ZincMineral

• Shortening a common coldPossibly helps

  The 2024 Cochrane Review pooled 34 trials and 8,526 participants, mostly adults [1].
  
  Zinc lozenges or syrup started early in a cold may shorten symptoms by about 2 days — but Cochrane rated that evidence low to very low certainty [1]. Effects on symptom severity were unclear, and zinc made little or no difference to whether people caught a cold at all [1].
  
  An earlier 2021 review of 28 trials and 5,446 participants found symptoms resolved about 2 days earlier than placebo [1]. Those trials mostly used zinc acetate or gluconate lozenges totalling 45–300 mg/day for up to two weeks [1].
  
  Formulation, dose and timing are exactly where the trials diverge. One older systematic review found lozenges above 75 mg/day shortened colds while lower doses did nothing [1]. ^[1]

• Acute diarrhea in childrenLikely helps

  A 2016 Cochrane Review covering 33 trials and 10,841 children aged 1 month to 5 years, mostly in Asian countries, found zinc shortened acute diarrhea by about half a day [1].
  
  It also cut the chance of diarrhea lasting 7 days or longer by 27% [1]. Children under 6 months showed no significant effect, on low-certainty evidence [1].
  
  That body of work sits behind the WHO and UNICEF recommendation of 20 mg/day for 10–14 days in acute childhood diarrhea [1]. For infants under 6 months the figure is 10 mg/day [1].
  
  The benefit is best established in zinc-deficient, malnourished populations, and may be marginal in well-nourished children [1]. ^[1]

• Childhood pneumonia incidence in low-income countriesPossibly helps

  A 2016 Cochrane Review of 6 trials in 5,193 children aged 2–59 months tested 10–20 mg/day for up to 20 months [1].
  
  Zinc lowered both pneumonia incidence and prevalence versus placebo in those low-income settings [1].
  
  Adding zinc to the care of children who already had pneumonia is a different question, and later reviews generally found no reduction in mortality and no faster recovery [1].
  
  So the evidence points at how often pneumonia occurred, not at what zinc does once a child is already ill [1]. ^[1]

• Advanced age-related macular degenerationLikely helps

  The AREDS trial enrolled 4,757 people who were already at high risk of advanced AMD [1].
  
  A daily supplement pairing 80 mg zinc oxide with vitamin C, vitamin E, beta-carotene and copper lowered 5-year risk of advanced AMD by 25% against placebo [1].
  
  AREDS2 (4,203 participants) confirmed the formulation's benefit, and found a 25 mg zinc version comparably effective [1]. The researchers described that lower-dose finding as preliminary [1].
  
  Note what this is not. Zinc was never given alone in these trials, and everyone enrolled already carried substantial AMD risk [1]. ^[1]

• Wound repair — oral versus topicalPossibly helps

  The evidence splits by route of administration and by deficiency status, and we are not collapsing that into one verdict [9].
  
  Zinc deficiency itself delays wound repair, and correcting a documented deficiency improves outcomes [1].
  
  But a Cochrane review of 6 small trials in arterial and venous leg-ulcer patients, none of them selected for deficiency, found no significant benefit from oral zinc [9].
  
  Topical zinc looks different. A pilot RCT (n=60) in stage I–II pressure ulcers reported partial wound closure in 83.34% of the 25% zinc oxide cream arm by day 14, against 60% on a silver-containing dressing [9]. ^[9]

• HIV — the trials disagreePossibly helps

  This is an open disagreement in the literature, not a settled result [1].
  
  Some individual trials reported fewer immunological-failure events and less diarrhea with zinc [1]. Cochrane reviews pooling trial data found little to no effect on CD4+ T-cell counts, viral load or mortality [1].
  
  Both readings rest on real data, so the conflict stays visible here rather than being resolved in one direction. ^[1]

• Type 2 diabetes markersPossibly helps

  Several meta-analyses report that zinc, across a very wide 4–240 mg/day span of study doses, modestly improves fasting glucose, insulin resistance and lipid markers [1].
  
