Short answer. Adult men need 11 mg of zinc a day and adult women 8 mg; children aged 1 to 13 need 3 to 8 mg, according to the NIH Office of Dietary Supplements. The adult upper limit is 40 mg a day from all sources. Citrate, gluconate and chelated forms are all well absorbed; zinc oxide is absorbed less well.
Zinc supplement forms at a glance
| Form | What the studies show | What to know |
|---|---|---|
| Zinc citrate | About 61% absorbed from 10 mg taken without food (15 adults) | Same as gluconate |
| Zinc gluconate | About 61% absorbed in the same trial | One of the most common forms |
| Zinc oxide | About 50% absorbed; three of 15 people absorbed little or none | Common in mass-market multivitamins |
| Zinc bisglycinate (glycinate) | 43.4% higher bioavailability than gluconate after one 15 mg dose (12 women) | Bound to glycine; one small single-dose study |
| Zinc picolinate | Hair, urine and red blood cell zinc rose only with picolinate over 4 weeks; serum zinc did not differ (15 adults) | Small 1987 study, not repeated |
| Every form | The label lists elemental zinc, the amount of the mineral itself, not the weight of the whole compound (NIH ODS) | |
Source: NIH Office of Dietary Supplements; Wegmüller 2014 (PMID 24259556); Gandia 2007 (PMID 18271278); Barrie 1987 (PMID 3630857).
What does zinc do in the body?
Zinc is an essential mineral that must come from food or supplements. Hundreds of enzymes need zinc to work. It plays a role in normal immune function, in making proteins and DNA, in wound healing, and in cell signaling and cell division. It supports healthy growth and development during pregnancy, infancy, childhood and the teen years, and it is involved in the sense of taste (NIH Office of Dietary Supplements).
The body holds only about 1.5 grams of zinc in women and 2.5 grams in men, mostly in muscle and bone. As intake rises, the amount absorbed rises too, but the share absorbed falls (NIH Office of Dietary Supplements).
How much zinc do children and adults need?
From 7 months there is a Recommended Dietary Allowance (RDA). The upper limit (UL) covers food and supplements combined and was set at the level where zinc starts to affect copper status.
| Age | Boys and men | Girls and women | Upper limit (UL) |
|---|---|---|---|
| 0–6 months | 2 mg (Adequate Intake) | 2 mg (Adequate Intake) | 4 mg |
| 7–12 months | 3 mg | 3 mg | 5 mg |
| 1–3 years | 3 mg | 3 mg | 7 mg |
| 4–8 years | 5 mg | 5 mg | 12 mg |
| 9–13 years | 8 mg | 8 mg | 23 mg |
| 14–18 years | 11 mg | 9 mg | 34 mg |
| 19 years and older | 11 mg | 8 mg | 40 mg |
| Pregnancy | — | 12 mg (14–18), 11 mg (19+) | 34 mg (14–18), 40 mg (19+) |
| Lactation | — | 13 mg (14–18), 12 mg (19+) | 34 mg (14–18), 40 mg (19+) |
Source: NIH Office of Dietary Supplements.
The Daily Value on labels is 11 mg for adults and children 4 and older. For young children needs and limits sit close together: a child aged 1 to 3 needs 3 mg and the upper limit is 7 mg, so a child's zinc dose belongs with the pediatrician.
Can you get enough zinc from food?
Most people in the US do. On average, children aged 2 to 11 get 7.6 to 9.7 mg a day from food, men 13 mg and women 9.2 mg. Fewer than 1% of children aged 2 to 8 fall below the average requirement once supplements are counted. The gaps are larger in some groups: 20.9% of teenage girls aged 14 to 18 and 15% of adults fall below it (NIH Office of Dietary Supplements).
| Food and serving | Zinc, mg |
|---|---|
| Oysters, Eastern, farmed, raw, 3 ounces | 32 |
| Beef, bottom sirloin, roasted, 3 ounces | 3.8 |
| Breakfast cereal fortified with 25% of the DV, 1 serving | 2.8 |
| Oats, cooked with water, 1 cup | 2.3 |
| Pumpkin seeds, roasted, 1 ounce | 2.2 |
| Lentils, boiled, ½ cup | 1.3 |
| Milk, 1%, 1 cup | 1.0 |
| Egg, 1 large | 0.6 |
Source: NIH Office of Dietary Supplements.
