How plant-based diets improve metabolic health and reduce diabetes risk – insights from a prospective cohort study

Aim

A key aim of this study was to elucidate the mechanisms by which plant-based foods can impact type two diabetes (T2DM).

It also investigates the differences between healthy and unhealthy plant-based options.

Method

The research generated data from the UK Biobank which encompasses over 500,000 volunteers between 40-69 years of age, recruited between 2006-2010.

Baseline assessment of dietary habits was conducted using the Oxford WebQ questionnaire, capturing information on 206 food types consumed within the previous 24 hours.

Plant-based diet quality was evaluated using a healthy plant-based index (hPDI) and an unhealthy plant-based index (uPDI).

Key findings

113,097 individuals were included in the final analyses after removing those with missing data, and other exclusion factors.

Characteristics of the study population

• There was an average follow-up duration of 12 years during which 2.3% developed T2DM

• Mean age at baseline was 55.8 years and 56.5% were female.

BMI and waist circumference were lower in participants with higher hPDI score. They were also more likely to be higher educated, physically active and older compared to the lowest quartile.

Participants in the highest uPDI quartile were younger, had a higher BMI, more likely to smoke and be less physically active than those with lower uPDI scores.

Associations between the PDIs and T2DM risk

“A healthful plant-based diet was associated with a 24% lower risk of T2DM, irrespective of genetic risk and other established T2DM risk factors.”

Those in the highest hPDI quartile had a 24% lower risk of T2DM compared to those in the lowest quartile. Conversely, those in the highest quartile of uPDI had a 37% higher risk of T2DM.

A normal association (non-linear) was found with both the healthy and unhealthy PDI groups.

Food groups

• Vegetables, tea, and coffee consumption were inversely associated with T2DM risk.

• T2DM risk increases alongside increased consumption of potatoes, refined grains and sugary drinks.

• The overall difference in risk were not driven by one specific food group but rather the dietary pattern as a whole.

Sensitivity analyses showed that the impact of plant-based diets remained consistent when a range of factors were controlled for. This suggests that the relationship with T2DM risk is stable across a variety of situations and timeframes.

Mediation analyses

BMI and waist circumference were the strongest mediators of the association between healthy plant-based foods and T2DM (28% of the total effect).

This followed by HbA1c (11%), triglycerides (9%) and ALT (5%). The following each contributed 4% mediation: urate, CRP, cystatin C, GGT and IGF-1.

For the uPDI, only BMI (7%) , triglycerides (13%) and waist circumference (17%) showed statistically meaningful effects.

Conclusion

A healthy plant-based diet is associated with lower T2DM risk due to a range of mediating factors moving beyond just weight and body fatness within this study population.

High quality components of these diets like fruits, vegetables, nuts, legume and wholegrains are particularly beneficial in line with existing dietary guidance to reduce T2DM risk.