This is an essential trace mineral and the second most abundant one in the body (iron being the most abundant). It is a component of almost every living cell, including those of the muscles & bones (which contain about 90% of the body’s zinc), skin, liver, kidney, brain, blood, eye, pancreas and, in males, the prostrate.
The total zinc content of an adult body is 1.4 - 2.5 grams.
Unlike other trace elements zinc does not get stored in the body. The healthy body keeps a stable equilibrium (homeostasis) by regulating the absorption and elimination of zinc.
Zinc’s function in the body is mainly enzymatic - in other words it is needed to make enzymes work properly, especially metalloenzymes (enzymes that have a metal linked to their protein). Zinc has been shown to be necessary as a cofactor for the correct function of over 70 of these.
Metalloenzymes regulate the metabolism of carbohydrates, lipids, and proteins.
So what is zinc’s use in diabetes?
The relationship between zinc and diabetes is complex and not fully understood. What is known is that Type 1 and Type 2 diabetics tend to be deficient in zinc.
1. Zinc and insulin.
Zinc has been to play a role in all stages of insulin metabolism, from production through secretion to utilisation and storage.
Zinc plays a protective role against beta cell destruction. A lack of zinc affects the ability of the pancreatic beta cells to respond to the body’s call to produce and secrete insulin. If the pancreas does not produce and secrete enough insulin the levels of glucose in the blood stay high.
This is also what happens if the insulin that is made does not work properly.
Decreased zinc has been implicated in a lack of insulin sensitivity. In other words the insulin receptors on the cell are being inhibited so not enough glucose is entering the cells.
In a study by Dilina N. Marreiro and colleagues, from University of Sao Paulo-SP in Brazil, it was found that zinc supplementation enhanced insulin sensitivity in obese women who were not zinc-deficient. (Be warned, it is all written in Portuguese and the translator, at least on my computer, does not work properly).
What they did state in conclusion of the study appears to read as follows -
“A short time of zinc supplementation improved insulin sensitivity in obese insulin resistant women without zinc deficiency. Although the mechanism concerning the effect of zinc supplementation is not completely understood, further studies are recommended to address the possible role of zinc therapy in insulin resistance states such as diabetes."
Yet another effect of zinc is that insulin becomes inactive in it’s presence and can then be stored.
2. Zinc and weight.
As an assistant in weight control zinc may work in a number of ways.
as seen above, a lack of zinc affects the insulin receptors on the cells which means the blood glucose levels go up, which means the beta cells produce more insulin, which means there is more unused insulin in the blood. As insulin promotes fat storage having high levels will also cause you to gain weight.
too much copper can increase the conversion of glucose into triglycerides (fats), leading to weight gain. If you think I appear to have got my minerals mixed up read on….
Zinc is what is known as a copper ‘antagonist’ or ‘competitor’ - in other words it competes with copper both for absorption in the intestine and for binding sites on albumin molecules. This causes lower levels of copper and thus the production of fewer triglycerides. It has been found that an excess of either of these two minerals leads to a deficiency in the other.
(Around the world, copper can be a problem because of an increase in the use of copper water pipes for water distribution. This is heavily increasing the intake of copper in many areas.)
a lack of zinc decreases the bloods levels of leptin, a hormone produced in the fat cells that has been found to regulate blood sugar by letting the brain know what available energy we have and whether we need to store more. Thus it plays a role in appetite control and the storage of fat and also appears to tell the liver what to do with it’s stored glucose.
So a decrease in zinc leading to leptin lack will cause the body to build more ‘fat body mass’ as opposed to lean body mass.
3. Zinc and cellular defence.
It is thought that many diabetic complications are, in part, brought about or worsened by oxidative stress.
Zinc combines with copper and selenium to play a key role in the cells defence against free radicals and a lack of zinc may be one of the causes of irreversible cell damage.
It’s antioxidative function is not only due to it’s being a constituent of enzymes, it also appears to be responsible for stimulating cellular stress signalling pathways and stabilising proteins so they are not as prone to oxidation.
Click here to see a study dealing with the Antioxidant effects of zinc supplementation in Tunisians with type 2 diabetes mellitus.
4. Zinc and the immune system.
Zinc has been found to be the micronutrient that has the strongest effect on the correct working of the immune system.
Low levels of zinc lead to the thymus-derived T cells, which are responsible for ‘switching on and off’ various immune function, not working properly.