The body absorbs anywhere from 5% to more than 50% of the zinc in food, depending on how much phytate the meal contains. Phytate is the form plants use to store phosphorus. It is found in whole grains, beans, nuts and seeds, and it binds zinc in the gut so less of it can be absorbed. A review of zinc absorption described phytate as having a strong negative effect, and found that lowering it through fermentation, sprouting or enzyme treatment markedly improves absorption. Protein in the same meal helps (Lönnerdal 2000).
Who is most likely to run low on zinc?
According to the NIH, these groups are most likely to get too little:
- People who eat a vegetarian or vegan diet. A meta-analysis of 26 studies found that vegetarians ate 0.88 mg less zinc a day and had lower serum zinc than non-vegetarians, with a larger gap in women and vegans (Foster 2013). Soaking beans, grains and seeds in water for several hours before cooking, and eating fermented foods, may improve how much zinc the body gets.
- Babies over 6 months who are fed only breast milk. Zinc in breast milk peaks in the first month and falls by about 75% by the ninth month, so from 7 months babies need foods or formula that contain zinc.
- Pregnant and breastfeeding women, whose needs rise by 3 mg and 4 mg a day.
- People with digestive conditions that affect absorption, or after weight-loss surgery, and people who drink heavily, since alcohol lowers absorption and raises the zinc lost in urine.
Signs that justify a conversation with a doctor include poor appetite, slow growth in a child, hair loss and frequent diarrhea in young children. None of these is specific to zinc, so they are reasons to get checked, not reasons to start a supplement on your own. The usual test is serum zinc, normally 80 to 120 mcg/dL; values below 70 mcg/dL in women and 74 mcg/dL in men suggest low status. Results shift with age, sex and the time of the blood draw, so a doctor reads them alongside the diet (NIH Office of Dietary Supplements).
Which form of zinc is best absorbed?
For most people the choice comes down to dose and comfort rather than form. The most precise comparison used stable isotopes to trace 10 mg of zinc taken without food by 15 adults. Zinc citrate and zinc gluconate were absorbed equally well, at about 61%. Zinc oxide was absorbed less, at about 50%, and three participants absorbed little or none of it (Wegmüller 2014).
Chelated forms have a smaller evidence base. In a crossover study of 12 healthy women, a single 15 mg dose of zinc bisglycinate produced 43.4% higher bioavailability than gluconate (Gandia 2007). In a 1987 study of 15 adults who took 50 mg a day of each form for four weeks, zinc in hair, urine and red blood cells rose only with picolinate, while serum zinc did not differ between forms (Barrie 1987).
A practical way to choose: avoid relying on zinc oxide, pick a form the person tolerates, and compare products by the elemental zinc on the label.
The absorption studies above gave zinc without food. The NIH lists nausea and stomach upset among the effects of high zinc intakes, so a person who feels queasy may prefer a light meal, ideally not one built on whole grains and beans.
Timing also matters with iron. Supplements that carry 25 mg of iron or more, taken at the same time as zinc, can reduce zinc absorption. Iron added to fortified foods does not have the same effect (NIH Office of Dietary Supplements; Lönnerdal 2000). Taking them at different times avoids this.
Can you take too much zinc?
Yes, and the main risk is to copper. Too much zinc can cause nausea, dizziness, headaches, stomach upset, vomiting and loss of appetite. Taking 50 mg or more for weeks can interfere with copper absorption, reduce immune function and lower HDL cholesterol (NIH Office of Dietary Supplements). Two older trials show the effect on copper:
- Healthy women who took 50 mg of zinc a day for 10 weeks had lower activity of a copper-dependent enzyme in red blood cells, along with lower ferritin and hematocrit. Adding iron corrected the iron effect but not the copper effect (Yadrick 1989).
- Healthy men who took 25 mg twice a day for 6 weeks also showed a drop in that copper enzyme by week 6, even though blood copper had not changed yet (Fischer 1984).
Food alone rarely reaches 50 mg; amounts that high usually come from supplements (NIH Office of Dietary Supplements). It is worth adding up the zinc in every product a person takes and comparing the total with the upper limit for their age. Whether long-term use calls for copper too is a question for your clinician.
