Zinc is an essential trace element, necessary for plants, animals, and microorganisms.
Zinc is found in nearly 100 specific enzymes (other sources say 300), serves as structural ions in transcription factors and is stored and transferred in metallothioneins.
It is typically the second most abundant transition metal in organisms after iron and it is the only metal which appears in all enzyme classes.
In humans, zinc plays ubiquitous biological roles.
It interacts with a wide range of organic ligands, and has roles in the metabolism of RNA and DNA, signal transduction, and gene expression.
It also regulates apoptosis*. A 2006 study estimated that about 10% of human proteins (2800) potentially bind zinc, in addition to hundreds which transport and traffic zinc.
* is the process of programmed cell death (PCD) that may occur in multicellular organisms.
Functions:
Zinc is included in most single tablet over-the-counter daily vitamin and mineral supplements. Preparations include zinc oxide, zinc acetate, and zinc gluconate.
It is believed to possess antioxidant properties, which may protect against accelerated aging of the skin and muscles of the body; studies differ as to its effectiveness.
Zinc also helps speed up the healing process after an injury.
It is also suspected of being beneficial to the body's immune system.
Zinc serves as a simple, inexpensive, and critical tool for treating diarrheal episodes among children in the developing world. Zinc becomes depleted in the body during diarrhea, but recent studies suggest that replenishing zinc with a 10- to 14-day course of treatment can reduce the duration and severity of diarrheal episodes and may also prevent future episodes for up to three months.
The Age-Related Eye Disease Study determined that zinc can be part of an effective treatment for age-related macular degeneration.
Zinc supplementation is an effective treatment for acrodermatitis enteropathica, a genetic disorder affecting zinc absorption that was previously fatal to babies born with it.
Gastroenteritis is strongly attenuated by ingestion of zinc.
In 2011, researchers at John Jay College of Criminal Justice reported that dietary zinc supplements can mask the presence of drugs in urine.
Although not yet tested as a therapy in humans, a growing body of evidence indicates that zinc may preferentially kill prostate cancer cells.
Because zinc naturally homes to the prostate and because the prostate is accessible with relatively non-invasive procedures, its potential as a chemotherapeutic agent in this type of cancer has shown promise.
However, other studies have demonstrated that chronic use of zinc supplements in excess of the recommended dosage may actually increase the chance of developing prostate cancer, also likely due to the natural buildup of this heavy metal in the prostate.
Zinc lozenges and the common cold:
There is strong evidence that zinc lozenges shorten the duration of colds.The most positive results have been found in studies in which zinc acetate was used, apparently because acetate does not bind zinc ions. Three high dose trials which used zinc acetate found an average 42% reduction in the duration of colds.
There is no concern of zinc toxicity in the dosages that were used in the zinc acetate trials with 80–100 mg/day of elemental zinc. The effect of zinc lozenges seems to take place locally in the oropharynx so that it is not a systemic effect, i.e., the effect is not a dietary supplement effect.
Topical use:
Topical administration of zinc preparations include ones used on the skin, often in the form of zinc oxide.Zinc preparations can protect against sunburn in the summer and windburn in the winter.
Applied thinly to a baby's diaper area (perineum) with each diaper change, it can protect against diaper rash.
Chelated zinc is used in toothpastes and mouthwashes to prevent bad breath.
Zinc pyrithione is widely applied in shampoos because of its anti-dandruff function.
Zinc ions are effective antimicrobial agents even at low concentrations.
What food zinc is found in:
Oysters, lobster and red meats, especially beef, lamb and liver have some of the highest concentrations of zinc in food.
Zinc supplements should only be ingested when there is zinc deficiency or increased zinc necessity (e.g. after surgeries, traumata or burns).
Persistent intake of high doses of zinc can cause copper deficiency.
The concentration of zinc in plants varies based on levels of the element in soil.
When there is adequate zinc in the soil, the food plants that contain the most zinc are wheat (germ and bran) and various seeds (sesame, poppy, alfalfa, celery, mustard).
Zinc is also found in beans, nuts, almonds, whole grains, pumpkin seeds, sunflower seeds and blackcurrant.
Other sources include fortified food and dietary supplements, which come in various forms.
A 1998 review concluded that zinc oxide, one of the most common supplements in the United States, and zinc carbonate are nearly insoluble and poorly absorbed in the body.
Top 10 Foods Highest in Zinc:
#1: Seafood (Cooked Oysters)
Zinc in 100g Per 3oz (85g) Per 6 Oysters (42g)
78.6mg 66.8mg 33.0mg
Other Seafood High in Zinc: Crab, and Lobster.
