Zinc

By: Paige Jensen

Functions

• Important helper to enzymes and reactions
• Structural support
• Participates at catalytic site
• Regulation gene transcription
• Shift shape to form “fingers”

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Food Sources

• Foods with high protein
• Animal products
• Red meat
• Seafood
• Poultry
• Pork
• Dairy products

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Digestion

• Hydrolyzed from amino acids and nucleic acids

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• Freed from food sources in the stomach and upper duodenum
• Acidic environment
• Proteases and nucleases

Absorption

• Duodenum & upper jejunum

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• Types of absorption:
• Carrier-mediated transport
• Diffusion

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Enhancers

• Acidic environments
• Amino acids
• Histidine and methionine
• Organic acids
• Citrate

Inhibitors

• Alkaline environments

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• Phytic acid
• Legumes, lentils, nuts
• Oxalic acid
• Spinach, berries, tea
• Polyphenols
• Tea, coffee, and some fibers
• Iron and calcium

Transport

• Bound to albumin and taken up in the liver
• Remaining zinc binds to α-macroglobulin
• Histidine and cysteine loosely transport in blood
• ZIPs
• ZnT6 excretion transporter

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Interactions

• Zinc is required in alcohol dehydrogenase (vitamin A)
• Decrease in copper absorption, due to excess zinc intake
• Cadmium replaces zinc fingers, disrupting the shape of the transcription factor proteins

Excretion

• Most excreted via feces
• ZIP5 facilitates the movement from the blood across the basolateral membrane into the enterocyte
• ZnT6 on the brush border moves it into the intestinal cell into the lumen for excretion via feces
• Very small amount is excreted via kidneys, skin, seman, and menses

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DRI

• Recommended Dietary Allowance
• Adult Men: 11 mg/day

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• Adult Women: 8 mg/day
• Pregnancy: 11 mg/day
• Lactation: 12 mg/day

Deficiency

• Children:
• Growth restriction (delayed sexual maturation), skeletal abnormalities, poor wound healing, diarrhea, skin rash/lesions/dermatitis
• Adults:
• Anorexia, diarrhea, lethargy, depression, skin rash/lesions/dermatitis, hypogeusia, alopecia, vision problems, and impaired immune function, protein synthesis and wound healing
• At risk population groups:
• Older adults, vegetarians, alcoholics

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Toxicity

• Tolerable Upper Intake Level (UL)
• 40 mg/day
• Interaction with copper
• Causes
• Supplement
• Denture creams
• Spray or gel

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Quick Review

• What is the primary food source for zinc?

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• How is zinc separated from the food source?

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• Name the 3 enhancers to zinc absorption.

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• Zinc is primarily excreted through ______________.

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• T/F Being an alcoholic has no affect on zinc deficiency.

Sources

• Gropper, S., Smith, J. (2018). Advanced nutrition and human metabolism 7^th ed. Belmont, CA: Wadsworth

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