This Many Vegetables Help Prevent Cancer, Science Says

There’s no single way to prevent cancer, but what you eat seems to play a role in risk. Decades of studies suggest that about 30% of the different types of cancers could be prevented through healthy dietary choices. And eating more vegetables seems to be at the top of the list.

“If any one food group were to be called out as protective, it would be vegetables,” Cynthia Thomson, PhD, RD, a professor at the University of Arizona, who studies the link between diet and cancer risk, noting their high level of bioactive compounds, or naturally occurring chemicals that may promote good health.

But, how many servings of veggies should you aim for? Here’s what the science says, plus why they matter and how to add more to your day.

The Science: How Many Servings Make a Difference?

There’s no exact number of vegetable servings that’s sure to lower your cancer risk, but your best bet is to aim for at least three servings per day, Thomson says.

Research backs up this number, says Sarah Pflugradt, Ph.D., RDN, CSCS, pointing to a 2021 meta-analysis of more than two dozen cohort studies. This review found that eating five servings of fruits and vegetables daily—broken into two servings of fruit and three of veggies) was linked to a lower risk of death from cancer and other causes.

These findings align with the 2020-2025 Dietary Guidelines for Americans and the recommendations from the National Cancer Institute:

To put servings into perspective:

• 1 cup raw, cooked, frozen or canned vegetables = 1 serving
• 2 cups raw leafy greens = 1 serving

Why Vegetables Help Lower Cancer Risk

There are three main reasons why vegetables may help decrease the risk of cancer.

They’re Rich in Bioactive Compounds

Veggies contain hundreds of bioactive compounds, which are naturally occurring chemicals with anti-cancer properties, Thomson says. Glucosinolates are one example.

“Cruciferous vegetables like Brussels sprouts, broccoli, cauliflower and kale contain nutrients called glucosinolates, which have been studied for being protective against certain cancers, such as prostate, breast, liver and colon,” Pflugradt says.

More specifically, these compounds may protect your cells from damage, reduce inflammation, help inactivate cancer-causing compounds and even inhibit tumor growth.

Pflugradt notes other examples of bioactive compounds that may be beneficial for cancer prevention:

• Vitamin C and beta carotene: found in many orange and red vegetables, such as bell peppers, carrots and sweet potatoes.
• Organosulfur compounds: found in alliums, think onions, garlic, leeks and shallots.

They Support a Healthy Weight

Vegetables are naturally low in calories and high in fiber, which helps you feel fuller for longer. Since obesity and overweight are linked to a higher cancer risk, vegetables can be a helpful part of weight management, says Thomson.

“This is one reason why supplements aren’t a one-to-one swap for veggies,” says Lauren Manaker, M.S., RDN, LD, CLEC. “Sure, you can meet your vitamin C needs with a supplement, but you’d be missing out on the fiber and many other beneficial compounds that work together in whole vegetables to protect your health. It’s the synergy of these nutrients that makes veggies so powerful.”

They Often Come with Other Healthy Choices

“People who select diets high in vegetables generally have diets with other healthy choices,” adds Thomson. This isn’t a direct benefit of consuming vegetables, but it’s essential to keep in mind that eating plenty of veggies is just one component of a healthy lifestyle that helps prevent cancer.

How to Get More Servings Daily 

Variety is key. “Not all vegetables have the same nutrients,” says Plfugradt. So aim for a colorful mix. 

Try these tips from our experts:

• Shop with your veggie goal in mind: “Each time you go to the grocery store, start your shopping in produce and buy enough for 15 to 20 servings per week,” Thomson says. Pick a rainbow of colors and try a new vegetable each week.
• Prep veggies for convenience: “Wash, chop and store them in the fridge so they’re ready to snack on or toss into meals,” Manaker says.
• Add greens to hot dishes: Stir greens, such as baby kale or spinach, into soups, pastas or grain bowls, says Pflugradt. 
• Blend veggies into smoothies. Frozen riced cauliflower adds creaminess and sneaks in an extra serving of veggies without altering the flavor, says Manaker. Leafy greens are another option.
• Stock your freezer: Keep frozen vegetables like peas, corn and green beans on hand for when you’re in a time crunch, recommends Pflugradt.
• Use bagged salads: “Pre-washed greens are a lifesaver for busy days,” Manaker says. “Add some protein and a simple dressing, and you’ve got a quick, veggie-packed meal.”
• Make it a challenge: Get competitive with a friend, coworker or family member, suggests Thomson. The exact rules can be your own—maybe you see who can hit their veggie goal most often in a month or who can eat the widest variety of veggies in a week.

“I really like to challenge people to try eating more vegetables for three to four weeks and see if they don’t feel so much better,” Thomson says. “At minimum, they will be glad to have regular bowel movements and overall more energy.”

Our Expert Take

While many factors affect the risk of cancer, nutrient-dense foods, such as fruits, vegetables, whole grains and nuts, have been shown to help lower it. But if you had to prioritize just one of those, it would have to be veggies, says Thomson.

Aim for at least three servings daily—and ideally more—while mixing up the types you eat to reap the most benefits. And remember, veggies are just one part of a healthy lifestyle that also includes staying active, getting enough sleep and limiting alcohol.