Cardiovascular health and cancer risk associated with plant based diets: An umbrella review.

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• A plant-based diet may help to reduce the risk of CVD and cancer, and their associated morbidities.
• However, the results of this umbrella review should be read with caution due to the low strength of evidence and the myriad of confounding factors that cloud interpretation.
• Risks for macro- and micronutrient deficiencies of fully plant-based diets cannot be ignored.
• Registered nutritional therapists and registered nutritionists are ideally placed to mitigate these risks with proper education, particularly essential in the case of those wishing to consume a fully plant-based diet where no dairy, eggs or fish are consumed.

Introduction

Cardiovascular diseases (CVD) and cancer are leading causes of morbidity and mortality worldwide. This umbrella review sought to synthesise evidence from existing systematic reviews and meta-analyses describing the effect of plant-based diets on the incidence of CVD and cancer, and related morbidities globally.

Methods

• Study design: umbrella review (review of reviews)
• Eligible article types: reviews, systematic reviews and meta-analyses reporting on the effect of vegetarian and vegan diets (“animal-free” and “animal product free”) compared to consumption of omnivorous diets, on health parameters associated with CVD, metabolic disorders, cancer, or their associated morbidities.
• Data were extracted and relevant meta-analyses reported. No further meta-analyses were performed in the present review.
• AMSTAR-R rating was applied to assess the quality of included articles and describe the strength of the evidence collated.

Results*

• From an initial search yield of 2502 articles, 49 were included in the final analysis.
• Vegetarian and vegan diets appeared to reduce/improve: Total and LDL cholesterol; Fasting glucose and HbA1c; Bodyweight/BMI; Inflammation
• Other indices including HDL cholesterol, triglycerides, and blood pressure were inconclusive.
• General results from three meta-analyses suggested favourable outcomes for cancer, though when analyses were stratified by cancer type, results were inconsistent.
• Though some studies scored well in the AMSTAR-R rating for some points, reporting was poor elsewhere.

Conclusion

• Plant-based or vegetarian and vegan diets may afford some protection against CVD and cancer, and their associated morbidities.
• An overall low quality of the included publications was accorded, which lowered the strength of evidence and reduced external validity of findings.
• The findings may be further affected by the potential risks in nutrient imbalance caused by restrictive dietary regimens.

*Due to the extensive data reporting and limited space in this review, readers are invited to consult the paper for specific data from meta-analyses on the indices described above.

• Nutritional therapists may consider a plant-based approach in cases of CVD or associated morbidities to help augment care but should exercise caution if recommending completely plant-based, as the evidence presented by this umbrella review is of low strength or inconclusive.
• Applications of plant based diets in cancer are inconclusive to date.
• Therapists should take care to provide sufficient education on mitigating risks of nutrient deficiency in both partially (vegetarian) and fully (vegan) plant-based diets

• Future studies could assess the impact of increasing the amount of vegetables in omnivorous or fish-based diets compared to vegetarian or full plant-based diets in relation to CVD and cancer incidence.