Discussion
anemia
IRON DEFICIENCY ANEMIA, SECONDARY, IRON DEFICIENCY, ANEMIA
In this study, we hypothesized that combined ingestion of methionine and threonine with iron increases iron absorption and utilization, resulting in the accelerated improvement of iron status during the short period of intervention. This study aimed to understand the effects of co-ingestion of methionine, threonine, and iron (FEMT) on blood parameters during the 6 weeks of the intervention, by comparing the effects with those of ingestion of iron alone (FE). Here, the primary outcome, serum iron level, was not different across the three groups. However, hemoglobin level, one of the secondary outcomes, was higher in the FEMT group than in the FE at 4 weeks of intervention. There was no significant difference between the FEMT and FE groups at 6 weeks of intervention; however, a similar trend of higher hemoglobin level in the FEMT group was also observed (The median dietary iron intake of our participants was lower than the dietary reference intakes (DRIs). Additionally, energy, vitamin D, and retinol intake, all of which are known to affect iron status [No significant effects were observed on blood parameters other than hemoglobin. Serum iron levels, the primary outcome of this study, were not affected by any intervention. Large intra- and inter-participant variations were observed, and serum iron levels increased from the screening test to week 0 of the intervention in many participants. While there is no clear explanation for this observation, serum iron levels may be influenced by the diurnal cycle [Our study suggests that methionine and threonine may influence hemoglobin synthesis through various functions, including absorption, transport, and dietary iron utilization. While methionine and threonine are reported as iron-chelate amino acids [Our study demonstrated the potential effect of combined ingestion of methionine and threonine with iron for rapid improvement in iron deficiency. To the best of our knowledge, no previous studies have shown that hemoglobin levels recover within 8 weeks after intervention with low doses of iron and other nutrients. However, some limitations should be noted. First, this study was conducted with healthy participants without anemia, and the effect of co-ingestion of methionine, threonine, and iron in women with iron deficiency anemia is unknown. Second, this study conducted exploratory with small size of participant. Larger study is needed to confirm the effect of methionine and threonine on hemoglobin level. Third, hemoglobin level in the PCG decreased during the study, which is probably due to the seasonal variation. Hemoglobin levels are reported to decrease with increasing temperatures in Japan [