Breast Cancer, Food, and Diet: Tips From an MSK Expert

Neil Iyengar, medical oncologist at Memorial Sloan Kettering, is seen holding a piece of fruit.

Neil Iyengar, MD, is a breast cancer oncologist at Memorial Sloan Kettering Cancer Center. His research focuses on the role of diet, food, and exercise in cancer.

Research shows that what we eat can directly affect our health, including complex diseases like breast cancer.

That may seem like common sense.

But what’s not so apparent is how to put the latest research into practice in our own lives, especially when dealing with the stress of a cancer diagnosis.

Breast cancer oncologist Neil Iyengar, MD, cares for people at Memorial Sloan Kettering Cancer Center (MSK). His extensive research on the connection between diet, exercise, and cancer has made him a nationally recognized authority on these topics.

Dr. Iyengar also founded the MSK Healthy Living program to help MSK patients with breast cancer live their best life during and after cancer. Each patient in the program is given a lifestyle plan tailored to their individual needs, covering everything from nutrition and exercise to psychological well-being, sleep, and more.

Each day, Dr. Iyengar helps the people he treats make better choices about what they eat. Here are his evidence-based insights and tips for some of the questions he is most frequently asked, including the latest research on alcohol and aspartame.

What is the connection between food and the risk of breast cancer?

It’s important to understand that no specific foods have been proven to directly prevent cancer or reduce the chance that cancer will come back.

Instead, research shows that what is important is a healthy pattern of eating that people can stick with and sustain. In broad terms, that means eating a plant-based, high-fiber diet and being mindful of what you eat so you avoid highly processed food and don’t binge.

A healthy eating pattern like that has proven to be much better for a person’s health — including lowering cancer risk — than highly specific, restrictive diets that are hard to maintain.

One of the most important factors in the relationship between diet and cancer is body fat. Fat is one of the most active tissues in our body. It is intended to store energy. But if we take in too many calories, our energy storage can become unbalanced. Then fat can become inflamed.

That sets off problems like diabetes and coronary artery disease. The excess fat can also go to places it is not supposed to, like our liver, muscles, and pancreas. Cancer cells use this excess fat as an energy source to grow. Both the quantity and quality of our fat tissue, which are heavily influenced by our eating patterns, can affect cancer.

Healthier Tips:

  • Eat a plant based-diet that is high in fiber. 
  • That means eating a wide range of fruits, vegetables, nuts, and legumes like beans. 
  • You can eat meat, but limit it to 20% or less of your diet 
    • Eat lean meats that are minimally processed. 
    • Minimize intake of red meats. 

Does healthy eating matter if a person is diagnosed with cancer?

Sometimes people tell me after they are diagnosed: “I always had a healthy eating pattern. What was the point? It didn’t matter.”

But a growing body of research suggests just the opposite. It shows that how a person has been eating over the years can impact how cancer might behave and how the body responds to cancer therapy.

Healthy eating is like money in the bank or insurance. If you are diagnosed with cancer, a history of healthy eating can potentially improve the outcome. There are positive benefits to a good diet even if cancer is diagnosed.

Healthier Tips:

  • Preparation is key.
  • Consider a meal delivery plan that is healthy and includes foods you enjoy. Or, set aside time to pre-prepare your meals for the upcoming week.
    • Take a meal with you to work or other places where healthy options may be hard to find.
    • I take a meal with me to work on days when I know I’ll be really busy so I’m not tempted to get something fast but unhealthy.
  • Stock up on healthy snacks like minimally processed nuts so it’s convenient to eat well.


Healthy eating is like money in the bank or insurance. If you are diagnosed with cancer, a history of healthy eating can potentially improve the outcome.
Neil M. Iyengar medical oncologist

What is your approach to diet during cancer treatment?

I find out about a patient’s needs as an individual — both medical and personal.

For example, some breast cancer tumors have genetic mutations that we want to target with specific therapies. We know those therapies may cause weight gain by affecting how metabolism functions and how the body uses insulin. We’ll focus on modifying the patient’s overall dietary habits in preparation for that therapy so there isn’t excess weight gain.

