Zinc

Written by Slawomir Gromadzki, MPH

COULD IT BE ZINC DEFICIENCY?

Do you complain about hair loss, low mood, white spots on fingernails, dry skin, changes in appetite, salty or sweet foods cravings, low stamina, fertility & prostate problems, lack of sex drive, recurrent infections, weight gain or weight loss, tiredness, sleep problems, hormonal imbalance, poor concentration & memory, and allergies?

Well, if you do experience some of these signs maybe it’s time to start being very serious about considering zinc deficiency.

Researchers suggest that due to soil depletion, poor refined diet, high sugar consumption, stress, stimulants (caffeine, alcohol, etc.), frequent orgasms (semen is very high in zinc), and other factors at least 2 billion people around the world suffer from lack of this vital trace mineral.

Zinc is present everywhere in our body and it is required to maintain normal metabolism (bodyweight), brain and nervous system function, healthy immune system, strong bones & teeth, night vision, acid production in the stomach, healthy liver, and normal blood glucose levels.

ZINC DEFICIENCY SYMPTOMS

Zinc deficiency may be associated with the following symptoms and health problems:

Weak immune system, frequent infections, increased risk of cancer and autoimmune diseases, prostate problems including prostate cancer and enlargement, hormonal imbalance, male infertility, erectile dysfunction, sleep problems, hair loss, diarrhoea, allergies, dry skin and skin lesions, lack of sex drive, mental lethargy, obesity, anorexia and bulimia nervosa, depression, chronic fatigue, insomnia, diabetes, psoriasis, acne, eczema, sinus problems, Alzheimer’s disease, AIDS, pyroluria (a metabolic condition characterized by extremely low zinc status), Lyme Disease, and even autism or autoimmune diseases. Some experts such as Dr Carl Pfeiffer also believe white spots on fingernails are often the result of a zinc deficiency. A deficiency of zinc or magnesium allows sodium levels to rise, contributing to water retention.

CAUSES OF ZINC DEFICIENCY

Soil depletion is regarded as one of the main reasons why we can be zinc deficient, because if this mineral is not present in the soil then also plants will be deprived of it. Soil depletion has been well documented and even organically grown vegetables may not contain the proper amount of minerals as organic farming usually only solves the pesticide pollution problem. It is, therefore, believed that the best way to receive vegetables high in zinc and other minerals is through the means of bio-dynamic farming, supplementing soils with natural compost, and through crop rotation.

Zinc deficiency is also exacerbated by certain drugs and eating too much of refined foods (all white flower products, white bread, sugar, sweets, pizza, spaghetti, etc.) which contain very little or no zinc.

High sugar consumption leads to insulin surges which use up our zinc. IUDs (intrauterine devices), which are usually made of copper, and birth control pills, which may contain copper, may cause excess copper that can be toxic and contribute to zinc deficiency as these two minerals are antagonistic to each other.

Mercury toxicity caused by using amalgam fillings, vaccines and fish consumption can block zinc and magnesium as mercury binds with these minerals. In this case, it is suggested that even supplementing zinc and magnesium will not solve this problem without proper detoxification and removing mercury from the body. One of the best ways to detoxify the body from mercury is by avoiding mentioned above sources and regular intake of organic chlorella >.

Caffeine-containing products inhibit the absorption of not only zinc but also magnesium, calcium, iron, manganese, and copper.

Also alcohol contributes to zinc, calcium, manganese, and chromium deficiency.

Iron and calcium supplements may reduce zinc absorption.

Frequent sex and masturbation can be one of the key causes of zinc deficiency. David Horrobin, M.D. and PhD from Oxford University, declared that “The amount of zinc in semen is such that one ejaculation may get rid of all the zinc that can be absorbed from the intestines in one day. This has a number of consequences. Unless the amount lost is replaced by an increased dietary intake, repeated ejaculation may lead to a real zinc deficiency with various problems developing, including impotence… It is even possible, given the importance of zinc for the brain, that 19th-century moralists were correct when they said that repeated masturbation could make one mad!” Also, Carl C. Pfeiffer, Ph.D., M.D., in his book on zinc stated: “In a zinc-deficient adolescent, sexual excitement and excessive masturbation might precipitate insanity.”

