Gardening can help reduce the risk of cancer and improve mental health

Summary: A new study reveals that community gardening helps reduce stress and anxiety and lowers cancer risks. Researchers found that those who gardened had higher fiber intakes and increased physical activity.

Source: University of Colorado

Get more exercise. Eat well. Make new friends.

As we compile our lists of resolutions aimed at improving physical and mental health in 2023, new research from CU Boulder suggests one addition could be having a major impact: gardening.

Funded by the American Cancer Society, the first randomized controlled trial of community gardening found that those who took up gardening ate more fiber and exercised more, two ways known to reduce the risk of cancer and chronic disease. They also saw their stress and anxiety levels decrease significantly.

The findings were published Jan. 4 in the journal Planetary Health Lancet.

“These findings provide strong evidence that community gardening could play an important role in the prevention of cancer, chronic disease and mental disorders,” said senior author Jill Litt, a professor in the Department of Environmental Studies at CU Boulder.

Filling the research gap

Litt has spent much of his career trying to identify affordable, scalable, and sustainable ways to reduce disease risk, especially among low-income communities.

Gardening seemed like an ideal starting point.

“No matter where you go, people say there’s something about gardening that makes them feel better,” said Litt, who is also a researcher at the Barcelona Institute for Global Health.

But it’s hard to find solid science about its benefits. Without evidence, it’s hard to get support for new programs, she said.

A few small observational studies have found that people who garden tend to eat more fruits and vegetables and are at a healthier weight. But it’s not clear whether healthier people just tend to garden or whether gardening affects health.

Only three studies have applied the gold standard of scientific research, randomized controlled trial, to the pastime. No one has looked specifically at community gardening.

To fill the gap, Litt recruited 291 non-gardening adults, average age 41, from the Denver area. More than a third were Hispanic and more than half were from low-income families.

After the last spring frost, half were assigned to the community gardening group and half to a control group who were asked to wait a year to start growing.

The gardening group received a free community garden, some seeds and seedlings, and an introductory gardening course through the nonprofit Denver Urban Gardens program and a study partner.

Both groups had periodic surveys of their nutritional intake and mental health, had body measurements and wore activity monitors.

A load of fibre

In the fall, those in the gardening group ate, on average, 1.4 grams more fiber per day than the control group, an increase of about 7 percent.

The authors note that fiber has a profound effect on inflammatory and immune responses, influencing everything from how we metabolize food to how healthy our gut microbiome is to how susceptible we are to diabetes and some cancers.

While doctors recommend 25 to 38 grams of fiber per day, the average adult consumes less than 16 grams.

“A one-gram increase in fiber can have large positive health effects,” said co-author James Hebert, director of the University of South Carolina’s cancer prevention and control program.

The gardening group also increased their physical activity levels by about 42 minutes a week. Public health agencies recommend at least 150 minutes of physical activity per week, a recommendation that only a quarter of the US population meets. With just two or three visits to the community garden per week, participants met 28 percent of that requirement.

Study participants also saw their levels of stress and anxiety decrease, with those who entered the study the most stressed and anxious seeing the greatest reduction in mental health problems.

Only three studies have applied the gold standard of scientific research, randomized controlled trial, to the pastime. No one has looked specifically at community gardening. Image is public domain

The study also confirmed that even novice gardeners can reap measurable health benefits from the hobby in their first season. As they have more experience and enjoy higher returns, Litt suspects those benefits will increase.

Relationships flourished

The study findings come as no surprise to Linda Appel Lipsius, executive director of Denver Urban Gardens (DUG), a 43-year-old nonprofit that helps about 18,000 people each year grow their own food in community gardens.

“It’s transformative, even life-saving, for so many people,” Lipsius said.

Many DUG participants live in areas where access to affordable fresh fruit and vegetables is otherwise extremely limited. Some are low-income immigrants who now live in apartments: having a garden allows them to grow food from their home country and pass down traditional recipes to family and neighbors.

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Social connection is also huge.

“Even if you come into the garden trying to grow your own food in a quiet place, you start looking at your neighbor’s plot and sharing techniques and recipes, and over time relationships blossom,” Litt said, noting that as you garden alone is good, community gardening can have additional benefits. “It’s not just about fruits and vegetables. It’s also about being in a natural outdoor space with others.”

