BMI in the Associations of Plant-Based Diets with Type 2 Diabetes and Hypertension Risks in Women: The E3N Prospective Cohort Study

A plant-based diet index to study the relation between diet and disease risk among adults: a narrative review

Plant-based diets (PBD) may offer various health benefits and contribute to a sustainable way of life, but, if not planned correctly, may also confer risks, e.g., by focusing on plant foods with low nutrient density, such as foods primarily consisting of refined carbohydrates. A plant-based diet index (PDI) differentiating between a healthful, unhealthful, and overall PBD, offers a promising approach to standardize and compare studies and integrate results. In this review we (1) summarize current evidence on the PDI and disease risk of relevance to public health, (2) discuss the methodology of the PDI and how it can be sensibly applied in further studies and (3) indicate areas with a lack of knowledge, such as vulnerable populations. In summary, our amalgamation shows, that adherence to a healthier plant-based diet is associated with an 8-68% lower risk for metabolic risk factors, diabetes, and cardiovascular disease, while adherence to an unhealthier plant-based diet is associated with a 10-63% higher risk. Although differences in calculation methods and underlying diet patterns between populations should be accounted for, the PDI can be a useful tool to assess adherence to different plant-based diet patterns and their association with health outcomes in cohort studies across cultures.

The Association Between Overall, Healthy, and Unhealthy Plant-Based Diet Index and Risk of Prediabetes and Type 2 Diabetes Mellitus: A Systematic Review and Dose-Response Meta-Analysis of Prospective Studies

CONTEXT

The global incidence of prediabetes and type 2 diabetes mellitus (T2DM) has increased substantially in recent years. Among the established, modifiable lifestyle factors associated with favorable prediabetes and T2DM risk, healthy dietary patterns have attracted considerable attention.

OBJECTIVE

The association between adherence to plant-based dietary pattern indices (PDIs), including the overall PDI (O-PDI), healthy PDI (H-PDI), and unhealthy PDI (U-PDI), and the risk of prediabetes and T2DM was investigated in this study.

DATA SOURCES

A literature search was conducted of the PubMed/Medline, Scopus, and Web of Sciences databases from their inception to February 2024. A systematic review and meta-analysis were conducted using random effects models and dose-response analyses. The Cochran Q test and the I2 statistic were used to evaluate heterogeneity between studies.

DATA EXTRACTION

A total of 16 publications, with data on a total of 721 012 participants, were identified for the meta-analysis.

DATA ANALYSIS

According to a pooled analysis, compared with the lowest category of O-PDI and H-PDI adherence, the highest category was associated with a 14% and 19% reduction in T2DM risk, respectively, for O-PDI (effect size [ES] = 0.86; 95%CI, 0.82-0.90; I2 = 57.7) and H-PDI (ES = 0.81; 95%CI, 0.75-0.88; I2 = 82.6). Greater adherence to U-PDI was significantly associated with an 10% increase in the risk of T2DM (ES = 1.10; 95%CI, 1.04-1.16). Consistent associations were found within the predetermined subgroups. As well, there was a nonlinear inverse association between O-PDI, H-PDI, and T2DM risk. No significant association was found between adherence to O-PDI (ES = 0.87; 95%CI, 0.75-1.01; I2 = 68%), H-PDI (ES = 0.99; 95%CI, 0.87-1.13; I2 = 0.0%), and U-PDI (ES = 1.09; 95%CI, 0.94-1.21; I2 = 22.9%) and risk of prediabetes.

CONCLUSION

These findings underscore the importance of dietary selections within the framework of a plant-based dietary pattern, particularly when incorporating healthful, plant-based foods, which may have potential benefits in reducing the T2DM risk.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42023459851.

Plant-Based Dietary Patterns and Incident Diabetes in the Atherosclerosis Risk in Communities (ARIC) Study

OBJECTIVE

Plant-based dietary patterns emphasize plant foods and minimize animal-derived foods. We investigated the association between plant-based dietary patterns and diabetes in a community-based U.S. sample of Black and White adults.

