Zinc
trace-mineral
Key Takeaways
- Zinc is required for the catalytic activity of hundreds of enzymes and plays roles in immune function, protein/DNA synthesis, and wound healing
- FDA daily value is 11 mg; adult men need 11 mg/day, women need 8 mg/day
- The body stores approximately 1.5 g (women) to 2.5 g (men) of zinc, mostly in skeletal muscle and bone
- Zinc deficiency affects many organs and varies by age: diarrhea in infants, growth delays in children, impaired wound healing and taste/smell in adults
- Zinc supplementation may improve sleep quality and reduce fatigue, though evidence requires further research (pmid:33441476)
Evidence Spectrum
14 studies reviewed →Immune function and wound healing
Zinc is critical for immune function, and its deficiency impairs both innate and adaptive immunity. A systematic review of wound care interventions found improved outcomes in patients with venous ulcers and pressure ulcers receiving zinc supplementation. Zinc is also found in cold lozenges and over-the-counter cold remedies, reflecting its established role in immune support.13
Cognitive function and energy
Zinc has recognized roles in energy-yielding metabolism, DNA synthesis, oxygen transport, and neuronal functions critical for brain function. Zinc deficiency can interfere with cognitive and psychological processes and contribute to fatigue.2
Age-related macular degeneration (AMD)
The AREDS formulation, which includes zinc, has been shown to reduce the risk of progression to late AMD. A Cochrane review of 26 studies (11,952 participants) found that people taking AREDS multivitamins (including zinc) were less likely to progress to late AMD (OR 0.72, 95% CI 0.58-0.90). The AREDS2 study explored lower zinc doses with similar results.67
Sleep quality improvement
A systematic review and meta-analysis noted that zinc supplementation may improve sleep quality, though the evidence base remains small and further research is needed.5
Hair loss prevention
A systematic review of 49 articles found that zinc deficiency may contribute to androgenetic alopecia, and supplementation showed potential benefits in improving hair growth. However, the evidence is not entirely consistent.4
14
Studies Reviewed
2 mg
RDA (Infants 0-6 months (AI))
40 mg
Upper Limit
Role in the Body
Zinc is an essential trace mineral involved in many aspects of cellular metabolism. It is required for the catalytic activity of hundreds of enzymes and plays critical roles in immune function enhancement, protein and DNA synthesis, wound healing, and cell signaling and division. Zinc also supports healthy growth and development during pregnancy, infancy, childhood, and adolescence, and is involved in the sense of taste. The total amount of zinc in the body is approximately 1.5 grams in women and 2.5 grams in men, with the majority stored in skeletal muscle and bone. Zinc homeostasis is maintained through dietary absorption, excretion into the gastrointestinal tract, and reabsorption in the gastrointestinal lumen. As zinc intake rises, the total amount absorbed increases, but the fractional absorption rate drops. Zinc status is typically assessed via serum or plasma concentrations, which normally range from 80 to 120 mcg/dL (12-18 mcmol/L). Concentrations below 70 mcg/dL in women and 74 mcg/dL in men suggest inadequate status. However, serum zinc is affected by factors including age, sex, time of day, and inflammation, making accurate assessment challenging.
- Catalytic activity of hundreds of enzymes
- Immune function enhancement
- Protein and DNA synthesis
- Wound healing
- Cell signaling and division
- Growth and development during pregnancy, infancy, and childhood
- Sense of taste and smell
- Antioxidant defense
- Neurological function and cognition
Supplement Forms
Zinc picolinate
RecommendedBioavailability: 20%
Chelated form with good absorption. Often recommended as a well-tolerated option.
Zinc citrate
RecommendedBioavailability: 18%
Good bioavailability and generally well-tolerated.
Zinc gluconate
RecommendedBioavailability: 14%
Commonly used in cold lozenges. Reasonable absorption.
Zinc acetate
RecommendedBioavailability: 14%
Also used in cold lozenges. Similar absorption profile to gluconate.