HEALTH BENEFITS OF ZINC

Necessary for the strong immune system

Zinc makes the immune system strong enough to fend off infections. In addition, it helps reduce the risk of various cancers and autoimmune diseases. Zinc strengthens our immune system by stimulating antibody production and it has proven to be even directly toxic to certain types of viruses. It also speeds up recovery & helps minimise unpleasant signs associated with flu or clod such as runny nose or tiredness. A study conducted at the Cleveland Clinic Foundation demonstrated that zinc “significantly reduced the duration of symptoms of the common cold.”

15-30mg Zinc (requires Quercetin) and 50-200mcg Selenium daily with meals in a good immune supplement, such as Betaimune, Beta Glucan Complex. Both minerals are absolutely crucial for strong immunity. Zinc has long been known for its potential antiviral effects. For example, over-the-counter remedies containing zinc with vitamin C have been shown to reduce the duration and symptoms of the common cold.[>]. There are numerous mechanisms of action through which zinc acts against viruses in the human body. These include (but are not limited to): Inhibition of RNA binding, Inhibition of RNA synthesis, Inhibition of viral polyprotein cleavage, Inhibition of viral replication, Metallothionein-dependent inhibition of viral replication, Virus inactivation, Viral protease enzyme inactivation [>].

Take Zinc with Quercetin for better results

Quercetin (500mg-1000mg twice daily) helps to increase the intracellular concentrations of Zinc by transporting it through the cell membrane. The major benefit of taking Quercetin with Zinc is that the quercetin will push the zinc into the center of the cell where the zinc can stop the virus from reproducing. Combination of Zinc with Quercetin has been found to be one of the most effective treatments against covid. “Antiviral Effects of Quercetin through Zinc Ionophore (ion carrier) Activity” (>). Quercetin is an increasingly well-known plant compound with potent anti-inflammatory effects. The SARS-CoV-2 outbreak resulted in renewed research efforts focusing on its effects as a zinc-ionophore, increasing intracellular zinc concentrations and thus Quercetin working as an antiviral. Preliminary studies in South Korea and China have pointed to Quercetin’s potential for inhibiting viral replication of SARS-CoV-2. In a 2014 publication, researchers demonstrated clearly that quercetin and a similar polyphenol (epigallocatechin-gallate) were capable of rapidly increasing zinc concentrations in Hepa 1-6 cells and liposomes. The mechanism of action was found to be independent of plasma membrane zinc transporters.[>]. A 2016 study examined fourteen polyphenols – including Quercetin – and their capacity to form complexes with zinc cations. The results confirmed that polyphenols have the capacity to transport zinc across a variety of lipid membranes.[>].

Promotes healthy libido, prostate, stamina & normal hormonal balance

Zinc benefits hormonal health and fertility because it plays an important role in hormone production, including testosterone (male sex hormone), thus promoting normal stamina, prostate health and helps build muscle mass in men.

The prostate cannot function properly without zinc as it contains more zinc than any other organ in the body.

Zinc is also needed for the production of female sex hormones oestrogen and progesterone which support fertility and greatly influence mood and menstruation.

Key beauty nutrient for healthy hair, skin & nails

Zinc deficiency can lead to deterioration of the protein that makes up the hair follicle thus causing hair shedding & loss.

Zinc is absolutely essential for beautiful skin as it helps skin maintain the supply of collagen which prevents wrinkly sagging skin. Without zinc, skin has also a hard time to repair itself as it is required for cell division.

Zinc deficiency can be a root cause of acne, nail splitting & abnormal discolorations of fingernails

Promotes normal appetite, body weight, metabolism and healthy blood glucose levels

Zinc deficiency is associated with insulin resistance, obesity, and often also with anorexia and bulimia nervosa. There are individuals who even claim to recover from anorexia and bulimia after taking zinc supplements because in their case the main problem was severe zinc deficiency.

A study on obese children, demonstrated that zinc supplementation significantly reduced blood glucose and insulin levels, thus reducing the conversion of sugar to fat (stimulated by high blood levels of insulin). Zinc has important effects on metabolism, and on the thermoregulation of obese individuals.

Obesity combined with zinc deficiency promotes the development of chronic systemic inflammation. Obese individuals have an increased incidence of developing zinc deficiency, have lower dietary zinc intake and therefore exhibit more systemic inflammation. Zinc deficiency perturbs immune functions and promotes systemic inflammation. Recent studies have demonstrated that obesity can be associated with systemic inflammation which leads to atherosclerosis, asthma, and other health problems. In obese people, adipose tissue releases specific adipokines which lead to infiltration by macrophages thus promoting the production of inflammatory mediators.

