Dr. Mouzannar and colleagues analyzed data on demographics, diet, and PSA levels from 1399 men who participated in the National Health and Nutrition Examination Survey (NHANES) from 2003 to 2006. They calculated a plant-based diet index (PDI) and healthful plant-based diet index (hPDI) based on responses to food frequency questionnaires. A higher score on PDI and hPDI indicates greater consumption of plant foods and healthful plant foods (such as whole grains, vegetables, fruits, nuts, legumes, tea, and coffee), respectively. The men had a median age of 54 years and a median PSA level of 0.9 ng/mL. Of these men, 69 (4.9%) had a PSA level of 4 ng/mL or higher.
Compared with men in the lowest quartile of hPDI score, those in the highest quartile had a significant decreased probability of having an elevated PSA (4 ng/mL or higher) after adjusting for multiple variables, with an odds ratio of 0.47.
The investigators found no significant association between PDI score and PSA level. The authors said the finding may be attributable to the limitations of the NHANES database, which lacks information regarding changes in participants’ dietary behavior.
Dr. Mouzannar’s team said their study is the first to evaluate the association between a graded plant-based diet index and PSA levels in men without prostate cancer. Still, the study had limitations. Data obtained using food-frequency questionnaires are subject to both self-serving and recall bias, they pointed out. What’s more, NHANES data are cross-sectional and do not include serial PSA measurements and medications or comorbidities that may alter PSA values. In addition, participants with a higher hPDI may have confounding factors associated with a healthy lifestyle that could influence PSA levels.
“Even with these limitations,” Dr. Mouzannar and colleagues wrote, “our study is relevant to the present literature because it provides a large sample size and investigates the potential association between dietary intake and PSA level.”