Personal goals during cancer treatment are important, too. For instance, patients have told me during treatment that they hope to slim down for a big event in their life, like a wedding. Then we start off with a dietary approach that’s focused on weight loss in a safe way, because we also know rapid weight loss is not good. 

I want to know what a person’s energy intake and output looks like. What are their eating habits? How physically active are they? (Which could include work or running around after young children.) Insights into a person’s life makes for better treatment.

Healthier Tips:

  • Know your treatments, and ask how they may be affected by your eating and lifestyle patterns.
  • Understand your individual needs and goals.

Can diet affect genetic risks for breast cancer, like BRCA mutations?

Some genetic conditions that are passed down from our parents, like the well-known BRCA 1 and BRCA 2 gene mutations, can significantly increase the chance of developing cancer, particularly breast and ovarian cancer.

Our own research and studies conducted elsewhere suggest that a healthy diet can help people with a BRCA mutation on several levels. First, by reducing obesity, people are less likely to develop cancer at a young age, in part because obesity damages tissue like breast tissue, which makes cancer more likely, particularly with BRCA mutations.

Research also suggests that people with a BRCA mutation who maintain a healthy diet live longer after cancer treatment.

A lot more work needs to be done, but we believe it’s possible that a healthy diet may help delay the onset of breast and other cancers for people who have these genetic syndromes. That’s important because many women with BRCA mutations consider removing their breasts or ovaries to protect themselves. Often these are young women at the start of their careers and in their childbearing years.

If we can delay the onset of cancer in part through diet, women may be able to consider those surgeries later in life, perhaps a decade or more. That would have a big impact on a person’s life.

Healthier Tips:

  • Tell your friends and family that you are trying to be healthy and ask them to support you — particularly if you have a high risk of developing cancer or have been diagnosed. Support from your social network can help a lot.
  • It’s easier to avoid temptations that aren’t around. Don’t bring unhealthy snacks into your home.

How does alcohol affect cancer?

Recent studies show, unfortunately, that there is no safe level of alcohol consumption. Even small, occasional consumption of alcohol can elevate the risk of cancer as well as cancer recurrence. That’s because alcohol damages DNA and has other negative effects. Alcohol also contributes to excess calorie intake and increased fat deposition that can lead to health issues, including cancer.

That said, this is a situation where people need to decide what’s important to them. The risk of cancer from alcohol rises as consumption increases. So occasional, very moderate drinking of alcohol has only a moderate increase in risk.

In a world where it seems nearly everything elevates the risk of cancer, a person may decide that consumption of a small amount of alcohol brings them a better quality of life. If people are aware and understand that more alcohol consumption increases risk, they can make an informed decision about how much risk they are willing to accept.

Healthier Tips:

  • Ask yourself if a small amount of drinking increases your quality of life.
  • If the answer is no, it may be better to stick to mocktails or seltzer.
Living Better During Cancer and Beyond: The MSK Healthy Living Program
Learn about the MSK Healthy Living program that provides breast cancer patients with a custom plan tailored to their needs to help with nutrition and exercise, integrative medicine; support for mental, emotional, and spiritual well-being and much more.

How does aspartame affect cancer risk?

The World Health Organization said that the artificial sweetener aspartame may possibly pose a risk of cancer. The U.S. Food and Drug Administration disagreed. We do not have definitive lifetime studies now. But research does show aspartame has troubling effects on the microbiome and other important biological pathways. So the health picture for this widely used product is not yet entirely clear.

However, there is another aspect that’s important. Artificial and non-nutritive sweeteners like aspartame can be a useful tool in transitioning someone from a highly processed, unhealthy, highly sweetened diet to a minimally processed, well-balanced diet.

The problem, though, is that many people use these products for a long period of time and never transition to a healthier diet. For some people, these can be a useful tool. But it’s important to keep the goal in mind, which is to reprogram our taste buds so that we don’t rely on heavily sweetened foods. And then stop using artificial sweeteners.

Healthier Tips:

  • Replace soda with seltzer when you want a fizzy drink.
  • When craving something sweet, go for a food that uses healthier, unrefined sugar such as beet sugar, date sugar, coconut sugar, or molasses.