Community gardening could play an important role in the prevention of cancer and mental disorders

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 solid evidence that community horticulture could play an important role in the prevention of cancer, chronic disease and mental disorders.”

Jill Litt, senior author, 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.

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 on traditional recipes to family and neighbors.

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.


University of Colorado Boulder

Magazine reference:

Small, JS, et al. (2023) Effects of a community horticulture intervention on diet, physical activity, and anthropometric outcomes in the United States (CAPS): A randomized, observer-blind controlled trial. The Lancet’s planetary health.

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