A diet rich in fruit and vegetables (FV) is beneficial for overall health, but new research suggests it is also linked to lower stress levels.
Investigators assessed dietary intake and perceived stress in over 8600 Australian adults aged 25 years or older and found that those with the highest FV intake had a 10% lower score on a perceived stress questionnaire compared with the lowest FV intake. The association was strongest in middle-aged adults, rather than younger adults or those who were of retirement age.
“In addition to the benefits for physical health, diets rich in fruits and vegetables are also likely to have benefits for mental well-being,” study investigator Simone Radavelli-Bagatini, a doctoral candidate at Edith Cowan University, Perth, Australia, told Medscape Medical News.
“People of all ages should consume the recommended servings of fruits and vegetables every day to get these benefits,” she said.
The study was published online April 15 in Clinical Nutrition.
Growing Evidence
There is a growing body of evidence showing that improving diet quality, including increasing FV intake, benefits mental health, the investigators note.
Bioactive nutrients and phytochemicals including vitamins C, E, and K, the B-group vitamins, carotenoids, and phenolic compounds found in fruit and vegetables may play a role in reducing stress levels.
“Recent studies have shown that modifiable lifestyle factors, including a diet rich in FV, have beneficial impact on mental health, such as depression,” they add.
However, previous research has not explored the relationship between FV intake and perceived stress. In addition, although observational studies have reported some cross-sectional associations between lower FV intake and higher perceived stress in young students, this research “did not include individuals of all ages.”
To explore the cross-sectional association between FV intake and perceived stress, the researchers turned to participants in the Australian Diabetes, Obesity and Lifestyle (AusDiab) Study — a national population-based survey of 20,347 Australian adults recruited between 1999 and 2000.
Participants, who were drawn from 42 randomly selected districts in Australia, attended a biomedical examination where they completed the food frequency questionnaire and the 30-item perceived stress questionnaire (PSQ).
A total of 8689 participants (mean age [SD] 47.4 [14.1] years, 49.8% female) met the inclusion criteria. Of these, 5031 were re-evaluated at 5 years (2004-2005).
The researchers also assessed serum carotenoid levels in 1187 participants at baseline. Demographic information included age, sex, relationship status, and educational level. Additional information collected included height, weight, physical activity, smoking status, and history of cardiovascular disease and diabetes.
Participants were divided into quartiles, based on FV intake:
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Q1: 0-243 g/day
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Q2: 244-344 g/day
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Q3: 344-473 g/day
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Q4: ≥ 473 g/day
Across the Lifespan
For all participants, the mean PSQ index value was .27 (.002). Q4 participants had lower unadjusted perceived stress scores, compared to Q1 participants (.27 [.006] vs .31 [.003], respectively) — a finding that remained virtually unchanged after adjusting for covariables.
When the researchers performed a subgroup analysis of FV intake and perceived stress stratified by age at time of recruitment, they found higher FV intake was associated with a lower perceived stress among middle-aged adults (aged ≥ 45 – < 65 years; P = .004), but not in the younger (< 45 years) or older (≥ 65 years) age groups.
An analysis that examined the effect by gender showed FV intake was associated with lower perceived stress in both sexes (P = .009 and P = .012), respectively.
Perceived stress was associated with change in FV over 5 years (P > .05).
Although serum carotenoid levels were inversely associated with perceived stress in the unadjusted model, the finding lost significance after adjusting for age and other confounding factors.
“We demonstrate for the first time that FV intake was associated with lower levels of perceived stress across the adult lifespan,” the researchers write.
The finding that lower FV intake was associated with higher stress levels in middle-aged participants “may be related to the different stressors that occur during the different stages of life including financial, professional, and family stressors in middle-aged adults vs social isolation stressors in older adults,” the investigators speculate.
“A novel and interesting finding from our study was that perceived stress was not associated with the change in FV intake over 5 years, suggesting that a higher intake of FV (perhaps via its constituents) may reduce perceived stress, rather than higher perceived stress leading to a lower consumption of FV,” they note.
They point to several limitations of the study, including the inability to determine causality from a cross-sectional study design and that they did not explore the “domains or types of stressors, which are likely to vary markedly by stage of life.”
Tangible Stress Control
Commenting on the study for Medscape Medical News, Uma Naidoo, MD, director of nutritional and lifestyle psychiatry, Massachusetts General Hospital, Boston, and nutrition educator at Harvard Medical School, said it is “exciting to see another study supporting the fact that eating whole plant-based foods, such as fruits and vegetables, has a positive impact on mental health.”
Naidoo, who is also a chef and the author of This Is Your Brain on Food, and was not involved in the study, noted: “Particularly throughout this past year, we have all experienced increased stress levels, and the findings of this study provide evidence to suggest tangible means for individuals to take control of their stress levels by simply increasing the amounts of fruits and vegetables they are eating.”
Also commenting on the study for Medscape Medical News, Doug Bremner, MD, professor of psychiatry and radiology, Emory University School of Medicine, Atlanta, Georgia, and director of the Emory Clinical Neuroscience Research Unit, called it an “interesting study, linking lower stress levels to eating fruits and vegetables.”
Bremner, president and cofounder of Laughing Cow Productions, who was not involved with the study, noted that although the researchers controlled for variables such as exercise, “there is always the possibility that some unknown factor that caused them [the participants] to eat better also helped reduce their perceived stress.”
The authors acknowledge that randomized controlled trials “are needed to establish causal evidence.”
The study received no specific funding. Radavelli-Bagatini, Bremner, and Naidoo have reported no relevant financial relationships. Author disclosures are listed in the article.
Clin Nutr. Published online April 15, 2021. Abstract
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