Does Eating Antioxidant-Rich Foods Help Prevent Cancer?

Blue berries in bowl

We all want to avoid chronic diseases like cancer, of course. But translating the intention into preventive action is challenging.

For starters, cancer and other chronic health conditions can often seem so far away — making it hard to see the bigger, more healthful picture day-in, day-out.

You might also be confused as to which lifestyle behaviors are truly helpful and which aren't. For instance, can including antioxidant-rich foods into your diet help reduce your cancer risk?

What are antioxidants and what do they do in the body?

Antioxidants are protective molecules naturally found in our bodies and in the foods we eat.

Some important antioxidants include:

  • Vitamin A
  • Vitamin C
  • Vitamin E
  • Lycopene
  • Polyphenols, including flavanoids
  • Selenium
  • Carotenoid, including beta-carotene, lycopene, lutein and zeaxanthin

"Their role is to protect our bodies from the damage that free radicals can cause," explains Dr. Renee Stubbins, an oncology dietitian at Houston Methodist. "Free radicals are molecules that lead to oxidative stress and potentially inflammation and cellular damage."

Dr. Stubbins uses the analogy of a browning piece of sliced apple to help explain oxidative stress and the protective power of antioxidants.

"When you cut an apple and it starts to brown, that's oxidation," Dr. Stubbins explains. "The old-fashioned trick to prevent this is to squeeze lemon juice on the apple. This works because lemons contain vitamin C (ascorbic acid), an antioxidant able to prevent the browning that oxidation causes."

In people, free radicals can come from environmental exposures, like pollution and tobacco smoke, as well as what we eat.

 If not kept in check by antioxidants, the inflammation and oxidative stress that results can lead to many chronic health conditions, including cancers, heart disease, arthritis, diabetes, Alzheimer's disease and more.

But Dr. Stubbins points out that antioxidants can only do so much to prevent these diseases.

"Take smoking for example," says Dr. Stubbins. "The excess free radicals and oxidative stress created can lead to a balance shift, where antioxidants can't keep up with the cellular damage that's happening. If this leads to mutations, cancer can ultimately arise."

Do dietary antioxidants play a role in cancer prevention?

The power of antioxidants is undeniable. But is preventing chronic diseases like cancer as simple as consuming more of these protective molecules through our diet?

"Laboratory studies show that antioxidants can kill cancer cells," says Dr. Stubbins. "It does get a little more complicated within the body and when we add the food element, though. A lot of things happen between digestion and absorption."

Still, she points out that there's a reason both the American Cancer Society and the American Institute of Cancer Research promote a plant-forward diet.

"Eating a diet rich in fruits and vegetables will be rich in antioxidants and other phytonutrients, which could potentially decrease the risk of cancer," says Dr. Stubbins.

Are you eating enough antioxidant-rich foods?

Virtually all vegetables and fruits are rich sources of antioxidants. So, the good news is that you're likely reaping their benefits if you're eating the recommended amount of fruits and vegetables per day.

The bad news? Only 1 in 10 of us actually do, according to the CDC.

"We should be aiming for at least five servings of fruits and vegetables per day," says Dr. Stubbins. "And, in terms of antioxidants, some of these fruits and vegetables are more functional than others."

For instance, sweet potatoes contain higher amounts of beta-carotene, vitamin A and vitamin C than regular potatoes.

"Both are still good, but from an antioxidant standpoint a sweet potato might be slightly better," Dr. Stubbins adds. "Additionally, broccoli has a little more antioxidant power than green beans, but green beans are still good for you."

Examples of foods high in antioxidants include:

  • Berries
  • Bananas
  • Apples
  • Citrus
  • Tomatoes
  • Bell peppers
  • Squashes
  • Broccoli
  • Carrots
  • Sweet potatoes

Eat the rainbow to reap the full benefits of antioxidants

While some foods have more antioxidants than others, remember that all fruits and vegetables contain some amount of these protective molecules. Adding color into your lineup helps provide a broader spectrum of protection.

"All of the different colors of fruits and vegetables — red, orange, yellow, green, blue, purple — indicate the presence of different antioxidants, and each antioxidant protects in a different way," explains Dr. Stubbins. "I'd rather you get five servings of five different fruits and vegetables a day than eat five servings of the same fruit or veggie, even if it's one that's particularly high in antioxidants."

Need help with your fruit and veggie variety?

"I always tell people to pick out a colorful option they've never seen or heard of before and find a recipe that helps you understand how to cook it," recommends Dr. Stubbins. "This can be as simple as choosing a purple or yellow carrot over an orange one, but you can also get really creative with this — like substituting mashed potatoes with parsnip purée."

A few of Dr. Stubbins' tips for exploring the rainbow of fruits and veggies include:

  • Going to a farmer's market and buying something of each color
  • Signing up for a produce box
  • Visiting your local international grocery store and trying the different variety of fruits and vegetables

Beware: Antioxidant supplements aren't a replacement for fruits and veggies

Maybe you've heard of an antioxidant supplement claiming to contain all manner of beneficial properties — anti-cancer, anti-aging, anti-inflammatory (anti-everything bad, it seems). Dr. Stubbins warns against these products. Dietary antioxidants work best when they come from your food, she emphasizes.

"Elderberry, reishi mushroom extract, black seed oil, snake oil, vitamin C packets — companies will say you can put the power of fruit or vegetable into an extract, pill or powder," warns Dr. Stubbins. "But there's no consistent clinical evidence supporting that these products actually work."

Plus, these supplements and products are not as "natural" as you may think. Many are either man-made or at least somewhat processed.

They're also not regulated by the FDA, meaning there's no quality control check to ensure safety and effectiveness.

"Placebo effect is a real thing," Dr. Subbins add. "We're convinced these supplements help us, but the evidence is lacking. And, in some cases, they could be harmful."

For cancer patients, for instance, some antioxidant supplements can actually work against chemotherapy and radiation therapy.

"I always tell my patients, if you really want to take a supplement, let's first be sure it doesn't do any harm," says Dr. Stubbins. "The most important thing is that you know the facts so that you can make an educated decision about what you're putting into your body."

Dec. 1, 2022