Effects of Low-Carbohydrate and Plant-Rich Diets on Survival in Breast Cancer

Breast cancer affects women worldwide, making research into treatment and prevention strategies very important. Diet and nutrition play an important role among the factors that can influence cancer patients’ survival and quality of life. New research reveals striking effects of a low-carbohydrate, plant-rich diet on survival in women with breast cancer.

Study Details

The study appeared on 10 June 2023 in Cancer as an online publication.

The analysis found a significant association between low-carbohydrate, plant-rich diets and “overall survival” among women with breast cancer. However, these diets had no clear effect on “breast cancer-specific survival.”

The study evaluated the diets of 9621 women with stage 1-3 breast cancer in two ongoing cohorts: the Nurses’ Health Study and Nurses’ Health Study II.

Diet scores were calculated from food-frequency questionnaires completed after breast cancer diagnosis. They covered overall low-carbohydrate diets as well as animal-rich and plant-rich low-carbohydrate diets.

Examples of Low-Carbohydrate and Plant-Rich Diets

A low-carbohydrate, plant-rich diet generally includes vegetables, fruit, legumes, seeds, nuts and whole grains. High-carbohydrate products such as sugary foods, white bread and processed foods are avoided. Examples include:

Low-Carbohydrate, Plant-Rich Foods:

• Leafy green vegetables (spinach, lettuce, chard, etc.)
• Other vegetables (broccoli, peppers, zucchini, etc.)
• Avocado
• Fruit, particularly low-glycemic-index fruit such as blueberries, strawberries, oranges and apples
• Nuts and seeds (almonds, walnuts, chia seeds, etc.)
• Legumes (lentils, beans, chickpeas, etc.)
• Whole grains (quinoa, oats, brown rice, etc.)

Low-Carbohydrate Protein Sources:

• Lean meats such as chicken and turkey
• Fish (salmon, tuna, mackerel)
• Eggs
• Cheese (mozzarella, cheddar, goat cheese)

Healthy Fats:

• Olive oil
• Hazelnut oil
• Coconut oil
• Avocado oil

Study Results

The study’s follow-up lasted an average of 12.4 years after breast cancer diagnosis.

During follow-up, there were 1269 deaths from breast cancer and 3850 deaths from all causes.

Note: Hazard ratio (HR = hazard ratio) measures the likelihood of an event (death in this study) occurring within a particular group (people following a particular diet here). A hazard ratio below 1 means that the event is less likely; a value above 1 means it is more likely.

The main study finding was:

• The hazard ratio for adherence to low-carbohydrate diets was 0.82. Comparing the fifth tier (highest adherence) with the first (lowest adherence), adherence at the fifth tier was found to reduce overall mortality risk by 18% (1-0.82 = 0.18 or 18%).
• The hazard ratio for adherence to plant-rich diets was 0.73. Comparing Q5 (the fifth quarter, meaning the highest adherence) with 1 (the lowest adherence), this means that adherence at Q5 reduced overall mortality risk by 27% (1-0.73 = 0.27 or 27%). These data indicate that people with greater adherence to low-carbohydrate and plant-rich diets have a lower overall mortality risk.
• However, adherence to these diets was not found to reduce the risk of breast cancer-specific death.

Other study findings:

• Adherence to animal-rich low-carbohydrate diets was not found to significantly affect overall or breast cancer-specific mortality risk. In other words, this type of diet had no clear effect on overall survival or survival specifically related to breast cancer.

• However, replacing 3% of total energy intake from carbohydrates with fish protein was found to reduce breast cancer-specific mortality risk by 17% and all-cause mortality risk by 15%. This suggests potential health benefits from increasing fish protein consumption in people with breast cancer.

These findings suggest that diet, particularly whether protein comes from plant or animal sources, may have an important effect on survival in people with breast cancer.

In particular, limiting carbohydrate sources such as fruit juice, sugary drinks and added sugars may improve general health and prolong overall survival. These foods are generally high in calories and low in nutritional value, and excessive consumption can lead to weight gain and other health problems.

Increasing protein and fat from plant sources may also be beneficial. Plant proteins and fats are generally healthier than those from animal sources and may reduce the risk of heart disease, diabetes and certain cancers.

However, the effects of such dietary changes vary between individuals and should always be discussed with a healthcare professional. These recommendations may reduce overall mortality risk without having a clear effect on breast cancer-specific survival.