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Are Plant-Based Diets Bad for Longevity? Let's Look at the Evidence

A study on elderly adults and longevity has been circulating in headlines suggesting that eating meat may be necessary to live to 100. A closer read of the research tells a different story.

What the study actually measured

The research followed adults age 80 and older in China, comparing omnivores, vegetarians who still ate eggs, dairy, or fish, and a smaller vegan subgroup, to see who reached age 100. The strongest association with lower odds of reaching 100 appeared only among participants who were underweight, a group in which low body weight is frequently a marker of frailty, chronic illness, or reduced appetite rather than diet choice alone.

Correlation, reverse causation, and what got lost in the headlines

Because the study is observational, it cannot establish that avoiding animal products caused shorter lifespans. Many older adults change how they eat after health decline sets in, meaning dietary labels can be a result of frailty rather than its cause. The study also did not track whether participants were meeting basic calorie, protein, or B12 needs, information that matters regardless of which diet a person follows.

• Most participants labeled vegetarian in the study still consumed eggs, dairy, or fish, making it a weak data point against fully plant based diets specifically.
• The clearer takeaway is that undernutrition and frailty are serious risks for the oldest populations, not that any single diet label determines lifespan.
• Well planned plant based diets can support long term health at any age, but any diet, plant based or not, carries risk if it is not adapted to the changing needs of an aging body.