A good night’s sleep is often described as the foundation of good health, and new research confirms that it also plays a major role in mental well-being.
But there’s another encouraging finding: eating more fruits and vegetables may help soften the blow when sleep doesn’t go as planned.
In a new study published in PLOS One, researchers led by Dr. Jack Cooper, formerly of the University of Otago in New Zealand, investigated how three everyday habits—sleep, diet, and physical activity—are connected to psychological well-being in young adults.
Unlike past research that has mainly focused on mental illness, this study looked specifically at positive mental well-being and how it is shaped by lifestyle choices.
The team analyzed data from three separate groups of young adults aged 17 to 25 in New Zealand, the U.K., and the U.S.
One was a large survey of more than 1,000 participants, another was a 13-day diary study involving over 800 New Zealanders, and the third was an eight-day study of 236 participants who also wore Fitbits to track their activity.
Across all three groups, sleep quality emerged as the strongest and most reliable predictor of how well participants felt the next day.
Eating more fruits and vegetables came in second, showing a clear link with higher levels of happiness and well-being. Interestingly, the researchers found that the benefits were noticeable not just between people but also within the same person—eating more fruit and vegetables on a given day led to a real-time boost in mood.
Physical activity also mattered. While it was linked to improved well-being, the effect was strongest when looking at daily differences for the same person—days when someone moved more than usual were days when they felt better. However, unlike sleep and diet, the effect was less clear when comparing across different individuals.
One of the most surprising findings was how these behaviors interacted. Eating more fruits and vegetables seemed to help cushion the negative effects of a poor night’s sleep. Similarly, a good night’s sleep helped protect against the well-being dip that might follow a day of lower fruit and vegetable intake.
The effects appeared to be independent and additive, meaning that the more healthy behaviors people practiced, the greater the overall benefit.
“Young adults don’t need to hit a perfect standard of health to feel better,” said Cooper. “Sleeping a little better, eating a little healthier, or even exercising just 10 minutes more than usual was linked to improvements in well-being that same day.”
Professor Tamlin Conner, senior author of the study, added that these findings are especially important for young adults navigating unique pressures such as leaving home, financial challenges, and academic or social stress.
“Sleep quality stood out as the most powerful predictor, but eating fruits and vegetables and staying active also made a real difference. These small daily habits can help young adults not just survive, but thrive.”
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