#2: Beef and Lamb (Cooked Lean Beef Shortribs)
Zinc in 100g 1 Rack of Ribs (315g) 1 Lean Ribeye Fillet (129g)
12.3mg 38.7mg 14.2mg
Lamb is also a good source of Zinc: Lean Foreshank, Lean Shoulder and Lean Cubed Lamb for Stewing.
#3: Wheat Germ (Toasted)
Zinc in 100g Per Cup (113g) Per Ounce (28g)
16.7mg 18.8mg 4.7mg
Crude or Untoasted Wheat Germ is also a good source of Zinc.
#4: Spinach
Zinc in 100g (Cooked) Per Cup (Cooked - 180g) 100g (Raw)
0.8mg 1.4mg 0.5mg
Other Green Leafy Vegetables High in Zinc: Amaranth Leaves, cooked, and Endive and Radiccio, raw.
#5: Pumpkin and Squash Seeds
Zinc in 100g Per Cup (64g) Per Ounce (28g)
10.3mg 6.6mg 2.9mg
Other Seeds High in Zinc: Sunflower, Chia, and Flaxseeds.
#6: Nuts (Cashews)
Zinc in 100g (Roasted) Per Cup (137g) Per Ounce (28g)
5.6mg 7.7mg 1.6mg
Other Nuts High in Zinc: Pine nuts, Pecans, Almonds, Walnuts, Peanuts, and Hazelnuts.
#7: Cocoa and Chocolate (Cocoa Powder)
Zinc in 100g Per Cup (86g) Per Tablespoon (5g)
6.8mg 5.9mg 0.3mg
Dark baking Chocolate is also high in Zinc.
#8: Pork & Chicken (Cooked Lean Pork Shoulder)
Zinc in 100g Per Steak (147g) Per 3oz (85g)
5.0mg 7.4mg 4.3mg
Chicken is also High in Zinc.
#9: Beans (Cooked Mung Beans)
Zinc in 100g Per Cup (124g) Per 3oz (85g)
0.5mg 0.6mgm 0.4mg
Other Beans High in Zinc: Baked Beans, Chickpeas and Kidney Beans.
#10: Mushrooms (Cooked White Mushrooms)
Zinc in 100g Per Cup Pieces (156g) Per Mushroom (12g)
0.9mg 1.4mg 0.1mg
Other Mushrooms High in Zinc: Morel, raw, Brown, raw and Portabella, grilled, Oyster, raw, and White, raw.
Top 10 High Zinc Foods by Nutrient Density
Fortified Cereals 52mg per 100 gram serving 15.5mg (103% DV) per cup.
Low Fat Yogurt with Fruit 0.7mg per 100 gram serving 1.6mg per cup (245 grams).
Milk 0.4mg per 100 gram serving 1mg per cup (244 grams)
Chicken Breast 1mg per 100 gram serving 1.4mg per cup (140 grams) 0.9mg for half a chicken breast (86 grams)
Cheddar Cheese 3.1mg per 100 gram serving 3.5mg per cup (113 grams) 0.9mg per ounce(oz) (28 grams).
Mozzarella 2.9mg per 100 gram serving 3.3mg per cup (112 grams) 0.8mg per ounce(oz) (28 grams).
Watermelon Seeds 10.2mg per 100 gram serving 11.1mg per cup (180 grams) 2.9mg per ounce (28 grams).
Venison (Cooked) 8.6mg per 100 gram serving 7.3mg per 3oz (85 grams) 25.3mg per roast (293 grams).
Veal 7.4mg per 100 gram serving 6.3mg per 3oz (85 grams) 12.9mg per piece (174 grams).
Fortified Peanut Butter 15.1mg per 100 gram serving 39.0mg per cup (258 grams) 4.8mg per 2 Tablespoons (32 grams).
Alfalfa Sprouts 0.9mg per 100 gram serving 0.3mg per cup (33 grams) 0.1mg per 2 Tablespoons (6 grams).
Asparagus (Cooked) 0.6mg per 100 gram serving 1.1mg per cup (180 grams) 0.4mg per 4 Spears (60 grams).
Rice Bran 6.0mg per 100 gram serving 7.1mg per cup (118 grams).
Hearts of Palm 3.7mg per 100 gram serving 2.1mg per 2 oz (54grams)
Seaweed (Kelp) 1.2mg per 100 gram serving 0.1mg per 2 Tablespoons (10 grams).