  The 2015 Cochrane review reached the opposite conclusion, finding the evidence insufficient [1].
  
  NIH's Office of Dietary Supplements still judges the overall body of evidence too thin to recommend zinc specifically for type 2 diabetes [1]. That gap between an older Cochrane review and newer meta-analyses is unresolved [1]. ^[1]

• Acne — inflammatory papule countPossibly helps

  A 2020 systematic review and meta-analysis covering 25 studies and 2,445 acne patients and controls found acne patients had significantly lower serum zinc than controls [7].
  
  In a 12-study subset, mean serum zinc was 96.3 mcg/dL in acne patients against 102.4 mcg/dL in controls [7].
  
  Zinc — oral or topical, alone or alongside other acne therapy — produced a significant reduction in inflammatory papule count [7]. Side-effect rates did not differ significantly from comparators [7].
  
  Because oral and topical arms were pooled, this does not tell you which route did the work [7]. ^[7]

• Topical zinc oxide as a skin barrierLikely helps

  Per WebMD's pharmacist-reviewed drug information, topical zinc oxide forms a physical barrier on the skin against wetness and irritation [11].
  
  It is a standard over-the-counter option for diaper rash and for rashes caused by urine or stool leakage [11]. It is generally well tolerated, with allergic reaction an uncommon but real possibility [11].
  
  This is a barrier-forming topical use. It says nothing about what an oral zinc capsule does [11]. ^[11]

• Diarrhea, slowed growth and loss of appetite — the usual early signs in infants and young children [1].
• Hair loss (alopecia), delayed growth and frequent infections become more prominent in older children [1].
• Impaired sense of taste and smell, which can occur at any age [1].
• In older adults, delayed wound repair plus changes in cognitive and psychological function [1].
• Deficiency during infancy or childhood can lead to reproductive problems later in adulthood [1].
• In lower-income countries, deficiency during pregnancy is linked to higher risk of preterm birth and low birth weight [1].
• Serum or plasma zinc runs 80–120 mcg/dL in healthy people. Below about 70 mcg/dL in women, or 74 mcg/dL in men, indicates inadequate status [1].
• Serum zinc is an imperfect marker. It shifts with sex, age, time of blood draw and infection, and does not closely track dietary intake [1].
• Roughly 15–40% of people with inflammatory bowel disease are zinc deficient, whether in active disease or in remission [1].
• About 50% of people newly diagnosed with celiac disease are at high risk of zinc inadequacy, sometimes persisting after a gluten-free diet starts [1].
• Low zinc status shows up in 30–50% of people with alcohol use disorder, since ethanol reduces intestinal absorption and increases urinary loss [1].
• Breast-milk zinc falls roughly 75% between month 1 and month 9, so breastfeeding alone stops meeting an infant's needs after about 6 months [1].
• Vegetarians and vegans absorb less, because phytates in plant foods bind zinc in the intestine [1].
• Pregnancy and lactation raise requirements by 3–4 mg/day. NHANES data from 2001–2014 put about 11% of US pregnant women below the Estimated Average Requirement [1].
• People who have had bariatric surgery, and children with sickle cell disease, also carry materially higher risk [1].^[1]

• Zinc glycinate / bisglycinateRaising plasma zinc. A 6-week RCT in 30 young women found glycinate significantly raised plasma zinc while gluconate an…

  Elemental content

  Zinc chelated to the amino acid glycine

  Absorption

  Highest acute plasma uptake in small studies. 43.4% more bioavailable than gluconate in a 12-woman crossover trial [3].

  Best for

  Raising plasma zinc. A 6-week RCT in 30 young women found glycinate significantly raised plasma zinc while gluconate and placebo did not [3].

• Zinc gluconateCold lozenges, where trials used 45–300 mg/day of total zinc .

  Elemental content

  Zinc bound to gluconic acid; the common cold-lozenge salt

  Absorption

  Absorbed as well as citrate, and better than oxide. The 2024 Nutrients review calls its own evidence mixed [3].

