Plant-based Diets and Healthy Aging

This study establishes a new cohort to investigate the role of vegetarian and plant-based diets in healthy aging, integrating functional, nutritional, and genetic data. The primary objective is to clarify how dietary patterns and nutrient intake influence aging-related health conditions, including sarcopenia, cognitive function, physical function, and psychological well-being, and investigate how the associations between diet and these health conditions may be modified by genetic risk factors.

Participants are Tzu Chi volunteers aged 40 years and older who undergo comprehensive health evaluations at Dalin Tzu Chi Hospital every three years. This population consists of a uniquely high proportion of vegetarians, non-smoking non-alcohol drinking individuals, and older adults who are active in communities and social engagement and community services; providing a unique opportunity to examine the role of plant-based diets and community services on aging related conditions without confounding by smoking and alcohol. Diet data are collected through a previously validated food frequency questionnaire, a short newly developed questionnaire - Taiwan Diet Quality Calculator - that will be validated within a subcohort of the current study, and food diaries for participants who are willing to provide such details. Nutritional biomarkers (e.g., serum vitamin B12, vitamin D, skin carotenoids), along with routine health examination values (complete blood counts, lipid profiles, renal and liver functions, bone mineral density) will also be collected. When funding permits, genome-wide genotyping, metabolomics, and other aging-related biomarkers will also be examined.

For cohort follow-up, study participants will be invited back for follow-up health examination every three years. In addition, data will also be linked to National Health Insurance Claim database, National Cancer registry, and National Mortality Registry in Taiwan to further ascertain relevant health outcomes.

By integrating comprehensive dietary assessments, nutritional biomarkers, health examination and genetic data, and aging-related functional outcomes, this cohort will provide an unique opportunity to examine dietary patterns, nutrient requirements, and lifestyle that best support healthy aging. The inclusion of genomic and metabolomic analyses will further enable the investigation of diet-gene interactions, supporting the development of precision nutrition strategies for individuals at elevated genetic risk. This research is expected to inform strategies for disease prevention and the maintenance of functional independence in older adults.

Time frame: From enrollment to three-year follow-up, six-year follow up

Cognitive function will be assessed using Montreal Cognitive Assessment \[MoCA\], Taiwanese version. (Score range 0-30, unit = points). A score ≥26 is generally considered normal, while scores \<26 suggest possible cognitive impairment. Outcomes will be reported both as continuous MoCA scores and as a binary classification (normal vs. impaired).

Time frame: From baseline to three-year follow-up, six-year follow-up

Appendicular skeletal muscle mass (ASM) will be assessed by bioimpedance analysis (BIA), with height-adjusted cutoffs of \<7.0 kg/m² in men and \<5.7 kg/m² in women defined as low ASM. Results will be reported as both continuous measures (kg/m²) and categorical measures (normal or low ASM).

Time frame: From baseline to three-year follow-up, six-year follow-up

Grip strength will be assessed using a handheld dynamometer, with cutoffs defined as \<28 kg for men and \<18 kg for women. Results will be reported as continuous measures (kg).

Time frame: From baseline to three-year follow-up, six-year follow-up

Sarcopenia will be defined as the combined presence of low ASM and low grip strength. Results will be reported as a binary outcome (yes/no).

Plant-based Diets and Healthy Aging - the Tzu Chi Aging Study (TCAS)