A) ENZYME FUNCTION AND METABOLISM
One of the primary catalytic nutrients in the body, zinc is an essential coenzyme (non-protein portion of an enzyme) in over 200 enzymes. Included among the countless functions of zinc-dependent enzymes are energy production; metabolism of proteins, fats and carbohydrates; protein synthesis and digestion; amino acid synthesis; detoxification of alcohols; and bone metabolism.
B) ANTIOXIDANT ACTIVITY
As with copper and manganese, zinc is an essential mineral component of the enzyme superoxide dismutase (SOD). SOD is one of the most powerful substances manufactured by the body for the purpose of protecting cells. The protective mechanism of SOD relates to its function as an antioxidant which neutralises superoxide free radicals. Although many parts of the body are adversely affected by superoxide radicals, they are particularly associated with tissue damage within the joints (i.e. arthritis) and eyes (i.e. cataracts). Interestingly, scientists have demonstrated a strong statistical association in mammalian species between tissue SOD levels and life expectancy.
C) IMMUNE SUPPORT AND FUNCTION
Although a deficiency in any essential nutrient can compromise immunity, zinc is considered by many authorities to be the most important of all nutrients in this respect. It is involved in practically every facet of immunity, including thymus function (the master gland of the immune system) and white blood cell (i.e. T-cell and lymphocyte) production and activity. Regarding thymus function, zinc supplementation has a dramatic impact on the secretion of the thymus hormone thymulin. Although this factor would benefit all ages, it is especially critical to restoration of immunological strength within the elderly. Zinc also possesses direct anti-viral properties – a fact which probably accounts for much of the localised anti-infective activity of lozenges containing zinc. According to research, zinc lozenges are an effective treatment for common cold symptoms. For example, in a double-blind placebo-controlled clinical trial employing 23mg zinc lozenges every two waking hours, 86% of the zinc users were symptom-free after one week compared to 46% of those taking the placebo (see Contraindications/ Cautions below).
D) SKIN HEALTH AND HEALING
Zinc’s influence on protein synthesis and related biological processes would encourage skin tissue regeneration, and in individuals who are deficient in zinc, supplementation has been shown to accelerate wound healing and treat skin ulcerations. Several double-blind clinical trials also report zinc’s effectiveness in acne therapy. In fact, zinc has achieved benefits comparable to the antibiotic drug tetracycline in cases where acne only affects the surface tissue of the skin. In patients with deeper acne lesions, zinc supplementation has been generally found to be more effective than tetracycline. (Most participants have needed around 3 months of supplementation before achieving significant results.) It is worth noting that clinical benefits in acne of the poorly absorbed sulphate form of zinc have been inferior to the better absorbed forms such as zinc gluconate or citrate. It is likely that the zinc’s benefits in acne therapy are not only due to its influence on tissue regeneration and healing. Its immunological properties, influence on hormones and retinal-binding protein and encouragement of anti-inflammatory prostaglandins probably also play a significant role. Not surprisingly, zinc is often deficient in patients with acne, as well as various other skin disorders such as psoriasis, eczema and dermatitis herpetiformis.
E) REPRODUCTIVE HORMONE INFLUENCE
In men, a lack of zinc is associated with lower testosterone, and in such cases, levels of this hormone improve with zinc supplementation [which, in turn, can have a considerable impact on sperm counts and male fertility (see male fertility below)]. Testosterone is essential for male sexual function, however the enzyme 5-alpha reductase converts it into the more powerful androgen dihydrotestosterone (DHT), which is associated with certain health disorders. For example, elevated DHT is linked to conditions such as prostate disease and male pattern baldness in men, and polycystic ovaries, infertility, hair loss and excessive body and facial hair in women. Zinc lowers 5-alpha reductase activity (thus lowering DHT levels), reduces cellular binding of androgens and lowers levels of the hormone prolactin. These properties account for much of its value in the hormone-related disorders listed above.
