Longevity Briefs: Plant-Based Diets Are Associated With Slower Ageing

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Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

Why is this research important: Consuming a plant-based diet doesn’t necessarily mean being vegetarian or vegan – it just means focussing primarily on plants as a source of nutrition. Evidence suggests that such a diet improves life expectancy and reduces your risk of developing age-related diseases like dementia. One question to which the answer is less clear is ‘do people consuming a plant-based diet actually age more slowly than those consuming a typical diet?’ Here we have a study in which researchers attempted to answer that question.

What did the researchers do: In this study, researchers recruited over 10,000 people in Taiwan, all 50+ years old. They were then followed up for 8 years. During this time, participants provided health data four times by filling in questionnaires (including about their dietary habits) and received physical examinations in which researchers measured various biomarkers of ageing.

Using this data, researchers estimated whether participants were biologically older or younger than expected at each of the four time points. They then categorised them into three groups or ‘ageing trajectories’ based on how this changed over the course of the 8 year follow up. These categories were ‘slow ageing’ (ageing more slowly than expected), medium-degree (ageing about as quickly as expected), and high-degree accelerated ageing (ageing more rapidly than expected).

Researchers then looked at whether plant-based diets were associated with slower ageing trajectories, as well as which specific plant-based foods were beneficial. In order to do this, they developed three methods of scoring participants’ diets. One method scored participants based on the intake frequency of plant-based foods. The other two methods also took into account the ‘healthiness’ of the plant-based foods that were being eaten. Whole grains, fruits, vegetables, rhizomes and legumes were considered healthy, while sugar, refined grains and salt-preserved vegetables were considered unhealthy.

Key takeaway(s) from this research:

• Participants in the medium and rapidly ageing groups were more likely to die from any cause than those in the slowly ageing group.
• Participants who consumed more plant-based foods in general were less likely to be in the medium or rapidly ageing group.
• Consuming healthier plant-based foods like fruits, vegetables and whole grains was associated with a slightly reduced chance of being in the medium or rapidly ageing group.

Unsurprisingly, participants in the more rapidly ageing trajectories were more likely to die during the followup period. People in the medium-degree ageing group were around 43% more likely to die of any cause than those in the slow ageing group when confounding factors were fully adjusted for. Those in the rapidly ageing group were over three times more likely to die in comparison to the slow ageing group.

There was an association between higher consumption of plant-based foods in general and reduced risk of accelerated ageing. The 20% of people with the highest scores for plant-based food intake were 25% less likely to be in the medium ageing group and 37% less likely to be in the rapidly ageing group when compared to the 20% of people with the lowest scores.

When the healthiness of plant-based foods was taken into consideration, the association with slower ageing was slightly stronger. The 20% of people with the highest scores for healthy plant-based food intake were 27% less likely to be in the medium ageing group and 38% less likely to be in the rapidly ageing group compared to the 20% with the lowest scores.

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It does therefore seem that consuming more plant-based foods, especially healthy ones, is associated with slower rates of ageing. The fact that researchers measured biological age at different points in time and looked at the progression of ageing over 8 years, rather than taking a single snapshot of biological age, is a notable strength of this study. 

On the other hand, this was an observational study, which means there were many confounding factors at play that are hard to fully account for. People who eat more plant-based foods are likely to look after their health in other ways, and are also wealthier and better educated on average. Intake of plant-based foods was also self-reported, which makes this data less accurate. Finally, this study was conducted in middle-aged Asians, so the results may not generalise to other ethnicities or age groups.