| Zinc | ||||||||
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- Why zinc is good for you
- Important zinc facts
- Groups at risk of zinc deficiency
- Symptoms of zinc deficiency
- Zinc and health
- Zinc in foods
- Zinc recommended daily intake (RDI)
- Zinc works best with
- Overdosage, toxicity and cautions for zinc
Zinc is extremely important for proper functioning of the immune system – current research shows that zinc supplements assist with quicker healing of the cold or flu.
Zinc also keeps the skin healthy, helps preserve eyesight and might even improve memory.
Over 200 different enzymes in the body depend on zinc to work properly. Zinc is necessary to make many hormones, including the ones that tell the immune system what to do when it is under attack from germs. Zinc is essential for making hormones that control growth and for the important male hormone testosterone.
There is some zinc in every one of the cells in the body, but most of it is in the skin, hair, nails and eyes (and in the prostate gland, for males).
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- The most easily absorbed form of zinc is zinc gluconate. Zinc picolinate, zinc citrate or zinc monomethionate are also good options. Zinc sulphate is likely to upset the stomach so skip it. Avoid zinc oxide – that form is really only useful in skin creams meant to block sunlight.
- Recent studies show that zinc can revitalise the thymus and get it working again.
- The infection fighting white blood cells contain a lot of the zinc present in the body.
- Zinc may help teenagers with pimples, especially if their diet does not contain the RDA of zinc
Groups at risk of zinc deficiency
Almost a century ago in Egypt, doctors noticed that poor, young boys who ate almost nothing but unleavened bread were very short and underdeveloped. It turned out that their diets had very little zinc. Once they started getting more zinc in their diet, they started growing normally again.
In modern society, such a serious zinc deficiency is very rare, although a slight zinc deficiency is quite common. Surveys show that many women only get about half the RDA. The groups at most at risk of zinc deficiency are:
- Strict vegetarians or vegans - animal foods such as meat and fish are the best dietary sources of zinc. Fruits have virtually none. Children who do not eat animal foods are most at risk for zinc deficiency
- People eating a very high fibre diet - the fibre, especially from whole grains, binds up the zinc in the diet and keeps it from being absorbed
- Pregnant or breastfeeding mothers – much of the nutrients eaten are passed onto the child and extra may be needed each day to top up supplies of zinc
- People over 50 years - the ability to absorb zinc from food drops as we age
- People who abuse alcohol - alcohol abusers do not eat very well in general and even moderate amounts of alcohol flush out the zinc stored in your liver and make you excrete it.
People in these groups at risk of deficiency should talk to a medical professional about zinc supplements BEFORE taking them.
Zinc deficiency has a number of symptoms such as:
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Generally speaking, most people do not have to worry much about being deficient in this mineral. Anyone who eats a reasonably well-balanced diet will get plenty of zinc, but some people are more prone to being deficient and should seek medical advice about supplementation.
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- The immune system - zinc may be a useful immune system booster in general. It seems to give a real boost to the thymus gland, especially in people over 40. By then, the thymus gland may have naturally shrunk quite a bit, so its not producing the hormones that stimulate the body to produce infection-fighting white blood cells it used to. Getting a little extra zinc may get the thymus working better again and help fight off illness faster
- Male infertility - men need zinc to produce testosterone and other male hormones, as well as healthy sperm and semen, so more zinc in the diet could help solve male infertility. In one study, men with low sperm counts took zinc supplements for six weeks after which their testosterone and sperm counts went up and nearly half of them had pregnant wives before the study was over
- Prostate problems - zinc can also be very helpful for treating and possibly even preventing prostate problems. As men age, the prostate often gets bigger naturally and can squeeze the urethra and cause a need to urinate frequently as well as other urination problems. Men with this problem often have low zinc levels and taking a zinc supplement can help improve the problem
- Healthy skin, nails and hair - zinc is really important for healthy skin. A shortage of zinc is often the cause of minor skin rashes and irritations that do not seem to have any real (medical) cause. These often clear up when patients start eating a diet higher in zinc or take zinc supplements. Zinc also sometimes helps people with psoriasis. Sometimes zinc shortage causes white spots on the fingernails or nails that break easily. Adding zinc to the diet could help clear up the problem
- Healing wounds - zinc is essential for healing wounds. Several studies show that patients recover from surgery faster if they get enough zinc. The effect is dramatic if the patient was low on zinc to begin with – it did not seem to work as well on patients who had good zinc levels prior to surgery. People who are scheduled for surgery should talk to their doctor about taking zinc supplements for a few weeks before and after the surgery
People who wish to take a zinc supplement should talk to a medical professional BEFORE taking it.
CURRENT RESEARCH
- Diabetes - some diabetics may be low on zinc because they do not absorb it well and also excrete it too quickly. Zinc supplements could help. Zinc might also help with the other problems diabetics often have - slow wound healing and frequent infections
- Macular degeneration - this serious eye problem is the leading cause of blindness in the elderly. The eyes naturally contain a lot of zinc and a lot of it is concentrated in the retina, the part of your eye affected by macular degeneration. Zinc supplements could help prevent or slow down vision loss from macular degeneration
- Memory - people who get the recommended daily intake of zinc do better on memory tests than those who do not
People who wish to take a zinc supplement should talk to a medical professional BEFORE taking it.
