A large new study followed 407,618 adults in six European countries for about 11 years and tracked the incidence of cancer, heart disease, and type 2 diabetes.

The researchers examined how closely people stuck to a healthful, plant-based diet and how that related to developing more than one of the health conditions.

Why this study matters

The project was led by Reynalda Córdova, a nutritional epidemiologist at the University of Vienna, working with colleagues across Europe.

Their team centered the analysis on real-world eating patterns and combined two major datasets to see long term effects.

Chronic diseases often show up in pairs or more. When someone has two or more at the same time, clinicians call it multimorbidity. Reducing the odds of multiple serious conditions can ease pressure on families and health systems.

In public health, preventing even a modest share of new cases matters because risk compounds when illnesses cluster.

The analysis used the term “cardiometabolic” to group heart and metabolic problems that often intersect with cancer risk.

By treating the co-occurrence of conditions as the outcome, the study focused on how disease accumulates over time rather than on single diagnoses.

Plant-based diets were rewarded

Participants came from the EPIC study, and the U.K. Biobank (a national research resource that invites adults to share health data for science). These two large cohort projects collect data that connects lifestyle and health records. 

Diet quality was scored using a healthful, plant-based diet index that rewards vegetables, fruits, whole grains, legumes, nuts, and coffee.

Dietary intake of refined grains, sweets, and animal products, on the other hand, reversed the points.

A companion unhealthful, plant-based diet index scores higher for refined plant foods and sugary drinks, reflecting differences in plant food quality.

The models estimated hazard ratio, which expresses how much risk changes with each 10-point rise in the score. This was calculated after accounting for age, sex, smoking, activity, and alcohol use.

Events were counted and sequenced to see whether a first diagnosis was followed by another, which mirrors how disease accumulates in life.

Plant-based diet and multimorbitity

Across the combined cohorts, 6,604 people developed two of the three illnesses during follow up.

A 10-point increase on the healthy plant diet score was linked to 11 percent lower risk in EPIC and 19 percent lower risk in UK Biobank data.

In adults younger than 60, the hazard ratio was 0.71, and in those of 60 or older it was 0.86. This shows a stronger association in midlife.

The pattern for the unhealthful plant score was positive in UK Biobank data, and null in EPIC, underscoring that not all plant-rich eating is the same.

“A healthy plant-based diet might reduce the burden of multimorbidity of cancer and cardiometabolic diseases among middle-aged and older adults,” concluded Córdova.

Healthful plant-based diet defined

Scores for the healthy pattern rise with vegetables, fruit, whole grains, beans, nuts, and coffee. Less reliance on refined carbs, sweets, and red or processed meat helps keep the score high.

The unhealthful score climbs with sodas, sweets, white bread, and other refined items. Those choices can crowd out fiber-rich foods that support steady energy and metabolic health.

Separating the healthful and unhealthful versions explains why a plant-based diet can help or harm, depending on the mix. Quality matters more than labels, and the scale captures that difference.

Why diet quality might matter

A Lancet review linked higher fiber intake with lower risk of several noncommunicable diseases and better glycemic control.

Fiber also feeds gut microbes that produce short chain fatty acids. These organic substances support metabolic and immune balance.

Other prospective evidence ties plant-based eating patterns to lower type 2 diabetes risk across populations.

A comprehensive meta-analysis reported that greater adherence to plant-based diets, especially those rich in healthful plant foods, was associated with a lower risk of type 2 diabetes.

These mechanisms align with the new results, where lower weight, lower inflammation, and better insulin sensitivity likely explain part of the link. Diet is not a cure, but quality changes can tilt the odds toward healthier aging.

How to interpret this safely

Self-reported diet is imperfect, and people may change how they eat after a diagnosis, which can blunt associations.

Differences that are not measured can also shift estimates, so the authors tested many scenarios to check robustness.

The inconsistency for the unhealthful score between EPIC and UK Biobank suggests that context and measurement matter. Food culture, recall frequency, and how outcomes are captured can all influence results.

Even with caveats, the direction and size of the associations fit prior literature on plant-rich patterns and long term health. That consistency adds confidence without assuming what a single study proves in every setting.

Small shifts in everyday choices

The findings do not require strict rules or total exclusion of animal products. They point to a pattern where plants take the lead while animal products and refined items take a back seat.

Small shifts that raise the healthful plant score are realistic and sustainable. Those shifts also track with widely recommended approaches to lifelong health.

The study is published in The Lancet Healthy Longevity.

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