Studies investigating the relationship between zinc and leptin show that zinc may critically impact leptin secretion. Zinc supplementation to the obese mice increases leptin levels and restoration of obesity-induced by sucrose. It means that low levels of this very important hormone and appetite suppressor, as well as leptin resistance which occurs in obesity, might have resulted from zinc deficiency. The relationship between zinc and leptin was examined also in humans who had zinc deficiency caused by refined diet. Zinc supplementation to these individuals resulted in a significant increase in leptin secretion.

Required for strong bones and teeth

Zinc helps vitamin D to work inside the cells of our body. It’s also important in making sure that the calcium we get from foods or supplements is used in our bones. Without zinc and vitamin D calcium tends to be deposited in kidneys (contributing to kidney stones) and in arteries, where together with cholesterol causes their hardening, thus contributing to heart attacks and strokes. Vitamin D and zinc work together to strengthen our bones and to help them develop properly.

Required for the production of stomach acid and proper protein digestion

Zinc is used in our body to produce stomach acid. Low stomach acid, therefore, can be a sign of zinc deficiency. That is why when the amount of zinc in our body is insufficient then the protein from food cannot be properly digested in the gastrointestinal tract. As a result, these undigested and too large protein molecules enter the bloodstream where they are recognized by the immune system as potentially dangerous foreign bodies, thus inducing immune reaction and histamine secretion which, in turn, creates allergy symptoms.

Other benefits

Zinc in our body regulates taste and appetite, improves metabolism, memory, and night vision.

Together with vitamin B6 and magnesium zinc is needed to produce tryptophan and then serotonin which regulates our appetite and mood.

Zinc is also necessary for optimal development and growth of the human body or maintaining proper blood sugar level.

It is believed that zinc may even work as an antioxidant preventing DNA damage and cancer. One of the new studies demonstrated that even relatively small zinc deficiency may lead to DNA damage thus contributing to cancer development.

Zinc also works as an antioxidant slowing down the ageing process and preventing healthy cells from becoming abnormal.

Like selenium, zinc is also used in our body to create superoxide dismutase (SOD), one of the most powerful antioxidants.

TESTIMONIALS

Concerning the influence of high in zinc foods (especially pumpkin seeds) on appetite, I have found an interesting experience described by Brian who wrote: “I tried low fat, near vegetarian diet with lots of fruits and I had lots of energy. Later, my health relapsed and I was hungry all the time despite drinking 1.5 l of green smoothie per day. When I ate a few handfuls of pumpkin seeds and a cup of quinoa, the food cravings dropped… It is best to soak the seeds to absorb more minerals”.

Another person suggests that zinc supplementation was very helpful in coping with anxiety: “I’ve had great success ridding myself of anxiety by taking (in divided doses) 50-100mg zinc, 200mg B6, and GLA each day. From what I’ve researched stress depletes both zinc and B6 so people who are prone to stress may be greatly benefited from taking these”.

DIETARY SOURCES OF ZINC

High amounts of zinc can be found in pumpkin seeds (often regarded as the highest source), garlic, Brazil nuts, wholemeal bread, whole grains, mushrooms, nuts, and seeds. These sources, however, are dependent on the presence of zinc in the soil. Unfortunately, if the soil is depleted from zinc, which in most cases is, the food also will contain an insufficient amount of this extremely important mineral. In this case, supplementation seems to be the only solution.

ZINC SUPPLEMENTS

As far as supplementation is concerned, zinc citrate, picolinate and gluconate are often believed to be the best forms (not more than 100 mg a day with a meal). I often take 15-25 mg of elemental zinc citrate per day after breakfast. I prefer citrate after I found out it’s the only form of zinc which doesn’t make me nauseated.

ZINC AND NAUSEA

Zinc supplements (including gluconate) often cause nausea and for this reason, they should be always taken after meals and not on an empty stomach. Unfortunately, even when ingested after meals zinc can still trigger nausea. I know it also from my own experience as I have tried various forms and most of them often lead to nausea. The only one which doesn’t seem to upset my stomach is zinc citrate.

Zinc gluconate is regarded as usually better tolerated by the stomach but it wasn’t true in my case. However, if you still prefer gluconate than citrate in spite of experiencing nausea try to reduce the amount to not more than 30mg a day after meal.

DOSAGE

The Recommended Daily Allowance for Zinc is about 10 to 15 mg for adults (men usually need more Zinc than women).

The upper safe limit for Zinc in the UK is 25mg (too low) and in US 40mg.

