- 1 What is Zinc
- 1.1 What Does Zinc Do
- 1.2 Zinc supplements
- 1.3 Other Sources of Zinc
- 1.4 What are some of the Benefits of Zinc on Health
- 1.5 How much zinc do you need ?
- 1.6 What foods provide zinc ?
- 1.7 Groups at Risk of Zinc Inadequacy
- 1.8 What happens if you don’t get enough zinc ?
- 1.9 Zinc Deficiency
- 1.10 Can too much zinc be harmful ?
- 1.11 Zinc and healthy eating
What is Zinc
Zinc is a nutrient that people need to stay healthy. Zinc is found in cells throughout the body, found mainly in bones, teeth, hair, skin, liver, muscle, leukocytes, and testes 1). It helps the immune system fight off invading bacteria and viruses. The body also needs zinc to make proteins and DNA, the genetic material in all cells. During pregnancy, infancy, and childhood, the body needs zinc to grow and develop properly. Zinc also helps wounds heal and is important for proper senses of taste and smell.
What Does Zinc Do
Zinc is an essential mineral that is naturally present in some foods, added to others, and available as a dietary supplement. Zinc is also found in many cold lozenges and some over-the-counter drugs sold as cold remedies.
Zinc is involved in numerous aspects of cellular metabolism. It is required for the catalytic activity of approximately 100 enzymes, including many nicotinamide adenine dinucleotide (NADH) dehydrogenases, RNA and DNA polymerases, and DNA transcription factors as well as alkaline phosphatase, superoxide dismutase, and carbonic anhydrase 2), 3) and it plays a role in immune function 4), 5), protein synthesis 6), wound healing 7), DNA synthesis 8), 9) and cell division 10). Zinc also supports normal growth and development during pregnancy, childhood, and adolescence 11), 12), 13) and is required for proper sense of taste and smell 14). A daily intake of zinc is required to maintain a steady state because the body has no specialized zinc storage system 15).
Supplements contain several forms of zinc, including zinc gluconate, zinc sulfate, and zinc acetate 16). The percentage of elemental zinc varies by form. For example, approximately 23% of zinc sulfate consists of elemental zinc; thus, 220 mg of zinc sulfate contains 50 mg of elemental zinc. The elemental zinc content appears in the Supplement Facts panel on the supplement container. Research has not determined whether differences exist among forms of zinc in absorption, bioavailability, or tolerability 17).
In addition to standard tablets and capsules, some zinc-containing cold lozenges are labeled as dietary supplements.
- Interactions with iron and copper
Iron-deficiency anemia is a serious world-wide public health problem. Iron fortification programs have been credited with improving the iron status of millions of women, infants, and children. Fortification of foods with iron does not significantly affect zinc absorption. However, large amounts of supplemental iron (greater than 25 mg) might decrease zinc absorption 18). Taking iron supplements between meals helps decrease its effect on zinc absorption 19).
High zinc intakes can inhibit copper absorption, sometimes producing copper deficiency and associated anemia 20), 21). For this reason, dietary supplement formulations containing high levels of zinc, such as the one used in the Age-Related Eye Disease Study Research Group (AREDS) study 22), sometimes contain copper.
Other Sources of Zinc
Zinc is present in several products, including some labeled as homeopathic medications, sold over the counter for the treatment and prevention of colds. Numerous case reports of anosmia (loss of the sense of smell), in some cases long-lasting or permanent, have been associated with the use of zinc-containing nasal gels or sprays 23), 24). In June 2009, the FDA warned consumers to stop using three zinc-containing intranasal products because they might cause anosmia 25). The manufacturer recalled these products from the marketplace. Currently, these safety concerns have not been found to be associated with cold lozenges containing zinc.
Zinc is also present in some denture adhesive creams at levels ranging from 17–34 mg/g 26). While use of these products as directed (0.5–1.5 g/day) is not of concern, chronic, excessive use can lead to zinc toxicity, resulting in copper deficiency and neurologic disease. Such toxicity has been reported in individuals who used 2 or more standard 2.4 oz tubes of denture cream per week 27), 28). Many denture creams have now been reformulated to eliminate zinc.
