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It can be hard to make informed, evidence-based decisions about diet and nutrition. This is especially true when trying to prevent and treat cancer.

During a recent episode of the �ձ�avɫ��Ƭ CancerCast podcast, two registered dieticians with certifications in cancer nutrition share their expert answers to common questions from patients. Emily Buchholtz, RD, CDN, CSO and Stephanie Roit, MS, RD, CDN, CSO are both registered oncology dietitians at �ձ�avɫ��Ƭ and NewYork-Presbyterian Hospital.

Here, Buchholtz and Roit discuss their evidence-based approach to how nutrition and diet can help prevent cancer, as well as the steps patients can take to eat healthfully in the first weeks and months after a cancer diagnosis.

What should we all understand about nutrition and cancer?

“The first thing I always want to mention and make sure people realize is cancer is very multifactorial,” asserted Buchholtz. “So it is not one particular item or one particular thing we do that will increase the risk.”

Certain foods do contribute to inflammation in the body, which increases our risk of cancer. “Things like white flour, for example, from bagels and pizza crust and regular pasta, high sugary things, so sodas and juices and ice cream and cookies,” said Buchholtz. “These things are okay to consume in moderation. But when we're eating them too often, what can occur is this inflammatory response in our body. And the more inflammation we accumulate over the years, the more DNA damage our body can accrue. And that DNA damage ultimately increases risk of cancer cell development.”

Other foods decrease inflammation, helping to reduce our risk of cancer. According to Buchholtz, these foods are unprocessed, plant-based foods: fruits and vegetables, whole grain carbohydrates, varying nuts and seeds, beans and lentils, as well as lean proteins like poultry, fish and eggs.

“These are all anti-inflammatory foods that provide a lot of vitamins, minerals and fiber that can really help promote a healthy diet, a healthy weight and reduce risk of cancer,” Buchholtz shared.

Can supplements help decrease the risk of cancer or support cancer treatment?

“The supplement industry is a really big industry in the United States and, unfortunately, it's not well regulated,” warned Roit. “You'll see a lot of claims on supplement bottles and from supplement companies that aren't well supported.”

The most recent research suggests that nutrients are best absorbed by the body from food sources, rather than supplements. “I think it's certainly a big topic and something that's best approached on an individual basis,” confirmed Roit, “but I can say there is a time and a place for supplements, certainly.”

Cancer patients are often instructed to avoid certain supplements during treatment to avoid any potential negative interactions.”If somebody is receiving a certain chemotherapy or treatment like Velcade, for example, it's very important to avoid green tea, green tea supplements,” Roit explained. “In those cases, that's where it's helpful to discuss your list with either your oncologist or your dietitian prior to taking it, so we don't end up with that problem.”

Does eating sugar lead to cancer growth?

There is a lot of fear and anxiety around eating sugar, especially for those who have been recently diagnosed with cancer. “A lot of patients have this fear that if they have a cookie or a piece of chocolate while going through treatment, cancer cells just start rapidly growing in their body, and that is completely false,” affirmed Buchholtz.

“What we know is that cancer is an inflammatory illness. And so, the more inflammatory foods, such as sugar, we eat creates this chronic cycle of inflammation in our body. So, whether you are someone sitting in to reduce risk of cancer or you are actively going through cancer treatment, we don't want people spending their whole day eating sugar. We want to focus on nourishing healthy foods. But if you want a serving of a sweet treat every few days, or you add a little bit of sugar in your coffee, that you spend the rest of the day eating clean and well-nourished foods, that is not going to impact your cancer cell development or the impact of the drugs treating the disease.”

Roit and Buchholz shared that they are frequently asked about the ketogenic (keto) diet. “The classic keto diet is really a strict ratio of a high-fat diet that can be up to 80 percent of your calories from fat,” said Roit. “Across the board, we can't say that the keto diet is beneficial for everyone … I think, hopefully, in the coming years, we'll have a little bit more information on specific tumor types and treatments where keto might be able to be used for a short amount of time to help, but we just don't have the research yet to support that.”

This high-fat diet may be difficult for some cancer patients to tolerate. Before beginning any type of restrictive diet, be sure to consult with a registered dietitian with expert knowledge in your specific condition.

What should those recently diagnosed with cancer do to eat healthfully?

Before starting treatment, it’s important to meet with a registered dietician with expert knowledge of cancer care. “We always like to meet with each person and really just make sure they have food stocked in the house that they like, that is easy to make and reliable … because most people feel a little queasy, more fatigued than usual,” explained Buchholtz. “So, things like whole grain bread, oatmeal, peanut butter, Greek yogurt, fresh or frozen fruits, prepared soups, canned beans, canned lentils, rotisserie chicken, eggs, just really simple protein-rich, well-balanced options that they can grab.”

Buchholtz also advised to focus on hydration during this time by stocking extra water and electrolyte-rich fluids.

How can cancer patients improve their diet to strengthen immunity?

The immune system may be affected throughout cancer treatment. Roit emphasized that all cancer patients should practice good hygiene to prevent illnesses, as well as taking steps to avoid food-borne germs and bacteria.

Beyond these preventive measures, patients can also consume more foods with nutrients that support the immune system. “Especially protein,” said Roit. “It's something that we emphasize a lot in our counseling. Not losing muscle mass, not losing weight and making sure that you're eating enough calories and protein can actually really help to support your immune system and reduce your risk for infection overall.”

How can cancer patients minimize nausea and dehydration with nutrition?

Many cancer patients experience nausea throughout treatment. Thankfully, many foods can help minimize this discomfort. “Simple, plain foods go a very long way,” asserted Buchholtz. “When you have a queasy stomach, you really want to try to choose cold, plain, bland foods until the nausea subsides. Greek yogurt with fruit, a smoothie, whole wheat bread with avocado or peanut butter.”

Buchholtz also advocated for drinking water and other liquids very slowly. “Another thing I notice a lot is that many of my patients tend to have coffee on an empty stomach in the morning, and that can also really interfere with nausea,” added Roit. “So, if you are a morning coffee drinker, try again to have something simple and plain first. Let that coat your stomach and then wait about 20 minutes and then go for the coffee.

Some cancer treatments lead to dehydration. Roit recommended incorporating other types of fluids, including broths, coconut water and some vegetable juices. In the case of more severe fluid loss, fluids with electrolytes and salt (such as Pedialyte) are beneficial.

Be sure to read part two of this series, listen to the full podcast episode and learn more about the expert cancer care from �ձ�avɫ��Ƭ.