Some specialists, however, recommend at least 25 mg and in some cases even 100 mg of zinc per day, but not more than that unless in specific situations and for a limited period of time as overdosing Zinc may lead to nausea, vomiting, and sometimes to stomach pain or diarrhoea.

Please keep in mind that the daily intake of Zinc from supplements depends on various dietary and lifestyle factors: Frequent sex, a diet high in sugar, white flour products, white rice, using stimulants (including caffeine), stressful lifestyle, etc. require higher daily dosages than recommended daily intake.

Please keep in mind that even if you avoid the mentioned above factors and you are on a healthy unrefined tied (higher in Zinc), you still need supplemental Zinc because due to the soil depletion even the best diet is can’t guarantee a sufficient intake of Zinc and other minerals.

Therefore, those who are on a good unrefined diet are recommended to take 15-30 mg of elemental Zinc after meal every day while individuals who are on a refined diet, use stimulants, are sexually very active (especially men as they lose large amounts of Zinc with semen) may need 30-70mg of elemental zinc daily after a meal with one day break after every week and one week break after every 3-6 months.

ZINC DOSAGES FOR VARIOUS HEALTH PROBLEMS (according to WebMD >)

Zinc deficiency: Two to three times the recommended dietary allowance (RDA) of zinc for 6 months. In people with moderate to severe deficiency, recommendations suggest taking four to five times the RDA for 6 months.
Diarrhoea: To prevent diarrhoea in infants, pregnant women have used 15 mg of zinc, with or without 60 mg of iron and 250 mcg of folic acid, starting 10-24 weeks into pregnancy through one month after giving birth.
Wilson’s disease: Zinc acetate (Galzin in the U.S.; Wilzin in Europe) is an FDA-approved drug for treating Wilson’s disease. The recommended dose, which contains 25-50 mg of zinc, is to be taken three to five times daily.
Acne: 30-150 mg elemental zinc daily has been used.
Macular degeneration: A combination of 80 mg of elemental zinc, 2 mg of copper, 500 mg of vitamin C, 400 IU of vitamin E, and 15 mg of beta-carotene taken daily for 5 years has been used in people with advanced age-related vision loss.
Anorexia nervosa: 14-100 mg of elemental zinc has been used daily.
Tumours in the colon and rectum: A combination supplement containing 200 mcg of selenium, 30 mg of zinc, 2 mg of vitamin A, 180 mg of vitamin C, and 30 mg of vitamin E has been taken daily for up to 5 years.
Common cold: One zinc gluconate or acetate lozenge, providing 4.5-24 mg elemental zinc, dissolved in the mouth every two hours while awake when cold symptoms are present.
Depression: 25 mg of elemental zinc has been used daily for 12 weeks along with antidepressant medications.
Taste disorder (hypogeusia): 140-450 mg of zinc gluconate has been taken in up to three divided doses daily for up to 4 months. Also, 25 mg of elemental zinc taken daily for 6 weeks has been used. A zinc-containing product called polaprezinc (Promac, Zeria Pharmaceutical Co., Ltd) has also been used.
Skin lesions: 2.5-10 mg/kg of zinc sulfate has been taken in three divided doses daily for 45 days.
Muscle cramps: 220 mg of zinc sulfate has been taken twice daily for 12 weeks.
Osteoporosis: A combination of 15 mg of zinc combined with 5 mg of manganese, 1000 mg of calcium, and 2.5 mg of copper has been used.
Attention deficit-hyperactivity disorder (ADHD): 55-150 mg of zinc sulfate containing 15-40 mg of elemental zinc has been taken daily for 6-12 weeks.
Stomach ulcers: 300-900 mg of zinc acexamate has been taken in one to three divided doses daily for up to one year. Also, 220 mg of zinc sulfate has been taken three times daily for 3-6 weeks.
Pregnancy-related complications: 25 mg of zinc has been taken daily in combination with vitamin A for 3 weeks to restore vision in pregnant women with night blindness. 30 mg of zinc has been taken daily for 6 weeks to lower blood sugar levels in people with diabetes during pregnancy.
Bedsores: A standard hospital diet plus 9 grams of arginine, 500 mg of vitamin C, and 30 mg of zinc has been used daily for 3 weeks.
Sickle cell anaemia: 220 mg of zinc sulfate three times daily has been used. Also, 50-75 mg of elemental zinc taken daily in up to two divided doses for 2-3 years has been used.
Leg ulcers: 220 mg of zinc sulfate taken three times daily has been used along with ulcer dressings.
Warts: 400-600 mg of zinc sulfate daily for 2-3 months. (SOURCE >)

TOLERABLE UPPER INTAKE LEVELS (UL) IN EUROPEAN UNION COUNTRIES (source >)

In the US the UL for adults is much higher than in the EU and it is set at 40 mg of elemental zinc per day. The National Institutes of Health considers 40 mg of zinc a day to be the upper limit dose for adults and 4 mg of zinc a day for infants under age 6 months.

