Zinc for Zinc Deficiency

If a blood test shows low zinc, supplemental zinc is the standard way to raise it, and the trial evidence for that biochemical job is consistent. In nursing-home adults with serum zinc below 70 µg/dL, 30 mg a day for 3 months raised serum zinc 16% more than placebo (31 participants, P=0.007). A multicentre double-blind trial in chronic liver disease found 83.2 versus 61.3 µg/dL at week 8, with 15 of 27 reaching the target on zinc and 1 of 26 on placebo.

The clinical payoff is less settled. The strongest symptom data come from acrodermatitis enteropathica, a hereditary or acquired zinc-absorption disorder (159 of 174 treated children responded in a literature review of case reports and small series). Taste-disorder trials also favour zinc, but they pooled people with and without low zinc. We found no large randomised trial that enrolled only people with confirmed low zinc and measured symptoms, and the dose that fixes the number is not always the dose in a multivitamin: in one 12-month trial, 30 mg a day left more than half of the group below target.

Zinc deficiency is a supply or loss problem. An estimated 17.3% of the world's population is at risk of inadequate zinc intake, and the risk rises with the phytate content of the national food supply (phytate is a plant compound that binds zinc). A meta-analysis of 26 studies found serum zinc 0.93 µmol/L lower in people on habitual vegetarian diets. Inflammatory bowel disease and bariatric surgery reduce absorption or raise losses, and thiazide diuretics increase zinc lost in urine.

A supplement delivers zinc directly, bypassing a low-zinc diet. In the conditions reviewed in the Japanese guideline, replacing zinc is also linked to downstream effects: low zinc promotes intestinal inflammation through macrophage activation in IBD, and in cirrhosis it disturbs nitrogen metabolism, which zinc supplementation can improve.

Blood zinc is tightly regulated, which is why it is a blunt instrument. A pooled analysis of adults found that each doubling of zinc intake corresponded to only about a 6% difference in serum zinc, and in the 3-month nursing-home trial, residents starting at 60 µg/dL or below did not reach 70 µg/dL on 30 mg a day. Serum zinc also moves with meals, time of day, inflammation and some drugs.

Correcting the number is also not the same as removing the cause. In one cirrhosis treatment series, serum zinc had drifted back to near baseline 3 months after treatment ended; the likely reason is that the underlying cause persists, though that series did not test it.

Doses vary with the cause and the person. Trials in older adults used 30 mg or 60 mg of elemental zinc a day; an HIV trial used 90 mg for 24 weeks; taste-disorder trials used the equivalent of 17-86.7 mg for three to six months; Japanese studies used 25 mg tablets of zinc acetate. Doses should be read as elemental zinc, which is the number declared on the Supplement Facts panel, not the weight of the zinc compound.

No cited trial compared forms. Zinc citrate and gluconate are absorbed at about 61% in young adults and zinc oxide at about 50%. Iron supplements providing 25 mg or more taken at the same time can reduce zinc absorption.

Also taking magnesium? Our guide on taking zinc and magnesium together covers the doses where the two interact.

Four randomised trials enrolled people selected for low zinc. In 31 nursing-home residents with serum zinc below 70 µg/dL, 30 mg a day for 3 months raised serum zinc 16% more than placebo (P=0.007); T cell numbers also rose. A 12-month trial in zinc-deficient residents compared 30 mg with 60 mg a day: both beat placebo (p<0.001), 60 mg brought everyone above 70 µg/dL, and 30 mg did so for 13 of 28 (46.4%). No effect on copper status was detected. The two nursing-home trials share an author.

In 57 people with chronic liver disease and serum zinc below 70 µg/dL, zinc acetate gave 83.2 versus 61.3 µg/dL at week 8 (15 of 27 versus 1 of 26 reached the target); a separate dose-adjustment study in 43 people found the rise was dose-dependent. In 95 adults with well-controlled HIV and low zinc, 90 mg a day for 24 weeks raised zinc levels, but inflammation markers did not consistently improve.

Studies of zinc acetate hydrate, which Japan approved for low zinc in 2017, report larger case series without control groups. Among 97 people with cirrhosis, 64.9%, 80.3% and 82.5% reached 80 µg/dL or more after 2, 4 and 6 months; 7.2% stopped for low copper. In 51 people with IBD, median serum zinc in Crohn's disease rose from 55.5 to 91.0 µg/dL by 4 weeks and activity scores improved, but ulcerative colitis activity did not change significantly.

A registry cohort of 996 people with IBD found that low zinc was associated with more hospitalisations, surgeries and complications in Crohn's disease (in ulcerative colitis, only hospitalisations reached significance), and that normalising zinc within 12 months was associated with improvement in those outcomes. This is observational, so it cannot show that zinc caused the improvement.

The clearest clinical response is in acrodermatitis enteropathica, a hereditary or acquired disorder of zinc absorption with rash, diarrhoea and hair loss. A review of 231 children found 91.4% of those given zinc responded, usually at 1-3 mg/kg a day, though zinc was often ineffective when a metabolic disorder was involved. In people with the condition, plasma zinc averaged 38.2 µg/dL with symptoms and 102 µg/dL after treatment.

These are case reports and small series rather than randomised trials, so publication bias is possible, but most treated children improved.

A meta-analysis of 12 randomised trials (938 people) found taste improvement was more likely with zinc (RR 1.38; 95% CI 1.16-1.64), pooled across idiopathic and zinc-deficient taste disorder. The authors cite benefit at 68-86.7 mg a day, which is above the adult upper limit and needs medical supervision. The Japanese guideline says taste improves in 50-82% of patients and treatment should run at least three months.

In children, effects are smaller and depend on baseline zinc. These are preventive trials in unselected children, mostly at 10-15 mg a day, not treatment trials in children with confirmed deficiency. A Cochrane review of 96 such trials found a slight increase in height (SMD 0.12), fewer diarrhoea episodes (RR 0.91) and more vomiting (RR 1.29). A review of 63 trials in children under 5 found no effect on height-for-age. A meta-analysis found larger growth responses in children with low initial height-for-age. The BOND expert panel treats a growth response to zinc as a sign of pre-existing deficiency. Our zinc for diarrhea page covers treatment of diarrhoea.

No large randomised trial has enrolled only people with confirmed low zinc and measured symptoms as the primary outcome; the 12-month nursing-home trial was not powered for clinical outcomes. The randomised trials above are small (31 to 95 participants) and short, and most of the treatment-series data are uncontrolled. Diagnosis relies on a blood marker that is itself imperfect.

In the trials, side effects were generally mild, but low copper was the main reason for stopping in the cirrhosis series (7.2% stopped, with significant falls in serum copper). Sixty mg a day for 12 months caused no adverse effects and no copper change in the nursing-home trial, and one of 51 people with IBD reported abdominal discomfort and nausea. The HIV trial at 90 mg a day did not report copper in its abstract. Excess zinc can cause nausea, dizziness, headaches, gastric distress, vomiting and loss of appetite, and vomiting was more common in children given zinc (RR 1.29).

Taking zinc with other supplements or medicines? Our guide on what not to take with zinc covers iron, calcium, antibiotics and high-dose copper effects.

Zinc interacts with some drugs in the gut and others increase zinc loss. The list below covers the interactions reported by the NIH Office of Dietary Supplements and the studies cited here.