Nutrients and Breast Cancer
Updated on November 10, 2025
All of the food you eat contains energy (calories), but foods have different amounts of nutrients. Nutrients are broken into two groups:
Macronutrients — such as protein, carbohydrates, and fat — are the nutrients the body needs in large quantities each day.
Micronutrients — vitamins and minerals — are needed in smaller amounts.
Nutrients provide the body with energy, repair cells, maintain healthy bones, and more. If you have — or had — breast cancer, understanding nutrients can help you eat a healthy diet that can help reduce or prevent treatment side effects and promote your overall health.
Macronutrients
Macronutrients (also called macros) play an important role in the body.
Protein
Proteins support the body in many ways, including building and repairing cells, creating hormones and enzymes, and boosting the immune system.
The USDA Guidelines (PDF) recommend that adults eat 0.8 grams of protein per kilogram of body weight each day to meet basic nutritional requirements — around 10% to 35% of your total daily calories. But during treatment for breast cancer, you may need more protein than usual as your body works to replace cells affected by treatment.
“We know that our macronutrient needs are increased by treatment, specifically our protein needs,” says Hillary Sachs, MS, RD, CSO, CDN. “There has been tons of research on [protein for] preserving muscle and regenerating new cells in the body, including blood cells and cells of the digestive tract, which we know are all affected by many treatments.”
When you eat protein, it breaks down into amino acids — the building blocks that help your cells do all of their everyday activities. Essential amino acids can’t be made by the body, so you must get them through your diet. There are nine essential amino acids.
A protein source is considered to be a complete protein if it provides all of the essential amino acids, whereas an incomplete protein is lacking in one or more of the essential amino acids.
Complete proteins include:
fish
poultry
eggs
beef
pork
dairy
soy (like tofu, edamame, and tempeh)
quinoa
buckwheat
nuts, including pistachios and almonds
seeds, including hemp and pumpkin seeds
nutritional yeast
Not every protein you eat has to be “complete,” though. Most vegetarians and vegans get enough protein (and essential amino acids) through plant-based sources. If you eat a plant-based diet, just make sure you’re getting a variety of protein sources.
Carbohydrates
Carbohydrates fuel the body, especially your muscles, brain, and other organs. There are a few types of carbohydrates:
Simple sugars are found in fruits, honey, milk, and malted grains.
Complex carbohydrates are found in whole grains, nuts and seeds, legumes, starchy vegetables, and some dairy products.
When you eat carbohydrates, they’re broken down into glucose, which can be used immediately as a source of fuel or can be stored for later use.
The USDA recommends that adults consume 45-65% of their total daily calories from carbohydrates. For example, on a 2,000-calorie diet, this translates to between 225 and 325 grams of carbohydrates per day.
Some people think cutting out carbohydrates, especially simple sugars, might help them lose weight or prevent disease. But experts recommend that people in treatment for breast cancer avoid cutting out any food groups or macronutrients.
“If you cut out carbohydrates, then you're going to be cutting out some sources of soluble fibers, which have detoxing benefits, but also serve as prebiotics, which serve as food for the good bacteria in our guts,” Sachs says. “Carbohydrates also have a lot of B vitamins, which help with energy and cell division.”
Fiber
Fiber is another type of carbohydrate. It’s a plant-derived nutrient that cannot be completely broken down by the digestive system.
“Fiber-rich carbohydrates … help to move things through the gut for excretion, but also bind to specific kinds of toxins to remove them,” says Sachs.
Eating a fiber-rich diet may even help to lower breast cancer risk. A 2020 review found that women who ate a diet high in fiber were 8% less likely to develop breast cancer. Other studies have shown that fiber reduces the risk of heart disease.
Fiber also promotes an overall feeling of fullness, enhances nutrient absorption, and helps maintain regular bowel movements.
The USDA recommends that women eat 25 to 28 grams of fiber per day and men eat 30 to 34 grams of fiber per day.
Fiber-rich foods include:
whole grains like oats, brown rice, and quinoa
legumes like beans, lentils, and peas
vegetables like broccoli, brussels sprouts, and sweet potatoes
fruits like apples, berries, and avocados
Added sugars
Many packaged and processed foods contain added sugars. They include sweeteners, corn syrup, and high-fructose corn syrup. These added sugars contain no nutritional value, but are calorically dense.