RESEARCH DESIGN AND METHODS

We included middle-aged adults from the Atherosclerosis Risk in Communities (ARIC) study without diabetes at baseline who completed a food-frequency questionnaire (n = 11,965). We scored plant-based diet adherence according to three indices: overall, healthy, and unhealthy plant-based diet indices. Higher overall plant-based diet index (PDI) scores represent greater intakes of all plant foods and lower intakes of animal-derived foods. Higher healthy plant-based diet index (hPDI) scores represent greater healthy plant food intake and lower intakes of animal-derived and unhealthy plant foods. Higher unhealthy plant-based diet index (uPDI) scores represent greater unhealthy plant food intake and lower intakes of animal-derived and healthy plant foods. We used Cox regression to estimate hazard ratios (HRs) for incident diabetes (defined according to self-reported diagnosis, medication use, or elevated blood glucose) associated with each index.

RESULTS

Over a median follow-up of 22 years, we identified 4,208 cases of diabetes among subjects. Higher PDI scores were associated with a lower risk of diabetes (quintile 5 vs. 1 HR 0.89 [95% CI 0.80, 0.98]; Ptrend = 0.01). hPDI scores were also inversely associated with diabetes risk (quintile 5 vs. 1 HR 0.85 [95% CI 0.77, 0.94]; Ptrend < 0.001). uPDI scores were not associated with diabetes risk.

CONCLUSIONS

A dietary pattern that minimizes animal-derived foods and emphasizes plant foods may reduce diabetes risk.

Macronutrient composition of plant-based diets and breast cancer risk: the E3N prospective cohort study

PURPOSE

Recent evidence suggests that plant-based diets may reduce the risk of breast cancer (BC). However, the macronutrient composition of plant-based diets and its potential impact on BC risk has not been well explored. This analysis investigated the association of macronutrient composition with BC risk across a spectrum of plant-based diet indexes using a multidimensional approach.

DESIGN

This study followed 64,655 participants from the Etude Epidémiologique auprès de femmes de la Mutuelle Générale de l'Education Nationale (E3N) cohort from 1993 to 2014. Diets were evaluated using validated 208-item diet history questionnaires at baseline (1993) and follow-up (2005), to calculate adherence to the overall plant-based diet (PDI), healthful plant-based diet (hPDI), and unhealthful plant-based diet (uPDI). The association of macronutrient composition with BC risk was assessed via generalized additive time-dependent Cox models across different levels of these indexes. Response surfaces were generated to visualize compositional associations at the 25th, 50th, and 75th percentile of each index (low, moderate, and high).

RESULTS

A total of 3,932 incident BC cases were identified during the 21-year follow-up. There was a significant association between macronutrient composition and BC risk for hPDI, uPDI, and PDI (all P < 0.001). Akaike information criterion favored the hPDI model for characterizing the association between macronutrients and BC. BC risk was highest for individuals with a lower hPDI score who also consumed a diet containing lower protein (10%), lower carbohydrate (35%), and higher fat (55%). The lowest risk of BC was observed in those with higher hPDI scores with the lowest intake of protein (10%). At higher PDI and uPDI, diets containing higher protein (30%) and fat (45%) had the highest BC risk.

CONCLUSION

These results demonstrate a complex relationship between macronutrient composition, plant-based diet quality, and BC risk. Further research is needed to examine specific foods that may be driving these associations.

REGISTRY

The protocol is registered at clinicaltrials.gov as NCT03285230.

High adherence to the French dietary guidelines decreases type 2 diabetes risk in females through pathways of obesity markers: Evidence from the E3N-EPIC prospective cohort study

OBJECTIVE

Obesity and type 2 diabetes (T2D) have been associated with low adherence to the 2017 French food-based dietary guidelines, as assessed by the Programme National Nutrition Santé - guidelines score 2 (PNNS-GS2). Whether the association between T2D and PNNS-GS2 is direct or mediated by obesity has been little investigated.