  Best for

  Cold lozenges, where trials used 45–300 mg/day of total zinc [1]. Also the salt in the withdrawn intranasal products — see interactions [6].

• Zinc citrateA straightforward everyday alternative to gluconate, on equal absorption evidence .

  Elemental content

  Zinc bound to citric acid

  Absorption

  Absorbed equally well as gluconate from capsules in a controlled comparison, and significantly better than oxide [3].

  Best for

  A straightforward everyday alternative to gluconate, on equal absorption evidence [3].

• Zinc oxideTwo very different jobs. It was the salt used in the AREDS eye formula at 80 mg , and it is the barrier ingredient in d…

  Elemental content

  Zinc bound to oxygen; also the topical skin-barrier ingredient

  Absorption

  Consistently the lowest across fortification and supplement studies [3].

  Best for

  Two very different jobs. It was the salt used in the AREDS eye formula at 80 mg [1], and it is the barrier ingredient in diaper-rash creams [11].

• Zinc picolinateA genuine conflict, not a ranking.

  Elemental content

  Zinc bound to picolinic acid

  Absorption

  Depends entirely on what you measure. Best on long-term tissue markers, oxide-like on acute plasma uptake [3][8].

  Best for

  A genuine conflict, not a ranking. In Barrie et al.'s 1987 crossover trial (15 volunteers, 50 mg elemental zinc/day for 4 weeks), picolinate alone significantly raised hair, urine and erythrocyte zinc [8][3].
  
  Citrate, gluconate and placebo did not move those markers [8]. Yet in that same trial picolinate's serum zinc rise was small and not statistically significant [3].
  
  A separate small study ranked 4-hour plasma uptake as glycinate > gluconate > picolinate = oxide, putting picolinate level with the worst-absorbed salt [3].

• Zinc acetateOne of the two lozenge salts used across the common-cold trials, alongside gluconate .

  Elemental content

  Zinc bound to acetic acid

  Absorption

  Not separately ranked in the absorption review carried here [3].

  Best for

  One of the two lozenge salts used across the common-cold trials, alongside gluconate [1].

• Intranasal zinc and permanent loss of smell

  This concerns nasal sprays and gels. It does not apply to oral lozenges or tablets.
  
  In June 2009 the FDA advised consumers to stop using three intranasal zinc gluconate cold products [6]. They were Zicam Cold Remedy Nasal Gel and Nasal Swabs [6].
  
  The advisory followed more than 130 reports of anosmia, loss of the sense of smell, which the agency said could be long-lasting or permanent [6]. Some people reported losing it after a single dose [6].
  
  A peer-reviewed case series of 17 patients who developed anosmia after intranasal zinc gluconate confirmed impaired smell testing in every one [5]. A burning sensation on application typically came first [5]. ^[6]

• Nausea and gastric distress

  High zinc intakes commonly cause nausea, gastric distress, vomiting, dizziness, headache and loss of appetite [1][2].
  
  These are the first signals of overshooting the 40 mg/day adult ceiling from all sources combined [1]. ^[1]

• Copper deficiency from sustained high doses

  This is the real hazard of long-term high-dose zinc, and it is easy to miss.
  
  Sustained intakes of 50 mg/day or more impair copper absorption, which can produce copper deficiency, reduced immune function and lower HDL cholesterol [1].
  
  That level is realistically reachable only through supplements or heavy denture-cream use, not from food alone [1][2]. The adult upper limit of 40 mg/day sits deliberately just below it [1]. ^[1]

• Levothyroxine — evidence not established

  Zinc is a divalent cation like calcium and iron, and both of those are well documented to reduce levothyroxine absorption when taken together [1].
  
  Zinc-specific human pharmacokinetic evidence is notably thinner. A registered trial, ISRCTN73459064, is testing whether 10 mg or 50 mg zinc doses affect levothyroxine absorption in healthy volunteers [1].
  
