On average, more than one in three people in the United States will develop cancer at some point in their lifetime, according to the American Cancer Society. And many of those cases, they say, can potentially be prevented, including by making changes to your diet.

Scientists have a good idea of what foods you should avoid to reduce your risk of cancer, such as red and processed meats, “fast” or processed foods, alcohol and sugary drinks. But knowing what to eat isn’t always straightforward, said Johanna Lampe, a cancer prevention researcher at the Fred Hutchinson Cancer Center in Seattle.

Many nutrition studies rely on people to accurately remember what they consumed up to a year ago, Dr. Lampe said. And it’s tricky to understand how single foods may influence your health when they’re part of a larger diet, she said, adding that your lifestyle, environment, hormones and genes can also play a role.

No single food can prevent cancer on its own, said Nigel Brockton, the vice president of research at the American Institute for Cancer Research in Washington, D.C. But following a healthy diet does seem to reduce the risk, he said.

Here are some foods that experts say are worth adding to your plate.

Broccoli and Its Cruciferous Cousins

Cruciferous vegetables like broccoli, brussels sprouts, cauliflower and cabbage are rich sources of isothiocyanates, plant compounds that help our cells clear out toxins and repair themselves, which are crucial for cancer prevention, Dr. Lampe said.

Broccoli sprouts, for instance, are rich in the isothiocyanate sulforaphane, which may boost our body’s natural lines of defense against daily damage to cells, she added. The compound has been linked to protection against several types of cancer, including prostate, breast, bladder and colorectal.

Research suggests consuming more than four or five servings of cruciferous vegetables per week is associated with a reduced risk of cancer and other chronic conditions.

Tomatoes and Tomato-Based Products

Studies have long connected tomatoes to the reduced risk of prostate cancer thanks to their abundant stores of lycopene, a potent antioxidant that gives tomatoes their red color.

But lycopene may be just one of many compounds in tomatoes that help defend against prostate cancer, said Nancy Moran, an assistant professor of nutrition at the Baylor College of Medicine in Houston. And limited research has found that lycopene may also possibly protect against other cancers like breast, lung and colorectal.

Processing tomatoes, such as by cutting or cooking them, helps us absorb lycopene more easily than when we eat them raw, Dr. Moran said. Consuming tomatoes with fat helps, too. So eating them cooked, such as in a sauce or with a healthy fat like olive oil, can help boost the health benefits you get from them.

Beans and Other Types of Legumes

Common bean varieties like black and kidney beans, and legumes like chickpeas, dry peas and lentils, are not only high in protein. They’re also great sources of fiber, which is crucial for gut and immune health, Dr. Brockton said.

Fiber is also linked with colorectal cancer prevention. The bacteria in our gut break fiber down into fuel for the cells lining the colon, which keeps them healthy and less likely to turn into cancer cells, Dr. Brockton said.

Henry Thompson, the director of the Cancer Prevention Laboratory at Colorado State University, said that in animal and human studies, the consumption of beans (and other pulses like chickpeas and lentils) has been linked with the prevention of obesity, which is tied to several cancers. One ongoing clinical trial in humans is testing whether eating canned beans reduces cancer risk.

According to Dr. Brockton, the protective benefits of fiber kick in after eating around 30 grams — or the amount in about two cups of black beans — per day.

Nuts, Especially Walnuts

Tree nuts are rich in healthy fats, protein and fiber, and studies have found that those who consume them tend to have reduced risks of various types of cancer, especially those of the digestive system.

Walnuts in particular contain exceptionally high levels of plant compounds called ellagitannins, which are converted by our gut bacteria into metabolites that may reduce cancer’s ability to grow and multiply.

Dr. John Birk, a gastroenterologist at UConn Health who has performed colonoscopies for people in clinical trials that investigate the colon health benefits of walnuts, said that it was easy to spot a “walnut colon.” The lining of the colon wall “has a healthier appearance, a sort of glistening reflection of the light shining on it from the endoscope,” he said.

Studies suggest that eating about a handful of tree nuts per day is linked with health benefits.

Berries

Fleshy fruits like strawberries, blueberries, cranberries, pomegranates and black raspberries are packed with antioxidants like vitamin C and flavonoids that help protect cells from stress and DNA damage that can increase cancer risk. Plant compounds called anthocyanins give berries their colorful hues and anti-inflammatory heft; and reducing inflammation is important, because it “is a big driver of cancer,” Dr. Brockton said.

Dorothy Klimis-Zacas, a professor of clinical nutrition at the University of Maine, said that a growing body of evidence suggested that certain compounds in berries may help reduce cancer’s ability to develop, grow and multiply.

For the most anti-inflammatory benefits, aim for about one-half to one cup of fresh or frozen (and ideally organic) berries per day, she said.

Garlic

This pungent allium contains high levels of allicin, a sulfur-containing compound that is responsible for garlic’s strong odor and cancer-fighting abilities.

In one long-term study of more than 3,000 people who live in a region of China known to have high rates of stomach cancer, researchers found that for every 2.2 pounds of garlic that participants consumed per year, they had a 17 percent reduced risk of developing the disease. That’s about five cloves of garlic per week, said Wen-Qing Li, a cancer epidemiologist at Peking University Cancer Hospital in Beijing and an author of the study.

Stomach cancer, while on the decline in the United States, is one of the leading causes of cancer deaths globally.

Other, mostly nonhuman, studies have suggested possible links between garlic consumption and reduced risks of other types of cancer, especially colorectal cancer.

According to Dr. Li, consuming garlic raw — pressed into oil for salad dressing or in guacamole, for example — will help “to keep the flavors and chemicals inside alive.”

Nikki Campo is a freelance writer in North Carolina.