Abstract
Purpose
To examine the association between dietary fiber intake and mortality risks (all-cause and cardiovascular) among U.S. adults with diabetes or prediabetes, and to evaluate the dose-response patterns of these associations.
Materials and methods
This longitudinal cohort study analyzed data from 3259 adults with diabetes or prediabetes from the 2011–2018 National Health and Nutrition Examination Survey (NHANES). Dietary fiber intake was assessed using two 24-hour dietary recall interviews. Mortality data were obtained through December 31, 2019. Multiple Cox proportional hazards models were used to evaluate associations between fiber intake and mortality outcomes, adjusting for demographic and health-related covariates.
Results
Higher dietary fiber intake was significantly associated with reduced all-cause mortality risk (HR = 0.98, 95% CI: 0.97–0.99, P = 0.0039). For cardiovascular mortality, a non-linear relationship was identified with a threshold at 26.2 g/day. Below this threshold, each gram increase in fiber intake was associated with a 3% reduction in cardiovascular mortality risk (HR = 0.97, 95% CI: 0.94–0.99, P = 0.0352), while no significant benefit was observed above this threshold.
Conclusions
Dietary fiber intake shows a protective effect against all-cause mortality in U.S. adults with diabetes or prediabetes. For cardiovascular mortality, moderate fiber intake up to 26.2 g/day appears beneficial, while higher intake may not provide additional cardiovascular benefits. These findings provide important evidence for developing targeted dietary recommendations in diabetes management.
Keywords: Dietary fiber, Diabetes/prediabetes, All-cause mortality, Cardiovascular mortality, Dose-response relationship
Introduction
Diabetes and its complications have become a major global public health challenge. According to the International Diabetes Federation (IDF) 2023 report, approximately 537 million adults worldwide have diabetes, a number expected to rise to 783 million by 2045 [1]. In the United States alone, about 37.3 million people have diabetes, and an additional 96 million adults are in a prediabetic state [2]. Cardiovascular complications remain the leading cause of death among individuals with diabetes, accounting for approximately 65% of deaths in this population [3, 4]. While medication plays a crucial role in managing diabetes, increasing evidence suggests that dietary interventions may significantly influence disease outcomes and reduce the risk of mortality [5, 6].
Dietary fiber is a type of carbohydrate found in plant-based foods that cannot be digested or absorbed by the human small intestine. It has become an important dietary component in managing diabetes. Previous studies have shown that increasing daily fiber intake from 20 g to 35 g can reduce premature mortality by 10–48% [7]. A large-scale European cohort study found a significant association between higher fiber intake and reduced risks of both all-cause and cardiovascular mortality [8]. Similarly, a study of middle-aged and older adults in South Korea found that fiber intake in people with diabetes was significantly inversely associated with mortality outcomes [9]. These beneficial effects may be attributed to fiber’s role in blood sugar control, inflammation reduction, and gut microbiota regulation [10–12].
However, there is still a significant gap in understanding the relationship between dietary fiber intake and mortality risk in the U.S. diabetic population. Existing evidence mainly comes from Asian or European cohorts, whose dietary patterns and racial characteristics differ significantly from those in the U.S [13, 14]. Furthermore, the dose-response relationship between fiber intake and mortality outcomes remains unclear, especially in individuals with diabetes or prediabetes. Although previous literature reviews have reported a reduction in mortality [7], there is a lack of detailed dose-response curve descriptions. Additionally, most studies have relatively short follow-up periods (with a maximum of 12 weeks), limiting the ability to draw conclusions about long-term health outcomes. While a study in Korea observed a clear dose-response relationship and confirmed the benefits of fiber intake in reducing cardiovascular mortality in diabetic patients [9], the primary sources of fiber in this population (e.g., kimchi, fruits) are region-specific. This regional variation may limit the generalizability of the findings to other ethnic groups and regions.