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| FOOD | AMOUNT | ZINC (mg) |
|---|---|---|
| Oysters, smoked | 85g | 103.0 |
| Oysters, canned | 85g | 77.3 |
| Oysters, raw | 6 medium | 76.4 |
| Beef liver | 85g | 5.2 |
| Beef, minced | 85g | 4.6 |
| Wheatgerm | 1/4 cup | 3.6 |
| Chickpeas | 1 cup | 2.5 |
| Lentils | 1 cup | 2.5 |
| White beans | 1 cup | 2.5 |
| Chicken without skin | 85g | 2.1 |
| Yoghurt | 1 cup | 2.0 |
| Black beans | 1 cup | 1.9 |
| Kidney beans | 1 cup | 1.9 |
| Lima beans | 1 cup | 1.8 |
| Turkey | 85g | 1.7 |
| Cashews, dry roasted | 28g | 1.6 |
| Pecans | 28g | 1.6 |
| Almonds, dry roasted | 28g | 1.4 |
| Sunflower seeds | 28g | 1.4 |
| Oatmeal | 1 cup | 1.1 |
| Swiss cheese | 28g | 1.1 |
| Milk 1% fat | 1 cup | 1.0 |
| Cheddar cheese | 28g | 0.9 |
| Split peas | 1/2 cup | 0.9 |
| Peanut butter | 2 Tbsp | 0.9 |
| Peanuts | 28g | 0.9 |
| Walnuts | 28g | 0.8 |
| Eggs | 1 large | 0.5 |
| Flounder | 85g | 0.5 |
| Wholewheat bread | 1 slice | 0.4 |
Zinc recommended daily intake (RDI)
| RDA | lifestage | age | amount |
|---|---|---|---|
| INFANTS | 0-6mths 7-12mths |
2mg 3mg |
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| CHILDREN | 1-3yrs 4-8yrs |
3mg 5mg |
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| CHILDREN | 9-13yrs male: 14-18yrs female: 14-18yrs |
8mg 11mg 9mg |
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| ADULTS | male: 19-50yrs female: 19-50yrs |
11mg 8mg |
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| SENIORS | male: 51+yrs female: 51+yrs |
11mg 8mg |
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| PREGNANT | <18yrs 19-50yrs |
13mg 11mg |
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| LACTATING | <18yrs 19-50yrs |
14mg 12mg |
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| TOLERABLE UPPER LIMIT | lifestage | age | amounT |
| INFANTS | 0-6mths 7-12mths |
4mg 5mg |
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| CHILDREN | 1-3yrs 4-8yrs |
7mg 12mg |
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| CHILDREN | 9-13yrs 14-18yrs |
23mg 34mg |
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| ADULTS | 19-50yrs | 40mg | |
| SENIORS | 51+yrs |
40mg | |
| PREGNANT | <18yrs 19-50yrs |
34mg 40mg |
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| LACTATING | <18yrs 19-50yrs |
34mg 40mg |
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| Toxic Levels | >150mg | ||
The tolerable upper limits should only be taken for short periods and only under medical supervision.
Overdosage, toxicity and cautions for zinc
Acute (>1,000mg) toxicity - dysfunction of the central nervous system, diarrhoea, dizziness, sore stomach, nausea, paralysis of extremities, slow tendon reflexes, tremor, vomiting
Chronic toxicity - alcohol intolerance, anaemia, increased LDL cholesterol and lowered HDL cholesterol, dehydration, electrolyte imbalance, lethargy, nausea, sore stomach, symptoms of copper and iron deficiency, vomiting, lowered immunity
Nausea and vomiting can occur at doses >150mg a day.
CAUTIONS
People taking the antibiotic tetracycline should NOT take zinc supplements. The zinc will keep the tetracycline from being absorbed into the bloodstream.
references
- Ali H, Baig M, Rana MF, Ali M, Qasim R, Khem AK. Relationship of serum and seminal plasma zinc levels and serum testosterone in oligospermic and azoospermic infertile men. J Coll Physicians Surg Pak. 2005 Nov;15(11):671-3
- Desouki MM, Geradts J, Milon B, Franklin RB, Costello LC. hZip2 and hZip3 zinc transporters are down regulated in human prostate adenocarcinomatous glands. Mol Cancer. 2007 Jun 5;6:37
- Ebisch IM, Pierik FH, DE Jong FH, Thomas CM, Steegers-Theunissen RP. Does folic acid and zinc sulphate intervention affect endocrine parameters and sperm characteristics in men? Int J Androl. 2006 Apr;29(2):339-45
- Gómez Y, Arocha F, Espinoza F, Fernández D, Vásquez A, Granadillo V. Zinc levels in prostatic fluid of patients with prostate pathologies. Invest Clin. 2007 Sep;48(3):287-94
- Li TX, Li Y. Synergistic effect of zinc and vitamin A on T cell functions. Biomed Environ Sci. 2007 Apr;20(2):131-4
- Mitchell WA, Meng I, Nicholson SA, Aspinall R. Thymic output, ageing and zinc. Biogerontology. 2006 Oct-Dec;7(5-6):461-70
- Mocchegiani E. Zinc and ageing: third ZincAge conference. Immun Ageing. 2007 Sep 20;4(1):5
- Osiecki, H. The Nutrient Bible. Bio-Concepts Publishing QLD, 2002
- Tubek S. Selected zinc metabolism parameters in women with arterial hypotension. Biol Trace Elem Res. 2007 Apr;116(1):73-9.
- Whitney EN, Cataldo DB, Rolfes SR. Understanding Normal and Clinical Nutrition, 6th Edition. Wadsworth/Thomson Learning, 2002
- Xi H, Kersh GJ. Early growth response gene 3 regulates thymocyte proliferation during the transition from CD4-CD8- to CD4+CD8+. J Immunol. 2004 Jan 15;172(2):964-71, accessed 27 Sep 07