RESEARCH METHODS

The study included 71,450 women from the E3N-EPIC cohort, mean age of 52.9 y (SD 6.7). The simplified PNNS-GS2 was derived via food history questionnaire. Multivariable Cox regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) of T2D. Causal mediation analyses were used to decompose the total effect of sPNNS-GS2 on T2D into a direct effect and indirect effect mediated by body mass index (BMI) or the waist-hip ratio (WHR).

RESULTS

During a mean follow-up of 19 y, 3679 incident T2D cases were identified and validated. There was a linear association between adherence to sPNNS-GS2 and T2D (P-nonlinearity = 0.92). In the fully adjusted model, each 1-SD increase in the sPNNS-GS2 was associated with a lower T2D risk [HR (95% CI), 0.92 (0.89, 0.95)]. The overall associations were mainly explained by sPNNS-GS2-associated excess weight, with BMI and WHR mediating 52% and 58% of the associations, respectively.

CONCLUSIONS

Higher adherence to French food-based dietary guidelines was associated with a lower risk of T2D in women, and a significant portion of this effect could be attributed to excess weight measured by BMI or WHR. This finding helps better understand the mechanisms underlying the diet-T2D association.

A healthful plant-based diet is associated with lower type 2 diabetes risk via improved metabolic state and organ function: A prospective cohort study

BACKGROUND

Plant-based diets are becoming increasingly popular due to favourable environmental footprints and have been associated with lower risk of type 2 diabetes mellitus (T2DM). Here, we investigated the potential mechanisms to explain the lower T2DM risk observed among individuals following plant-based diets.

METHODS

Prospective data from the UK Biobank, a cohort study of participants aged 40 to 69 years at baseline, was evaluated. Associations between healthful and unhealthful plant-based indices (hPDI and uPDI) and T2DM risk were analysed by multivariable Cox regression models, followed by causal mediation analyses to investigate which cardiometabolic risk factors explained the observed associations.

RESULTS

Of 113,097 study participants 2,628 developed T2DM over 12 years of follow-up. Participants with the highest hPDI scores (Quartile 4) had a 24 % lower T2DM risk compared to those with the lowest scores (Quartile 1) [Hazard Ratio (HR): 0.76, 95 % Confidence Interval (CI): 0.68-0.85]. This association was mediated by a lower BMI (proportion mediated: 28 %), lower waist circumference (28 %), and lower concentrations of HBA1c (11 %), triglycerides (9 %), alanine aminotransferase (5 %), gamma glutamyl transferase (4 %), C-reactive protein (4 %), insulin-like growth factor 1 (4 %), cystatin C (4 %) and urate (4 %). Higher uPDI scores were associated with a 37 % higher T2DM risk [HR: 1.37, 95 % CI:1.22- 1.53], with higher waist circumference (proportion mediated: 17 %), BMI (7 %), and higher concentrations of triglycerides (13 %) potentially playing mediating roles.

CONCLUSION

Healthful plant-based diets may protect against T2DM via lower body fatness, but also via normoglycaemia, lower basal inflammation as well as improved kidney and liver function.

Association between endometriosis and risk of type 2 diabetes: Results from the prospective E3N cohort

OBJECTIVE

Several studies suggest an association between endometriosis and the risk of cardio-metabolic diseases. This study aimed to prospectively evaluate the association between history of endometriosis and incident type 2 diabetes.

STUDY DESIGN

E3N is a prospective cohort of 98,995 French women aged 40-65 years at inclusion. Multivariable Cox regression models were used to estimate hazard ratios and 95 % confidence intervals for the association between endometriosis and incident type 2 diabetes. We evaluated effect modification by age, body mass index, infertility treatment, adherence to the Mediterranean diet, and menopausal status.

