Overview
Zinc is an essential trace mineral involved in hundreds of enzymatic reactions, immune function, protein synthesis, wound healing, DNA synthesis, cell division, and testosterone production. While frank deficiency is uncommon in developed countries, mild insufficiency is widespread, particularly in elderly, vegetarians, and those with GI conditions.
Primary applications focus on immune support and cold duration reduction (zinc lozenges), preventing/treating zinc deficiency, wound healing support, testosterone support in deficient men, skin health (acne, particularly inflammatory acne), and taste/smell function.
Evidence quality is good to strong for immune function and cold treatment, moderate for deficiency correction and testosterone support, with research spanning decades.
Safety is good at appropriate doses (15-30 mg daily) but chronic high doses (above 40-50 mg) can cause copper deficiency, immune suppression paradoxically, and GI issues.
What it means
Zinc lozenges actually shorten colds (acetate/gluconate forms, 75mg+ daily, start within 24hrs). Daily supplement (15-30mg) supports immune function and testosterone IF you're deficient. BIG warning: doses above 40-50mg long-term cause copper deficiency (anemia, neurological problems). Always balance zinc with copper or cycle off. Picolinate or glycinate forms best absorbed.
Functions and Applications
Primary functions: cofactor for 300+ enzymes, immune cell function (T cells, NK cells, cytokine production), protein and DNA synthesis, wound healing and tissue repair, testosterone production and reproductive health, taste and smell (zinc deficiency classic cause of ageusia/anosmia), and skin health (cell turnover, inflammation reduction).
Immune Function and Colds
For immune support and cold treatment, zinc lozenges (zinc acetate or gluconate, 75+ mg daily, started within 24 hours of symptoms) reduce cold duration by 33-50% in meta-analyses. Effects are dose and timing dependent.
What it means
Cold lozenge meta-analysis: ~40% shorter cold duration IF you start within 24hrs and use 75mg+ daily. After symptoms start, it's too late. Keep lozenges handy for first sniffle.
Deficiency Signs
Deficiency symptoms include impaired immune function and frequent infections, hypogonadism and low testosterone, impaired wound healing, hair loss, diarrhea, loss of taste/smell (ageusia/anosmia), skin lesions, and growth retardation in children.
Forms Comparison
Forms: Zinc picolinate (well-absorbed, often recommended), zinc glycinate (chelated, gentle on stomach, well-absorbed), zinc gluconate (moderate absorption, common in lozenges), zinc citrate (good absorption), zinc sulfate (cheap, poorly tolerated, lower absorption), and zinc acetate (for lozenges, effective for colds).
Picolinate, glycinate, or citrate are preferred for daily supplementation. Save gluconate/acetate for cold lozenges.
Dosing and Copper Balance
Typical supplemental doses: 15-30 mg daily for general support and deficiency prevention. 30-50 mg daily for therapeutic use (acne, wound healing). Cold treatment lozenges: 75-100 mg daily in divided doses (every 2-3 hours while awake) for duration of cold.
Critical copper balance issue: Zinc competes with copper absorption. Chronic zinc supplementation above 30-40 mg daily can induce copper deficiency (anemia, neutropenia, neurological problems). To prevent: add copper supplement (1-2 mg copper for every 15 mg zinc), cycle zinc supplementation (not continuous year-round), or use multivitamins with balanced zinc/copper ratios.
What it means
The zinc-copper seesaw: high zinc blocks copper absorption. Long-term 50mg+ zinc without copper = eventually you get copper-deficiency anemia and nerve problems. Solution: add 1-2mg copper OR cycle zinc (4-6 weeks on, 2-4 weeks off).
Upper limit: 40 mg daily. Chronic intake above this increases copper deficiency risk and paradoxically impairs immune function.
Safety and Testing
Testing: Serum zinc has limitations (doesn't reflect tissue stores well) but low levels indicate deficiency. Zinc taste test (subjective) or advanced testing (RBC zinc, zinc in hair) provide additional information.
Zinc supplementation is valuable for immune support (especially colds), addressing deficiency in at-risk populations, and testosterone support in deficient men, with good safety when used appropriately and attention to copper balance.
References
Hemilä H. Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and the role of zinc dosage. JRSM Open. 2017;8(5):2054270417694291.
Prasad AS, Mantzoros CS, Beck FW, Hess JW, Brewer GJ. Zinc status and serum testosterone levels of healthy adults. Nutrition. 1996;12(5):344-348.