To address these knowledge gaps, we conducted a cohort study using data from the 2011–2018 National Health and Nutrition Examination Survey (NHANES). The objectives of this study were to: (1) examine the association between dietary fiber intake and all-cause mortality in U.S. adults with diabetes or prediabetes; (2) investigate the relationship between fiber intake and cardiovascular mortality in this population; and (3) evaluate the dose-response patterns of these associations using multivariable adjustment models. This study provides new insights into the potential protective effects of dietary fiber in a representative U.S. population, which may inform evidence-based dietary recommendations for diabetes management and prevention.
Materials and methods
Study population
To ensure national representativeness, NHANES is a comprehensive and ongoing cross-sectional survey conducted in the United States. It uses a stratified, multistage, cluster-random sampling method to collect dietary and health data from the general population. This study utilized data from the 2011–2018 NHANES database, which included 39,156 participants. Initially, participants under the age of 18 were excluded (n = 15331). Next, based on the 2024 American Diabetes Association guidelines [15], participants who did not meet the diagnostic criteria for diabetes or prediabetes were excluded (n = 19985). Diabetes was defined by any of the following: (1) self-reported diabetes, (2) insulin injection or use of antihyperglycemic medications, (3) HbA1c ≥ 6.5%, (4) fasting blood glucose (FBG) ≥ 7.0 mmol/L, or (5) 2-hour postprandial glucose (2hPG) ≥ 11.1 mmol/L. Prediabetes was defined by: (1) HbA1c 5.7–6.4%, (2) FBG 5.6–6.9 mmol/L, or (3) 2hPG 7.8–11.0 mmol/L. Participants without dietary fiber intake data were then excluded (n = 488). Finally, after excluding participants with missing mortality data (n = 93), the study included a total of 3259 participants (Fig. 1).
Fig. 1.
Flow chart of study participants
Assessment of dietary fiber intake
Dietary fiber intake, measured in grams per day, was used as the primary exposure variable. Dietary data were collected through two 24-hour dietary recall interviews, using the Automated Multiple-Pass Method (AMPM) developed by the United States Department of Agriculture (USDA). This method is designed to provide an efficient and accurate way to assess intake for large national surveys, incorporating a range of standardized food-specific questions and response options. The AMPM has been validated in a large study and shown to be an effective tool for accurately collecting energy intake data from adults [16]. The first interview was conducted at a mobile examination center, followed by a second phone interview three to ten days later. Fiber intake was averaged from the two-day dietary recall data (if available); if two days of data were missing, the intake was averaged using available data. The NHANES dietary assessment includes total dietary fiber intake but does not differentiate between soluble and insoluble fiber. Total dietary fiber includes fiber from all food sources, such as grains, fruits, vegetables, legumes, and from dietary supplements, which are assessed separately via a dietary supplement questionnaire and included in the total intake. Participants were categorized into four quartiles (Q1, Q2, Q3, Q4) based on their fiber intake, with Q1 serving as the reference group.
Ascertainment of mortality
To assess all-cause and cardiovascular mortality, we used publicly available mortality data provided by the National Center for Health Statistics (NCHS). These data were linked to death certificates from the National Death Index (NDI) using a probabilistic matching algorithm. Follow-up mortality data was updated through December 31, 2019. Causes of death were classified according to the ICD-10, with cardiovascular deaths including codes I00–I09, I11, I13, and I20–I51. All-cause mortality refers to the total number of deaths from all causes.
Assessment of covariates
The covariates included in this study were selected based on demographic and health-related factors, including age, sex, race, education level, income-to-poverty ratio, body mass index (BMI), moderate physical activity, smoking behavior, hypertension status, and energy intake. These variables were chosen from previous literature due to their potential as confounders and their biological relevance. Income-to-poverty ratio was calculated as the ratio of family income to the poverty threshold for the same period and region in the United States, with a cutoff value of 2. Moderate physical activity was defined as engaging in any moderate-intensity sports, fitness, or recreational activities that cause slight increases in breathing or heart rate (such as brisk walking, bicycling, swimming, or volleyball) for at least 10 min continuously during a typical week. Smoking behavior is classified based on whether one smokes at least 100 cigarettes in a lifetime. Hypertension was defined as either a physician’s diagnosis or self-reported use of antihypertensive medications. Energy intake was assessed using two 24-hour dietary recall interviews conducted by trained interviewers. All variables were collected following standardized NHANES protocols, and additional methodological details can be found at http://www.cdc.gov/nchs/nhanes.
