Clinical Study #1:
Iron absorption from soybean ferritin in nonanemic women.
Lönnerdal, Bo., et al. Iron absorption from soybean ferritin in nonanemic women. Am J Clin Nutr 2006;83:103–7. DOI: 10.1093/ajcn/83.1.103
Objective: To study iron absorption from legume ferritin
Design: This study used a ‘randomized, crossover design’ in order to compare different forms of iron absorption. 16 non-anemic women, in a fasted state, received a standardized meal randomized to contain either 1 mg of iron from ferrous sulphate or from soybean ferritin. The meals were consumed with 60 mL of apple juice. After 4 weeks, blood was drawn to measure the degree of incorporation of the radiolabeled iron into red blood cells. They were then given another meal (with the alternate iron source to whichever one their first meal contained) containing 1 mg of iron from ferrous sulphate or from soybean ferritin. Another 4 weeks later, the subjects had their blood drawn and iron absorption was checked again by measuring the degree of radiolabeled iron incorporated into red blood cells.
Results: Whole body iron absorption was 29.9% for soybean ferritin and 34.3% for ferrous sulphate. Iron incorporation into red blood cells was 33% for soybean ferritin and 35.3% for ferrous sulphate.
Conclusions: These were not considered statistically significant differences so both forms of iron were considered equal. An inverse relationship between iron status and iron absorption was noted for both forms of iron, meaning that the physiological iron regulating sensors of the subjects worked for both forms of iron to allow for increased or decreased absorption depending on their individual iron status.
Clinical Study #2:
Absorption of Iron from Ferritin Is Independent of Heme Iron and Ferrous Salts in Women and Rat Intestinal Segments
Theil, E., et al. Absorption of Iron from Ferritin Is Independent of Heme Iron and Ferrous Salts in Women and Rat Intestinal Segments. J Nutr. 2012;142(3):478-483. DOI: 10.3945/jn.111.145854
Objective: To measure intestinal absorption and red blood cell incorporation of ferritin iron in healthy women with or without non-ferritin iron competitors
Design: 73 healthy women received 0.5 mg radiolabeled ferritin iron on 4 specific days over a 15 day period either by itself or with varying amounts (4.5 mg to 49.5 mg) of iron from ferrous sulphate, ferrous sulphate with ascorbic acid or hemoglobin. Some of the iron capsules were enteric coated and others not. Their iron status was measured prior to day 1 of the study and then again at day 14 and day 28 to determine the amount of radiolabeled ferritin iron that had been incorporated into red blood cells.
Rat intestinal segments were perfused with radiolabeled ferritin iron and compared with perfusion of a chelated form of ferric iron in order to compare absorption rate and mechanism.
Results: Nine times concentrations of ferrous sulphate and heme iron had no effect on the absorption of ferritin iron for the women. Enteric coated ferritin iron capsules had superior absorption to the non-enteric coated ferritin and ferrous sulphate capsules. Ferritin iron in the rat intestine was absorbed more slowly than with ferric iron.
Conclusions: Ferritin iron is absorbed by different pathways and mechanisms than both iron salts and heme iron. Inhibition of ferritin iron absorption only occurs when relatively large (greater than 10x) amounts of other iron sources are in competition in the digestive tract. The slower absorption rate and intact protein cage of the ferritin iron help protect the intestinal lining from free radical damage.
Clinical Study #3:
Pea Ferritin Stability under Gastric pH Conditions Determines the Mechanism of Iron Uptake in Caco-2 Cells
Antonio Perfecto, et al. Pea Ferritin Stability under Gastric pH Conditions Determines the Mechanism of Iron Uptake in Caco-2 Cells, The Journal of Nutrition, Volume 148, Issue 8, August 2018, Pages 1229–1235. DOI: https://doi.org/10.1093/jn/nxy222
Objective: To measure the stability of pea ferritin iron under simulated gastric conditions and measure iron intake into intestinal cells.
Design: Intestinal caco-2 cells were introduced to two types of pea ferritin iron – one exposed to gastric acid and one not – and absorption was tested. This was in combination with dietary inhibitors of iron absorption. The production of free radicals was also compared between pea ferritin iron and ferrous sulphate.
Results: The pea ferritin exposed to an acidic pH of 2-4 (simulating stomach conditions) was degraded by 50-70% and its iron released for absorption by normal, nonheme iron pathways. The absorption was 26-40% worse than the native pea ferritin not exposed to an acidic pH, which was instead absorbed into intestinal cells with the protein cage intact. Compared to ferrous sulphate, the native, non-degraded pea ferritin iron resulted in 60% fewer free radicals produced than ferrous sulphate. The non-degraded pea ferritin iron absorption was also unaffected by dietary chelators of iron.
Conclusions: Some studies with soybean have shown that native legume ferritin is unaffected/undegraded by gastric acid conditions, but this study found that pea ferritin is. Enteric coating of pea ferritin iron could help ensure its optimal absorption. Intact pea ferritin iron is absorbed into intestinal cells by endocytosis, with its protein cage intact and is less irritating to intestinal cells.
Clinical Study #4:
Restorative effect of bean ferritin iron on low hemoglobin level in premenopausal women with menstruation-induced anemia: A randomized, double-blind placebo-controlled intergroup trial
Takeda R., Kuriyama Y., Yoshida Y. Restorative effect of bean ferritin iron on low hemoglobin level in Premenopausal Women with Menstruation-Induced Anemia: A randomized, double-blind placebo-controlled intergroup trial. Functional Foods in Health and Disease 2024; 14(3):169-183. DOI: https://www.doi.org/10.31989/ffhd.v14i3.1331
Objective: Administer bean ferritin iron to premenopausal Japanese women for nine weeks, starting immediately after menstruation, to evaluate their recovery from low hemoglobin levels as one sign of anemia.
Design: Participants in the test supplement group received an iron intake of 5 mg from one capsule containing bean extract (SloIron®) for five weeks, which was increased to 10 mg (i.e., two capsules) from the 6th to the 9th week. The study evaluated the change in hemoglobin levels as the primary endpoint, and hematocrit, red blood cell count, serum iron, MCH (mean corpuscular hemoglobin), MCHC (mean corpuscular hemoglobin concentration), serum ferritin, TSAT (TIBC), serum zinc, serum copper, anemia symptoms questionnaire, OSA sleep inventory, and the anti-fatigue questionnaire as the secondary endpoints.
Results: Results showed a significant difference (P=0.03) in the change in hemoglobin levels between the groups after nine weeks of intake, confirming the restorative effect of bean ferritin on low hemoglobin levels caused by menstruation. Moreover, a significant difference (P=0.01) was observed in the amount of change in MCHC between the two groups after five weeks of intake, and after nine weeks of intake, a significant difference in the change in both MCH (P=0.02) and MCHC (P<0.01) was observed between the groups. A significant difference (P=0.03) was observed in the change in serum ferritin levels after nine weeks of intake.
Conclusion: The study confirmed that iron supplementation from bean ferritin is an effective treatment for low hemoglobin and low ferritin levels caused by menstruation.