RESULTS

Age at inclusion was 51 ± 6 years and there were 2672 incident cases of type 2 diabetes. A total of 4606 women reported surgically-confirmed endometriosis among 83,582 women with no history of diabetes at inclusion. Endometriosis was not associated with type 2 diabetes risk in a model adjusted for age, BMI, physical activity, smoking, education, age at menarche and oral contraceptive use (hazard ratio [HR] = 1.09; 95 % confidence interval [CI] = 0.92-1.29), neither after further adjustment for family history of diabetes, hypertension and menopausal status (HR = 0.97;95%CI = 0.80-1.16). The relationship did not differ by age at inclusion, BMI, infertility treatment, diet or menopausal status (p > 0.05).

CONCLUSIONS

Surgically-confirmed endometriosis was not associated with the risk of type 2 diabetes in this large cohort, confirming that endometriosis is not a risk marker for type 2 diabetes.

Plant-Based Dietary Indices in Relation to Nutrient and Food Group Intakes in Preschool-Aged Children

Dietary guidance promotes plant-based foods, yet minimal research has examined intake in children. This study examined plant-based food intake in preschool-aged children using plant-based dietary index (PDI) metrics and related these metrics to nutrient and food group intakes. Dietary data were collected from preschool-aged children (n = 283, 3.45 ± 1.22 years) from the Guelph Family Health Study at baseline using the Automated Self-Administered 24-Hour Dietary Assessment Tool. Food intake servings were assigned to 16 food groups for calculation of overall PDI (oPDI), healthful PDI (hPDI), and less healthful (lhPDI) scores and summarized into tertiles for energy-adjusted comparisons. For oPDI, participants in the highest vs. lowest tertile had higher intakes of nutrients and food groups to encourage (e.g., dietary fiber, fruits) as well as lower intakes of nutrients to encourage (e.g., calcium, vitamin D). For hPDI, participants in the highest vs. lowest tertile had higher intakes of nutrients and food groups to encourage and lower intakes of those to limit (e.g., saturated fat, sweets and desserts). For lhPDI, participants in the highest vs. lowest tertile had higher intakes of nutrients and food groups to limit and lower intakes of those to encourage. These results can inform dietetic practice for dietary guidance that promotes plant-based foods in children.

Associations between plant-based dietary patterns and risks of type 2 diabetes, cardiovascular disease, cancer, and mortality - a systematic review and meta-analysis

BACKGROUND

Plant-based dietary patterns are gaining more attention due to their potential in reducing the risk of developing major chronic diseases, including type 2 diabetes (T2D), cardiovascular disease (CVD), cancer, and mortality, while an up-to-date comprehensive quantitative review is lacking. This study aimed to summarize the existing prospective observational evidence on associations between adherence to plant-based dietary patterns and chronic disease outcomes.

METHODS

We conducted a systematic review and meta-analysis of evidence across prospective observational studies. The data sources used were PubMed and MEDLINE, Embase, Web of Science, and screening of references. We included all prospective observational studies that evaluated the association between adherence to plant-based dietary patterns and incidence of T2D, CVD, cancer, and mortality among adults (≥ 18 years).

RESULTS

A total of 76 publications were identified, including 2,230,443 participants with 60,718 cases of incident T2D, 157,335 CVD cases, 57,759 cancer cases, and 174,435 deaths. An inverse association was observed between higher adherence to a plant-based dietary pattern and risks of T2D (RR, 0.82 [95% CI: 0.77-0.86]), CVD (0.90 [0.85-0.94]), cancer (0.91 [0.87-0.96]), and all-cause mortality (0.84 [0.78-0.92]) with moderate to high heterogeneity across studies (I2 ranged: 47.8-95.4%). The inverse associations with T2D, CVD and cancer were strengthened when healthy plant-based foods, such as vegetables, fruits, whole grains, and legumes, were emphasized in the definition of plant-based dietary patterns (T2D: 0.79 [0.72-0.87]; CVD: 0.85 [0.80-0.92]; cancer: 0.86 [0.80-0.92]; I2 ranged: 53.1-84.1%). Association for mortality was largely similar when the analyses were restricted to healthy plant-based diets (0.86 [0.80-0.92], I2 = 91.9%). In contrast, unhealthy plant-based diets were positively associated with these disease outcomes. Among four studies that examined changes in dietary patterns, increased adherence to plant-based dietary patterns was associated with a significantly reduced risk of T2D (0.83 [0.71-0.96]; I2 = 71.5%) and a marginally lower risk of mortality (0.95 [0.91-1.00]; I2 = 0%).