Statistical analysis
The NHANES survey uses a complex, multi-stage probability sampling design to ensure that the results are representative of the U.S. non-institutionalized population. In our study, we incorporated sample weights, stratification, and clustering into the analysis. Participants were grouped into four quartiles (Q1-Q4) based on their dietary fiber intake. Continuous variables are reported as means and standard deviations (SDs), while categorical variables are reported as frequencies and percentages. Group differences for categorical variables were assessed using weighted chi-square tests, and baseline characteristics of the four groups were compared using weighted linear regression for continuous variables.
We established three models to control for confounders and used a weighted multivariable Cox proportional hazards model to estimate the relationship between dietary fiber intake and both all-cause and cardiovascular mortality. Model 1 did not adjust for any covariates. Model 2 adjusted for age, sex, and race. Model 3 further adjusted for education level, income-to-poverty ratio, body mass index (BMI), moderate physical activity, smoking behavior, hypertension, and energy intake.
To explore the dose-response relationship between dietary fiber intake and mortality, we applied generalized additive models and smooth curve fitting. After detecting nonlinearity, we conducted threshold effect analysis using recursive techniques to identify inflection points. We then applied piecewise linear regression models on both sides of these points. All analyses were performed using R (http://www.Rproject.org) and Empower Stats (http://www.empowerstats.com), with a significance level set at p < 0.05.
Results
Table 1 presents the baseline characteristics of the study population stratified by dietary fiber intake quartiles. Most demographic and clinical characteristics showed significant differences across fiber intake groups (P < 0.001), except for age (P = 0.053). Higher fiber intake was associated with a greater proportion of men and higher educational levels. The high-fiber group also exhibited more favorable health behaviors and outcomes, including lower BMI, reduced smoking rates, and higher participation in moderate physical activity. The prevalence of hypertension showed a significant trend, decreasing with increasing fiber intake quartiles. Income-to-poverty ratio was positively correlated with fiber intake, while energy intake consistently increased across quartiles. A marginally significant trend (P = 0.046) was observed regarding diabetes status, with the highest fiber intake group showing a slightly lower prevalence of diabetes and a higher prevalence of prediabetes compared to the lowest intake group.
Table 1.
Characteristics of the study population based on dietary fiber intake quartiles
| Dietary fiber intake (g/day) | Q1 (< 10.30, N = 798) |
Q2 (10.31–15.05, N = 833) |
Q3 (15.06–21.55, N = 816) |
Q4 (> 21.56, N = 812) |
P value |
|---|---|---|---|---|---|
| Age (years) | 60.57 ± 14.09 | 62.01 ± 13.17 | 60.87 ± 13.88 | 60.57 ± 12.73 | 0.053 |
| Gender (%) | < 0.001 | ||||
| Men | 40.98 | 48.26 | 53.92 | 64.66 | |
| Women | 59.02 | 51.74 | 46.08 | 35.34 | |
| Race (%) | < 0.001 | ||||
| Mexican American | 35.21 | 37.21 | 32.84 | 28.57 | |
| Non-Hispanic White | 33.33 | 29.65 | 25.74 | 8.60 | |
