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Folsom, Calif., March 2, 2026 — A new study published in the journal Clinical Nutrition suggests that women who consumed a diet containing flavonoid-rich foods such as blueberries, strawberries, apples and citrus fruits scored higher in feelings of happiness and optimism over time.

Researchers from Queen’s University Belfast and the Harvard T.H. Chan School of Public Health analyzed 18 years of follow-up data from the U.S. Nurses’ Health Study, which included over 36,000 women aged 60 years and older.

The investigation focused on the relationship between dietary flavonoid intake and two components of psychological well-being: happiness and optimism.

Flavonoids are naturally occurring compounds present in a variety of plant foods. However, the researchers found that women who consumed approximately three servings per day of flavonoid-rich foods such as blueberries, strawberries, apples and citrus fruits demonstrated a 3% to 16% greater likelihood of sustained happiness and optimism.

The results suggest a bidirectional relationship, where women who maintained higher levels of happiness and optimism were more likely to sustain a healthier, flavonoid-rich diet over time.

The U.S. Nurses’ Health Study primarily consists of non-Hispanic, white, highly educated female health professionals. Future research should aim to replicate these findings in more diverse populations.

“What we found most compelling is the potential for a ‘virtuous cycle’ between diet and mental outlook,” said lead researcher Aedin Cassidy, Ph.D. “Not only do flavonoid-rich foods like berries and apples appear to bolster long-term happiness and optimism, but women who feel better are also more likely to maintain those healthy habits. It suggests that simple, everyday dietary choices can be a powerful tool for supporting psychological resilience as we age.”

About the U.S. Highbush Blueberry Council 

Established in 2000, the U.S. Highbush Blueberry Council [3] (USHBC) is a federal agriculture research and promotion program with independent oversight from the United States Department of Agriculture (USDA). USHBC represents blueberry growers and packers in North and South America who market their blueberries in the United States and overseas, and works to promote the growth and well-being of the entire blueberry industry. USHBC is committed to providing blueberries that are grown, harvested, packed and shipped in clean, safe environments. Learn more at ushbc.blueberry.org [4].

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