Zinc is necessary for the functioning of over 300 different enzymes and, as such, it plays a vital role in an enormous number of biological processes. Zinc is widely distributed in microorganisms, plants, and animals. In humans, the highest concentrations of zinc are found in the liver, pancreas, kidneys, bone, and muscles. Zinc is highly concentrated in parts of the eye, prostate gland, sperm, skin, hair, and nails. Cooking acidic foods in galvanized cookware used to be a possible source of excess zinc intake. The widespread use of stainless steel and plastic materials to prepare and store foods has largely eliminated this problem. Galvanized pipes in older plumbing systems used to leach zinc into drinking water supplies, but modern plumbing has phased out the use of galvanized pipes.
2-50mg elemental zinc daily. Doses of zinc sulfate as high as 220mg, three times a day have been evaluated for the treatment of sickle cell disease.(
1)
25mg daily.
23% elemental zinc contained in zinc sulfate
14.3% elemental zinc contained in zinc gluconate
Tablets, capsules, liquid, and lozenges.
15mg
15-35mg
- Infants < 6 months: 2mg (Adequate Intake, AI)
- Infants 7-12 months: 3mg
- Children 1-3 years: 3mg
- Children 4-8 years: 5mg
- Children 9-13 years: 8mg
- Males 14-18 years: 11mg
- Females 14-18 years: 9mg
- Males >19 years: 11mg
- Females >19 years: 8mg
- Pregnancy 14-18 years: 13mg
- Pregnancy >19 years: 11mg
- Lactation 14-18 years: 14mg
- Lactation >19 years: 12mg
Interactions and Depletions
Zinc arginate, ascorbate, aspartate, citrate, gluconate, glycinate, histidinate, methionate, oxide, picolinate, and sulfate.
Zinc absorption takes place in the intestinal lumen. Zinc absorption depends on the secretion of a zinc-binding factor from the pancreas.
Zinc is relatively non-toxic, and although toxicity has been reported in humans, it is uncommon. Ingestion of high levels of zinc can induce a copper deficiency. Doses of 45mg/day are safe, but regular intake greater than 150mg/day could be a problem.
Zinc toxicity can cause diarrhea, dizziness, drowsiness, vomiting, loss of muscle coordination, and lethargy.
Inhalation of zinc oxide in certain industrial environments can also be a source of excess exposure.
Zinc gluconate lozenges may cause a mild stomach upset and a metallic taste in the mouth while using them.(
2) Larger doses of other zinc salts have been associated with GI symptoms.
Prenatal zinc supplementation in malnourished pregnant women of third world countries has been shown to adversly affect the infants' mental development.
These findings should not warrant concern in well nourished pregnant women eating a well-balanced diet.(3)
Helps regulate a wide variety of immune system activities, including T-lymphocytes, CD4, natural killer cells, and interleukin II.
Cofactor for the antioxidant enzyme Zn/Cu superoxide dismutase.
Facilitates wound healing, especially in burns, surgical, and other types of scars.
Although its mechanism is not known at this time, zinc apparently possesses antiviral activity.
Zinc is necessary for the maturation of sperm, for ovulation, and for fertilization.
Involved in sensory perceptions of taste, smell and vision. Necessary for salt-taste perception, dark adaptation, and night vision.
Controls the release of stored vitamin A from the liver.
Is a component of insulin and recently was discovered to be a regulator of insulin activity.
Promotes the conversion of thyroxine to triiodothyronine.
Zinc supplementation did have an impact on improved local-free survival (LFS) at three years for patients with Stages III-IV neck and head cancer when also receiving concurrent chemoradiotherapy.(4)
Alopecia areata is an autoimmune disorder which results in hair loss. Researchers found that patients with alopecia areata had low levels of zinc suggesting zinc may play a roll in triggering the autoimmune response.(5)
Researchers found that children with moderate asthma benefited from the intake of vitamin C, omega-3 fatty acids and zinc separately or in combination.(6)
A study found that zinc supplementation reduced depression and anger and there was a significant increase in blood levels of zinc in young women.(7)
Zinc gluconate lozenges(
8) and zinc nasal gel(
9) substantially reduce the symptoms (coughing, headache, hoarseness, congestion, nasal drainage, and sore throat) and the duration of the common cold. A review of 10 trials could not confirm whether zinc supplementation could prevent ear infections.(
10)
Zinc deficiency causes a decrease in antibody-mediated responses to both T-cell dependent and T-cell independent antigens and reduced natural killer cell activity and delayed-type hypersensitivity (DTH) reactions.(
11),(
12)
Numerous studies report low zinc levels in individuals with acne, and oral zinc supplementation helps a substantial number of these patients.(
13),(
14)
Zinc inhibits 5-alpha reductase activity, which reduces the conversion of testosterone to dihydrotestosterone and decreasing hyperplastic growth in the prostate gland.(
15)
Patients with inflammatory bowel disease improve rapidly with zinc supplementation ranging from 210-750mg of zinc sulfate daily.(
16),(
17)
Two zinc-dependant enzymes are required for vision; patients taking 80mg of zinc daily for two years had much less vision loss than controls.(
18),(
19)
Zinc enhances vitamin D activity and is essential for bone formation. Women with higher zinc intake have greater forearm bone mineral content.(
20),(
21),(
22)
Individuals with eczema(
23) and psoriasis(
24) are frequently found to have low zinc levels.
When zinc levels are low, zinc supplementation speeds wound healing;(
25) topical applications speeds the healing of open wounds.(
26)
Zinc sulfate (220mg three times a day) decreased pain and reduced the size of gastric ulcers much faster than placebo controls.(
27)
Zinc has anti-inflammatory properties, probably due to its antioxidant activity in the enzyme superoxide dismutase. In a double-blind study, patients taking 220mg of zinc sulfate 3 times daily gained improvement in joint swelling, morning stiffness, walking time, and the patient's own impression of overall disease activity.(
28),(
29)
Individuals with IDDM(
30) and NIDDM(
31) have been found to be zinc deficient.
Symptoms and Causes of Deficiency
Marginal zinc deficiencies are reported to be common in the United States. Because of its extensive range of biological activities, zinc deficiency can cause a wide range of deficiency symptoms. The symptoms of zinc deficiency are: acne, impaired sense of smell and taste, delayed wound healing, anorexia, decreased immunity, frequent infections, depression, photophobia, night blindness, problems with skin, hair and nails, menstrual problems, joint pain, and involuntary, cyclical movements of the eyeball (nystagmus).
- Zinc deficiency conditions were first reported in the 1950s in growing children and adolescent males from Iran, Iraq, and Turkey. Diets low in animal protein and high in phytate-containing grains produced symptoms of dwarfism, hypogonadism and failure to mature sexually.
- Pregnant women have greater zinc needs. Deficiency can cause impaired fetal development, low birth weight infants, and birth defects. Stretch marks during pregnancy are also partially due to zinc deficiency.
- Zinc deficiency can be caused by inadequate dietary intake due to foods grown on zinc depleted soils. Food processing also removes zinc, so fast foods and processed foods are also zinc depleted.
- Protein and/or calorie-restricted diets can lead to zinc deficiency.
- Zinc depletion is frequently seen in the following medical conditions: alcoholism, macular degeneration, diabetes, malignant melanoma, liver and kidney diseases, malabsorption syndromes such as celiac sprue, and inflammatory bowel diseases such as Crohn’s disease.
·
The best dietary sources of zinc are lean meats, liver, eggs, and seafood (especially oysters). Whole grain breads and cereals are also good sources of zinc.