Dietary Acid Load Shows No Significant Link to Breast Cancer Risk in Iranian Case-Control Study

A hospital-based case-control study from Iran has found no significant association between dietary acid load and the odds of breast cancer, despite prior suggestions that an acidic dietary environment might promote tumor growth. The research, conducted among women attending a clinic in Kerman City, also reported no significant links between dietary acid load estimates and tumor size or the Ki-67 proliferation marker, offering a cautious counterpoint to hypotheses that have circulated in nutrition and oncology research.

The study, published in BMC Nutrition, recruited 155 newly diagnosed breast cancer patients whose diagnoses were confirmed by histopathological examination. Participants were selected using convenience sampling from the Javad Al-Aemeh Clinic in Kerman City between September 2021 and March 2023. The researchers, led by Adele Khodabakhshi and colleagues, set out to determine whether dietary acid load, a measure of the acid-generating potential of the diet, was associated with pathobiological markers of breast cancer and with the risk of the disease itself in Iranian women.

Dietary acid load was estimated using a 168-item food frequency questionnaire, a tool that asks participants to recall their habitual intake of a wide range of foods. From these dietary data, the researchers calculated three established indices: potential renal acid load, known as PRAL; net endogenous acid production, or NEAP; and net acid excretion, NAE. These measures estimate the burden that the diet places on the body’s acid-base regulatory systems.

The scientific rationale for examining dietary acid load in cancer stems partly from observational and ecological studies that have reported positive associations between dietary acid load and the risk of chronic diseases. There is also limited evidence suggesting that an acidic environment may promote the growth of certain cancer cells and tumors. The new study tested this idea in a clinical population by relating dietary acid load indices to both disease status and tumor characteristics.

To assess tumor biology, the researchers examined several pathobiological markers, including tumor stage, tumor size, histological grade, and Ki-67, a protein used in pathology laboratories as an indicator of how rapidly cancer cells are dividing. The team used linear regression to test whether NEAP and NAE estimates were associated with tumor size or Ki-67 levels, and logistic regression to estimate the odds of breast cancer across tertiles of the dietary acid load indices.

The results were largely null. Using linear regression, the researchers observed no significant associations between NEAP and NAE estimates and tumor size or the Ki-67 marker, with p-values exceeding 0.05. In logistic regression models, the odds ratios and their 95 percent confidence intervals for breast cancer across tertiles of NEAP and NAE showed no significant associations with breast cancer risk, either before or after adjustment for potential confounders, compared with the reference group. In other words, women whose diets generated the highest estimated acid loads did not show significantly different odds of breast cancer than those with the lowest loads, once the data were analyzed.

The authors concluded that dietary acid load was not significantly associated with the risk of breast cancer in this population. They emphasized, however, that high-quality prospective studies are necessary to further specify the relationship between dietary acid load and breast cancer risk among the Iranian population. This is an important caveat, because the case-control design used here has inherent limitations. Case-control studies compare people who already have a disease with those who do not, and they rely on retrospective dietary recall, which can be influenced by changes in eating habits after diagnosis and by recall bias. Convenience sampling, rather than random selection, may also limit how well the findings generalize to other populations.

The study adds to a small body of research examining dietary acid load and health outcomes. Related work in this field includes a case-control study of dietary acid load and the odds of prostate cancer published in 2025, an exploratory analysis of dietary acid load among United States cancer survivors using NHANES data from 2022, and a 2023 study reporting that higher dietary acid load was associated with an increased risk of metabolic syndrome. Together, these studies suggest that dietary acid load may matter for some chronic conditions, but the evidence for cancer remains inconsistent and, in the case of breast cancer in this Iranian sample, did not support a significant association.

The research was published as an open access article in BMC Nutrition on October 12, 2026, and is currently available as a peer-reviewed, accepted version that carries a permanent DOI and remains citable, with a final version of record to follow. The work was based entirely on hospital evidence from a single clinic in Kerman City, underscoring both the practical value of clinical nutrition research and the need for larger, more representative studies before firm conclusions can be drawn about diet and breast cancer risk.

Subject of Research: Association between dietary acid load and breast cancer risk and tumor markers in Iranian women

Article Title: The association between dietary acid load index with tumor stage and size, histological grade, Ki-67 marker, and the odds of breast cancer: a case-control study based on hospital evidence

Article References: Khodabakhshi, A., Nasab, S. A. R., Rafeeinia, A., Hesami, S., Bazyar, H., & Aghamohammadi, V. (2026). The association between dietary acid load index with tumor stage and size, histological grade, Ki-67 marker, and the odds of breast cancer: a case-control study based on hospital evidence. BMC Nutrition. https://doi.org/10.1186/s40795-026-01510-1

Image Credits: AI Generated

DOI: 10.1186/s40795-026-01510-1

Keywords: dietary acid load, breast cancer, case-control study, Ki-67, PRAL, NEAP, NAE, food frequency questionnaire, Iran, tumor markers, nutrition, BMC Nutrition