What are some of the Benefits of Zinc on Health
- Age-related macular degeneration (AMD):
Researchers have suggested that both zinc and antioxidants delay the progression of age-related macular degeneration (AMD) and vision loss, possibly by preventing cellular damage in the retina 29), 30). In a population-based cohort study in the Netherlands, high dietary intake of zinc as well as beta carotene, vitamin C, and vitamin E was associated with reduced risk of AMD in elderly subjects 31). However, the authors of a systematic review and meta-analysis published in 2007 concluded that zinc is not effective for the primary prevention of early AMD 32), although zinc might reduce the risk of progression to advanced AMD.
The Age-Related Eye Disease Study (AREDS), a large, randomized, placebo-controlled, clinical trial (n = 3,597), evaluated the effect of high doses of selected antioxidants (500 mg vitamin C, 400 IU vitamin E, and 15 mg beta-carotene) with or without zinc (80 mg as zinc oxide) on the development of advanced AMD in older individuals with varying degrees of AMD 33). Participants also received 2 mg copper to prevent the copper deficiency associated with high zinc intakes. After an average follow-up period of 6.3 years, supplementation with antioxidants plus zinc (but not antioxidants alone) significantly reduced the risk of developing advanced AMD and reduced visual acuity loss. Zinc supplementation alone significantly reduced the risk of developing advanced AMD in subjects at higher risk but not in the total study population. Visual acuity loss was not significantly affected by zinc supplementation alone. A follow-up AREDS2 study confirmed the value of this supplement in reducing the progression of AMD over a median follow-up period of 5 years 34). Importantly, AREDS2 revealed that a formulation providing 25 mg zinc (about one-third the amount in the original AREDS formulation) provided the same protective effect against developing advanced AMD.
Two other small clinical trials evaluated the effects of supplementation with 200 mg zinc sulfate (providing 45 mg zinc) for 2 years in subjects with drusen or macular degeneration. Zinc supplementation significantly reduced visual acuity loss in one of the studies 35) but had no effect in the other 36).
A Cochrane review concluded that the evidence supporting the use of antioxidant vitamins and zinc for AMD comes primarily from the AREDS study 37). Individuals who have or are developing AMD should talk to their health care provider about taking a zinc-containing AREDS supplement.
- The common cold
Researchers have hypothesized that zinc could reduce the severity and duration of cold symptoms by directly inhibiting rhinovirus binding and replication in the nasal mucosa and suppressing inflammation 38), 39). Although studies examining the effect of zinc treatment on cold symptoms have had somewhat conflicting results, overall zinc appears to be beneficial under certain circumstances. Several studies are described below in which zinc is administered as a lozenge or zinc-containing syrup that temporarily “sticks” in the mouth and throat. This allows zinc to make contact with the rhinovirus in those areas.
In a randomized, double-blind, placebo-controlled clinical trial, 50 subjects (within 24 hours of developing the common cold) took a zinc acetate lozenge (13.3 mg zinc) or placebo every 2–3 wakeful hours. Compared with placebo, the zinc lozenges significantly reduced the duration of cold symptoms (cough, nasal discharge, and muscle aches) 40).
In another clinical trial involving 273 participants with experimentally induced colds, zinc gluconate lozenges (providing 13.3 mg zinc) significantly reduced the duration of illness compared with placebo but had no effect on symptom severity 41). However, treatment with zinc acetate lozenges (providing 5 or 11.5 mg zinc) had no effect on either cold duration or severity. Neither zinc gluconate nor zinc acetate lozenges affected the duration or severity of cold symptoms in 281 subjects with natural (not experimentally induced) colds in another trial 42).
In 77 participants with natural colds, a combination of zinc gluconate nasal spray and zinc orotate lozenges (37 mg zinc every 2–3 wakeful hours) was also found to have no effect on the number of asymptomatic patients after 7 days of treatment 43).
