Are all vegetarian diets healthy?

"Our study highlights the variable nutritional quality of plant foods," said author Dr. Matina Kouvari of Harokopio University, Athens, Greece. "This finding was more evident in women. Prior research has shown that women tend to eat more plant-based foods and less animal-based products than men. But our study suggests that this does not guarantee healthier food choices and in turn better health status."

Most dietary studies define plant-based diets simply as "vegetarian" or "low in meat," thereby treating all plant foods as equal. The unique aspect of this study was that it examined the type of plant-based foods consumed, in addition to the overall amount. Healthy plant-based products were principally the least processed foods, such as whole grains, fruits, vegetables, nuts, olive oil, and tea/coffee. Unhealthy plant-based products consisted of juices, sweetened beverages, refined grains, potatoes, and any kind of sweets (e.g. chocolate, Greek traditional desserts, etc.).

The study examined the link between the amount and quality of plant-based foods and heart health over a 10-year period.

In 2001 and 2002, the ATTICA study randomly selected a sample of adults living in Athens who did not have cardiovascular disease or other chronic conditions. The current analysis was conducted in 146 obese participants with normal blood pressure, blood lipids, and blood sugar. Diet was assessed using a questionnaire about usual habits in the previous year. It listed 156 foods and beverages commonly consumed in Greece, with photographs to help define portion sizes.

Within a decade, nearly half of these obese participants had developed high blood pressure, high blood lipids, and high blood sugar -- a combination that is particularly risky for heart health.

Men who consumed more plant-based foods were less likely to have this decline in health status. A trend was also observed in women, but it did not reach statistical significance.

Regarding the quality of plant-based foods, healthier choices were linked with maintaining normal blood pressure, blood lipids, and blood sugar. Conversely, consuming unhealthy plant-based foods was associated with developing high blood pressure, high blood lipids, and high blood sugar. These relationships were stronger in women compared to men.

Dr. Kouvari said: "Eating less meat is beneficial for heart health, particularly when it is replaced with nutritious plant foods such as whole grains, fruits, vegetables, nuts, and olive oil."

She noted that the analysis was conducted in obese individuals and the findings should not be extended to other weight categories.