It also causes a decrease in the function of other white blood cells, for instance the B lymphocytes which are responsible for antibody production and the macrophage, who ‘gobbles up’ foreign particles in the blood and tissues and also warns the T cells to the presence of antigens.
Zinc has also been shown to have a strong antiviral affect.
It is no wonder that if our zinc levels are low we tend to get more respiratory infections.
5. Zinc and wound healing.
Because of zinc’s role in collagen synthesis (the main protein of connective tissue) and also in the multiplication of many cells, such as epithelial cells and fibroblasts (a type of cell found just underneath the surface of the skin) it plays an important role in the healing of wounds.
Diabetics, specially those with high blood glucose, tend to have trouble getting wounds to heal. Zinc may help.
6. Zinc in pregnancy.
Being diabetic adds a new challenge to being pregnant. It may well be worth asking your doctor about zinc as it has been shown that low levels are associated with preeclampsia in the mother, premature birth, retarded growth and low birth weight in the baby. This is possibly due to the fact that zinc is needed for proper cell division.
Slow growth of the infant, in the first few months of life, has been associated with low levels of zinc in the mother’s breast milk.
7. Zinc and sexual function.
This is of particular importance to my male readers because it is in male sexual function that zinc plays such an important part. And believe me I know just how important this is - after all I spend my lunch breaks in a canteen filled with men!!
Inadequate levels of zinc can result in low levels of the male hormone testosterone, limit sperm formation and decrease sperm mobility. At this rate, if your wife is also diabetic she will probably not have to worry about the challenges of pregnancy!
Where do we get zinc from?
The foodstuff with the highest concentration of zinc is oysters - considering the effect of zinc on male sexual function is it any wonder these have been hailed as the ultimate aphrodisiac! Consider here also the fact that zinc is very susceptible to destruction during cooking and how are oysters supposed too be best eaten? - raw. Makes one wonder doesn’t it?
Zinc amounts are also pretty high in other types of shellfish such as shrimps and crab, fish, poultry and (dare I say it) red meat and cheeses eg. Ricotta, Swiss & Gouda. These foods are your best bet when it comes to dietary zinc.
“But what about us vegetarians?” I can hear you cry. All is not lost, though getting enough zinc may be difficult.
Zinc is found in some quantity in whole grains, bran, legumes eg. lima beans, black-eyed peas, pinto beans, soybeans & peanuts, brewer’s yeast, miso, tofu, nuts eg. pecans, Brazil nuts, almonds, walnuts, and hazelnuts and seeds eg. sunflower and pumpkin, plus peas, mushrooms and, wait for it, the ubiquitous broccoli.
However many of the non meat and fish sources also contain phytic acid which binds to zinc and prevents it being absorbed. This is especially true of wheat, corn (maize), legumes, brown rice and those non-fermented soyfoods. People whose diets consist of a lot of cereal and little protein have been found to be zinc deficient.
The nuts and uncooked veggies would appear to be a vegetarian’s best bet.
So how much do we need?
When looking at the recommended daily allowance (RDA) listed below remember it is the minimum amount recommended for healthy people and not those who are ill or have a chronic disease..
Birth to 6 months - 2mg
7 - 12 months - 3mg
1 - 3 years - 3mg
4 - 8 years -5mg
9 - 13 years - 8mg
Males 14 - 18 years - 11mg
Females 14 - 18 years - 9mg
Males 19 years and older - 11 mg
Females 19 years and older - 8 mg
14 to 18 years - 13 mg
19 years and older -11 mg
14 to 18 years - 14 mg
19 years and older - 12 mg
(of elemental zinc) for people with major zinc deficiency are:-
Males - 30 - 60mg a day
Females - 30 - 45mg a day.
Though you will often see 15mg a day listed as the recommended daily intake one must remember that there are a number of zinc ‘antagonists’ in ones diet and upping the intake may be necessary.
Generally diabetics will benefit from around 25mg daily.
Studies have been done on people taking up to 50mg a day and no adverse side effects showed up.
However we must be aware that too much zinc can also be harmful.
The effects are usually noticed when levels 10-25 times the RDA are taken. In the short term you will experience stomach cramps, nausea, dizziness, headache, metallic taste in mouth and vomiting but in the long term you may have increased sweating, loss of muscle co-ordination, alcohol intolerance, hallucinations, decreased HDL levels and possibly anaemia along with a lack of copper - if you take over 30 milligrams of zinc on a daily basis for more than 1-2 months, you should also take 1 to 2 milligrams of copper each day as well.
