As the common proverb goes, an apple a day keeps the doctor away. After a recent Penn State study, it appears the same may be true about avocados.

Nutritional science researchers Kristina Petersen and Penny Kris-Etherton found, in a study of 1,008 U.S. consumers, that eating just one avocado a day improved overall diet quality among participants.

“Previous observational research suggests avocado consumers have higher diet quality than non-consumers,” Petersen said in a press release. “So, we developed this study to determine if there is a causational link between avocado consumption and overall diet quality.” 

The scientists examined changes in the Healthy Eating Index, a measure of diet quality based on national Dietary Guidelines, after the addition of a daily avocado. 

They used an exploratory analysis approach to examine changes over 26 weeks. Petersen and Pugh hoped to assess the link between HEI and food intervention on cardiometabolic risk–related outcomes, as few past clinical trials have evaluated diet quality change.

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They randomly split participants into two groups. One continued its usual diet, limiting avocado intake, while the other incorporated one avocado a day.

Of the control group, 72% were female. The self-reported racial and ethnic distribution of the cohort was 69% white, 21% Hispanic, 15% Black, and 6% Asian. The remaining 10% either did not answer, were listed as American Indian, or checked multiple races or ethnicities.

At week 26, a greater increase in the HEI score was observed in the avocado-supplemented diet group than in the habitual diet group. The reason for the change was more surprising than the outcome.

 “We determined that participants were using avocados as a substitute for some foods higher in refined grains and sodium,” Petersen said. “In our study, we classified avocados as a vegetable and did see an increase in vegetable consumption attributed to the avocado intake, but also participants used the avocados to replace some unhealthier options.”

Petersen said she hopes implementation of healthier diets will help reduce incidents of chronic and preventable conditions, like heart disease, type 2 diabetes, and kidney disease.

The Avocado Nutrition Center supported the study but did not contribute to data analysis or interpretation, the university said.