In new research published in BMC Medicine, the authors recruited a large cohort of participants in order to assess how plant-based foods affect aging trajectories .
Benefits of plant-based diets
Previous research has shown that consumption of plant-based foods is associated with healthy aging [2,3]. It can also help to decrease the risk of mortality , prevent the development of chronic diseases [5,6], and improve neurological health, such as by lowering the risk of dementia  and cognitive impairment .
This new study aimed to determine the influence of a plant-based diet on the aging trajectory of the middle-aged Asian population. Researchers recruited over 10,000 people 50 years and older in Taiwan. Participants provided health data four times during the eight years after enrollment, underwent physical examinations, and filled out relevant questionnaires.
Researchers aimed to go beyond a single assessment of biological age. Instead, they performed repeated measures of biomarkers over the years, which allowed for the creation of aging trajectories.
Building aging trajectories
These researchers used their obtained data to measure aging in multiple dimensions. They also calculated multi-dimensional aging acceleration, which compares of their multi-dimensional aging metric to chronological age. To analyze trajectories, both multi-dimensional aging and its acceleration derivative were calculated four times at different time points.
During the analysis, researchers identified three aging trajectories. People in the slowly aging group had biological ages that were generally lower than their chronological age across four measurements. Compared to the slow-aging trajectory group, the medium group had a 1.56-fold higher risk of all-cause mortality. For the rapidly aging group, the risk was 3.72-fold higher. Associations slightly decreased when researchers adjusted for education, marital status, and health behaviors.
Beneficial and harmful plant-based foods
Not all plant-based foods are beneficial. Therefore, the authors created a plant-based diet index, a healthy plant-based diet index, and an unhealthy plant-based diet index. These categories distinguish between plant-based foods that are beneficial or harmful to aging and health in the long term.
Healthy plant foods include whole grains, fruits, vegetables, rhizomes, and legumes. Less healthy plant foods included sugar, refined grains, and salt-preserved vegetables.
The researchers divided participants into five groups (quintiles) based on the overall plant-based diet index. Compared to the participants from the lowest quintile, participants in the highest quintile were 25% less likely to be in the medium group and 37% less likely to in the rapidly aging group. Researchers also observed that the unhealthy plant-based diet index was reduced in the slowly aging group, while the healthy plant-based diet index was increased in this group.
Then, the researchers divided the participants into five groups, this time based on their healthy plant-based diet index and unhealthy plant-based diet index. People in the highest healthy plant-based diet index quintile were 27% less likely to be in the medium aging group and 38% less likely to belong to the rapidly aging group. On the other hand, people in the highest unhealthy plant-based diet index quintile were 72% more likely to be in the medium group and 70% more likely to belong to the rapidly aging group.
Taking a closer look, theresearchers noted that increased consumption of fresh fruit, fresh vegetables, and legumes were the main drivers of the positive associations with aging observed in this study. The main drivers of the detrimental effects observed included refined grain, salt-preserved vegetables, and dairy products.
Limitations and conclusions
The study has a few limitations. For example, the food intake data comes from a self-reported questionnaire, which can introduce some errors. Additionally, the study population consists mainly of middle-aged Asians, so these results cannot be generalized to other populations and ethnicities.
Nevertheless, this study points out that aging trajectories can better capture the dynamic nature of aging than a measurement conducted at a single time point. It can also help to identify populations with various risks of age-related diseases and mortality. The authors also note that people making public health recommendations should distinguish between healthy and unhealthy plant-based foods.
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