Abstract
Phytate (PA) serves as a phosphate storage molecule in cereals and other plant foods. In food and in the human body, PA has a high affinity to chelate Zn2+ and Fe2+, Mg2+, Ca2+, K+, Mn2+ and Cu2+. As a consequence, minerals chelated in PA are not bio-available, which is a concern for public health in conditions of poor food availability and low mineral intakes, ultimately leading to an impaired micronutrient status, growth, development and increased mortality. For low-income countries this has resulted in communications on how to reduce the content of PA in food, by appropriate at home food processing. However, claims that a reduction in PA in food by processing per definition leads to a measurable improvement in mineral status and that the consumption of grains rich in PA impairs mineral status requires nuance. Frequently observed decreases of PA and increases in soluble minerals in in vitro food digestion (increased bio-accessibility) are used to promote food benefits. However, these do not necessarily translate into an increased bioavailability and mineral status in vivo. In vitro essays have limitations, such as the absence of blood flow, hormonal responses, neural regulation, gut epithelium associated factors and the presence of microbiota, which mutually influence the in vivo effects and should be considered. In Western countries, increased consumption of whole grain foods is associated with improved health outcomes, which does not justify advice to refrain from grain-based foods because they contain PA. The present commentary aims to clarify these seemingly controversial aspects.
Highlights
Phytate (PA) serves as a phosphate storage molecule in cereals and other plant foods
A poor mineral status, most significantly of calcium, potassium, magnesium, zinc, iron and manganese are associated with an impaired immune function and elevated chronic disease risks
A poor magnesium status is associated with increased risks of diabetes and osteoporosis [7,8] and mineral-trace element deficiencies are related to impaired immune competence, especially in the elderly, and stunted growth in children [9,10,11]
Summary
A sufficient daily supply of minerals and trace-elements in the food that we consume, their subsequent exposure to digestion enzymes (bio-accessibility) and the quantitative absorption and supply to cells and organs (bio-availability) are crucial for our micronutrient status. Chinese communities, where many low-income families reside [12,13] These families largely rely on ‘monotonous’ consumption, mostly of one particular crop rich in PA, such as rice or corn [14,15], often resulting in mineral deficiency and related impaired growth and health. The following sections will provide a brief introduction to the molecular aspects of PA, phytase and the presence of PA in various grains and bread For this critical commentary, available data (period 1990-today) were searched for in common electronic databases such as PubMed, ScienceDirect, Web of Science, and other connected data bases at the Maastricht university online library. Searches were performed for the key words phytic acid, phytate, phytase, in combination with digestion, bio-accessibility, bio-availability minerals, trace-elements, sourdough, yeast, bread making, food processing, fermentation, microbial metabolism, health effects, micronutrient deficiencies, immune, chronic disease, hidden hunger and stunted growth. Inclusion criteria were as follows: peer reviewed papers in English language: original research, critical reviews and commentaries
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