A short-term intervention of ingesting iron along with methionine and threonine leads to a higher hemoglobin level than that with iron alone in young healthy women: a randomized, double-blind, parallel-group, comparative study

PURPOSE: Enhancing iron absorption and utilization is important for amelioration iron status faster and thereby, for improving quality of life. Dietary protein and amino acids, including methionine and threonine, have been reported to facilitate the absorption and utilization of dietary iron. Here, we investigated the effect of combined ingestion of methionine, threonine, and iron on the improvement of iron status during a short-term intervention, by comparing that with iron ingestion alone in healthy young women. METHODS: This was a randomized, double-blind, parallel-group, comparative study with 45 participants (aged 20–39) randomly assigned to three groups (n = 15 each): one group was administered 200 mg methionine, 400 mg threonine, and 6 mg iron once daily (FEMT); another ingested 6 mg iron alone (FE); and the third group ingested a placebo (PCG). Blood samples and dietary nutrient data were collected before the intervention (week 0) and after 2, 4, and 6 weeks. Serum iron, hemoglobin, transferrin, and ferritin levels were measured. RESULTS: Blood hemoglobin levels were significantly higher in the FEMT than in the FE group (P < 0.05) at week 4. Serum iron, transferrin, and ferritin levels were not changed across groups. In addition, our analyses showed that the observed increase in hemoglobin levels was affected by the intervention rather than changes in dietary nutrient intake. CONCLUSIONS: Ingestion of methionine and threonine with low doses of iron leads to a higher hemoglobin levels than that with iron alone in a short period of 4 weeks. TRIAL REGISTRATION: University Hospital Medical Information Network Clinical Trial Registry (UMIN000046621). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00394-023-03213-w.