|Mineral Nutrient :: Zinc|
|Content Below:||What is Zinc · Benefits · Deficiency Signs · Foods · Supplements · RDA · Toxicity|
Zinc is one of the essential micro-minerals that the body needs for growth and development, and to function properly. It is present in all cells in the body, though most highly concentrated in the skin, hair, nails, eyes, bone and liver, and in men in the prostate and semen.
It is involved in stimulating over 100 different enzymes which control 300 biochemical reactions that sustain life. We need a small intake of it daily, as our bodies do not store zinc.
Zinc is found in different forms in food. These vary widely in response to processing and cooking. Water-soluble forms are more prone to loss. For instance, almost half the zinc in beans is lost during cooking.
It is also found in supplements, and in many cold lozenges and remedies.
Its role in the functioning of enzymes responsible for so many (over 300) bio-chemical processes in the body makes zinc vital to health. It is also a cofactor of superoxide dismutase (SOD), an important antioxidant enzyme.
It is one of the nutrients that the body uses to maintain healthy skin and mucous membranes, and to rebuild damaged skin, which makes it useful for skin disorders such as acne, eczema, and psoriasis. It is especially known for fighting flu, colds, and infections.
The many ways that zinc benefits the body are summarized here.
|::||Zinc Benefits & Functions|
|1.||constituent of the antioxidant enzyme superoxide dismutase (SOD) that helps fight harmful free radicals associated with degenerative diseases like cancer, Alzheimer’s, and cardiovascular disease|
|2.||essential for the body’s immune (defensive) system to work properly and for optimal functioning of immune cells|
|3.||promotes anti-viral activity and helps fight infections|
|4.||research suggests that zinc, together with other antioxidants may slow the progression of age-related macular degeneration and loss of vision, by minimising retinal cell damage|
|5.||plays a role in many enzymatic processes in the body, including those involved in carbohydrate and protein metabolism|
|6.||regulates cell division and synthesis of DNA (genetic material in cells), and is hence essential for reproduction, repair of the body, and normal growth especially in childhood and adolescence|
|7.||needed for normal fetal development|
|8.||needed for growth of the reproductive organs and for sperm maturation|
|9.||necessary for protein synthesis and collagen formation|
|10.||helps maintain integrity of skin and mucous membranes; important for preventing and healing leg and peptic / gastric ulcers and canker sores|
|11.||promotes healing of wounds, especially after burns or surgery|
|12.||has been shown to treat or reduce severity of acne vulgaris, especially when combined with other acne treatments|
|13.||regulates insulin activity and blood sugar balance for control of diabetes|
|14.||regulates metabolic rate (rate at which energy is used) and thyroid hormone production|
|15.||has been shown to help reduce symptoms of sickle cell anaemia|
|16.||some evidence that it improves the ratio of HDL (“good”) cholesterol to LDL (“bad”) cholesterol|
|17.||supports optimal functioning of smell and taste senses|
|18.||popularly used in prevention of colds and to lessen the severity and duration of cold symptoms like nasal congestion, coughing, hoarseness|
|19.||may protect the liver against damage from toxins like cadmium and lead|
|20.||may help treat herpes simplex|
|21.||regulates appetite, and appears to be beneficial in treating symptoms of anorexia nervosa in young adults|
|22.||may help children with beta-thalassemia to increase in height, if taken over a long period|
|23.||has been shown to reduce duration and severity of diarrhoea in zinc deficient or under-nourished children|
|24.||preliminary studies suggest that children with ADHD (attention deficit hyperactivity disorder) tend to have low zinc levels; but supplements appear to only reduce hyperactivity and impulsiveness without improving attention|
|25.||preliminary research indicates that zinc may be effective in managing Wilson’s disease (an inherited disorder of copper metabolism)|
|26.||studies with Crohn’s disease patients have shown some positive results|
Zinc Deficiency Symptoms and Causes
Severe deficiency, especially among children and younger adults, is rare, but research shows that up to one-third of older adults have zinc intakes below the recommended daily requirements, despite the fact that zinc is available in common foods.
At the same time, research is now showing that even mild deficiency can lead to health problems such as poor digestion, lower healing ability, lower resistance to disease, and other zinc deficiency symptoms.