In September of 2007, Caruso and colleagues published a structured review of the effects of zinc lozenges, nasal sprays, and nasal gels on the common cold 44). Of the 14 randomized, placebo-controlled studies included, 7 (5 using zinc lozenges, 2 using a nasal gel) showed that the zinc treatment had a beneficial effect and 7 (5 using zinc lozenges, 1 using a nasal spray, and 1 using lozenges and a nasal spray) showed no effect.
More recently, a Cochrane review concluded that “zinc (lozenges or syrup) is beneficial in reducing the duration and severity of the common cold in healthy people, when taken within 24 hours of onset of symptoms” 45). The author of another review completed in 2004 also concluded that zinc can reduce the duration and severity of cold symptoms 46). However, more research is needed to determine the optimal dosage, zinc formulation and duration of treatment before a general recommendation for zinc in the treatment of the common cold can be made 47).
As previously noted, the safety of intranasal zinc has been called into question because of numerous reports of anosmia (loss of smell), in some cases long-lasting or permanent, from the use of zinc-containing nasal gels or sprays 48), 49), 50).
- Zinc supplementation for the prevention of pneumonia in children aged two to 59 months
Recent Cochrane Review published 4th December 2016, showed that zinc supplementation was significantly associated with reducing the incidence and prevalence of pneumonia among children aged from two to 59 months 51).
- Diarrhea in children
Children in developing countries often die from diarrhea. Studies show that zinc dietary supplements help reduce the symptoms and duration of diarrhea in these children, many of whom are zinc deficient or otherwise malnourished. The World Health Organization and UNICEF recommend that children with diarrhea take zinc for 10–14 days (20 mg/day, or 10 mg/day for infants under 6 months). It is not clear whether zinc dietary supplements can help treat diarrhea in children who get enough zinc, such as most children in the United States.
Acute diarrhea is associated with high rates of mortality among children in developing countries 52). Zinc deficiency causes alterations in immune response that probably contribute to increased susceptibility to infections, such as those that cause diarrhea, especially in children 53).
Studies show that poor, malnourished children in India, Africa, South America, and Southeast Asia experience shorter courses of infectious diarrhea after taking zinc supplements 54). The children in these studies received 4–40 mg of zinc a day in the form of zinc acetate, zinc gluconate, or zinc sulfate 55).
In addition, results from a pooled analysis of randomized controlled trials of zinc supplementation in developing countries suggest that zinc helps reduce the duration and severity of diarrhea in zinc-deficient or otherwise malnourished children 56). Similar findings were reported in a meta-analysis published in 2008 and a 2007 review of zinc supplementation for preventing and treating diarrhea 57), 58). The effects of zinc supplementation on diarrhea in children with adequate zinc status, such as most children in the United States, are not clear.
The World Health Organization and UNICEF now recommend short-term zinc supplementation (20 mg of zinc per day, or 10 mg for infants under 6 months, for 10–14 days) to treat acute childhood diarrhea 59).
In a 2016 Cochrane Review 60) involving thirty-three trials that included 10,841 children, among children with acute diarrhoea, the authors don’t know if treating children with zinc has an effect on death or number of children hospitalized (very low certainty evidence). In children older than six months, zinc supplementation may shorten the average duration of diarrhoea by around half a day (low certainty evidence), and probably reduces the number of children whose diarrhoea persists until day seven (moderate certainty evidence). In children with signs of malnutrition the effect appears greater, reducing the duration of diarrhoea by around a day (high certainty evidence). Conversely, in children younger than six months, the available evidence suggests zinc supplementation may have no effect on the mean duration of diarrhoea (low certainty evidence), or the number of children who still have diarrhoea on day seven (low certainty evidence). Zinc supplementation increased the risk of vomiting in both age groups (moderate certainty evidence). Among children with persistent diarrhoea, zinc supplementation probably shortens the average duration of diarrhoea by around 16 hours (moderate certainty) but it probably increases the risk of vomiting (moderate certainty evidence). The review authors concluded that zinc supplementation may be of benefit in children aged six months or more, in areas where the prevalenceof zinc deficiency or the prevalence of malnutrition is high 61). In addition, the current evidence does not support the use of zinc supplementation in children less six months of age, in well-nourished children, and in settings where children are at low risk of zinc deficiency 62).
