Breast Cancer Treatment and Nutrition: A Key Step Toward Recovery

By: Director Szu-Tzu Chao, Department of Nutrition

During breast cancer treatment, many patients face side effects, physical changes, and nutrition-related challenges, and it is common to wonder how diet should be adjusted. In reality, chemotherapy, endocrine (hormone) therapy, surgery, and radiation therapy can all affect appetite and nutritional status. Even after treatment ends, maintaining a balanced diet and a healthy body weight remains an important foundation for recovery and for reducing the risk of recurrence.

Recovery After Treatment and Weight Management

During the recovery phase after treatment, ongoing weight monitoring and a balanced diet can help lower breast cancer recurrence risk. Studies have shown that in premenopausal women, BMI, body weight, and fat mass can increase significantly during chemotherapy. Another study reported that six months after treatment, patients may experience lower bone density, reduced muscle mass, and increased fat mass, resulting in sarcopenic obesity (having low muscle mass along with excess body fat). This pattern is associated with a higher risk of recurrence and mortality.

Obesity is a recognized risk factor for breast cancer recurrence and breast cancer-related death. This is especially important after menopause. Research cited here indicates that for postmenopausal women, each 5 kg/m² increase in BMI is associated with an 8% to 29% increase in breast cancer mortality. For this reason, weight management should be part of the overall treatment plan after breast cancer surgery. It may help reduce recurrence risk and improve long-term outcomes.

Nutrition and Lifestyle Guidance During Treatment and Recovery

Dietary patterns can meaningfully influence breast cancer prognosis and survival. Research suggests that compared with a high-fat, high-sugar Western-style diet, an eating pattern centered on whole grains, legumes (beans), vegetables, and fruit may help lower recurrence risk.

During treatment and recovery, nutrition should support energy needs and maintain strength and immune function. The recommendations described here include a daily energy target of 25 to 30 kcal per kilogram of body weight, protein 1.2 to 1.5 grams per kilogram, carbohydrates at about 55% of total calories, fat under 30%, and dietary fiber 25 to 30 grams per day. The recommended weight range is a BMI of 18.5 to 24. If a patient is overweight, a gradual approach is suggested by reducing intake by 500 to 1,000 kcal per day to support steady, healthy weight loss.

A plant-forward pattern is encouraged, using whole grains, vegetables, and fruit as the main carbohydrate sources, and choosing foods in their most natural, minimally refined forms. Examples include brown rice, oats, and mixed-grain rice. Whole foods provide antioxidants and fiber. In general, mixed grains are preferred over white rice, and whole fruit is more nutritious than fruit juice.

Meals are ideally balanced and varied, with each meal including a staple (grain or starchy food), a protein source, and vegetables. The daily targets listed here include 1 to 2 bowls of whole grains, 2 to 3 bowls of vegetables, and 1.5 to 2 bowls of fruit, with an emphasis on choosing fruits and vegetables of different colors to increase nutrient variety.

Fat intake should be moderated, since high-fat diets may increase estrogen production and potentially support cancer cell growth. The guidance here recommends limiting red meat, processed meats, and fried foods. For protein, prioritize soy products, fish, lean meats, eggs, and low-fat dairy, rotating these options across meals.

Healthy lifestyle habits are also emphasized. These include drinking about 2,000 mL of plain water per day, maintaining regular physical activity, limiting alcohol, and avoiding high-dose supplements.

Common Misunderstandings and Practical Reminders

The key goal for breast cancer nutrition is not simply “eat more” or “eat high protein,” but to aim for balanced nutrition. Research has found that breast cancer patients receiving chemotherapy often decrease their intake of fruits and vegetables (especially dark green and orange-yellow vegetables) and legumes. This can lead to inadequate intake of calcium, iron, magnesium, B vitamins, vitamin C, and zinc. These nutrient gaps have been reported to correlate with higher body fat, higher BMI, and a higher waist-to-hip ratio.

For this reason, beyond keeping meals balanced, patients are also encouraged to increase plant foods rich in anti-inflammatory phytochemicals, such as allium vegetables (garlic, onions, scallions), which have antioxidant and anti-inflammatory properties. Cruciferous vegetables (broccoli, Chinese kale, and leafy greens like bok choy) provide vitamin C, vitamin K, and chlorophyll and are described here as supporting anti-cancer enzyme activity. Red, yellow, and orange vegetables (carrots, tomatoes, red peppers) are rich in lycopene and polyphenols, which are beneficial antioxidants.

Nutrition management for breast cancer should begin early in the treatment course and continue after treatment ends. Balanced eating, healthy weight maintenance, and regular physical activity can reduce treatment-related side effects, lower recurrence risk, and improve quality of life.

Reference

Dietary Guidelines for Breast Cancer Patients: A Critical Review. Advances in Nutrition. 2017;8:613–623.