Study of the association of niacin and vitamin B6 intake with endometriosis: Evidence from NHANES 2003-2006.

Objective: This study aims to investigate the association between dietary intake of niacin and vitamin B6 and the prevalence of endometriosis using data from the National Health and Nutrition Examination Survey (NHANES) 2003-2006.

Methods: We conducted a cross-sectional analysis using data from women aged 25-45 years in the 2003-2006 NHANES. Niacin and vitamin B6 intake were assessed using 24-h dietary recalls, and endometriosis status was determined by self-report. Covariates included age, race, body mass index, poverty income ratio, smoking status, and alcohol consumption. Weighted logistic regression models were used to evaluate the association between vitamin intake and endometriosis, with stratified analyses performed for different age groups. Data visualization included scatter plots with locally estimated scatterplot smoothing (LOESS) curves to illustrate the relationship between nutrient intake and the probability of endometriosis.

Results: A total of 1467 participants were included, of whom 7.17% (105 individuals) reported having endometriosis. There were significant differences in dietary intake of niacin and vitamin B6 between participants with and without endometriosis. In the unadjusted model, vitamin B6 intake was significantly negatively associated with endometriosis (odds ratio [OR], 0.79 [95% confidence interval (CI), 0.62-0.99], P = 0.033), and niacin intake showed a marginally significant negative association (OR, 0.98 [95% CI, 0.96-1.00], P = 0.019). In the models adjusted for age and race, the negative association between vitamin B6 and endometriosis remained significant (OR, 0.80 [95% CI, 0.63-1.01], P = 0.044), and the association for niacin remained marginally significant (OR, 0.98 [95% CI, 0.96-1.00], P = 0.023). In the fully adjusted model, the negative association for vitamin B6 remained significant (OR, 0.79 [95% CI, 0.63-0.99], P = 0.033), and the association for niacin remained marginally significant (OR, 0.98 [95% CI, 0.96-1.00], P = 0.021). Age-stratified analysis showed that niacin intake was not significantly associated with endometriosis in women aged 35 years and younger (OR, 0.98 [95% CI, 0.95-1.02], P = 0.3), whereas vitamin B6 intake was significantly negatively associated with endometriosis in women older than 35 years (OR, 0.75 [95% CI, 0.56-0.99], P = 0.048). Scatter plots with LOESS curves indicated a negative trend between higher intakes of niacin and vitamin B6 and the probability of endometriosis.

Conclusions: The findings suggest that dietary vitamin B6 intake is negatively associated with the prevalence of endometriosis, particularly among women older than 35 years, highlighting the potential role of dietary adjustments in managing endometriosis. Niacin intake also showed a protective effect, although this was less pronounced than vitamin B6. These results provide a basis for further research into the relationship between diet and endometriosis.