Zinc

Athletes take this supplement in the hope that they improve strength and athletic performance, while others take it to stave off the common cold.  Despite being available over the counter in a number of doses and forms, it is not without its potentially serious side-effects.  Should you be taking zinc, and if so how much?

Zinc is a Metal or mineral, like iron or copper, essential for all life on earth including our own.  It helps the cells in our body function- from the immune system to our DNA. It is mostly found in shell fish, meat and diary, and as a result strict vegetarians are often low in Zinc.

Actions

• Endocrine (producing hormones)

• Metabolic ( Using fuel such as glycogen from stored sugar )

• Immune system

• Enzyme function

• Sending messaging between cells

• Protein synthesis from mRNA ( which is copied form your DNA)

Conditions linked to low levels ( Deficiency) of zinc in the blood:

• Vegetarians: due to a diet high in phytic acid

• Malnutrition

• Persistent diarrhoea: Ulcerative colitis, Crohn's, and Coeliac disease

• Alcoholism

• Aging: which is also associated with low levels of Growth Hormone ( GH) and Insulin-like Growth-factor 1( IGF-1), and in men low levels of testosterone

• Poor wound healing

• Dermatitis with persistent diarrhoea (Acrodermatitis enteropathica-an Inherited disease)

• Anaemia: sickle cell and thalassaemias

• Inflammation: as seen in the joints of patients with rheumatoid arthritis.

Food sources of Zinc

• melon,

• cocoa,

• pumpkins

• Nuts

• Shell-fish

• Eggs

• Beef,

• Liver,

• Cheese/yogurt

Foods or medication that reduce Zinc absorption

• Phytic acid from vegetables

• Iron supplements

• Penicillamine- sometimes used in rheumatoid arthritis ( Chelates Zinc)

• Alcohol

The body stores only a small amount of zinc, so it relies on the regular intake of good natural foods to maintain these stores.

Oral Zinc Supplements

There are different zinc salts available to buy as a supplement.  Zinc acetate is used in Wilson's disease, whereas Zinc sulphate and Zinc aspartate are often found in over-the counter preparations.

What happens if you take to much Zinc?

If you have normal levels of zinc in your blood and you start taking high dose supplement of zinc, you will block the absorption of copper from the gut; the copper is then lost through your bowel motion.  Low copper can result in anaemia and low white cell blood count.  Copper is essential for cells to function.  

We use zinc tablets to treat a condition where the body accumulates copper, called Wilson's disease.  This is a genetic disease which initially presents with anaemia or low white cell count, and later with dementia.

What is considered high dose Zinc?

Recommended daily dose for men is 12mg. Studies show that regular daily intake of 25mg to 50mg of Zinc salt, such as Zinc acetate, can lower the copper level below normal; but each person responds differently.  Some people still have normal copper levels with 25 mg and 50mg daily doses of Zinc. 

When should you take Zinc supplements?

• Malnutrition: People who are unable to eat foods with adequate nutrients in their diet. The Zinc preparation should be prescribed by a physician.

• Mal-absorption conditions: Conditions affecting the intestines of stomach. Zinc should be prescribed by a physician.

• Common cold: there is moderate evidence that taking zinc within 24 hours of onset of the common cold, can shorten the course of this illness. Also in children at least 5 months of zinc supplements will reduce the need for antibiotics for similar illnesses. (Cochrane review 2012)

• Wilson's disease: rare inherited condition causing too much copper in the body.

Others uses where scientific evidence or consensus opinion is lacking

• Aging:it is unclear if low zinc levels are part of the aging process, or if aging itself leads to lower levels of zinc. Some studies have shown that supplemental zinc improves how the immune system works ( improved T-cell function)( Haase & Rink,2009)

• Auto-immune disease: One study in 1976 showed improvement in Rheumatoid Arthritis(RA), but in 1982 two small studies using high dose zinc sulphate showed no benefit. To date there are no studies showing benefits to patients with Systemic lupus erythematosus (SLE).

• Athletic performance: Evidence is weak, but it may enhance athletic performance. i.e. only one study showed it improves strength, testosterone and IGF-1 levels. But there are other studies showing no such benefits.

• Sickle cell disease: Zinc supplementation may reduce the number of sickle-cell 'crisis'. The number of studies are small but recent research supports its use. You should speak to your physician before starting zinc.

