Grand Rounds

Could Plant-Based Diets Help Prevent Type 2 Diabetes?

BACKGROUND AND PURPOSE:

There is data suggesting that plant-based diets (e..g, lacto-ovo-vegetarian and vegan) may be useful in the management of type 2 diabetes, CVD and cancer
Data on the role of these diets for primary prevention of type 2 diabetes is limited
Qian et al. (JAMA Intern Med., 2019) sought to determine if there is an association between plant-based diet and risk of type 2 diabetes

Systematic review and meta-analysis
- Full-text assessments and data abstraction were independently conducted by two authors
Inclusion criteria
- Prospective observational studies
- Studies that that examined the association between adherence to plant-based diet and type 2 diabetes
Participants
- Adults ≥18 years
Exposure
- Adherence to plant-based dietary patterns defined as
  - Higher consumption of plant-based foods
  - Lower consumption or exclusion of animal-based foods
Data analysis
- Meta-analysis was conducted using the random-effects method
- Overall relative risk (RR) and 95% CI calculated
Primary outcomes
- Level of adherence to a plant-based diet
- Incidence of type 2 diabetes

9 studies | 307,099 participants | 23,544 cases of type 2 diabetes
Higher adherence to a plant-based dietary pattern was significantly associated with a lower risk of type 2 diabetes
- RR, 0.77 (95% CI, 0.71 to 0.84)
Consistent associations were observed across predefined subgroups
- Age | Sex | Global region | Definitions of plant-based diets (e.g., vegetarian or vegan pattern vs plant-based dietary scores)
- The association was stronger when the following healthy plant-based foods were included in the definition of plant-based patterns
  - Fruits | Vegetables | Whole grains | Legumes | Nuts
  - RR 0.70 (95% CI, 0.62 to 0.79)
Associations maintained even after controlling for BMI
Most studies were considered good quality for the following
- Dietary assessment
- Disease outcomes
- Statistical adjustment for confounding factors
A dose-response association was identified between plant-based dietary indices and decreasing risk of type 2 diabetes

Better adherence to a plant-based diet was inversely associated with the risk of type 2 diabetes
Results were broadly consistent
Plant-based diets may be useful for the primary prevention of type 2 diabetes
These diets are even more effective when enriched with known healthful plant-based foods
The dose-response finding would indicate that one does not need to eat a meatless diet to benefit from increased consumption of plant-based diet

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