Napa Cabbage (Cooked) 0.1mg per 100 gram serving 0.2mg per cup (109 grams).
Green Peas 1.2mg per 100 gram serving 1.9mg per cup (160 grams) 1.5mg per half cup (80 grams).
Sesame Seeds (Tahini) 10.5mg per 100 gram serving 1.5mg per tablespoon (14 grams) 2.9mg per 1 ounce serving (28 grams).
Flat Fish (Flounder or Sole) 0.6mg per 100 gram serving.
What symptoms and disorders zinc deficiency may cause:
Zinc deficiency is usually due to insufficient dietary intake, but can be associated with malabsorption, acrodermatitis enteropathica, chronic liver disease, chronic renal disease, sickle cell disease, diabetes, malignancy, and other chronic illnesses.
Symptoms of mild zinc deficiency are diverse.
Clinical outcomes include depressed growth, diarrhea, impotence and delayed sexual maturation, alopecia, eye and skin lesions, impaired appetite, altered cognition, impaired host defense properties, defects in carbohydrate utilization, and reproductive teratogenesis.
Mild zinc deficiency depresses immunity, although excessive zinc does also.
Too little zinc can lead to hair loss, skin problems, diarrhoea and poor wound healing.
Animals with a diet deficient in zinc require twice as much food in order to attain the same weight gain as animals given sufficient zinc.
Zinc is an essential mineral of exceptional biologic and public health importance. Zinc deficiency affects about two billion people in the developing world and is associated with many diseases.
In children it causes growth retardation, delayed sexual maturation, infection susceptibility, and diarrhea, contributing to the death of about 800,000 children worldwide per year.
Zinc deficiency may have effects on virtually all parts of the human immune system.
Zinc deficiency has been associated with major depressive disorder (MDD).
Despite some concerns, western vegetarians and vegans have not been found to suffer from overt zinc deficiencies any more than meat-eaters.
Major plant sources of zinc include cooked dried beans, sea vegetables, fortified cereals, soyfoods, nuts, peas, and seeds.
However, phytates* in many whole-grains and fiber in many foods may interfere with zinc absorption and marginal zinc intake has poorly understood effects. There is some evidence to suggest that more than the US RDA (15 mg) of zinc daily may be needed in those whose diet is high in phytates(#), such as some vegetarians.
These considerations must be balanced against the fact that there is a paucity of adequate zinc biomarkers, and the most widely used indicator, plasma zinc, has poor sensitivity and specificity.
Diagnosing zinc deficiency is a persistent challenge.
* Phytic acid (known as inositol hexakisphosphate (IP6), or phytate when in salt form), is the principal storage form of phosphorus in many plant tissues, especially bran and seeds.
Phytate is not digestible to humans or nonruminant animals.
(#) Inositol or its phosphates and associated lipids are found in many foods, in particular fruit, especially cantaloupe and oranges. In plants, the hexaphosphate of inositol, phytic acid or its salts, the phytates, are found. These serve as phosphate stores in the seed. Phytic acid occurs also in cereals with high bran content and also nuts and beans.
Problems related to excess zinc doses:
Excessive absorption of zinc suppresses copper and iron absorption.
Consumption of excess zinc can cause ataxia, lethargy and there is evidence of induced copper deficiency in those taking 100–300 mg of zinc daily.
A 2007 trial observed that elderly men taking 80 mg daily were hospitalized for urinary complications more often than those taking a placebo. The UK RDA of zinc is 5.5 to 9.5 mg for men and 4 -7 mg for women.
Levels, of 100-300 mg may interfere with the utilization of copper and iron or adversely affect cholesterol.
There is also a condition called the zinc shakes or "zinc chills" that can be induced by the inhalation of freshly formed zinc oxide formed during the welding of galvanized materials.
Zinc is a common ingredient of denture cream which may contain between 17 and 38 mg of zinc per gram. There have been claims of disability, and even death, due to excessive use of these products.
The U.S. Food and Drug Administration (FDA) has stated that zinc damages nerve receptors in the nose, which can cause anosmia. Reports of anosmia were also observed in the 1930s when zinc preparations were used in a failed attempt to prevent polio infections.On June 16, 2009, the FDA said that consumers should stop using zinc-based intranasal cold products and ordered their removal from store shelves. The FDA said the loss of smell can be life-threatening because people with impaired smell cannot detect leaking gas or smoke and cannot tell if food has spoiled before they eat.
Recommended doses for people in the UK:
The UK RDA of zinc is 5.5 to 9.5 mg for men and 4 -7 mg for women.