What to know about triple-negative breast cancer and diet

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The National Cancer Institute (NCI) advises that good nutrition is important before, during, and after cancer treatment.

A registered dietitian or nutritionist can help a person with cancer make dietary changes that may assist with the following:

• maintaining a moderate body weight
• maintaining physical strength
• keeping body tissues healthy
• decreasing appetite-suppressing side effects of cancer treatment, which may include:
  • altered sense of smell or taste
  • nausea or vomiting
  • mouth sores
  • pain
  • fatigue
  • depression
  • stress or anxiety

A doctor or dietitian can advise a person on how to consume enough calories, protein, vitamins, and minerals to support their overall health. They may suggest the following:

• eating smaller, more frequent meals throughout the day
• adding butter, cheese, or condiments to foods to increase their calorie content
• adding seasoning to foods to improve their taste
• eating foods at room temperature to reduce their odor if the smell is causing nausea
• blending foods so that they are easier to digest
• engaging in light exercise before meals to help stimulate appetite

Certain foods contain compounds that can influence gene expression and cancer progression. However, cancer is a complex disease, and compounds that are beneficial against some cancers and for some people may not be beneficial for others.

Nutrient-dense foods

A diet rich in nutrient-dense foods, such as vegetables, fruits, and whole grains, helps provide the vitamins and minerals a person needs for their overall health.

The American Cancer Society (ACS) advises that people consume the following foods to promote overall health and reduce the risk of certain diseases, including some cancers:

• a variety of vegetables, including dark green, red, and orange types
• fiber-rich legumes, such as beans and peas
• whole fruits of different colors
• whole grains, such as brown rice, quinoa, and oats

A 2019 meta-analysis concluded that a dietary pattern of consuming fruit, vegetables, and whole grains has a stronger link to a reduced risk of breast cancer than a dietary pattern of eating red and processed meats and animal fats.

However, certain factors can influence these results, including whether a person is in premenopause or postmenopause and whether the breast cancer is hormone-dependent.

Many studies have found a link between a Western dietary pattern high in ultra-processed foods and added sugars and an increased risk of certain cancers, including breast cancer.

Western dietary patterns also tend to be very high in calories, which can lead to weight gain and obesity. People assigned female at birth who have excess weight or obesity are at an increased risk of developing breast cancer.

Additionally, a 2021 study found that obesity had correlations with shorter disease-free survival and shorter overall survival among people with TNBC.

Phytochemicals

Phytochemicals are chemical compounds that come from plants. Research shows many phytochemical compounds have anticancer properties.

Epigenetics is the study of how external factors switch genes on or off. A 2020 review investigating epigenetic regulation and dietary control of TNBC indicated that the following phytochemicals could help manage the disease:

• folate in dark green leafy vegetables and fruits
• resveratrol in dark-colored fruits such as grapes and berries
• genistein in soybeans, legumes, grains, and vegetables
• curcumin in turmeric
• epigallocatechin 3-gallate in green tea
• sulforaphane in broccoli
• withaferin in the herb ashwagandha

However, the authors acknowledge that the body may not absorb the active molecules in these compounds effectively. Additionally, scientists do not fully understand how these phytochemicals interact with one another.

Soy

Soy contains compounds called isoflavones that can act similarly to the hormone estrogen.

Yet research into the effects of soy on breast cancer has yielded conflicting results. Since TNBC is not a hormone-responsive breast cancer, soy is unlikely to have any effect on its progression.

However, a 2017 study looked at gene expression in women with TNBC. The researchers found that those with high soy intake pre-diagnosis had more tumor suppressor genes and fewer cell growth-related genes. This suggests soy consumption may have some protective effects.

However, it is worth noting that this study only involved participants in China. Soy is much more prevalent in the diets of Chinese and Japanese populations than those of Western populations. As a result, these findings may not apply to people in different parts of the world.

The ACS advises people to limit or avoid the following foods and beverages:

• red and processed meats
• sugar-sweetened drinks
• highly processed foods
• refined grain products, such as white bread and pasta
• alcohol

A smaller 2016 study investigating TNBC in women with dense breasts found that people who ate the following foods had a higher risk of developing this type of cancer:

• meat
• animal fat
• eggs
• grains

The ketogenic, or keto, diet is a diet that is high in fat and very low in carbohydrates, with a moderate amount of protein. This dietary approach induces a process called ketosis, a metabolic state where the body burns fats for fuel.

The NCI advises that although a keto diet is difficult to follow, it is generally safe. The organization explains that the purpose of the diet is to decrease the amount of glucose the tumor cells need in order to grow and reproduce.

A 2019 review of ketogenic diets in treating cancer suggests such diets may enhance the effectiveness of treatments and increase quality of life. However, further studies are necessary to confirm these effects. Additionally, there is currently no research on the keto diet specifically for people with TNBC.

If a person with TNBC is interested in trying a ketogenic diet, they should discuss it with their medical team to check whether it is safe and appropriate for their specific health needs.

Following specific dietary patterns may help reduce the risk of certain types of cancer, including breast cancer. They may also help support overall health and improve treatment outcomes in those undergoing treatment for TNBC.

The following meal-planning tips derive from the research and recommendations above:

• Fill at least half the plate with different colored vegetables at every meal.
• When making a stir-fry, substitute meat for tofu and include leafy greens, such as kale, red peppers, and carrots.
• Swap meat for beans and pulses in curries, casseroles, and chilies.
• Opt for whole grain types of rice, bread, and pasta.
• Replace packaged breakfast cereals with oatmeal.
• Snack on fruits, such as berries, cherries, and grapes.
• Try out herbs and spices that may have therapeutic benefits, such as turmeric, ginger, and parsley.
• Swap sweet treats for dark chocolate and a handful of walnuts for anti-inflammatory and antioxidant benefits.

Although these tips help promote overall health and can help ensure a person is getting the nutrients they need, it is not always possible for an individual with cancer to eat in a specific way. Often, cancer treatments take their toll on appetite and energy and could lead to symptoms such as nausea and taste changes.

Getting enough calories and protein and maintaining body weight and muscle mass are most important for people with cancer. If someone can consume only specific foods and textures, that is perfectly fine. The focus should be on eating whatever foods work for an individual, whether health experts consider them beneficial against cancer or not.

If anyone has specific questions about diet and TNBC or breast cancer in general, they can speak with their healthcare team. A healthcare team, including a registered dietitian specializing in cancer nutrition, can help people develop a plan to help them maintain their energy and support their overall health.

The ACS provides a range of recipes for people to try, including:

• tomato and basil frittata
• Cuban-style black beans and rice
• pearl couscous tabbouleh

Learn more about eating a varied, nutritious diet by visiting the Nutrition Hub.

Research has not yet identified an ideal diet for people with TNBC. However, evidence suggests that a whole food diet rich in fruits and vegetables, whole grains, and legumes is beneficial to help prevent cancer and support health during cancer treatment.

Additionally, people living with cancer may benefit from avoiding or limiting their consumption of processed, high fat, and high sugar foods. Some may also consider increasing their intake of certain plant compounds.

Anyone who has received a cancer diagnosis or is undergoing treatment for cancer should speak with their oncologist before making significant dietary changes.