Vegetarian diets may hinder healthy aging—unless diet quality is high

By Priyanjana Pramanik, MSc.Reviewed by Susha Cheriyedath, M.Sc.Apr 2 2025

A major study finds that vegetarian diets could reduce the chances of aging healthily—unless older adults eat high-quality plant-based foods rich in nutrients.

Study: Vegetarian diet and healthy aging among Chinese older adults: a prospective study. Image Credit: Weidong / Shutterstock

In a recent study published in the journal npj Aging, researchers investigated the impact of vegetarian diets on healthy aging in older adults in China.

Their findings indicate that vegetarians may be less likely to achieve healthy aging than omnivores. However, this difference may be driven by diet quality, as vegetarians with higher-quality diets showed no significant difference from omnivores in healthy aging.

Background

Vegetarian diets, which emphasize plant-based foods while restricting or eliminating animal products, are becoming more common. Research has linked these diets to reduced risks of cancer, diabetes, obesity, and cardiovascular diseases, particularly in middle-aged and younger populations.

They are also associated with benefits such as improved metabolic health. However, little is known about their effects on older adults, who may face nutritional deficiencies from vegetarian diets due to reduced intake of essential nutrients such as calcium, iron, vitamin B12, omega-3 fatty acids, and protein.

These deficiencies could contribute to muscle loss, bone fractures, and disability. Additionally, the influence of vegetarian diets on health outcomes, including cognitive function, mental health, and chronic diseases in older adults, remains unclear.

Since healthy aging rates remain low, identifying modifiable protective lifestyle factors is crucial to promote better health in later life.

About the Study

In this study, researchers utilized data collected from the Chinese Longitudinal Healthy Longevity Survey to investigate the impact of vegetarian diets on healthy aging, taking into account diet quality.

This ongoing cohort study included individuals aged 60 and older across 22 provinces in China. Multiple survey waves were conducted between 1998 and 2018 to assess health status, diet, and lifestyle. Ethics approval was obtained, and participants provided informed consent.

The study included 2,888 participants who were initially healthy and had dietary data available for analysis. Researchers defined healthy aging as the ability to survive until 80 without experiencing serious chronic diseases, cognitive decline, physical impairments, or poor mental health.

Chronic diseases were self-reported, while cognitive function was assessed using the Mini-Mental State Examination (MMSE). Physical function was measured through Activities of Daily Living (ADL), and mental health was evaluated using a psychological well-being index.

Dietary intake was assessed using a simplified food frequency questionnaire. Participants were categorized as vegan, ovo-vegetarian, pesco-vegetarian, or omnivorous, and diet stability from age 60 was examined.

The healthy plant-based diet index (hPDI) — which prioritizes whole grains, fruits, and vegetables — and unhealthy plant-based diet index (uPDI) — which includes refined grains and sugary beverages — were also calculated. Logistic regression models were used to estimate the associations between diet patterns and healthy aging, while adjusting for demographic, lifestyle, and health factors.

Findings

The participants were, on average, 72.1 years old, and 45% were female. Those following vegetarian diets were less likely to be male and more likely to belong to the Han ethnic group. On average, they had lower income and education levels—factors that may partially explain observed health disparities. Only 13% of participants followed a vegetarian diet, and fewer than 3% were vegan.

Over the six years of follow-up, 572 participants met the criteria for healthy aging. Vegetarians were 35% less likely to attain healthy aging than omnivores. Among vegetarians, vegans had the lowest odds, being 57% less likely to achieve healthy aging than omnivores (OR = 0.43; 95% CI: 0.21–0.89).

Long-term adherence to vegetarian diets was linked to a higher risk of chronic diseases, physical disability, and cognitive impairment. Vegetarians had nearly double the odds of experiencing physical function impairment (OR = 1.95; 95% CI: 1.25–3.04) and cognitive impairment (OR = 2.05; 95% CI: 1.26–3.33) compared to omnivores. Those who remained omnivorous from 60 onward were 78% more likely to achieve healthy aging than consistent vegetarians.

Similarly, individuals who were initially vegetarian but adopted omnivore diets had improved health outcomes (though this finding was not statistically significant). Further analysis showed a dose-response association between stricter vegetarian diets and poorer health outcomes (p-trend < 0.05).

Diet quality played a role, as vegetarians with poor plant-based diets displayed a significantly higher risk of chronic diseases (60% [OR = 1.60; 95% CI: 1.17–2.18]), physical limitations (95% [OR = 1.95; 95% CI: 1.25–3.04]), and cognitive decline (105% [OR = 2.05; 95% CI: 1.26–3.33]). Sensitivity analyses confirmed the robustness of these findings.

Conclusions

This study examined the impact of vegetarian diets on healthy aging in older adults. Findings indicate that maintaining an omnivorous diet from age 60 was linked to higher odds of attaining healthy aging than consistent vegetarianism, particularly for vegans.

While diet quality influenced outcomes, vegetarians following high-quality diets (hPDI, emphasizing whole foods) showed no significant disadvantage relative to omnivores. These results suggest that vegetarianism may not universally promote healthy aging and highlight the need for a balanced diet incorporating animal-based nutrients.

Prior research on vegetarian diets and health outcomes has been inconsistent, largely focusing on middle-aged adults. This study adds to the literature by considering overall health in older adults.

Potential drawbacks of vegetarian diets include deficiencies in protein, vitamin B12, and vitamin D, which may contribute to impaired physical and cognitive function. No clear association was found between vegetarian diets and mental health outcomes.

Researchers caution that observed differences may partly reflect socioeconomic factors, as vegetarians in the study tended to have lower income and education levels.

Limitations

Limitations include reliance on self-reported diet data and potential misclassification. The findings may not generalize beyond the Chinese population. The small sample size of vegans (n = 83) may limit statistical power and the stability of subgroup analyses. Future research should explore nutritional supplementation and dietary modifications to support healthy aging, ensuring guidelines are tailored to individual needs.