Food-sourced guanidinoacetic acid and methylation cycle biomarkers in individuals aged one year and older: a population-based cross-sectional study.

Purpose: Several preliminary studies suggest dietary guanidinoacetic acid (GAA) might impact methyl group availability and/or methylation biomarkers, fueling ongoing debates. This study aimed to explore the relationship between dietary GAA intake and plasma indicators of the methylation cycle in individuals aged one year and older, using data from the 2001-2002 National Health and Nutrition Examination Survey (NHANES).

Methods: Dietary information was obtained from individuals who completed a 24-hour Dietary Recall, with total daily intake of GAA calculated by aggregating all relevant food items. Relevant variables related to the methylation cycle, such as red blood cell (RBC) folate and serum folate, vitamin B12, total homocysteine (tHCy), and methylmalonic acid (MMA), were identified from the NHANES 2001-2002 laboratory assessments.

Results: A total of 9,115 individuals (51.3% females) were included in the final analysis. Linear regression unveiled a significant association between higher GAA intake and diminished RBC folate (p < 0.001), serum folate (p < 0.001), and MMA levels (p = 0.007). It also revealed an elevation in tHCy levels with increased GAA intake (p < 0.001). These associations remained significant even after adjusting for demographic variables and dietary factors pertinent to the methylation cycle (p < 0.05).

Conclusion: Our findings suggest that dietary exposure to GAA (resulting in conversion to creatine) could be considered a nutritional factor associated with the consumption of methyl groups in the general population.