| Non-Hispanic Black | 9.27 | 12.24 | 18.14 | 25.12 | |
| Other Race | 22.18 | 20.89 | 23.28 | 27.71 | |
| Education level (%) | < 0.001 | ||||
| Less than high school | 35.18 | 26.51 | 27.22 | 28.55 | |
| High school | 23.83 | 26.63 | 23.52 | 17.80 | |
| More than high school | 40.98 | 46.87 | 49.26 | 53.65 | |
| Income to poverty ratio | 1.94 ± 1.44 | 2.26 ± 1.53 | 2.41 ± 1.56 | 2.59 ± 1.58 | < 0.001 |
| BMI (kg/m2) | 33.04 ± 8.12 | 33.18 ± 7.87 | 32.12 ± 7.45 | 31.48 ± 7.32 | < 0.001 |
| Smoking status (%) | < 0.001 | ||||
| Yes | 57.16 | 47.48 | 46.99 | 44.51 | |
| No | 42.84 | 52.52 | 53.01 | 55.49 | |
| Hypertension (%) | < 0.001 | ||||
| Yes | 72.20 | 70.35 | 67.04 | 62.52 | |
| No | 27.80 | 29.65 | 32.96 | 37.48 | |
| Moderate activity (%) | < 0.001 | ||||
| Yes | 26.85 | 33.17 | 37.75 | 40.44 | |
| No | 73.15 | 66.83 | 62.25 | 59.56 | |
| Energy intake (Kcal/day) | 1295.16 ± 518.96 | 1698.46 ± 571.07 | 1996.60 ± 614.90 | 2432.70 ± 801.98 | < 0.001 |
| Diabetes status (%) | 0.046 | ||||
| Diabetes | 86.59 | 84.99 | 82.72 | 82.02 | |
| Prediabetes | 13.41 | 15.01 | 17.28 | 17.98 |
Mean ± SD for continuous variables: the P value was calculated by the weighted linear regression model. (%) for categorical variables: the P value was calculated by the weighted chi-square test
Table 2 shows the association between dietary fiber intake and mortality outcomes in individuals with diabetes and prediabetes. For all-cause mortality, a significant negative association between fiber intake and mortality risk was observed in all models. In the fully adjusted model (Model 3), each additional gram of daily fiber intake was associated with a 2% reduction in mortality risk (HR = 0.98, 95% CI: 0.97–0.99, P = 0.0039). Quartile analysis revealed significantly lower mortality risks in the third (15.06–21.55 g/day) and fourth (greater than 21.56 g/day) quartiles compared to the lowest fiber intake group (< 10.30 g/day), with hazard ratios of 0.73 (95% CI: 0.54–0.98, P = 0.0360) and 0.73 (95% CI: 0.53–0.99, P = 0.0412), respectively. A significant dose-response relationship was observed (P for trend = 0.037), indicating that higher fiber intake was associated with progressively lower mortality risk, even after adjusting for multiple confounders.
Table 2.
Multivariate adjustment analysis of dietary fiber intake and all-cause and cardiovascular mortality in patients with diabetes and prediabetes
| No. deaths/total | Model HR (95% CI) P value |
Model 2 HR (95% CI) P value |
Model 3 HR (95% CI) P value |
|
|---|---|---|---|---|
| All-cause mortality | ||||
| Dietary fiber intake (g/day) | 402/3259 | 0.97 (0.96, 0.98) < 0.0001 | 0.97 (0.96, 0.98) < 0.0001 | 0.98 (0.97, 0.99) 0.0039 |
| Dietary fiber intake quartile | ||||
| Q1 (< 10.30 g/day) | 118/798 | Reference | Reference | Reference |
| Q2 (10.31–15.05 g/day) | 118/833 | 0.93 (0.72, 1.20) 0.5655 | 0.85 (0.66, 1.10) 0.2161 | 0.92 (0.70, 1.21) 0.5577 |
| Q3 (15.06–21.55 g/day) | 94/816 | 0.74 (0.56, 0.96) 0.0259 | 0.69 (0.53, 0.90) 0.0068 | 0.73 (0.54, 0.98) 0.0360 |
| Q4 (> 21.56 g/day) | 72 /812 | 0.57 (0.43, 0.76) 0.0002 | 0.58 (0.43, 0.78) 0.0003 | 0.73 (0.53, 0.99) 0.0412 |
| P for trend | < 0.001 | < 0.001 | 0.037 | |
| CVD mortality | ||||
| Dietary fiber intake (g/day) | 126/3259 | 1.00 (0.97, 1.02) 0.7410 | 0.99 (0.97, 1.02) 0.6661 | 0.99 (0.96, 1.01) 0.3060 |
