Iron Bioavailability from Moringa oleifera Leaves Is Very Low

Abstract

Iron deficiency is the most common essential nutrient deficiency in the world and is particularly prevalent in developing countries. Efforts to improve iron nutriture by providing iron supplements has not been successful. A different strategy with promise is to encourage consumption of iron‐rich indigenous plants. One such plant is Moringa oleifera (Moringa), a tree whose leaves are relatively rich in iron, and whose consumption has been promoted on this basis. However, the iron bioavailability from Moringa has not been reported. This study was conducted to evaluate the iron bioavailability of air dried Moringa leaves, either as is, or as incorporated into a typical meal consumed in rural Uganda. Four experimental diets were formulated to test the bioavailability of the iron using the hemoglobin regeneration efficiency (HRE) ratio assay. Male rats were depleted of iron by feeding an iron deficient diet (2.5 mg Fe/kg) for 4 wks, then assessed for whole blood hemoglobin concentration. Rats were then fed 1 of 4 diets containing 20 mg Fe/kg for either 9 (n=3) or 13 days (n=8). Iron was incorporated into the purified diets as ferrous sulfate or ferric orthophosphate as well‐absorbed and poorly absorbed iron sources, respectively. Dried Moringa leaf powder was incorporated into either a purified diet (38.7 g Moringa/kg diet, dry wt basis) or into a diet largely composed of a typical Ugandan meal containing rice and ground nuts (5.42 g Moringa/kg diet, dry wt basis). In the Ugandan meal‐based diet, 14% of the iron derived from the Moringa and the remainder from the rice and ground nuts. All diets were balanced for macronutrient composition. For reference, 8 animals were maintained on an iron‐containing diet throughout the study. Whole blood hemoglobin concentration was 4.3 g/dL following the 4 weeks of iron depletion. After 9 days of repletion the HRE ratio was 2.6 for ferrous sulfate, 1.0 for ferric orthophosphate, 0.05 for Moringa‐containing purified diet, and 0.59 for Moringa‐containing Ugandan meal‐based diet. After 4 more days of repletion, the HRE ratio was 2.7 for ferrous sulfate, 1.2 for ferric orthophosphate, 0.4 for Moringa‐containing purified diet, and 0.4 for Moringa‐containing Ugandan meal‐based diet. Thus, iron from Moringa, is poorly available. Further, Moringa, even when present at only approx. 0.5% of the diet, as in Ugandan meal‐based diet, appears to strongly inhibit absorption of iron present in other components of the diet, such as rice and ground nuts. The phytic acid content of the dried Moringa leaves was found to be 63.97 mg phytic acid/g dry wt., giving a phytate/Fe molar ratio in the Moringa leaves of approx. 10.5. It is suggested that the low bioavailability of iron from Moringa is due to its high phytic acid concentration. Regardless, our findings suggest that the use of Moringa, as dried leaves, to improve iron nutriture will not be successful and may even result in a worsening of iron status. However, processing of Moringa to reduce or remove its phytic acid could improve it iron bioavailability.Support or Funding InformationSupported by a grant from the International Pediatric Research Foundation

Effect of Moringa oleifera Leaf Powder on Hematological Profile of Male Wistar Rats

“…First, the bioavailability of iron in Moringa leaves is low due to its high phytic acid content. 60 Phytic acid is the largest storage form of phosphorus in cereals and legumes. Phytic acid is considered an antinutritional compound in foodstuffs because under natural conditions, phytic acid will form bonds with divalent minerals (Ca, Mg, Fe) and proteins to become compounds that are difficult to dissolve.…”

“…This causes minerals and proteins to not be absorbed by the body, or their digestibility is low. 60 Second, iron in Moringa leaves cannot be absorbed properly due to the presence of nonabsorbable complexes with phytic acid, tannins, and some dietary fiber which can bind with iron in the intestinal lumen. 61 In addition, the quercetin content of Moringa leaves can increase iron uptake in the apical enterocyte area but reduce iron output in the basolateral area and reduce the expression of ferroportin (FPN) in the intestine.…”

Medicinal utilization and nutritional properties of drumstick (Moringa oleifera)—A comprehensive review

“…Because of the high levels of phytic acid in moringa, iron is not bioavailable at all (Hollman et al., 1999; Manach et al., 1997). In moringa leaves, 5,6,7,8, 5‐formyl‐5,6,7,8, 5‐methyl‐5,6,7,8, and 10‐formylfolic acid are the main types of folate that may be present (Gallaher et al., 2017). When compared to other green vegetables, moringa leaves contain a high biological value of several different forms of folate.…”