Chemotherapy for breast cancer can cause measurable reductions in brain gray matter, which translates into cognitive impairment (commonly referred to as "chemo brain"). Chemotherapy also disrupts the formation of new nerve cells (neurogenesis) in the brain. In other words, chemo brain is caused by physiological brain damage rather than being a part of a woman's emotional response to breast cancer diagnosis and treatment (as was once thought).

Typically, most of the effects of chemo brain disappear over time, but some symptoms may persist for decades. There are no proven drug treatments for chemo brain and cognitive training interventions have had inconsistent outcomes. On the other hand, regular exercise has been shown to improve some aspects of chemo brain. Now a new study has reported that moderate to vigorous physical activity may improve information processing speed in breast cancer survivors, especially among overweight or obese women.

Characteristics of chemo brain

Chemo brain is characterized by impaired verbal ability, reduced information processing speed, and diminished executive functioning. Processing speed refers to the ability to automatically and fluently perform relatively easy or routine cognitive tasks, especially when high mental efficiency (i.e., attention and focused concentration) is required. Executive functioning refers to the ability to organize thoughts and activities, manage time well, prioritize tasks, and make decisions. Symptoms of chemo brain can vary greatly between breast cancer patients. Examples are problems with spelling and typing, difficulty summoning words, verbal slips, memory problems, mental fog, slow reasoning, and reduced ability to multi-task.

Foods that help protect the brain

A wide variety of foods have been shown to have neuroprotective properties, in part by reducing oxidative stress in the brain. Below are foods that have been shown to have neuroprotective effects while at the same time protecting against breast cancer. All of the foods listed are safe to use in moderation during chemotherapy, radiation and endocrine treatment.

Arctic char, wild
Bell peppers
Currants, black

Grapes, red
Green tea
Hot peppers
Lake trout

Olives and olive oil
Pomegranates & pomegranate juice
Red, brown & green algae
Salmon, wild

Alcohol can increase neural damage, as can exposure to heavy metals such as cadmium, mercury and lead. Diets high in saturated fat, trans fats and/or sugar have been found to be associated with cognitive decline. The soy isoflavones genistein and daidzein have been shown to induce neurotoxicity at high concentrations and should not be taken as supplements. High blood pressure, high cholesterol and high blood sugar also can harm the brain.

Latest research finds physical activity may improve information processing speed

The study referenced at the beginning of this news story was designed to investigate the relationship between physical activity and cognitive functioning in postmenopausal breast cancer survivors. The study included 136 women whose cognitive functioning was assessed using a comprehensive neuropsychological test. Physical activity over a one-week period was measured using hip-worn accelerometers. Linear regression models were used to calculate the associations between minutes per day of physical activity at various intensities on individual cognitive functioning domains.

Moderate to vigorous physical activity was found to be associated with improved information processing speed. In particular, 10 min of moderate to vigorous physical activity was associated with a 1.35-point higher score (out of 100) on the information processing speed domain; the score was 1.29 points higher when chemotherapy was added to the model. The authors found a significant interaction between body mass index (BMI) and moderate to vigorous physical activity. In comparing women with BMIs under 25 kg/m2 to those with BMIs of 25 and over, the favorable association between moderate to vigorous physical activity and processing speed was stronger in the overweight and obese women, but not statistically significant in those with BMIs under 25. Light physical activity was not found to be significantly associated with any of the cognitive function measures. The authors conclude that moderate to vigorous physical activity may improve information processing speed in breast cancer survivors, particularly among overweight or obese women.

Please see our article on chemo brain for more information.