Acid-producing diet, smoking history increase mortality risk among breast cancer survivors
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Acid-producing diets and past smoking history appeared independently and jointly associated with increased risk for mortality among a cohort of breast cancer survivors, according to study results published in Journal of Clinical Medicine.
Compared with survivors who never smoked but had a high dietary acid load intake, survivors with a history of heavy smoking had a threefold higher risk for mortality if they also had higher intake of an acid-producing diet, researchers noted.
“Approximately 35% to 40% of breast cancer survivors are past smokers, and breast cancer survivors, especially past smokers, need specific dietary guidelines,” Tianying Wu, MD, PhD, associate professor in the division of epidemiology and biostatistics San Diego State University’s School of Public Health, told Healio. “Cancer survivors have reduced capacity to excrete acid compared with noncancer survivors. More importantly, breast cancer survivors who are past smokers with higher past smoking intensity have reduced capacity to excrete excess acid compared with survivors who are never smokers. Because of this, they are more susceptible to acid-producing diets. Yet, current American Cancer Society dietary guidelines do not consider the impacts of acid-producing diets for breast cancer survivors.”
Acid-producing diets include high consumption of meats, cheeses and soft drinks, whereas carbohydrates and fats produce acids but in lower levels compared with proteins. Fruits and vegetables are alkaline-producing foods that help balance acids produced by proteins.
“Of note, there is a complexity when comparing plant-based protein vs. animal-based protein — we need to pay attention not only to their protein contents, but also their mineral contents,” Wu said. “Although both sources can produce acids, plant-based diets tend to have more minerals, such as potassium, to balance acids.”
Wu and colleagues sought to assess consumption of acid-producing diets, determined by potential renal acid load (PRAL) and net endogenous acid production (NEAP) scores, among 2,950 early-stage breast cancer survivors included in the prospective Women’s Healthy Eating and Living study. Researchers assessed past smoking intensity via pack-years of smoking.
Total mortality, breast cancer-specific mortality and breast cancer recurrence served as primary outcomes.
By median follow-up of 7.3 years, 295 deaths had occurred, including 249 breast cancer-specific deaths, and 490 survivors had experienced disease recurrence.
Looking at dietary acid load intake, those in the highest NEAP quartile vs. the lowest had increased risk for total mortality (HR =1.54; 95% CI, 1.04-2.29) and breast cancer-specific mortality (HR = 1.52; 95% CI, 1.01-2.32), but they were not at increased risk for breast cancer recurrence. Pack-years of smoking appeared significantly associated with all three outcomes.
Researchers also found joint associations between increased dietary acid load intake and pack-years of smoking and increased overall mortality, as well as breast cancer-specific mortality.
Compared with women in the lowest tertile of NEAP and zero pack-years of smoking, women in the highest NEAP tertile who had more than 15 pack-years of smoking had the greatest overall mortality risk (HR = 3.23; 95% CI, 1.99-5.26).
In addition, dietary acid scores were associated with an increased risk for recurrence among women who smoked, but not among women who did not smoke (P < .05).
“We plan to study whether impacts of other dietary patterns were different by past smoking status among breast cancer survivors,” Wu said. “Individualized nutrition is an important emerging trend and is one of the emphases of 2020-2030 strategic plans for the NIH’s nutrition research. Breast cancer survivors, especially those who are past smokers, need precision care.”
For more information:
Tianying Wu, MD, PhD, can be reached at San Diego State University, Hardy Tower, Room 172, 5500 Campanile Drive, San Diego, CA 92182; email: tianying.wu@sdsu.edu.
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