Nutrition

Or, Iron deficiency: An Unmet Global Need

Iron deficiency is the most common and widespread nutritional deficiency in the world, according to the World Health Organization [1]. Iron deficiency is rampant in developing countries and is especially prevalent among young children and pregnant mothers. Young children are particularly at risk due to the large amount of iron required during periods of rapid growth. Similarly, expectant mothers require heightened levels of iron during pregnancy, and if this demand is not met, the transfer of iron to the developing fetus may be affected. This problem even persists after birth, since if an infant is born with insufficient iron, postnatal acquisition of additional iron is typically insufficient to make up this deficit [2].

Iron deficiency has remained relatively persistent over time, despite attempted public health interventions, in large part due to challenges in delivering and distributing health care in resource-poor settings. Current prevention and treatment methods require routine provision of supplies of iron supplements or iron-fortified foods, and such items are difficult to aquire or economically prohibitive for populations at greatest risk of iron deficiency [3]. In addition, many of the iron-enriched foods provided by such programs are usually imported from outside sources instead of grown locally. Our aim is to provide developing populations with an economically and logistically superior alternative to distributing iron-rich foods and supplements, which to date have not met this persistent global need.

Phytate

Or, The Iron Lockbox and its Key

Phytate is the salt form of phytic acid, also known as inositol hexakisphosphate or IP6. This molecule chelates and sequesters phosphorous and iron in plant tissues. Only ruminant animals such as cows and sheep produce an enzyme in their rumen that can separate the phosphorous and iron from the phytate. Therefore, humans should limit their intake of phytate as it interferes with the absorption of calcium, iron, and zinc, which can also be chelated by phytate.

Phytases are enzymes that catalyze the hydrolysis of phytate, or phytic acid, releasing six phosphate groups from phytate. The dephosphorylation of phytate and the consequent release of phosphate groups from the inositol ring reduces phytate’s mineral binding strength. Consequently, the hydrolysis of phytate increases the bioavailability of iron in the human body.

Harnessing phytase to enhance iron bioavailability has some precedence in biotechnology. In animal feed, Jan Pen, et al. [7] engineered transgenic seeds as a novel feed additive for improved phosphorous utilization. They engineered phytase from Aspergillus niger in tobacco seeds, providing a stable and convenient packaging of the enzyme. The phytase enzyme helped release phosphorous from phytate. Taewan Kim, et al. [8] also attempted to shift the pH-dependent activity profile of the Aspergillus niger phytase in order to enhance its effectiveness inside the stomach as an animal feed additive. They were successful in shifting the pH optimum of one mutant to pH 3.8, demonstrating that it is feasible to improve the function of phytase under stomach pH conditions by protein engineering. Each of these examples highlights the utility and potential of harnessing phytases to improve nutrition, but these approaches do not directly enable preventing iron deficiency in humans.

Sources:

1. http://www.who.int/nutrition/topics/ida/en/index.html
2. http://jn.nutrition.org/content/138/12/2523.full
3. http://www.ncbi.nlm.nih.gov/pubmed/11943635
4. http://www.rebuild-from-depression.com/soaking-beans/
5. http://www.nature.com/nbt/journal/v11/n7/abs/nbt0793-811.html
6. http://aem.asm.org/content/72/6/4397.short
7. http://www.nature.com/nbt/journal/v11/n7/abs/nbt0793-811.html