CONCLUSIONS

Better adherence to plant-based dietary patterns, especially those emphasizing healthy plant-based foods, is beneficial for lowering the risks of major chronic conditions, including T2D, CVD, cancer, as well as premature deaths.

REGISTRATION OF REVIEW PROTOCOL

This review was registered at the PROSPERO International Prospective Register of Systematic Reviews ( https://www.crd.york.ac.uk/PROSPERO/ ) with the registration number CRD42022290202.

Scoping review of the association of plant-based diet quality with health outcomes

Introduction

The association of plant-based dietary patterns with health outcomes has traditionally been assessed without considering nutritional value. The plant-based dietary index (PDI), first published in 2016, overcomes this limitation with both a healthful PDI (hPDI) and an unhealthful PDI (uPDI), based on the quality of plant foods consumed plus the frequency of animal foods. We sought to summarize the breadth of research using the hPDI and uPDI to gain insight into how the quality of plant-based dietary patterns might be associated with health outcomes.

Methods

Scoping review of studies that used the PDI, hPDI, or uPDI to report associations with health outcomes. Multiple databases were searched from 2010 through April 2023 with 2 authors independently assessing eligibility and extracting data. In addition to assessing the association of the indices to health outcomes, we determined the frequency of concordant or discordant findings for hPDI versus PDI and for hPDI versus uPDI.

Results

We included 95 articles (54% longitudinal, 37% cross-sectional, and 9% case-control) with a median sample size of 3,646. Higher hPDI levels were associated with favorable health outcomes in 36% of comparisons (most often for obesity, mortality, diabetes, cardiovascular disease, and psychiatric disorders), compared to 25% for the PDI and only 2% for the uPDI. Conversely, higher levels of the uPDI were associated with unfavorable health outcomes in 33% of comparisons, in contrast to under 1% for the hPDI and 2% for the PDI. When the hPDI association to an outcome was discordant with the uPDI or PDI, the significance and directionality always favored the hPDI over the uPDI, and nearly always favored the hPDI over the PDI.

Discussion

Dietary indices that account for the quality of plant foods can show health benefits that might be missed by a generic plant-based index. A greater focus on the quality of plant foods could improve nutrition guidelines, raise awareness about the benefits of adding unrefined plant foods to the diet, and empower consumers to make incremental additions of such foods to displace unhealthy foods. We anticipate increasing use of indices that address food quality in future research.

A healthful plant-based eating pattern is longitudinally associated with higher insulin sensitivity in Australian adults

BACKGROUND

A healthful plant-based eating pattern is associated with lower type 2 diabetes risk; however, the association with its preceding state, compromised insulin sensitivity, is less well-established, particularly in younger populations with repeated measures of diet over time.

OBJECTIVE

We aimed to examine the longitudinal relationship between a healthful plant-based eating pattern and insulin sensitivity in young to middle-aged adults.

METHODS

We included 667 participants from the Childhood Determinants of Adult Health (CDAH) study, a population-based cohort in Australia. Healthful plant-based diet index (hPDI) scores were derived from food frequency questionnaire data. Plant foods considered 'healthful' were scored positively (e.g., whole grains, fruit, vegetables), with all remaining foods scored reversely (e.g., refined grains, soft drinks, meat). Updated homeostatic model assessment (HOMA2) estimated insulin sensitivity from fasting insulin and glucose concentrations. We used linear mixed-effects regression to analyse data from two time points: CDAH-1 (2004-06, aged 26-36 years) and CDAH-3 (2017-19, aged 36-49 years). hPDI scores were modelled as between- and within-person effects (i.e., a participant's overall mean and their deviation from said mean at each time point, respectively).