- Wound healing
Zinc helps maintain the integrity of skin and mucosal membranes 63). Patients with chronic leg ulcers have abnormal zinc metabolism and low serum zinc levels , and clinicians frequently treat skin ulcers with zinc supplements 64). The authors of a systematic review concluded that zinc sulfate might be effective for treating leg ulcers in some patients who have low serum zinc levels 65), 66). However, research has not shown that the general use of zinc sulfate in patients with chronic leg ulcers or arterial or venous ulcers is effective 67).
- Immune system
Severe zinc deficiency depresses immune function 68), and even mild to moderate degrees of zinc deficiency can impair macrophage and neutrophil functions, natural killer cell activity, and complement activity 69). The body requires zinc to develop and activate T-lymphocytes 70), 71). Individuals with low zinc levels have shown reduced lymphocyte proliferation response to mitogens and other adverse alterations in immunity that can be corrected by zinc supplementation 72), 73). These alterations in immune function might explain why low zinc status has been associated with increased susceptibility to pneumonia and other infections in children in developing countries and the elderly 74), 75), 76), 77).
How much zinc do you need ?
Intake recommendations for zinc and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB) at the Institute of Medicine of the National Academies 78). Dietary Reference Intake is the general term for a set of reference values used for planning and assessing nutrient intakes of healthy people. These values, which vary by age and gender 79), include the following:
- Recommended Dietary Allowance (RDA): average daily level of intake sufficient to meet the nutrient requirements of nearly all (97%–98%) healthy individuals.
- Adequate Intake (AI): established when evidence is insufficient to develop an RDA and is set at a level assumed to ensure nutritional adequacy.
Tolerable Upper Intake Level (UL): maximum daily intake unlikely to cause adverse health effects 80).
The current RDAs for zinc are listed in Table 1 81). For infants aged 0 to 6 months, the FNB established an AI for zinc that is equivalent to the mean intake of zinc in healthy, breastfed infants.
Table 1. The amount of zinc you need each day depends on your age. Average daily recommended amounts for different ages are listed below in milligrams (mg):
|Life Stage||Recommended Amount|
|Birth to 6 months||2 mg|
|Infants 7–12 months||3 mg|
|Children 1–3 years||3 mg|
|Children 4–8 years||5 mg|
|Children 9–13 years||8 mg|
|Teens 14–18 years (boys)||11 mg|
|Teens 14–18 years (girls)||9 mg|
|Adults (men)||11 mg|
|Adults (women)||8 mg|
|Pregnant teens||12 mg|
|Pregnant women||11 mg|
|Breastfeeding teens||13 mg|
|Breastfeeding women||12 mg|
Most infants (especially those who are formula fed), children, and adults in the United States consume recommended amounts of zinc according to two national surveys, the 1988–1991 National Health and Nutrition Examination Survey 82) and the 1994 Continuing Survey of Food Intakes of Individuals 83).
However, some evidence suggests that zinc intakes among older adults might be marginal. An analysis of National Health and Nutrition Examination Survey data found that 35%–45% of adults aged 60 years or older had zinc intakes below the estimated average requirement of 6.8 mg/day for elderly females and 9.4 mg/day for elderly males. When the investigators considered intakes from both food and dietary supplements, they found that 20%–25% of older adults still had inadequate zinc intakes 84).
Zinc intakes might also be low in older adults from the 2%–4% of U.S. households that are food insufficient (sometimes or often not having enough food) 85). Data from National Health and Nutrition Examination Survey indicate that adults aged 60 years or older from food-insufficient families had lower intakes of zinc and several other nutrients and were more likely to have zinc intakes below 50% of the RDA on a given day than those from food-sufficient families 86).
What foods provide zinc ?
