4 grocery store items colon cancer doctors avoid — and 3 they love

• Diet isn't the only factor that contributes to colon cancer, but it often plays a role.
• Some of the clearest links have been drawn to sugar and red meat.
• Experts recommend getting in more greens like broccoli, and drinking coffee if you like it.

One of the most common questions that doctors treating colon cancer get is: "what else can I do?"

Since colon cancer starts in the digestive tract, the food we put in ours is — rightly or wrongly — one of the first places people look, wondering: Is there some food I can eat that will help fight cancer, or some cancer-causing thing I should eliminate from my diet, stat?

The truth is that how cancer emerges inside a body is quite complex. There isn't usually one single thing a person can do to stop it.

While attending the world's biggest cancer conference earlier this month, I figured I'd cut through some of the noise out there and ask top colon cancer doctors directly what they generally recommend.

Dr. Paul Oberstein, a medical oncologist at NYU Langone who specializes in gastrointestinal cancers, says his patients are often hunting for a winning superfood that can combat colon cancer. He fields questions routinely about the merits of avocados, pine nuts, and other items. Could adding those single items to the grocery cart help?

While he says he's "doubtful" any single food can really make the difference in cancer recurrence, there are a few well-trodden truths doctors live by. These are backed by reams of study data from around the world.

Colon cancer doctors shun the meats and the sweets

We still can't say for sure whether there's one specific diet that is best to combat cancer, and especially one diet that's best for you in particular.

Plus, people with seemingly "clean" diets do get digestive cancers, even in their 30s and 40s.

That being said, these four foods are consistently included in diets that seem to lead to cancer diagnoses later on, so oncologists warn against them:

Red meat

Sorry to everyone firing up the grill this summer! Study after study suggests that there really is something about red meat (and especially processed meats like hot dogs and deli cuts) that does the kind of DNA damage that can lead to colon cancer.

Oberstein says patients often want to get prescriptive about it: Can I have red meat once a week? Twice a month? He's not really comfortable getting that granular with his advice, based on the data available.

"We just don't have the quantification and the confidence to say it's either for sure going to help, or you can't have it ever," he told Business Insider.

Dietician Lindsey Wohlford from MD Anderson Cancer Center created a chart in 2016 that recommends no more than two softballs' worth of red meat (18 oz.) per week.

Sugar-sweetened beverages, including fruit juice and syrupy drinks

It's common knowledge in the medical community that over-consumption of sugar-sweetened beverages — including fruit juices, flavored coffees, and soda — can sharply up a person's risk of all kinds of diseases, from diabetes to colon cancer.

Sugary drinks are more potent than sweet foods because liquid sugar is absorbed very fast — sometimes too fast. It can saturate the small intestine, spilling excess sugar into the colon. There's also evidence from animal studies that excess fructose — abundant in sugar and high fructose corn syrup — can escalate tumor growth.

Ultraprocessed foods, especially refined grains and sweets

The latest research on young colon cancer also suggests that young people who report eating more sugary foods tend to have a higher risk of developing late-stage colon cancer.

Dr. Andrea Cercek, co-director of the Center for Young Onset Colorectal Cancer at Memorial Sloan Kettering, is leading this research. She said it's not exactly a new idea that sugar can drive cancer growth.

"There's even data in animal models that fructose can lead to polyps," Cercek told BI. Her latest find opens up new questions about what might be prompting more aggressive cases of young colon cancer. "Is sugar maybe somehow driving and accelerating this process?" Cercek asked.

Alcohol — especially binge drinking and drinking on an empty stomach

In a very basic sense, alcohol is just fermented sugar, and it seems to carry a lot of the same cancer risks. Additionally, our liver breaks down alcohol into acetaldehyde, a known cancer-causing chemical that can damage DNA. Finally, alcohol dampens nutrient absorption and can kill off good bacteria in your gut.

In study after study, alcohol consumption is linked to more colon cancer diagnoses, and in general the more you drink, the greater your risk.

Evidence suggests there might be something especially harmful about binge drinking or drinking on an empty stomach, when it comes to colon cancer. Most cancer doctors are not going to insist you can't enjoy a glass of wine or beer now and then, but they would probably say it's best to have it with a meal.

Colon cancer doctors love greens and a morning cuppa Joe

If you're feeling hopeless now, buck up! There are a few tried-and-true items cancer doctors recommend adding to your shopping cart.

Greens

Leafy salad greens are rich in all kinds of nutrients that are great at fighting off cancer, like folate and fiber.

A special shout-out should go to the cruciferous green veggies like broccoli, Brussels sprouts, and kale, which are called "brassicas." They harbor bioactive compounds which are released when we chew them that have anti-inflammatory and anti-cancer effects.

Fiber sources, like beans and whole grains

Fiber has a reputation for being great at keeping folks full and regular. But that's not all that it does. It also picks up debris in your gut, helping clear out the junk, and dropping off good guy bacteria.

That's why Dr. Pashtoon Kasi, a medical oncologist at City of Hope who specializes in GI cancers, said it's "not just fiber for fiber's sake."

He says it's underappreciated how fiber is "ameliorating or modulating the microbiome" in ways that may help prevent cancer in the long run.

Coffee (without sugar)

"Coffee comes up in every study," Oberstein said.

This is great news for him personally, because he runs on the stuff. (But he says you don't need to feel pressured to start drinking coffee if you don't enjoy it.)

There seems to be something deeply beneficial about the anti-inflammatory properties of coffee. Studies show that coffee isn't just good at preventing colon cancer (in one study, coffee drinkers had roughly 26% lower odds of contracting colon cancer) — people with colon cancer diagnoses who drink several cups of coffee a day also lower their odds of death.

The takeaway: add veggies and beans in where you can

If you're looking for more widespread dietary advice, the National Comprehensive Cancer Care network guidelines for colon cancer patients recommend sticking to a "low glycemic load" diet, which means choosing more foods that are slow to digest and pack a fiber-rich punch. Low-glycemic foods include all kinds of fruits, veggies, nuts, beans, and whole grains.

Dr. Kimmie Ng, a medical oncologist at Dana-Farber, where she is the founding director of the young-onset colorectal cancer center, says her recommendations fit this basic framework:

"A diet less in red meat and processed foods and more in healthy proteins and fruits and vegetables is generally what we recommend," she told BI. "We know that that's typically anti-inflammatory and just healthier overall for a variety of chronic diseases, including cancer."