Gardening may reduce risk for cancer, improve mental health
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Gardening appeared associated with increased fiber intake and moderate-to-vigorous activity and decreased levels of stress and anxiety among a diverse urban population, according to a study published in Lancet Planetary Health.
The results showed gardening may be a viable intervention for those most vulnerable to chronic diseases, including cancer, and mental health, researchers concluded.
Rationale and methods
“We have been investigating gardens as a health promotion strategy for the past 2 decades and have done qualitative and observational studies of gardens to understand how they work in terms of affecting changes in health behaviors, health status and mental well-being,” Jill S. Litt, PhD, professor in the department of environmental studies at University of Colorado Boulder, told Healio. “However, the evidence was limited by a profound issue — we could never answer the question about whether it was the garden causing changes or whether the people who came to garden were already healthy and engaged in meaningful activities and, thus, saw the world differently.”
The observer-blind, randomized, controlled trial included 291 individuals (mean age, 41.5 years; 82% women; 66% non-Hispanic) on waiting lists for Denver Urban Garden community gardens who had not gardened within the past 2 years.
Researchers randomly assigned individuals 1:1 in block sizes of two, four or six to either a community garden plot (intervention group; n = 145) or to remain on waitlists and not garden (control group; n = 146). Participants completed three diet recalls, 7-day accelerometry, surveys and anthropometry during spring (timepoint 1, or T1), autumn (T2) and winter (T3). Of note, researchers excluded data at T3 due to the COVID-19 pandemic.
Diet, physical activity and anthropometry served as primary outcomes. Secondary outcomes included perceived stress and anxiety.
“Randomly assigning study participants to gardening or the waitlist reduces bias and allowed us to examine the cause and effect between the intervention and our study outcomes of diet, physical activity and mental health,” Litt said.
Findings
Results showed significant time-by-intervention effects for fiber intake (P = .034), which corresponded to mean between-group difference of 1.41 grams per day at T2 (99.5% CI, 2.09-4.92), as well as for moderate-to-vigorous physical activity (P = .012), for mean between-group difference of 5.8 minutes per day (99.5% CI, 4.44 to 16.05).
“This study was not a nutrition study, so we did not give out any health advice but we gave people the tools and plants they needed to get started,” Litt said. “With more time in the garden, fiber intake could increase as people learn how to garden and increase their garden yields.”
Physical inactivity is also recognized as one of the most important risk factors for chronic disease, including cancer, she added.
“Getting people to move more is important for physical and mental health because it can reduce inflammation, improve immune system function, improve metabolism, and prevent obesity or control body weight,” Litt said. “It also can prevent high blood levels of insulin, which can increase risk for cancers of the breast and colon.”
Researchers additionally observed no significant time-by-intervention interactions for combined fruit and vegetable intake, Healthy Eating Index-2010, sedentary time, BMI or waist circumference (P > .04 for all).
Compared with the control group, those in the intervention group experienced greater reductions in perceived stress and anxiety between T1 and T2.
A limitation of the study included the exclusion of data at T3 to account for the COVID-19 pandemic due to the potential effect on primary and secondary outcomes, which the researchers excluded before unblinding and any analysis had occurred.
Implications
With stronger evidence, governments and nonprofits may be more likely to adopt and maintain these kinds of health promotion and community development programs, Litt told Healio.
“This study offers evidence in support of community-based solutions, such as gardens, to help promote behavior changes including diet and physical activity and reduce other cancer risk factors such as stress and anxiety,” she said. “For physicians looking for recommendations to provide their patients, this type of strategy could go a long way to support health and reduce risk for chronic disease. Telling someone to eat better, to be more active, to lose weight and to not be stressed is not effective.”
However, engaging individuals in fun activities that make them feel good and support eating better, being more active and feeling less stress and anxiety is a great way to reduce disease burden and promote healthy living, Litt continued.
“We are now moving into a broader area of research involving nature-based social prescribing across six cities in Australia, Europe and South America,” she said. “The aim of the project is to build on the knowledge gained through the gardens trial and expand the type of nature-based activities that are socially supported in communities where people live and work. Through a peer-supported group intervention, we will examine whether a 12-week intervention can reduce loneliness, which is an underappreciated risk factor for chronic disease and mental health disorders across the lifespan.”
References:
- Litt JS, et al. Lancet Planet Health. 2023;doi:10.1016/S2542-5196(22)00303-5.
- The scientific reasons you should resolve to start gardening in 2023 (press release). Available at: www.colorado.edu/today/2023/01/05/scientific-reasons-you-should-resolve-start-gardening-2023. Published Jan. 5, 2023. Accessed Jan. 17, 2023.
For more information:
Jill S. Litt, PhD, can be reached at jill.litt@colorado.edu.
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