Zinc oxide
Bioavailability: 10%
Contains high percentage of elemental zinc but has lower bioavailability. More commonly used in topical applications (sunscreen, diaper cream).
Zinc sulfate
Bioavailability: 12%
Inexpensive but may cause more GI side effects than chelated forms.
Food Sources
Oysters
78.6 mg per 100g (highest known food source)
Beef
4-9 mg per 100g
Crab and lobster
6-7 mg per 100g
Pork
2-4 mg per 100g
Chicken (dark meat)
2-3 mg per 100g
Pumpkin seeds
7.8 mg per 100g
Cashews
5.6 mg per 100g
Chickpeas (cooked)
1.5 mg per 100g
Fortified breakfast cereals
varies (commonly 25-100% DV per serving)
Deficiency
Prevalence: Zinc deficiency is a concern globally, particularly in low- and middle-income countries with limited access to zinc-rich animal foods. Vegans and vegetarians may be at higher risk due to lower bioavailability of zinc from plant sources. Plant-based diets show lower zinc intake and status compared to meat-eaters.
Symptoms:
- In infants and children: diarrhea, impaired growth, loss of appetite
- In older children: alopecia (hair loss), delayed growth, frequent infections
- In adults: impaired wound healing, altered taste and smell
- In older adults: delayed wound healing, cognitive and psychological changes
- In pregnant women: increased risk of maternal morbidity and adverse birth outcomes (premature birth, low birth weight)
Risk Factors:
- Vegetarians and vegans (phytates in plant foods reduce zinc absorption)
- Pregnant and lactating women
- Older adults
- People with gastrointestinal disorders (Crohn's disease, ulcerative colitis)
- People with sickle cell disease
- Alcoholics
- People in low- and middle-income countries with limited access to animal foods
Safety & Interactions
Possible Side Effects:
- • Nausea and vomiting (especially on empty stomach)
- • Diarrhea and abdominal cramps
- • Metallic taste in mouth
- • Chronic excessive intake (>40 mg/day) can cause copper deficiency
- • Headache
Drug Interactions:
- • Copper: chronic zinc supplementation above the UL can induce copper deficiency by competing for absorption
- • Iron: zinc and iron compete for absorption; take separately if supplementing both
- • Antibiotics (tetracyclines, quinolones): zinc reduces absorption; separate by 2+ hours
- • Penicillamine (used for rheumatoid arthritis): zinc reduces absorption; separate by 2+ hours
- • Diuretics: thiazide diuretics can increase zinc excretion
Contraindications:
- • Do not exceed 40 mg/day from all sources long-term without medical supervision
- • Use caution with denture adhesive creams containing zinc (can lead to excessive intake)
Frequently Asked Questions
How much zinc do I need daily?
The FDA daily value is 11 mg. Adult men need 11 mg/day and women need 8 mg/day. The tolerable upper intake level is 40 mg/day from all sources. Pregnant and lactating women have slightly higher requirements.
Can zinc help with colds?
Zinc lozenges (gluconate or acetate forms) taken within 24 hours of cold symptom onset may reduce the duration of symptoms. Zinc is found in many over-the-counter cold remedies. However, zinc nasal sprays have been associated with loss of smell and should be avoided.
What are the best food sources of zinc?
Oysters contain far more zinc per serving than any other food (78.6 mg per 100g). Other good sources include beef, crab, lobster, pork, pumpkin seeds, cashews, and fortified cereals. Animal sources provide more bioavailable zinc than plant sources.
Can too much zinc be harmful?
Yes. Chronic intake above 40 mg/day can cause copper deficiency, which may lead to anemia and neurological problems. Acute side effects of excess zinc include nausea, vomiting, and diarrhea. Always stay within the tolerable upper intake level unless directed by a healthcare provider.
Research Sources
15 peer-reviewed studies analyzed from PubMed. 7 directly cited in this review.