The USDA recommends limiting added sugars to less than 10% of total caloric intake, with no more than 12 teaspoons per day. The American Heart Association recommends even less — no more than 6 teaspoons a day for women, and no more than 9 teaspoons for men.
Fat
Dietary fat has many important functions, such as being a major source of energy for your body. It also helps you to absorb vitamins A, D, E, and K.
“Fats have a lot of anti-inflammatory properties, which we know is helpful in getting through treatment and helping people feel good,” says Sachs.
Saturated fat is found in meat, dairy, butter, coconut oil and cream, baked goods, and some savory snacks.
Unsaturated fat is found primarily in plant sources.
Monounsaturated fat is found in olive oil; nuts such as almonds, cashews, and pecans; canola oil; avocados; olives; and nut butters like peanut or almond butter.
Polyunsaturated fat is found in walnuts and sunflower seeds; salmon; and flax, corn, soybean, and safflower oils.
Trans fat is a type of unsaturated fat, but it’s unique in its structure. It’s sometimes found in meat and dairy products, but many trans fats are artificial. They’re found in fried food, baked goods, margarine, and certain vegetable oils.
Your body needs both saturated and unsaturated fats, but there are no health benefits to artificial trans fats — and they can be harmful to your health. The FDA banned companies from adding trans fats to packaged foods in 2018, but it’s still legal to sell packaged foods with up to 0.5 grams of trans fat per serving.
The USDA recommends that total fat intake should be between 20% and 35% of total daily calories, with saturated fat intake limited to less than 10% of daily calories.
Micronutrients
Micronutrients are vitamins and minerals that are essential for human growth, development, immune system function, and much more.
Vitamins
Essential vitamins cannot be produced by the body, so they must be supplied by your diet — or, in the case of vitamin D, by sun exposure.
There are 13 essential vitamins, classified into two categories:
Fat-soluble vitamins: A, D, E, and K. They support bone health, blood clotting, immune function, vision, and more.
Water-soluble vitamins: B-complex (such as B6, B12, and folate) and C. They support immune health, energy metabolism, brain function, and more.
People get most of their vitamins from a balanced diet that includes fruits, vegetables, whole grains, lean protein, and dairy products.
Minerals
Minerals are important for growing and maintaining healthy bones, muscle function, and more. All minerals are considered essential, but macrominerals are needed in larger amounts than trace minerals.
Macrominerals include:
calcium
magnesium
sodium
potassium
Trace minerals include:
iron
copper
iodine
selenium
Minerals are found in the highest quantities in dairy products, beef, shellfish, whole grains, and dark, leafy greens.
Supplements
There’s a big difference between getting your nutrients from food and taking dietary supplements (vitamins, minerals, and herbals/botanicals).
When you take a supplement, you're getting a highly concentrated dose that you would probably never get from food. This can lead to changes in how your body processes other nutrients and substances in the body. While some supplements may be beneficial, others may reduce the effectiveness of certain breast cancer treatments.
On the other hand, certain breast cancer treatments may sap your body's supplies of some vitamins or minerals. Be sure to talk to your doctor before starting any supplement so they can inform you of any risks and benefits.
Water
Water is considered an essential nutrient. It makes up about 50% to 66% of your total body weight. It regulates your temperature, moves other nutrients through your body, and gets rid of waste.
In general, you should aim to drink 6 to 8 glasses of water a day. But breast cancer treatment can sometimes cause diarrhea or vomiting, and losing a lot of fluids can lead to dehydration.
If you've lost fluids because of diarrhea or vomiting, you need to replace both the fluids and the essential substances, like electrolytes, in them.
The World Health Organization (WHO) recommends oral rehydration salts (ORS) for managing dehydration from vomiting. You can buy oral rehydration salts at stores and online, or you can make them at home with:
1 liter of water
6 teaspoons of sugar
0.5 teaspoon of salt
Alcohol
Alcohol contains energy, but no nutrients.
The USDA recommends that if you drink alcohol at all, it should be done so in moderation. Moderate drinking is classified as up to one standard drink per day for women and up to two standard drinks per day for men.
But studies show that alcohol increases the risk of breast cancer. So it’s a wise choice to drink very little, if at all.