Table 1.

Dietary sources, recommended daily intake (RDI), daily permissible limit (DPL), immune functions, and supplementation effects of Cu, Se, and Zn

Trace elements	Dietary sourcea	Contenta	RDIb	DPLc	Immune functions	Deficiency	Supplementation effects	References
Cu	Beef meat	12.5 mg/100 g	0.9 mg/day	10 mg/day	- Supported macrophage function and natural killer (Nk) cell activity	-Decreased interleukin-2 (IL-2) production and IL-2 mRNA in T-lymphocytes	- Inhibited NF-kB activation - Increased IL-2 synthesis	- Percival [23] - Hopkins and Failla [13]
	Oysters, shellfish	4.9 mg/100 g
	Mushroom	1 mg/100 g
	Nuts	2 mg/100 g
Se	Tuna	100 μg/100 g	55 μg/day	300 μg/day	- Increased T and B lymphocyte function - Increased the antioxidant enzyme activity	- Decreased Nk cell activity - Reduced the GSH-Px activity - Increased the expression of the inflammatory cytokine, IL-6, and TNF-α	-Improved immune function - Induced up-regulation of the IL-2 - Stimulated T-cell proliferation - Increased the TNF-α and IFN-γ	- Guillin et al. [11] - Alexander et al. [1] - Zhang et al. [35]
	Sardines	90 μg/100 g
	Shellfish	85 μg/100 g
	Chicken	25 μg/100 g
	Eggs	20 μg/100 g
	Nuts	1700 μg/100 g
	Cereals	19 μg/100 g
Zn	Oysters	61 mg/100 g	11 mg/day	40 mg/day	- Antiviral function - RNA polymerase inhibition - Enhanced the Nk cells activity - Activation of antibody production	- Induced viral infection vulnerability - Risk factor for pneumonia - Increased inflammation	- Reduced common cold severity - Increased the T-cell production	- Barnett et al. [2] - Read et al. [25] - de Almeida Brasiel [4]
	Beef	11 mg/100 g
	Chicken	2 mg/100 g
	Wheat	17 mg/100 g
	Beans, lentils	1 mg/100 g

^aUS Department of Agriculture [29]; European Food Safety Authority [7]

^bOtten et al. [22]

^cWHO/FAO [33]