One more caution: zinc nasal gels and sprays. In a series of 17 patients, all had an impaired sense of smell on testing after using an intranasal zinc gluconate gel, noticed within 48 hours of use (Alexander 2006).
Does zinc interact with medicines?
The NIH lists three groups:
- Quinolone and tetracycline antibiotics, such as ciprofloxacin and tetracycline. Zinc and the antibiotic can bind in the gut and reduce the absorption of both. Taking the antibiotic at least 2 hours before or 4 to 6 hours after zinc minimizes this.
- Penicillamine. Zinc reduces its absorption and action, so the two should be taken at least 1 hour apart.
- Thiazide diuretics, such as chlorthalidone and hydrochlorothiazide, increase the zinc lost in urine and lower serum zinc.
Which ASDHelp products contain zinc?
Doses are copied from each label. Add up zinc from every product taken and compare it with the upper limit for the person's age.
- Trace Minerals: 30 mg as TRAACS zinc bisglycinate chelate per capsule, with 2 mg of copper as bisglycinate chelate. Label directions: adults, 1 capsule a day; not for anyone under 14. 30 mg is above the upper limit for ages 13 and under.
- Formula C: 15 mg as TRAACS bisglycinate chelate per 6 capsules, inside a multivitamin with no copper. Label directions: adults or children 4 and older, 6 capsules a day with food. 15 mg is above the 12 mg upper limit for ages 4 to 8.
- D-Tox Complex: 15 mg as zinc bisglycinate chelate per 2 capsules. Label directions: 2 capsules a day with meals; no children's dose on the label.
- Gut Restore Peach Flavor: 17 mg from 75 mg of zinc L-carnosine per 8 g scoop. Label directions: one scoop a day.
- Spectrum Formula Advance: 10 mg as Albion zinc bisglycinate chelate per scoop, in an iron-free, copper-free multivitamin powder. Label directions: adults, 1 scoop a day; children as directed by a healthcare professional. 10 mg is above the 7 mg upper limit for ages 1 to 3.
- Spectrum Formula Chewable + Iron: 7.5 mg as zinc bisglycinate chelate per 4 chewable tablets, in a children's multivitamin. The top of the label range (4 tablets a day at ages 1 to 3, 8 tablets from age 4) gives 7.5 mg or 15 mg, above the 7 mg and 12 mg upper limits; check the amount with the pediatrician.
Questions to take to your doctor
- Is there a reason to check zinc status, and how should the serum result be read given the time of day and age?
- How much zinc do all of our current products add up to each day, and how does that compare with the upper limit for each person's age?
- If we take zinc for months, should we also take copper or check copper status?
- Do any of our medicines, such as an antibiotic or a diuretic, call for separate timing or monitoring?
Sources
- NIH Office of Dietary Supplements. Zinc fact sheet for health professionals. ods.od.nih.gov
- National Academies. Dietary Reference Intakes tables (NCBI Bookshelf). ncbi.nlm.nih.gov/books/NBK545442
- Wegmüller R et al. Zinc absorption by young adults from supplemental zinc citrate is comparable with that from zinc gluconate and higher than from zinc oxide. J Nutr 2014. PMID 24259556
- Gandia P et al. A bioavailability study comparing two oral formulations containing zinc (Zn bis-glycinate vs. Zn gluconate) after a single administration to twelve healthy female volunteers. Int J Vitam Nutr Res 2007. PMID 18271278
- Barrie SA et al. Comparative absorption of zinc picolinate, zinc citrate and zinc gluconate in humans. Agents Actions 1987. PMID 3630857
- Lönnerdal B. Dietary factors influencing zinc absorption. J Nutr 2000. PMID 10801947
- Foster M et al. Effect of vegetarian diets on zinc status: a systematic review and meta-analysis of studies in humans. J Sci Food Agric 2013. PMID 23595983
- Yadrick MK et al. Iron, copper, and zinc status: response to supplementation with zinc or zinc and iron in adult females. Am J Clin Nutr 1989. PMID 2912000
- Fischer PW et al. Effect of zinc supplementation on copper status in adult man. Am J Clin Nutr 1984. PMID 6486080
- Alexander TH, Davidson TM. Intranasal zinc and anosmia: the zinc-induced anosmia syndrome. Laryngoscope 2006. PMID 16467707
These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent any disease. This article is educational and is not medical advice.