.
There are some limitations to this study. The accuracy of the dietary data might have been affected by recall bias. It was expected that under-reporting of total energy intake varied among the ethnic groups. Tomoyasu et al. (2000), for example, found that African Americans under-reported energy less frequently than other racial groups . However, the validation study of the QFFQ used in the MEC showed that it captured total nutrient intake relatively well [17, 18]. Previous MEC studies have demonstrated that there are similarities in some of the major food choices among these ethnic groups [33–35], thus adaptation to Western diet among the different ethnic groups may also have influenced how these dietary factors impact disease. Addition of data regarding food choices, including food subgroup information may be useful to further elucidate associations between diet and stroke. Many factors can also influence the accuracy of ICD coding for stroke , and some research suggests that misclassification of stroke cases may be as high as 20% . As previous studies have found the effects of diet on ischemic versus hemorrhagic stroke to be similar [7, 38, 39], and considering the potential misclassification related to ICD coding and relatively small number of stroke cases observed in this study, the current analyses did not differentiate outcomes of ischemic versus hemorrhagic stroke. Selection bias may also be a concern due to the large number of exclusions. Nonetheless, large sample sizes were still maintained for the final analyses, thus considerable differences between those excluded and included would be necessary to have impacted results. The initial response rates varied among the ethnic groups, and thus may also have led to selection bias or impacted generalizability, although MEC participants were found to be highly representative of the population in Hawaii and Los Angeles when comparing the cohort distributions across educational levels and marital status with corresponding census data . In addition, dietary patterns may change considerably over a lifetime, and thus the single assessment of dietary intake may not be reflective of long-term dietary exposure. Finally, although the sample size of the MEC study is large enough to support analyses of various outcomes, this study was specifically designed to assess associations between diet and cancer risk, rather than stroke.
Several strengths of this study also warrant mention. It is the first large prospective study to investigate the associations between risk of fatal stroke with adherence to the USDA dietary recommendations for fruit and vegetable intake among these five ethnic groups. The use of a validated QFFQ and a single FCT, which were specifically developed for this multiethnic population, as well as a standard method of food grouping for all ethnic groups based on national recommendations , should also facilitate comparisons with other studies. The availability of information on a wide variety of covariates allowed adjustment for possible confounders.