While vegetarian diets can help promote better health, certain plant-based foods are healthier than others, based on a recent study looking at the quality of vegetarian foods and mortality risk.

Published in the American Heart Association journal Circulation, this study tracked the diets of more than 75,000 US adults for more than a decade. It looked at how changes in plant-based foods impact mortality risk and if there’s a difference based on food quality.

The analysis included 49,407 women from the Nurses’ Health Study and 25,907 men in the Health Professionals Follow-Up Study, both of which have tracked the health of US professionals since the 1980s and 90s. Participants were between 33 and 75 years old and free of heart disease at the start of each study. They completed dietary questionnaires every two years and outcomes were tracked through 2014.

Overall, researchers found that diets rich in plant-based foods, rather than animal-based foods like meat and dairy, were linked to lower risk of death. However, mortality risk varied based on the quality of plant-based foods chosen.

In this study, healthy plant-based foods were defined as whole grains, fruits, vegetables, nuts, beans or legumes, vegetable oils, tea and coffee. Unhealthy plant-based foods included fruit juices, refined grains, potatoes, sugar-sweetened beverage and desserts.

Over a 12-year study period, researchers found that adults who increased consumption of these healthy foods had 10% lower risk of death than those whose diet remained stable. On the other hand, adults who increased consumption of unhealthy plant-based foods had 12% greater risk of death than those whose diets remained stable over the study period.

Researchers also found that the more participants increased their consumption of healthy plant-based foods, the lower their risk for heart-related death. The more they increased consumption of unhealthy items, the greater their risk for heart-related mortality.

What findings show, according to authors, is that just because a food is vegetarian does not mean it’s healthy. Plant-based foods can vary in quality and nutritional value, and it’s important to choose the most nutritional items as part of a well-balanced diet. For example, it’s better to choose whole grains over refined grains and to eat a piece of fruit instead of drinking fruit juice. It’s also important to consume plenty of the healthy plant-based foods like vegetables and nuts, while limiting unhealthy items like cookies and sugar-sweetened beverages.

Many studies confirm that healthy dietary choices can promote better health, and findings suggest that making healthy changes—even in middle age—could add years to your life.