RESULTS

The median follow-up duration was 13 years. In our primary analysis, each 10-unit difference in hPDI score was associated with higher log-HOMA2 insulin sensitivity [95% confidence interval], with between-person (β = 0.11 [0.05, 0.17], P < .001) and within-person effects (β = 0.10 [0.04, 0.16], P = .001). The within-person effect persisted despite accounting for compliance with dietary guidelines. Adjustment for waist circumference attenuated the between-person effect by 70% (P = .26) and the within-person effect by 40% (P = .04).

CONCLUSIONS

In young to middle-aged Australian adults, a healthful plant-based eating pattern (determined using hPDI scores) was longitudinally associated with higher insulin sensitivity, and therefore, potentially lower type 2 diabetes risk later in life.

Higher Adherence to Plant-Based Diet Lowers Type 2 Diabetes Risk among High and Non-High Cardiovascular Risk Populations: A Cross-Sectional Study in Shanxi, China

This study aimed to investigate the association between the plant-based diet index (PDI) score and T2D risk among residents of Shanxi Province, China, and explore whether the association was influenced by different levels of cardiovascular risk. A total of 50,694 participants aged 35-75 years were recruited between 2017 and 2019, and they were further divided into the high cardiovascular risk population (HCRP; n = 17,255) and the non-high cardiovascular risk population (non-HCRP; n = 33,439). The PDI was calculated based on food frequency from a food frequency questionnaire (FFQ). Incident T2D was defined based on elevated plasma glucose (≥7 mmol/L) or hypoglycemic medicine use. We investigated the association of the PDI andT2D risk using a two-level generalized estimating equation and restricted cubic splines model. The results showed that quartile 4 of the PDI indicated significantly reduced T2D risk in the total population (OR: 0.83; 95% CI: 0.75-0.92), HCRP (OR: 0.80; 95% CI: 0.71-0.91), and non-HCRP (OR: 0.80; 95% CI: 0.74-0.87) compared with corresponding quartile 1 (OR = 1). In stratified analysis, the negative associations between PDI and T2D risk were stronger in the total population with the elderly (age > 60 years), BMI < 24, and men, and in the non-HCRP with men and BMI 24-28, and in the HCRP with the elderly and BMI < 24 than those with corresponding subgroups (p_interaction < 0.05). Linear curves were observed for the total population and non-HCRP, but an L-shaped association was observed for the HCRP. Therefore, our results suggest that higher PDI scores may effectively attenuate the T2D risk in the Chinese population and non-HCRP, and a beneficial association of PDI with T2D risk was observed in the HCRP at a certain threshold level. Longitudinal studies and intervention trials are required to validate our study findings.

Plant-Based Diets and the Incidence of Asthma Symptoms among Elderly Women, and the Mediating Role of Body Mass Index

We aimed to test the hypothesis that adherence to a healthful plant-based diet (hPDI) is associated with a subsequent decrease in the incidence of asthma symptoms, with an opposite association with adherence to an unhealthful plant-based diet (uPDI). In addition, we evaluated a potential mediating role of body mass index (BMI) and the modifying effect of smoking. Among 5700 elderly women from the French Asthma-E3N study with dietary data in 1993 and 2005, we assessed the incidence of asthma symptoms in 2018 among women with no asthma symptoms in 2011. BMI was evaluated in 2008. Mediation analyses in the counterfactual framework were used to disentangle total, direct, and indirect effects mediated by BMI. We found that both healthful and unhealthful plant-based diets were associated with a lower incidence of asthma symptoms over time, mediated by BMI (OR (95%CI) for the indirect effect: 0.94 (0.89-1.00) for hPDI and 0.92 (0.70-1.00) for uPDI)). Associations with both healthful and unhealthful PDIs were mediated by changes in BMI by 33% and 89%, respectively. Plant-based diets (healthful and unhealthful) were associated with subsequently reduced incidences of asthma symptoms over time, partly or almost totally mediated by BMI according to their nutritional quality.