| Dietary fiber intake quartile | ||||
| Q1 (< 10.30 g/day) | 37/798 | Reference | Reference | Reference |
| Q2 (10.31–15.05 g/day) | 43/833 | 1.12 (0.73, 1.72) 0.6026 | 1.11 (0.72, 1.72) 0.6426 | 1.12 (0.70, 1.82) 0.6319 |
| Q3 (15.06–21.55 g/day) | 27/816 | 0.91 (0.56, 1.47) 0.6917 | 0.87 (0.54, 1.43) 0.5920 | 0.71 (0.42, 1.21) 0.2093 |
| Q4 (> 21.56 g/day) | 19/812 | 0.91 (0.54, 1.53) 0.7184 | 0.90 (0.53, 1.51) 0.6787 | 0.71 (0.41, 1.25) 0.2372 |
| P for trend | 0.588 | 0.544 | 0.370 |
Model 1: no covariates were adjusted
Model 2: age, gender, and race were adjusted
Model 3: age, gender, race, education level, income to poverty ratio, body mass index, moderate activity, smoking behavior, and the existence of hypertension and energy intake were adjusted
However, as shown in Table 2, no significant association was found between dietary fiber intake and cardiovascular disease mortality in individuals with diabetes or prediabetes, whether analyzed as a continuous variable (HR = 0.99, 95% CI: 0.96–1.01, P = 0.3060) or across quartiles. The highest fiber intake group showed a non-significant 29% reduction in cardiovascular disease mortality risk compared to the lowest intake group (HR = 0.71, 95% CI: 0.41–1.25, P = 0.2372), with no apparent dose-response relationship (P for trend = 0.370).
Figure 2 presents the smoothed curve fitting and generalized additive model (GAM) showing the association between dietary fiber intake and both all-cause and cardiovascular mortality in individuals with diabetes and prediabetes. For all-cause mortality (Fig. 2a), the risk of death generally decreased steadily with increasing fiber intake. In contrast, for cardiovascular mortality (Fig. 2b), the association exhibited a distinct non-linear pattern, suggesting a more complex relationship.
Fig. 2.
Dose-response relationships between dietary fiber intake and the probability of all-cause (a) and cardiovascular disease (CVD) (B) in participants with diabetes or prediabetes. The solid line and dashed line represent the estimated values and their corresponding 95% confidence intervals. Age, gender, race, education level, income to poverty ratio, body mass index, moderate activity, smoking behavior, and the existence of hypertension and energy intake were adjusted
To better understand the potential threshold or saturation effect of dietary fiber intake on cardiovascular mortality risk in this population, we conducted both standard linear and piecewise linear regression analyses (Table 3). While the standard linear model showed no significant association between fiber intake and cardiovascular mortality (HR = 0.99, 95% CI: 0.96–1.01, P = 0.3060), the piecewise linear regression revealed a significant threshold effect at 26.2 g/day. Below this threshold, each additional gram of fiber intake was associated with a 3% reduction in cardiovascular mortality risk (HR = 0.97, 95% CI: 0.94–0.99, P = 0.0352). However, above 26.2 g/day, this association reversed, showing a non-significant trend of increased risk (HR = 1.08, 95% CI: 0.99–1.17, P = 0.0880). The likelihood ratio test (P = 0.046) confirmed that the piecewise linear model provided a significantly better fit than the standard linear model, supporting the presence of a non-linear relationship between dietary fiber intake and cardiovascular mortality risk.
Table 3.