Continued high doses are thought to accelerate the development of atherosclerosis and to weaken the immune system.
High doses of zinc can also interfere with some medications, such as ACE inhibitors, antibiotics, anti-inflammatories, HRT and some immunosuppressants.
It has been suggested that doses of more than 150mg a day may affect the ability of the body to use other essential minerals.
What are the symptoms of zinc deficiency?
These vary depending on the level of the deficiency. The list below is random and does not relate to the level of deficiency.
Skin disorders eg. Dermatitis, Eczema, Psoriasis, Acne
Recurrent bacterial or yeast infections, such as thrush
Slow healing of wounds
Loss of sense of taste and smell
Loss of appetite and anorexia
Nail problems such as white spots on fingernails, hang nails, inflammation of cuticles, transverse lines and poor nail growth.
Night blindness - zinc is needed to transport Vitamin A (Retinol) from the liver to the retina..
Sleep and behavioural disturbance
Infertility and impotency
Poor, stunted growth in children
Delayed sexual development in children
Alopecia (hair loss) and dandruff
Amenorrhea - lack of menstrual period
Why should we be short of zinc?
Newly diagnosed or uncontrolled diabetics may be short of zinc because of the amount that is lost in the urine.
A diet high in refined foods ( such as the one that got us type 2’s to this point) is going to be low in zinc.
The consumption of too much coffee has been shown to lead to a significant depletion of several vitamins and minerals, of which zinc is one. How many of us depend on ‘mother’s, (or father’s), little helper’ to kick start our day and then need frequent top ups just to get us through?
The elderly tend to be zinc deficient because their intake of zinc is inadequate.
Drinking excessive amounts of alcohol, with it’s accompanying lack of food, and thus zinc, leads to deficiency.
Unless vegetarians consume reasonable quantities of assorted nuts, seeds and raw peas, mushrooms and broccoli their diet is going to contain inadequate zinc.
Those who have substituted soybeans and soybean products for meat and cheese have done themselves no favours zinc wise because soybeans have the highest levels of phytic acid of any legume and this chelates (binds with) zinc and makes it unable to be absorbed.
Zinc is absorbed from the small intestine and any disease that hinders absorption of food will result in a zinc deficiency eg. Crohn's disease, ulcerative colitis, or inflammatory bowel disease. Likewise any disease that results in diarrhoea will make us deficient in zinc.
If we have too much copper in our bodies our zinc levels will be low. Zinc and copper compete for binding sites on the protein albumin so too much of one causes a lack of the other.
A study done on 66 men over a 5 day period showed that continued physical and psychological stress caused an average 33% drop in zinc levels - so watch out for stress!
A condition known as Pyroluria is caused by the overproduction of kryptopyrrole during the synthesis of haemoglobin. These pyrroles bind to vitamin B6 and to zinc which is then eliminated with the urine, causing a deficiency of vitamin B6 and zinc.
Types of zinc supplements.
Like many mineral supplements zinc is not available on it’s own but rather bound to another substance. These include zinc sulfate, zinc citrate, zinc gluconate, zinc acetate, zinc glycerate, zinc picolinate, and zinc monomethionine.
When trying to work out how much supplemental zinc to take remember to take into consideration the amount you may be getting from your diet. Generally this is around 10-15mg a day.
Each zinc formulation will contain a different amount of elemental zinc. For instance one brand of 220mg zinc sulfate tablets contain 55 grams of elemental zinc while the same brand of 220mg zinc gluconate tablets contained 31mg.
The amount of elemental zinc in each tablet is listed in milligrams on the product label. Usually this is between 30 and 50mg.
Zinc sulfate is the most widely available and least expensive but it is not the most bioavailable (easily absorbed) and has been known to cause stomach upset.
To assist in minimising this problem try taking it with a high protein meal.
If the stomach problem persists change to another type of zinc, such as zinc citrate or picolinate.
Zinc should not be taken at the same time as iron or calcium supplements.
For every 15mg of zinc you need to take 1mg of copper to retain the correct balance.
There has been some concern about giving type1 diabetics zinc supplements because of a report that stated they increased glycosylation (the attachment of glucose to protein).