Low levels of zinc can be due to insufficient intake of foods containing zinc or to intestinal problems such as irritable bowel disorders that lead to poor absorption of nutrients, or inadequate output by the pancreas, preventing proper digestion.
Birth control pills, caffeine, alcohol, dairy foods, and certain diuretics may reduce zinc absorption as well. Consume them separately from zinc.
Zinc levels can also be lowered because of conditions that cause the body to need more zinc, or to excrete more of it, such as liver cirrhosis, chronic diarrhea,diabetes, excess fibre intake, drinking of hard water, and profuse sweating (as for instance from athletic training or manual labour).
As foods high in zinc are mainly from animal sources, and the phytates in grains and legumes interfere with zinc absorption, those who don’t eat red meat might need to take fortified cereals or supplements.
The zinc deficiency symptoms that have been identified are tabled here.
|::||Zinc Deficiency Symptoms|
|1.||impaired sense of smell or taste (common zinc deficiency symptoms)|
|2.||impaired immune function, with frequent colds and infections|
|3.||susceptibility to pneumonia and other infections in malnourished children and the elderly, related to impaired immune function; reversible with zinc supplementation|
|4.||skin ulcers (patients with chronic leg ulcers often have low zinc levels)|
|5.||slow wound healing|
|6.||retardation of growth in infants and children|
|7.||delayed sexual maturation|
|8.||hypogonadism in males (where the body does not produce enough of the hormone testosterone needed for male growth and development)|
|9.||impotence or low sperm counts|
|10.||reduced thryoid hormone output|
|11.||lowered glucose tolerance with increased risk of diabetes|
|12.||decreased metabolic rate (rate at which the body uses up energy)|
|15.||lack of appetite|
|16.||unexplained weight loss|
|19.||skin rashes or skin lesions|
|20.||eye lesions, symptomized by pain, blurred vision, dry eyes or photophobia (excessive sensitivity to light)|
|21.||night blindness (difficulty with seeing in the dark)|
Generally the best sources of zinc are high-protein foods. Plant-foods and grains are not considered good sources, as the bio-availability of the zinc in them is low. Phytates present in legumes and whole-grains tend to bind with zinc and inhibit its absorption.
Apart from meat, most foods provide less than 10% of the recommended daily requirement per serving.
Foods high in zinc are
· liver · meat (beef, chicken, lamb, pork, venison) · mushrooms · raw oysters.
Other foods containing zinc include
· brewer’s yeast · fortified breakfast cereals · fortified dairy products (milk, cheese, yogurt) · banana, durian · basil, thyme · egg yolks · fish · legumes (adzuki beans, baked beans, chickpeas, hyacinth beans, kidney beans, lima beans, green peas) · maple syrup · miso · nuts (almonds, cashews, peanuts, pecans, pine) · peanut butter · seeds (mustard, pumpkin, safflower, sesame, sunflower, and watermelon seeds) · sea-food (crab, lobster, shrimp) · seaweed such as dulse, kelp · soy lecithin · soybeans · vegetables (asparagus, broccoli, chard, collard greens, mustard greens, spinach, summer squash) · wheat germ · whole grains (brown rice, millet, oats, rye, wheat) · rice bran.
Taking vitamins and minerals in their correct balance is vital to the proper functioning of all vitamins. They work synergistically, which means that the effectiveness of any one nutrient requires, or is enhanced, sometimes dramatically, by the presence of certain other nutrients.
For this reason, if you are looking to take supplements for maintenance of optimal health, the recommended approach is to take a multi-vitamin that has the proper balance of all the necessary nutrients your body needs.
For a list of reputable top ranked vitamin and mineral supplements chosen in an independent supplement review, see Best Multivitamin Supplements. Many of these are manufactured to pharmaceutical or nutraceutical GMP compliance, which is the highest multivitamin standard possible.
Keep in mind, however, that while mineral supplements are useful to plug nutritional gaps that are almost inevitable in modern diets, and to ensure we get optimal doses of nutrients, they are no substitute for a good diet. Instead, use them to complement a healthy diet and lifestyle.
