Table 3.

Results of studies assessed for the ZSI: LA:DGLA, Zn-related gene expression, and Zn status effects on gut microbiota modulation.

Reference	Zn Content (μg Zn/g)	Zn Status Measures
		LA:DGLA (Erythrocyte)	Zn-Related Gene Expression	Gut Microbiota Modulation	Other (Not Included in ZSI)
Beasley et al., 2020 [20]	Control: 16.6 ± 0.06 (standard wheat) Biofortified: 19.2 ± 0.03 (nicotianamine-enhanced Zn- and Fe-biofortified wheat)	In the biofortified relative to the control group: ↓ LA:DGLA at 2 weeks ↓ LA:DGLA at 4 weeks onwards (trend, not significant)	In the biofortified relative to the control group: ↔ ZnT1 ↔ ZnT5 ↔ ZnT7 ↔ ZIP1 ↔ ZIP4 ↔ ZIP6 ↔ ZIP9 ↔ Δ6-desaturase	In the biofortified relative to the control group: ↓ α-diversity Change in β-diversity At the phyla level: ↑ 1.9-fold the proportion of Actinobacteria ↓ 1.2- and 2.0-fold, respectively, the proportion of Firmicutes and Proteobacteria At the family level: ↑ abundance of Enterococcaceae ↓ 1.7-fold the proportion of Lachnospiraceae At the genera level: ↑ Enterococcus abundance ↓ Dorea abundance ↑ 1.9- and 1.5-fold, respectively, proportion of Bifidobacterium and Lactobacillus ↓ proportion of Streptococcus (1.7-fold), Coprococcus (1.4-fold), Ruminococcus (1.2-fold) Faecalibacterium (2-fold), and Escherichia (2-fold)	In the biofortified relative to the control group: ↔ Serum ↔ Liver ↔ Nail ↔ Feathers
Knez et al., 2018 [21]	Low Zn: 32.8 ± 0.17 (standard wheat) High Zn: 46.5 ± 0.99 (Zn-biofortified wheat)	In the high-Zn relative to the low-Zn group: ↓ LA:DGLA (2 weeks onwards)	In the high-Zn relative to the low-Zn group: ↓ ZnT1 ↓ ZnT5 ↓ ZnT7 ↓ ZIP4 ↓ ZIP6 ↓ ZIP9 ↓ Δ6-desaturase	See Reed et al., 2018 [18]	In the high-Zn relative to the low-Zn group: ↑ Serum Zn (2 weeks onwards) ↑ Feather Zn ↑ Nail Zn
Reed et al., 2018 [18]	Low Zn: 32.8 ± 0.17 (standard wheat) High Zn: 46.5 ± 0.99 (Zn-biofortified wheat)	See Knez et al., 2018 [21]	See Knez et al., 2018 [21]	In the high-Zn relative to the low-Zn group: ↔ α-diversity Change in β-diversity At the phyla level: ↔ Firmicutes, Actinobacteria, and Proteobacteria At the genera level: ↑ Dorea, Clostridiales, unclassified Clostridiales, Ruminococcus, Lachnospiraceae, and unclassified Lachnospiraceae ↓ Lactococcus, Verrucomicrobium, Bacteroides, Bacteroidales, and unclassified Bacteroidales At the species level: ↑ Lactobacillus reuteri ↓ Akkermansia muciniphila	See Knez et al., 2018 [21]
Reed et al., 2015 [17]	Zn deficient: 2.5 ± 0.02 Zn adequate (control): 42 ± 0.25	See Reed et al., 2014 [13]	See Reed et al., 2014 [13]	In the Zn-adequate relative to the Zn-deficient group: ↑ α-diversity (species richness and diversity) Changes (expansion) in β-diversity At the phyla level: ↑ Firmicutes ↓ Proteobacteria At the family level: ↑ Peptostreptococcaceae and unclassified Clostridiales ↓ Enterococcaceae and Enterobacteriaceae At the genera level: ↑ unclassified Clostridiales and unclassified Peptostreptococcaceae ↓ Enterococcus, unclassified Enterococcus, unclassified Enterobacteriaceae, and unclassified Ruminococcaceae At the species level: ↑ Ruminococcus lactaris, Enterococcus sp., Clostridium lactatifermentans, and Clostridium clostridioforme ↓ Clostridium indolis and an unclassified member of the Bacteroidales (Unclassified S24–7)	See Reed et al., 2014 [13]
Reed et al., 2014 [13]	Zn deficient: 2.5 ± 0.02 Zn adequate (control): 42 ± 0.25	In the Zn-adequate relative to the Zn-deficient group: ↓ LA:DGLA (1 week onwards)	In the Zn-adequate relative to the Zn-deficient group: ↔ ZnT1 ↔ ZnT5 ↔ ZnT7 ↔ ZIP6 ↔ ZIP9 ↑ Δ6-desaturase	See Reed et al., 2015 [17]	In the Zn-adequate relative to the Zn-deficient group: ↑ Serum Zn ↑ Feather Zn ↑ Nail Zn

↔no change; ↑ increased; ↓ reduced.