It is this glycosylation that is measured in the HbA1c test and that is the standard by which ones diabetic control is measured. An increase is usually indicative of a deterioration in ones condition.
Because zinc increases the lifespan of blood cells this may lead to artificially increased lab results. It will be up to your doctor to evaluate the benefits of zinc in your own particular case.
How long will you have to take this supplement?
This is not an instant cure. If the zinc depletion is marginal then taking supplements for a few months may cause the symptoms to disappear. However severe zinc depletion may take a year or more before all symptoms go away.
Getting ones zinc balance right can depend on a number of outside factors as well as the extra supplementation. If you get ill, have a very stressful time, injure yourself, or, in children and adolescents, have a sudden growth spurt, you will upset the balance.
Like diabetes, zinc deficiency can be treated but that does not mean it is cured. Once supplementation is discontinued and one is still not getting sufficient zinc from ones diet then the symptoms will return. It may well require life-long treatment.
Testing for zinc deficiency.
Though there are a number of tests that can be done to check zinc status they tend to be costly and inaccurate. Lab tests for nutritional status tend to be less precise than for other medical conditions. Also the levels of the nutrients in blood samples are not necessarily indicative of the levels available at the site where they actually work and so a normal blood test result may not truly reflect a deficiency. Zinc's main functions are intracellular therefore blood levels do not reflect total body stores.
Zinc is one of the nutrients that is particularly hard to test for.
Your doctor will frequently use logical assessment of your medical history and current condition to determine whether you are zinc deficient rather than lab tests.
Some of the questions he may ask you are:-
1. Do you think your sense of taste and smell are not as good as they used to be?
2. Do you have acne now as an adult but possibly didn't have it as a teenager?
3. Do you suffer from frequent colds and flu. Are they often accompanied by other infections like earache?
4. Does your hair grow slowly? Is it dry with brittle ends? Is it hair going prematurely grey?
5. What are your nails like? Do they have white flecks, peel and fray easily or grow very slowly?
6. If you are male do you suffer from an enlarged prostate or prostatitis?
7. Is your skin dry and cracked?
8. Do you get fungal skin infections?
9. Do wounds such as cuts or rashes heal slowly?
10. Do you sunburn easily?
11. Are your eyes very sensitive to sunlight or bright lights?
12. Have you been diagnosed with macular degeneration?
13. Do you have any form of glucose imbalance such as diabetes.
14. As a male have you been diagnosed with low sperm counts?
15. Have you ever suffered from impotence or erection problems?
16. Are your lips regularly dry, cracked or chapped?
17. Do you get often get herpes-type cold sores (fever blisters)?
If you answer yes to a number of these you may well be zinc deficient. Your doctor may choose to give you zinc supplements for a short period to see if your symptoms improve. If they do then he and you will have to decide on whether to change your diet so you are getting more zinc or if that is not an option then to continue supplementation.
If it is decided more testing needs to be done what tests are available?
1. Zinc Taste Test (Oral Zinc Test)
Because we know that taste and smell are dependant on there being enough zinc in the body we are able to get an idea of the zinc status by giving the patient a standard test solution of zinc sulphate for tasting and comparing the response to defined standards.
This is a very quick, 10 second test that can be done at home or in the doctors rooms.
Obviously assessment of altered taste perception by zinc 'taste tests' is very subjective and cannot be considered scientifically accurate.
2. Serum Zinc
This is the simplest way of assessing zinc status but the factors that can cause inaccuracies are high.
3. Plasma zinc
This is the main lab test done to establish zinc deficiency. Although it is very good at picking up major deficiencies it is quite insensitive to marginal deficiency because a change in plasma zinc does not occur until zinc intake is extremely low. So a patient with `normal' results may still be deficient.
4. Zinc Tolerance Test
This test measures the changes in plasma zinc after zinc is orally administered.
5. Hair zinc
This is a test often used in research studies where it’s results are of more use than in general practise because of the ability of the researchers to keep a tight control over external factors.
6. Urinary zinc excretion
Again this is an unreliable test because though low amounts may indicate zinc deficiency the results are influenced by other factors.
7. New tests
Serum alkaline phosphatase enzyme reactivation
Leukocyte zinc content correlates well with muscle zinc content and so may offer an improved indication of zinc status.
For more information on the above tests, visit our zinc diagnostic tests page.
Some interesting websites
checked and updated April 2013.