Zinc is found in a wide variety of foods. You can get recommended amounts of zinc by eating a variety of foods including the following:
- Oysters, which are the best source of zinc. Oysters contain more zinc per serving than any other food.
- Red meat, poultry, seafood such as crab and lobsters, and fortified breakfast cereals, which are also good sources of zinc. They provide the majority of zinc in the American diet.
- Beans, nuts, whole grains, and dairy products, which provide some zinc.
Phytates (is the principal storage form of phosphorus in many plant tissues, especially bran and seeds), which are present in whole-grain breads, cereals, legumes, and other foods—bind zinc and inhibit its absorption 87), 88), 89). Thus, the bioavailability of zinc from grains and plant foods is lower than that from animal foods, although many grain- and plant-based foods are still good sources of zinc 90).
The U.S. Department of Agriculture’s (USDA’s) Nutrient Database website 91) lists the nutrient content of many foods and provides a comprehensive list of foods containing zinc arranged by nutrient content 92) and by food name 93).
|Oysters, cooked, breaded and fried, 3 ounces||74.0||493|
|Beef chuck roast, braised, 3 ounces||7.0||47|
|Crab, Alaska king, cooked, 3 ounces||6.5||43|
|Beef patty, broiled, 3 ounces||5.3||35|
|Breakfast cereal, fortified with 25% of the DV for zinc, ¾ cup serving||3.8||25|
|Lobster, cooked, 3 ounces||3.4||23|
|Pork chop, loin, cooked, 3 ounces||2.9||19|
|Baked beans, canned, plain or vegetarian, ½ cup||2.9||19|
|Chicken, dark meat, cooked, 3 ounces||2.4||16|
|Yogurt, fruit, low fat, 8 ounces||1.7||11|
|Cashews, dry roasted, 1 ounce||1.6||11|
|Chickpeas, cooked, ½ cup||1.3||9|
|Cheese, Swiss, 1 ounce||1.2||8|
|Oatmeal, instant, plain, prepared with water, 1 packet||1.1||7|
|Milk, low-fat or non fat, 1 cup||1.0||7|
|Almonds, dry roasted, 1 ounce||0.9||6|
|Kidney beans, cooked, ½ cup||0.9||6|
|Chicken breast, roasted, skin removed, ½ breast||0.9||6|
|Cheese, cheddar or mozzarella, 1 ounce||0.9||6|
|Peas, green, frozen, cooked, ½ cup||0.5||3|
|Flounder or sole, cooked, 3 ounces||0.3||2|
* DV = Daily Value. DVs were developed by the U.S. Food and Drug Administration to help consumers compare the nutrient contents of products within the context of a total diet. The DV for zinc is 15 mg for adults and children age 4 and older. Food labels, however, are not required to list zinc content unless a food has been fortified with this nutrient. Foods providing 20% or more of the DV are considered to be high sources of a nutrient.[Source 94)]
Most Americans get enough zinc from the foods they eat.
However, certain groups of people are more likely than others to have trouble getting enough zinc:
- People who have had gastrointestinal surgery, such as weight loss surgery, or who have digestive disorders, such as ulcerative colitis or Crohn’s disease. These conditions can both decrease the amount of zinc that the body absorbs and increase the amount lost in the urine.
- Vegetarians because they do not eat meat, which is a good source of zinc. Also, the beans and grains they typically eat have compounds that keep zinc from being fully absorbed by the body. For this reason, vegetarians might need to eat as much as 50% more zinc than the recommended amounts.
- Older infants who are breastfed because breast milk does not have enough zinc for infants over 6 months of age. Older infants who do not take formula should be given foods that have zinc such as pureed meats. Formula-fed infants get enough zinc from infant formula.
- Alcoholics because alcoholic beverages decrease the amount of zinc that the body absorbs and increase the amount lost in the urine. Also, many alcoholics eat a limited amount and variety of food, so they may not get enough zinc.
- People with sickle cell disease because they might need more zinc.