Zinc RDA (Recommended Dietary Allowance)
The Food & Nutrition Board of the Institute of Medicine, National Academy of Sciences, in their 1997-2001 collaboration between the US and Canada, set the daily Adequate Intake (AI) of Zinc as follows.
|Life Stage | Gender||Zinc Dosage | Day|
|Infants 0-6 mths||2* mg|
|Infants 7-12 mths||3 mg|
|Children 1-3 yrs||3 mg|
|Children 4-8 yrs||5 mg|
|Girls 9-13 Yrs||8 mg|
|Boys 9-13 Yrs||8 mg|
|Females 14-18 Yrs||9 mg|
|Males 14-18 Yrs||11 mg|
|Females 19-50 Yrs||8 mg|
|Males 19-50 Yrs||11 mg|
|Females older than 50 Yrs||8 mg|
|Males older than 50 Yrs||11 mg|
|Pregnant Women 14-18 Yrs||12 mg|
|Pregnant Women 19-50 Yrs||11 mg|
|Lactating Mothers 14-18 Yrs||13 mg|
|Lactating Mothers 19-50 Yrs||12 mg|
These dosages are the minimum required per day to ward off deficiency. In therapeutic use of this nutrient, dosage is increased as necessary for the ailment, keeping in mind Zinc toxicity levels.
1 µg = 1 mcg = 1 microgram = 1/1,000,000 of a gram
1 mg = 1 milligram = 1/1,000 of a gram
* Indicates AI figures based on Dietary Reference Intake (DRI) figures
Zinc Overdose Symptoms, Toxicity Level & Side Effects
Zinc is considered safe and normally well-tolerated at recommended doses.
However when taken in excess, symptoms of zinc overdose can include :
- metallic or bitter taste in the mouth
- abdominal cramps or pain
- diarrhea (sometimes mixed with blood)
- intestinal bleeding
- suppressed immune function (from doses above 100 mg daily)
- increased LDL (“bad”) and decreased HDL (“good”) cholesterol
- impaired iron function
- impaired formation of red blood cells leading to anemia
- liver inflammation or liver failure (inacute cases)
- kidney disorders (in acute cases)
- urinary problems such as urinary tract infections, especially among males
These symptoms should go away when intake is normalized.
Zinc can also affect the status of other nutrients, the most important of which are copper and calcium. Even at normal levels, it can cause copper deficiency unless the diet includes copper-rich foods. High levels of zinc can also hinder absorption of calcium.
People with kidney disease should lower their intake as they are at higher risk of zinc overdose, since excess is normally removed through urine.
The Food and Nutrition Board of the Institute of Medicine has set Tolerable Upper Intake Levels (UL) for zinc. These are the levels above which there is risk ofzinc side effects, especially when taken over a long time.
Tolerable Upper Intake Levels (UL) for Zinc per Day
|0 to 6 months||4 mg||4 mg|
|7 to 12 months||5 mg||5 mg|
|1 to 3 years||7 mg||7 mg|
|4 to 8 years||12 mg||12 mg|
|9 to 13 years||23 mg||23 mg|
|14 to 18 years||34 mg||34 mg||34 mg||34 mg|
|19 years and above||40 mg||40 mg||40 mg||40 mg|
The ULs do not apply to the therapeutic use of zinc for medical treatment, which should be under medical supervision.
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|1.||Institute of Medicine, Food and Nutrition Board. Dietary reference intakes for vitamin A, vitamin K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc. Washington, DC: National Academy Press; 2001.|
|2.||U.S. National Libary of Medicine [NLM] & National Institutes of Health [NIH]: MedlinePlus. NLM-NIH home page. <http://www.nlm.nih.gov/medlineplus>. Use the built-in search function to find specific data. Accessed 2009 March – June.|
|3.||National Institutes of Health, NIH Clinical Center: Office of Dietary Supplements [ODS]. ODS home page. <http://ods.od.nih.gov>. Use the built-in search function to find specific data. Accessed 2009 Mar – Jun.|
|4.||The George Mateljan Foundation: The world’s healthiest foods [WHFoods]. WHFoods home page. <http://www.whfoods.com>. Accessed 2009 March – June.|
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