Cornell team creates tool to better define zinc deficiency
Called the Zinc Status Index (ZSI), researchers from the University, think the method may help in determining zinc status that is made all the more difficult by how the mineral is used in the human body.
“Because of the complexity and sophistication of zinc metabolism, it is very difficult to accurately measure zinc status.” said Elad Tako, Associate Professor of Food Science at the College of Agriculture and Life Sciences, who co-developed the index.
“With global food insecurity and increasing domestic obesity rates, malnutrition is hitting vulnerable and low-income populations. These issues are a major concern, as they can lead to dietary zinc deficiency.”
Writing in the journal Nutrients, the team that also includes Jacquelyn Cheng, doctoral student in food science, and Haim Bar, Associate Professor from the University of Connecticut, explains how the Index uses a statistical model and hinges on three pillars.
One of the pillars concerns the ratio of two fatty acids - linolenic acid to dihomo-gamma-linolenic acid (LA:DGLA ratio) indicating the subject’s physiological status.
The second and third pillars concern the gene expression of zinc dependent proteins, that are affected by zinc status; and the gut microbiome as an additional tool to reflect zinc physiological status.
Dr Tako’s team had previously demonstrated that mild zinc deficiency could alter gene expression in the body, and that a lack of zinc adversely affects the composition of intestinal microbial populations and hence zinc metabolism.
Mild and moderate deficiency
“It is possible to detect severe zinc deficiency,” Dr Tako says. “However, it is difficult to differentiate between mild and moderate cases of zinc deficiency.”
“Therefore, relying on only one biomarker may sometimes be an issue, which has led us to think how we could develop an accurate zinc status index, based on a panel of predictive biomarkers.”
Along with Dr Tako’s findings, five selected studies were also included in the ZSI’s creation. Here the studies found that with lower dietary Zn intake, erythrocyte LA:DGLA ratio increased,
In addition, mRNA gene expression of Zn-related proteins in duodenal and liver tissues was altered, and gut microbiota populations differed.
Currently, there is no universally accepted single measure to assess Zn status. Widely used biomarkers of Zn status include plasma, whole blood, and urine Zn, which decrease in severe Zn deficiency.
The World Health Organization (WHO) has estimated that one-third of the global population is at risk for Zn deficiency based on the calculated proportion of individuals with intakes below country-level daily Zn requirements.
To recognize Zn deficiency in its early states, the WHO has indicated a need to develop additional robust indicators of Zn status and to further expand on already known clinical markers.
Emerging biomarkers of Zn status that require further investigation include Zn-dependent proteins, Zn kinetics, taste acuity, oxidative stress, and DNA integrity.
Assessing dietary supplements
“The ZSI can be used to assess the efficacy of dietary interventions in target populations,” the team concludes.
“For example, in the context of the assessment of Zn-biofortified staple food crops, relevant dietary supplements or fortifiers, and other nutritional approaches that are used to improve Zn status.
“Zn deficiency is often missed due to the inflammation status of the subject (and when serum/plasma Zn concentrations are used as Zn physiological status), which is especially pertinent in vulnerable populations,” they add.
“Thus, the development and usage of the ZSI is highly relevant for the accurate measurement of Zn physiological status. Further studies are warranted to further train and refine the ZSI model.”
Published online: doi.org/10.3390/nu13103399
“Zinc Status Index (ZSI) for Quantification of Zinc Physiological Status.”
Authors: Jacquelyn Cheng et al.