  That trial exists precisely because the question is open. Many clinicians extrapolate the same several-hour separation used for other divalent cations, which is a precaution by analogy rather than a zinc-specific finding [1]. ^[1]

• Pregnancy

  The upper limit is 34 mg/day for pregnant teens and 40 mg/day for pregnant adults — the same ceiling as for non-pregnant adults [1].
  
  Exceeding it risks nausea, dizziness, headaches and vomiting [1][2].
  
  NIH's Office of Dietary Supplements notes that routine zinc supplementation in pregnancy does not appear to reduce risk of low birth weight, stillbirth or neonatal death [1]. It might lower preterm birth risk somewhat [1]. ^[1]

• Quinolone and tetracycline antibiotics

  Quinolones such as ciprofloxacin, and tetracyclines such as tetracycline and doxycycline, bind zinc in the gut [1].
  
  Both the antibiotic and the zinc end up less well absorbed when taken together [1].
  
  NIH's Office of Dietary Supplements advises taking the antibiotic at least 2 hours before, or 4–6 hours after, a zinc supplement [1][2]. ^[1]

• Penicillamine

  Zinc reduces absorption of penicillamine, a drug used in rheumatoid arthritis and Wilson disease [1].
  
  NIH's Office of Dietary Supplements advises separating the two doses by at least 1 hour [1][2]. ^[1]

• Thiazide diuretics

  Chlorthalidone and hydrochlorothiazide increase urinary zinc excretion [1].
  
  Over long-term use that can lower serum zinc concentrations [1][2]. ^[1]

• High-dose iron supplements

  Supplements carrying 25 mg or more of elemental iron, taken at the same time as zinc, can reduce zinc absorption and plasma zinc concentrations [1].
  
  The iron used to fortify foods does not do this, because it is a poorly soluble form [1]. ^[1]

• Magnesium, at very high zinc doses

  One study used 142 mg/day of supplemental zinc and found possible interference with magnesium absorption and balance [1].
  
  That is more than three times the adult upper limit, so it is not a live concern at ordinary supplement doses [1]. ^[1]

Per USDA data compiled by NIH's Office of Dietary Supplements, oysters are far and away the richest source [1].

Farmed eastern oysters, raw, carry 32 mg per 3 oz — 291% of the Daily Value [1]. Cooked Pacific oysters run 28.2 mg per 3 oz, or 256% [1].

Beef contributes the most zinc to the US diet overall, about 20% of total intake, simply because people eat it far more often [1]. A 3 oz roasted bottom sirloin carries 3.8 mg, 35% of the DV [1].

Other solid sources: blue crab, cooked, 3 oz at 3.2 mg; zinc-fortified breakfast cereal, one serving at 2.8 mg; roasted pumpkin seeds, 1 oz at 2.2 mg [1].

Then broiled pork loin chop, 3 oz at 1.9 mg; roasted turkey breast, 3 oz at 1.5 mg; cheddar cheese, 1.5 oz at 1.5 mg; boiled lentils, half a cup at 1.3 mg [1].

Fortified breakfast cereals are a major contributor to US intake, especially among children and teens [1]. Fruits and vegetables contain very little zinc [1].

Beans, nuts and whole grains do contain zinc, but phytates — the plant storage form of phosphorus — bind it in the intestine and block part of its absorption [1].

That is why absorption from mixed diets ranges from about 5% to over 50%, depending on how much phytate-containing plant food the diet carries [1].

Neither NIH Office of Dietary Supplements fact sheet — consumer or health-professional — gives an explicit food-timing instruction for zinc [1][2].

What is documented is tolerability, not a timing rule. High zinc intakes commonly cause nausea, gastric distress and vomiting [1].

So the common consumer guidance, from a registered-dietitian-reviewed piece at Health.com, is to take zinc with a meal if it upsets your stomach [12]. Read that as practical advice rather than an official dosing recommendation [12].

One piece of timing genuinely is not optional. Keep quinolone or tetracycline antibiotics 2 hours before, or 4–6 hours after, your zinc [1].