Low-quality plant-based diets may spoil potential health benefits

Plant-based diets have grown in popularity due to their perceived health-promoting benefits, but many studies on the topic have shown inconsistent results. That inconsistency may be caused by the composition of these diets, according to a new study, which linked high-quality plant-based eating protocols with protection against certain types of stroke.

For the purposes of this study, the researchers considered plant-based diets to be ones that primarily revolve around plant foods while excluding most animal products. Vegetarians fell into a different category, one classified as consuming no more than one serving of fish or meat each month.

Furthermore, not all plant-based diets — whether vegetarian or otherwise — are the same. A healthy plant-based diet focuses more on foods like whole grains, leafy greens, and other things high in fiber and nutrients like beans. In comparison, a lower-quality plant-based diet involves more foods like potatoes, refined grains, and products with added sugar.

The study, which comes from the Harvard T.H. Chan School of Public Health, linked healthy plant-based diets with an overall drop in stroke risk of 10-percent, including reduced risk of experiencing an ischemic stroke (there weren't any observed benefits between these diets and hemorrhagic stroke, though).

The findings were based on an analysis of data on more than 209,000 adults who participated in the Nurses' Health Study I and II, as well as the Health Professionals Follow-up Study. However, a second analysis wasn't able to link vegetarian diets with a decrease in stroke risk — and that, the researchers note, may be due to the small number of participants who met this classification.

Likewise, the researchers say that low-quality plant-based diets — such as ones with lots of refined bread, fried potatoes, and sugary snacks — may explain why past studies have found inconsistent associations between plant-based diets and their impact on stroke risk. Ultimately, plant-based diets may help protect one's health, but only if they focus on healthy foods.