Women with breast cancer who exclusively ate a whole-foods, plant-based diet, lost weight, improved cholesterol levels and other key metabolic factors, had less fatigue, and perceived that they felt sharper mentally and generally better.
The outcomes are from a small study by researchers at the University of Rochester Medical Center and Wilmot Cancer Institute. Study participants were individuals with stage 4 breast cancer, who will be on lifelong treatment.
These patients are typically excluded from dietary studies, but with their survivorship numbers growing, it presented an opportunity to make an impact both short- and long-term, said research leader Thomas M. Campbell, MD, an assistant professor of Family Medicine at URMC and an expert on using plant-based diets to improve health.
The study included 30 patients who were on stable treatment and could tolerate food. Researchers randomly divided participants into two groups: One received standard care, and the intervention group ate meals provided by the research team for eight weeks.
The diet consisted solely of fruits, vegetables, whole grains (including whole grain pasta), legumes (beans), potatoes, and nuts and seeds. Participants agreed to avoid animal-based foods (meat, eggs, and dairy), and all oils and added solid fats. They also took a daily multivitamin.
Weekly assessments occurred, and the study reported 95 percent compliance.
“It’s exciting to see that these major dietary changes were feasible, well-tolerated, and acceptable to the clinical trial participants,” Campbell said.
No calorie restriction was involved. Individuals were encouraged to eat as often as they wanted of food that was “on plan.”
The women started with an average BMI of 29.7, which is borderline obese. The patients in the whole-foods plant-based group lost one to two pounds per week for eight weeks, without mandated exercise.
This is significant because individuals with breast cancer often gain weight during treatment, which is risky. Why? Too much body weight increases insulin levels and hormones like estrogen and testosterone in the blood, which can fuel cancer.
Another encouraging study result is that researchers saw a reduction in blood samples of IGF-1, a growth factor that has been associated with many common cancers, as well as less inflammation.
“Although we cannot say anything yet about whether the diet can stop cancer progression from this small study, we saw preliminary results that suggest favorable changes within the body, which is very positive,” Campbell said.
To better understand the implications for cancer growth, the team is collaborating with Isaac Harris, PhD, at Wilmot, in a bench-to-clinic investigation recently funded by the American Cancer Society.
Scientists know that cancer cells rely on amino acids to survive, and the patients who followed the plant-based diet had changes in their blood levels of amino acids. Harris is studying the effect of amino acid composition on cancer cell survival, and the effect of the amino acids on various cancer drugs.
The journal Breast Cancer Research and Treatment published the primary study, which is believed to be the first of its kind. The breast cancer trial had enough significant results that two additional papers were also published from the dietary intervention: a second study in the same journal, and a third study in Frontiers in Nutrition, all in March 2024.
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