Threshold effect analysis of dietary fiber intake on CVD mortality in participants with diabetes or prediabetes
| CVD mortality | Adjusted HR (95% CI) P value |
|---|---|
| Fitting by the standard linear model | 0.99 (0.96, 1.01) 0.3060 |
| Fitting by the two-piecewise linear model | |
| Inflection point | 26.2 |
| Dietary fiber intake < 26.2 (g/day) | 0.97 (0.94, 0.99) 0.0352 |
| Dietary fiber intake > 26.2 (g/day) | 1.08 (0.99, 1.17) 0.0880 |
| Log likelihood ratio | 0.046 |
Age, gender, race, education level, income to poverty ratio, body mass index, moderate activity, smoking behavior, and the existence of hypertension and energy intake were adjusted
Discussion
In our prospective cohort study of U.S. adults with diabetes and prediabetes, we observed a significant negative association between dietary fiber intake and all-cause mortality risk. For cardiovascular mortality, a non-linear relationship was identified, with a threshold at 26.2 g of fiber per day. Below this threshold, each additional gram of fiber was associated with a 3% reduction in cardiovascular mortality risk. Our findings align with previous studies in several key aspects. Notably, our results are consistent with those from large European cohort studies, which also found a significant link between higher dietary fiber intake and reduced all-cause mortality [8]. Similarly, our study supports findings from research on middle-aged and older adults in Korea, where a negative correlation was observed between fiber intake and mortality in diabetic patients [9].
However, there are some notable differences between our study and prior research. Specifically, while Cunha et al. [17] reported a significant negative association between fiber intake and cardiovascular mortality, our study found a non-linear relationship in diabetes and prediabetes. Below the 26.2-gram threshold, increasing fiber intake was associated with lower cardiovascular mortality risk. However, above this threshold, additional fiber intake no longer conferred any benefit and may even be linked to adverse outcomes. This finding aligns with the recent meta-analysis by Reynolds et al. [18], which identified a daily intake of 25–30 g of dietary fiber as optimal for cardiovascular health. Potential mechanisms for the inverse relationship at high fiber intake include: (1) excessive fiber may impair the absorption of essential minerals, particularly calcium, iron, and zinc, which are crucial for cardiovascular health, as demonstrated by Shah et al. [19]; (2) research by Chambers et al. [20] suggests that very high fiber intake may alter the gut microbiota composition, potentially disrupting the production of beneficial short-chain fatty acids; (3) for patients with diabetic gastroparesis, excessive fiber may further delay gastric emptying and impair nutrient absorption [21]. A large-scale meta-analysis in the general adult population [22] provided important evidence on the complex relationship between fiber intake and mortality. The nonlinear relationship found in this analysis indicates that moderate increases in fiber intake—especially for those with lower intake—can yield significant health benefits, whereas excessive intake may not provide proportional additional benefits. Our study further complements these findings in the context of individuals with diabetes and prediabetes.
From a mechanistic perspective, dietary fiber may reduce all-cause mortality through various pathways, including improving blood sugar control, lowering inflammation, and modulating the gut microbiome [23–25]. However, for cardiovascular mortality, excessive fiber intake may limit the absorption of certain micronutrients or be incompatible with the dietary patterns of specific populations, thus diminishing its protective effects [26]. Additionally, the source of fiber (e.g., the ratio of soluble to insoluble fiber) in different studies could affect the comparability of results [27]. Future research should further investigate the impact of fiber source and type on cardiovascular health.
The findings of this study have important clinical implications for the management of diabetes and prediabetes. As the first large-scale study based in the U.S., we not only established a link between fiber intake and mortality risk but also identified a key threshold of 26.2 g per day for cardiovascular mortality risk. This provides valuable guidance for more precise dietary recommendations. Based on these results, we suggest that clinicians consider daily fiber intake as an important monitoring metric when creating personalized nutrition plans. For patients with fiber intake below recommended levels, interventions to achieve adequate intake should be prioritized. Additionally, these findings offer strong evidence for policymakers to incorporate increased fiber consumption into public health strategies for diabetes prevention and management. However, given the potential risks of exceeding the identified threshold, future research should explore the mechanisms of different types of dietary fiber and determine optimal intake levels for various populations, providing scientific support for more targeted nutrition interventions.