Groups at Risk of Zinc Inadequacy
In North America, overt zinc deficiency is uncommon 95). When zinc deficiency does occur, it is usually due to inadequate zinc intake or absorption, increased losses of zinc from the body, or increased requirements for zinc 96), 97), 98). People at risk of zinc deficiency or inadequacy need to include good sources of zinc in their daily diets. Supplemental zinc might also be appropriate in certain situations.
- People with gastrointestinal and other diseases
Gastrointestinal surgery and digestive disorders (such as ulcerative colitis, Crohn’s disease, and short bowel syndrome) can decrease zinc absorption and increase endogenous zinc losses primarily from the gastrointestinal tract and, to a lesser extent, from the kidney 99), 100), 101), 102). Other diseases associated with zinc deficiency include malabsorption syndrome, chronic liver disease, chronic renal disease, sickle cell disease, diabetes, malignancy, and other chronic illnesses 103). Chronic diarrhea also leads to excessive loss of zinc 104).
The bioavailability of zinc from vegetarian diets is lower than from non-vegetarian diets because vegetarians do not eat meat, which is high in bioavailable zinc and may enhance zinc absorption. In addition, vegetarians typically eat high levels of legumes and whole grains, which contain phytates that bind zinc and inhibit its absorption 105), 106).
Vegetarians sometimes require as much as 50% more of the RDA for zinc than non-vegetarians 107). In addition, they might benefit from using certain food preparation techniques that reduce the binding of zinc by phytates and increase its bioavailability. Techniques to increase zinc bioavailability include soaking beans, grains, and seeds in water for several hours before cooking them and allowing them to sit after soaking until sprouts form 108). Vegetarians can also increase their zinc intake by consuming more leavened grain products (such as bread) than unleavened products (such as crackers) because leavening partially breaks down the phytate; thus, the body absorbs more zinc from leavened grains than unleavened grains.
- Pregnant and lactating women
Pregnant women, particularly those starting their pregnancy with marginal zinc status, are at increased risk of becoming zinc insufficient due, in part, to high fetal requirements for zinc 109). Lactation can also deplete maternal zinc stores 110). For these reasons, the RDA for zinc is higher for pregnant and lactating women than for other women (see Table 1) 111).
- Older infants who are exclusively breastfed
Breast milk provides sufficient zinc (2 mg/day) for the first 4–6 months of life but does not provide recommended amounts of zinc for infants aged 7–12 months, who need 3 mg/day112), 113). In addition to breast milk, infants aged 7–12 months should consume age-appropriate foods or formula containing zinc 114). Zinc supplementation has improved the growth rate in some children who demonstrate mild-to-moderate growth failure and who have a zinc deficiency 115), 116).
- People with sickle cell disease
Results from a large cross-sectional survey suggest that 44% of children with sickle cell disease have a low plasma zinc concentration 117), possibly due to increased nutrient requirements and/or poor nutritional status 118). Zinc deficiency also affects approximately 60%–70% of adults with sickle cell disease 119). Zinc supplementation has been shown to improve growth in children with sickle cell disease 120).
Approximately 30%–50% of alcoholics have low zinc status because ethanol consumption decreases intestinal absorption of zinc and increases urinary zinc excretion 121). In addition, the variety and amount of food consumed by many alcoholics is limited, leading to inadequate zinc intake 122), 123), 124).
What happens if you don’t get enough zinc ?
Zinc deficiency is rare in North America. It causes slow growth in infants and children, delayed sexual development in adolescents and impotence in men. Zinc deficiency also causes hair loss, diarrhea, eye and skin sores and loss of appetite. Weight loss, problems with wound healing, decreased ability to taste food, and lower alertness levels can also occur.
Many of these symptoms can be signs of problems other than zinc deficiency. If you have these symptoms, your doctor can help determine whether you might have a zinc deficiency.
Dietary deficiency is unlikely in healthy persons. Secondary zinc deficiency can develop in the following 125):
- Patients taking diuretics
- Patients with diabetes mellitus, sickle cell disease, chronic kidney disease, liver disease, chronic alcoholism, or malabsorption
- Patients with stressful conditions (eg, sepsis, burns, head injury)
- Elderly institutionalized and homebound patients (common).