Litt said she hopes the findings will encourage health professionals, policy makers and land planners to look to community gardens and other spaces that encourage people to gather in nature as a vital part of the public health system. The evidence is clear, she said.

Gardening work.

Researchers from the Colorado School of Public Health, Colorado State University and Michigan State University also contributed to this study.

About this mental health and cancer research news

Author: Lisa Marshall
Source: University of Colorado
Contact: Lisa Marshall – University of Colorado
Image: Image is public domain

Original research: Free access.
“Effects of a community gardening intervention on diet, physical activity, and anthropometric outcomes in the United States (CAPS): A randomized, observer-blind, controlled trial” by Jill Litt et al. Planetary Health Lancet


Abstract

Effects of a community horticulture intervention on diet, physical activity, and anthropometric outcomes in the United States (CAPS): A blinded, randomized, controlled study

Background

Unhealthy diet, physical inactivity, and social disconnection are important modifiable risk factors for NCDs and other chronic diseases, which could be alleviated through nature-based community interventions. We tested whether a community gardening intervention could reduce these common health risks in an adult population diverse in terms of age, ethnicity, and socioeconomic status.

Methods

In this blinded, randomized, controlled study, we recruited individuals who were on waiting lists at the Denver Urban Garden for Community Gardens in Denver and Aurora (CO, USA), aged 18 years or older, and who had not practiced gardening in the last 2 years . Participants were randomly assigned (1:1), using a randomized block design in blocks of two, four, or six, to receive a community garden (intervention group) or remain on a waitlist and not in garden (control group). Researchers were masked by group allocation. The primary outcomes were diet, physical activity, and anthropometry; secondary outcomes were perceived stress and anxiety. During spring (April to early June, before randomization; timepoint 1 [T1]), autumn (late August to October; time point 2 [T2]), and winter (from January to March, after the intervention; time point 3 [T3]), participants completed three dietary boosters, 7-day accelerometry, surveys, and anthropometry. Analyzes were performed using the intention-to-treat principle (that is, including all participants randomly assigned to groups and assessed as randomized). We used mixed models to test the hypothesis time to intervention at an α level of 0.04, with T2 and T3 intervention effects at an α level of 0.005 (99.5% CI). Due to the potential effects of the COVID-19 pandemic on outcomes, we have excluded all participant data collected after February 1, 2020. This study is registered with ClinicalTrials.gov, NCT03089177 and data collection is now complete.

Results

Between January 1, 2017 and June 15, 2019, 493 adults were screened and 291 completed baseline measures and were randomly assigned to the intervention (n=145) or control (n=146) groups ). Mean age was 41.5 years (SD 13.5), 238 (82%) of 291 participants were female, 52 (18%) were male, 99 (34%) identified as Hispanic, and 191 (66%) identified as non-Hispanic. 237 (81%) completed measurements before the onset of the COVID-19 pandemic. A participant (<1%) nel gruppo di intervento ha avuto un evento allergico avverso in giardino. Sono stati osservati significativi effetti time-by-intervent per l'assunzione di fibre (p=0·034), con una differenza media tra i gruppi (intervento meno controllo) a T2 di 1·41 g al giorno (99·5% CI –2·09 a 4·92), e per l'attività fisica da moderata a intensa (p=0·012), con una differenza media tra i gruppi di 5·80 minuti al giorno (IC 99·5% da –4·44 a 16·05 ). Non abbiamo trovato interazioni significative nel tempo per intervento per l'assunzione combinata di frutta e verdura, indice di alimentazione sana (misurato utilizzando l'indice di alimentazione sana-2010), tempo sedentario, indice di massa corporea e circonferenza della vita (tutti p>0 04). Difference score models showed greater reductions between T1 and T2 in perceived stress and anxiety among participants in the intervention group than those in the control group.

Interpretation

Community gardening can provide a nature-based solution, accessible to a diverse population, including new gardeners, to improve well-being and important behavioral risk factors for noncommunicable and chronic diseases.

Financing

American Cancer Society, University of Colorado Cancer Center, University of Colorado Boulder, National Institutes of Health, US Department of Agriculture National Institute of Food and Agriculture, Michigan AgBioResearch Hatch projects.

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