This study has several notable strengths. First, it is based on a stratified, multi-stage sampling design from the NHANES database, ensuring a representative sample of the non-institutionalized U.S. population. Second, we used three stepwise-adjusted multivariable Cox proportional hazards models for data analysis, controlling for potential confounders such as demographic characteristics, socioeconomic status, and lifestyle factors. Additionally, the study’s long follow-up period and large sample size enhance the reliability of the results. Notably, we used generalized additive models and smooth curve fitting to explore the dose-response relationship in depth and innovatively applied piecewise linear regression to identify a key threshold for cardiovascular mortality risk.
Nevertheless, there are several important limitations to consider. First, dietary fiber intake was assessed using two 24-hour dietary recalls, which may not accurately reflect participants’ habitual intake patterns due to recall bias and day-to-day variations in diet. This short-term assessment method might underestimate or overestimate actual fiber consumption for some participants, potentially affecting the strength of observed associations. Second, although we adjusted for multiple known confounders, residual confounding from unmeasured variables remains possible. Particularly, factors such as the source of dietary fiber (e.g., grains, fruits, vegetables) and quality (e.g., ratio of soluble to insoluble fiber) were not accounted for in our analysis but might influence health outcomes differently. Third, the observational nature of this study precludes causal inference between fiber intake and mortality outcomes. Additionally, mortality outcomes based on death certificates may be subject to misclassification, which could affect the internal validity of our findings. Fourth, because the study only included non-institutionalized individuals aged 18 and older, the findings may not be generalizable to children, adolescents, or institutionalized populations, limiting the applicability of our results to the broader U.S. population. Furthermore, since the study focused on the U.S. population, caution should be exercised when applying the results to populations in other countries or regions with differing dietary habits, lifestyle factors, or healthcare systems. Despite these limitations, our findings provide valuable evidence supporting the protective role of dietary fiber in individuals with diabetes and prediabetes, particularly highlighting the non-linear relationship with cardiovascular mortality.
Conclusions
Our study demonstrates a significant negative correlation between dietary fiber intake and all-cause mortality in U.S. adults with diabetes or prediabetes. For cardiovascular mortality, we found a non-linear relationship with a critical threshold at 26.2 g of dietary fiber per day. Below this threshold, each additional gram of dietary fiber was associated with a 3% reduction in cardiovascular mortality risk. However, above this threshold, increased fiber intake no longer correlated with reduced cardiovascular mortality risk and may even increase the risk. These findings provide valuable evidence for developing targeted dietary recommendations for diabetes management. While our results support the protective role of dietary fiber, they also suggest that excessive intake beyond the identified threshold may not offer additional cardiovascular benefits. This study offers valuable insights for clinical practice and public health strategies but further research is needed to explore the mechanisms of different fiber types and determine the optimal intake levels for various populations.
Acknowledgements
Not applicable.
Author contributions
YW and XC participated in the conception and design of the experiments; XC and LT performed most of the experiments; LT and YW analyzed and interpreted the data; XC and YW drafted the paper and critically revised it for intellectual content. All authors read and approved the final manuscript. And that all authors agree to be accountable for all aspects of the work.
Funding
No funding was received.
Data availability
The data that support the findings of this study are available from NHANES and don’t require any permissions. Data sharing is not applicable to this article as no new data were created or analyzed in this study.
Declarations
Ethics approval and consent to participate
All participants gave their informed agreement, and the project was authorized by the National Center for Health Statistics Research Ethics Review Board.
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Clinical trial number
Not applicable.
Footnotes
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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Associated Data
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Data Availability Statement
The data that support the findings of this study are available from NHANES and don’t require any permissions. Data sharing is not applicable to this article as no new data were created or analyzed in this study.