Maternal zinc deficiency may cause fetal malformations and low birth weight 126).
Zinc deficiency in children causes impaired growth, impaired taste (hypogeusia), delayed sexual maturation, and hypogonadism. In children or adults, manifestations also include alopecia, impaired immunity, anorexia, dermatitis, night blindness, anemia, lethargy, and impaired wound healing 127).
Zinc deficiency should be suspected in undernourished patients with typical symptoms or signs. However, because many of the symptoms and signs are nonspecific, clinical diagnosis of mild zinc deficiency is difficult. Laboratory diagnosis is also difficult. Low albumin levels, common in zinc deficiency, make serum zinc levels difficult to interpret; diagnosis usually requires the combination of low levels of zinc in serum and increased urinary zinc excretion. If available, isotope studies can measure zinc status more accurately.
Zinc deficiency is characterized by growth retardation, loss of appetite, and impaired immune function. In more severe cases, zinc deficiency causes hair loss, diarrhea, delayed sexual maturation, impotence, hypogonadism in males, and eye and skin lesions 128), 129), 130), 131). Weight loss, delayed healing of wounds, taste abnormalities, and mental lethargy can also occur 132), 133), 134), 135), 136), 137), 138). Many of these symptoms are non-specific and often associated with other health conditions; therefore, a medical examination is necessary to ascertain whether a zinc deficiency is present.
Zinc nutritional status is difficult to measure adequately using laboratory tests 139), 140), 141) due to its distribution throughout the body as a component of various proteins and nucleic acids 142). Plasma or serum zinc levels are the most commonly used indices for evaluating zinc deficiency, but these levels do not necessarily reflect cellular zinc status due to tight homeostatic control mechanisms 143). Clinical effects of zinc deficiency can be present in the absence of abnormal laboratory indices . Clinicians consider risk factors (such as inadequate caloric intake, alcoholism, and digestive diseases) and symptoms of zinc deficiency (such as impaired growth in infants and children) when determining the need for zinc supplementation 144).
Treatment of zinc deficiency consists of elemental zinc 15 to 120 mg po once/day until symptoms and signs resolve 145).
Can too much zinc be harmful ?
Yes, if you get too much. Signs of too much zinc include nausea, vomiting, loss of appetite, stomach cramps, diarrhea, and headaches. When people take too much zinc for a long time, they sometimes have problems such as low copper levels, lower immunity, and low levels of HDL cholesterol (the “good” cholesterol).
- Zinc Toxicity
The recommended upper limit in adults for zinc intake is 40 mg/day; the upper limit is lower for younger people. Toxicity is rare 146).
Ingesting doses of elemental zinc ranging from 100 to 150 mg/day for prolonged periods interferes with copper metabolism and causes low blood copper levels, RBC microcytosis, neutropenia, and impaired immunity; higher doses should be given only for short periods of time and the patient followed closely.
Ingesting larger amounts (200 to 800 mg/day), usually by consuming acidic food or drinking from a galvanized (zinc-coated) container, can cause anorexia, vomiting, and diarrhea. Chronic toxicity may result in copper deficiency and may cause nerve damage.
Metal fume fever, also called brass-founders’ ague or zinc shakes, is caused by inhaling industrial zinc oxide fumes; it results in fever, dyspnea, nausea, fatigue, and myalgias. Symptom onset is usually 4 to 12 h after exposure. Symptoms usually resolve after 12 to 24 h in a zinc-free environment.
Diagnosis of zinc toxicity is usually based on the time course and a history of exposure.
Treatment of zinc toxicity consists of eliminating exposure to zinc; no antidotes are available.
Zinc and healthy eating
People should get most of their nutrients from food because foods contain vitamins, minerals, dietary fiber and other substances that benefit health. In some cases, fortified foods and dietary supplements may provide nutrients that otherwise may be consumed in less-than-recommended amounts.
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