• Alzheimer's disease: There are some studies showing that, due to high levels of copper in the soil or water from copper pipes, higher than normal levels of copper in the blood is linked with Alzheimer's disease.

• Wound healing: In a large review of all studies carried out until 1998, there was no advantage to taking oral zinc sulphate, even when blood zinc levels were low. A lot of the studies were not of good quality, so this conclusion may not be entirely valid.

Recommended daily dose

This depends on the preparation of zinc and whether you are an adult, male or female.

• Children 1-3 yrs 3mg/day

• Children 4-8 yrs 5mg/day

• Children 9-13 yrs 8mg/day

• Adolescents same as for adults

• Adult women: 8mg/day

• Pregnant women: 12mg/day

• Adult men: 12mg/day

Measuring Zinc levels

In the UK a routine Zinc level check is not available.  In cases where a patient has an existing disease, that would predispose them to low zinc, it will be checked.  But the result itself may not truly reflect the Zinc level.  Zinc levels vary diurnally- with day and night- and it is difficult to pick up border-line low zinc levels.

Topical Zinc(applied to skin)

Zinc is also used to treat skin conditions such as dandruff and inflamed skin, and to protect from the sun's harmful UV rays. 

• Zinc pyrthione is effective at treating dandruff.

• Zinc soap is useful for managing facial dermatitis such as seborrheic dermatitis.

• Zinc oxide is mildly anti-inflammatory and used for napkin rash in babies and also for seborrhoeic dermatitis.

• Zinc oxide is also an effective sun block.

Summary

Zinc is essential for life.  Some people may have low zinc levels due to poor nutrition, aging, conditions that reduce absorption of Zinc, or other drugs interfering with Zinc absorption. 

There is reasonable scientific evidence that, oral Zinc supplements taken within 24 hours of the onset of the common cold, reduces the duration of illness.  And that if taken for at least 5 months through winter will have positive affects on other aspects of the immune system, reducing antibiotic use in children. 

Athletes, elderly people and anyone with sickle-cell anaemia may benefit from regular zinc supplementation.  Despite its role in regulating the immune system, evidence to support its use in rheumatoid arthritis and lupus is lacking.  Although, this hasn't stopped many alternative health care practitioners prescribing to patients with autoimmune diseases.

Recommended daily dose is 12mg/day for men and 8mg/day for women.  Daily supplemental doses of 50mg Zinc and above are not safe for individuals who do not have Wilson's disease.  Most Zinc supplements contain between 12mg and 25mg of Zinc.  At present, in the UK, you cannot have Zinc levels checked routinely in the National health service (NHS). 

Eating a varied diet of fish, eggs, nuts, and meat will keep your Zinc levels normal if you are otherwise healthy.  If you feel you are not obtaining sufficient Zinc in your diet then recommended supplement should not exceed 25 mg/day.  Nasal zinc sprays should be avoided.

References

Meenu Singh & Rashmi R Das. Zinc for the common cold. Cochrane Review: Article first published online: 2 JUL 2012

Brilla LR, Conte V. Effects of a novel Zinc-magnesium formulation on hormones and strength. Journal of Exercise physiology Online 2000;3:26-36

Maggini S, Beveridge S, Suter M. A combination of high-dose vitamin C plus zinc for the common cold. Journal of internal Medicine Research 2012;40:28-42

Chasapis CT, Loutsidou AC, Spiliopoulou CA, et Al. Zinc and human health: An update. Archives toxicology 2012;86:521-34

Prasad AS. Zinc deficiency. BMJ. 2003;326(7386):409-410

Hajo Haase and Lothar Rink. Review: The immune system and the impact of zinc during aging.  Immunity & Ageing 2009, 6:9

Nossent J, Lester S, Rischmueller M, and Zalewski P.  "No Zinc deficiency but a putative immunosuppressive role for labile Zn in patients with systemic autoimmune disease".  Current Rheumatology Review. 2015 Oct 26.

Peretz A1, Cantinieaux B, Nève J, Siderova V, Fondu P. Effects of zinc supplementation on the phagocytic functions of polymorphonuclears in patients with inflammatory rheumatic diseases.Journal of Trace Elements Electrolytes Health Disease. 1994 Dec;8(3-4):189-94.

P.C. Mattingly & A.G.Mowat. Zinc sulphate in rheumatoid arthritis. Annals of the Rheumatic Diseases, 1982, 41, 456-457