PREGNANCY AND LACTATION

Available data indicate that pregnant women do not have increased susceptibility to zinc supplementation. Therefore the UL of 25 mg zinc per day applies also to pregnant and lactating women (source >).

ZINC AND COPPER

A proper balance between zinc and copper is critical to maintaining health. Zinc and copper compete against one another as they are antagonists. Therefore, having too much of one may cause deficiency of the other. Taking zinc supplements is important because zinc prevents copper accumulation and toxicity. On the other hand, taking zinc supplements alone can lead to copper deficiency which may contribute to premature grey hair and hair loss, weak immunity, poor bone health, arthritis, muscle and/ or joint pain, fatigue, digestive problems, Crohn’s disease, low body temperature, feeling cold, skin problems, unexplained weight loss, or bruising.

To prevent copper deficiency due to zinc supplementation, it is recommended to take 1mg of copper per every 25mg of zinc.

ZINC AND QUERCETIN

– Quercetin (500mg-1000mg twice daily) helps to increase the intracellular concentrations of Zinc by transporting it through the cell membrane. Combination of Zinc with Quercetin has been found to be one of the most effective treatments against covid. “Antiviral Effects of Quercetin through Zinc Ionophore (ion carrier) Activity” (>). Quercetin is an increasingly well-known plant compound with potent anti-inflammatory effects. The SARS-CoV-2 outbreak resulted in renewed research efforts focusing on its effects as a zinc-ionophore, increasing intracellular zinc concentrations and thus Quercetin working as an antiviral. Preliminary studies in South Korea and China have pointed to Quercetin’s potential for inhibiting viral replication of SARS-CoV-2. In a 2014 publication, researchers demonstrated clearly that quercetin and a similar polyphenol (epigallocatechin-gallate) were capable of rapidly increasing zinc concentrations in Hepa 1-6 cells and liposomes. The mechanism of action was found to be independent of plasma membrane zinc transporters.[>]. A 2016 study examined fourteen polyphenols – including Quercetin – and their capacity to form complexes with zinc cations. The results confirmed that polyphenols have the capacity to transport zinc across a variety of lipid membranes.[>].

OTHER RECOMMENDATIONS

If possible avoid iron and calcium supplements as they reduce zinc absorption.

In case you have to take high doses of iron and calcium you should include zinc supplementation as well.

Vitamin D and selenium, on the other hand, increase the bioavailability of zinc.

CONTRAINDICATIONS

If you’re taking amiloride, prednisone, cyclosporine or any other medicine that suppresses your immune system (immunosuppressant) you shouldn’t take zinc supplements without talking to your physician first.

Don’t use intranasal zinc as this form of zinc has been linked with the loss of the sense of smell.

INTERACTIONS WITH OTHER VITAMINS & MINERALS

– Zinc leads to copper deficiency.

– 50mg of zinc per day reduces iron and copper levels.

– Zinc impairs iron absorption in water solutions but doesn’t cause iron deficiency when zinc supplements taken with meals.

– Supplements of high levels (142 mg/day) of zinc might reduce magnesium absorption.

– Supplementing with nicotinic acid (B3) might provide a dose-dependent improvement in hepatic zinc levels and better antioxidant markers.

– Iron, copper and calcium supplements may compete with zinc for absorption.

INTERACTIONS WITH MEDICATION

Using oral zinc while on antibiotics such as quinolone or tetracycline can interfere with their ability to fight bacteria. Taking the antibiotic two hours before or four to six hours after taking zinc can minimize this effect.

ADDITIONAL INFORMATION

Unfortunately, it is often believed that meat products are better sources of zinc because plant foods which are high in zinc such as nuts, seeds (especially pumpkin seeds), whole grains, garlic, legumes, or mushrooms, contain much more phytate (phytic acid) which tends to reduce zinc absorption from these products.

Some researchers, however, regard the ability of phytate to bind with metals as also beneficial because it does not allow our organism to absorb too much of the heavy metals which are toxic. Apart from that, phytic acid also binds with radioactive substances preventing their absorption and carrying them out of our organism.

There is no doubt that if a plant-based diet is unrefined and consists of a variety of products including whole grains, legumes, as well as some nuts, seeds, and mushrooms, it provides more than adequate amounts of zinc, while the phytic acid present in these products only prevents us from absorbing too much of this mineral.

However, since we should avoid high intake of phytic acid it is better to reduce its possible negative influence in a very simple way: Soaking grains, legumes (beans), seeds, and nuts in filtered water overnight greatly reduces the amount of phytic acid. But in order to achieve this goal you need to remove the water in which these foods were soaked. Some believe that as soon as the amount of phytic acid is reduced in this way, also enzymes present in these foods will be able to improve the digestion process in our gastrointestinal tract.

Many nutritionists encourage us today to consume oysters which are high in zinc but it is a very bad idea as shellfish such as oysters, mussels or clams consume decaying organic matter that sinks to the sea floor, including sewage. In addition, they are often contaminated with bacteria or viruses and that is why we are warned to not consume raw or undercooked oysters. Our Creator who knows best our nutritional needs forbade us in Leviticus 11 to eat so-called “unclean” animal foods including shellfish. In “Eating by the Book” nutritionist David Meinz suggests wisely that, “God, in His wisdom, created certain creatures (pigs, shellfish, crabs, etc.) whose sole purpose is to clean up after the others? Their entire ‘calling’ may be to act exclusively as the sanitation workers of our ecology. God may simply be telling us that it’s better for us not to consume the meat of these trash collectors”.

Written by Slawomir Gromadzki, MPH

SOURCES AND REFERENCES

– Suzuki, H.; Asakawa, A.; Li, J. B.; Tsai, M.; Amitani, H.; Ohinata, K.; Komai, M.; Inui, A. (2011). Zinc as an appetite stimulator – the possible role of zinc in the progression of diseases such as cachexia and sarcopenia. Recent Pat Food Nutr Agric. 2011 Sep; 3(3):226-31.

– Su JC, Birmingham CL. Zinc supplementation in the treatment of anorexia nervosa. Eat Weight Disord 2002; 7:20-2.

– David F. Horrobin, M.D., Ph.D., Zinc, St. Albans, Vt.: Vitabooks, Inc., 1981, p. 8.

– Carl C. Pfeiffer, Ph.D., M.D. Zinc and Other Micro-nutrients, Keats: New Canaan, Conn., 1978, p. 45.

– Jing MY, Sun JY, Wang JF. The effect of peripheral administration of zinc on food intake in rats fed Zn-adequate or Zn-deficient diets. Biol Trace Elem Res 2008; 124:144-56.

– Birmingham CL, Gritzner S. How does zinc supplementation benefit anorexia nervosa? Eat Weight Disord 2006; 11:e109-11.

– Safai-Kutti S. Oral zinc supplementation in anorexia nervosa. Acta Psychiatr Scand Suppl 1990; 361:14-7.

– Selvais PL, Labuche C, Nguyen XN, Ketelslegers JM, Denef JF, Maiter DM. Cyclic feeding behaviour and changes in hypothalamic galanin and neuropeptide Y gene expression induced by zinc deficiency in the rat. J Neuroendocrinol 1997; 9:55-62.

– Lee RG, Rains TM, Tovar-Palacio C, Beverly JL, Shay NF. Zinc deficiency increases hypothalamic neuropeptide Y and neuropeptide Y mRNA levels and does not block neuropeptide Y-induced feeding in rats. J Nutr 1998; 128:1218-23.

– Kennedy KJ, Rains TM, Shay NF. Zinc deficiency changes preferred macronutrient intake in subpopulations of Sprague-Dawley outbred rats and reduces hepatic pyruvate kinase gene expression. J Nutr 1998; 128:43-9.

– Jing MY, Sun JY, Wang JF. The effect of peripheral administration of zinc on food intake in rats fed Zn-adequate or Zn-deficient diets. Biol Trace Elem Res 2008; 124:144-56.

– Birmingham CL, Gritzner S. How does zinc supplementation benefit anorexia nervosa? Eat Weight Disord 2006; 11:e109-11.

– Safai-Kutti S. Oral zinc supplementation in anorexia nervosa. Acta Psychiatr Scand Suppl 1990; 361:14-7.

– Mantzoros CS, Prasad AS, Beck FW, Grabowski S, Kaplan J, Adair C, et al. Zinc may regulate serum leptin concentrations in humans. J Am Coll Nutr 1998; 17:270-5.

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