F) PROSTATE HEALTH
The proliferation of prostate gland cells is triggered by the hormone dihydrotestosterone (DHT). In puberty this process is necessary for normal sexual development, however when prostate tissue growth is over-stimulated by DHT in adulthood then benign prostate hyperplasia or BPH (prostate enlargement) can result. It has been reported that more than half of all men are affected by BPH at some point during their life. Interestingly, in older males the elevation of prostate DHT (and thus the increased risk of BPH) coincides with an overall reduction in the body’s testosterone levels and an increase in female hormones such as oestrogen and prolactin. As mentioned above, zinc reduces the activity of 5-alpha reductase, the enzyme responsible for the conversion of testosterone into dihydrotestosterone (DHT). Zinc also reduces cellular binding of androgens and reduces prolactin levels. Oestrogen antagonises zinc uptake, which may cause 5-alpha reductase levels to rise if intake of the mineral is not increased sufficiently to compensate. Not surprisingly, clinical trials demonstrate that zinc supplementation reduces both symptoms of prostate enlargement and prostate size in most patients with BPH.
G) MALE FERTILITY
Zinc deficiency is associated with reduced testosterone levels in men, and it has been established that testosterone depletion improves with zinc supplementation. Zinc is also critical to the production and motility of sperm. As such, zinc status has a significant impact on male fertility. This fact is underlined by a clinical trial highlighting that in men with both low testosterone and low sperm counts, testosterone levels increased and average sperm counts were 2.5 times higher after 6-7 weeks of zinc supplementation (60mg per day). In fact, 41% of the men successfully impregnated their partners during the course of the study – which is even more remarkable considering that the couples had been incapable of achieving pregnancy for at least 5 years prior to the study.
H) BLOOD SUGAR BALANCE
Glucose metabolism and general blood sugar balance is dependent on adequate zinc status. Among other relevant functions, zinc is needed in order for insulin to be manufactured and secreted by the pancreas. Zinc also works along with chromium and various other nutrients to facilitate the cellular utilisation of insulin. While zinc is eliminated from the body more rapidly in diabetics than in non- diabetics, an important 1992 study reported that zinc supplements increase insulin levels in both insulin-dependent and non-insulin dependent diabetic patients.
I) EYE HEALTH
As mentioned above, zinc is an essential mineral component of the cell-protective antioxidant enzyme superoxide dismutase (SOD), which protects the cells from superoxide free radicals. Although this type of free radical adversely affects cells throughout the body, the eyes are especially susceptible to superoxide damage, which often manifests as cataracts. In fact, blood levels of zinc are often deficient in cataract patients, leading among other problems, to impaired glucose metabolism in the lens. Zinc supplements have been shown to aid glucose utilisation in the eye tissue. Lack of retinal zinc is also linked to low levels of the antioxidant enzyme catalase, which when deficient, is associated with the development of macular degeneration. A double-blind clinical trial published in the journal Archives in Opthamology reported that macular degeneration patients taking lOOmg of zinc per day over 1-2 years had considerably less vision loss than those taking a placebo (see Contraindications/Cautions below).
J) MENTAL HEALTH AND FUNCTION
Zinc status can have a considerable influence on many aspects of mental development, function and performance as well as emotional health and psychological balance. For example, zinc deficiency is implicated in learning disorders, Attention Deficit Disorder, hyperactivity, mental retardation, depression, dementia (including Alzheimer’s Disease), schizophrenia and organic mental disorder. In the case of children with learning disorders, a build-up of the heavy metal cadmium is often implicated in the development of reading difficulties. Zinc can antagonise cadmium, and a 1984 study reported that the zinc-cadmium relationship significantly reflected on reading performance. Even in adults, zinc can impact on learning; a double-blind trial of 34 women from age 18-40 indicated that zinc supplementation improved performance in both associated learning of word combinations and in reproduction of visual images. In the case of dementia and Alzheimer’s Disease, thus far there are only small-scale studies showing clinical improvement. However, it is worth noting that Alzheimer’s patients typically have significantly reduced levels of zinc in the brain and cerebrospinal fluid. Scientists have also observed that nerve cell damage and the accumulation of neurofibrillary tangles in the brain increase when zinc is deficient.
K) GROWTH AND DEVELOPMENT
Zinc is necessary for proper growth and development of the foetus, and appears to play an important part in maintaining biochemical and physiological health and stability in the pregnant woman. Depleted maternal zinc levels are implicated in several pregnancy-related and developmental problems such as premature birth; low birth weights; neural tube defects and other neurological problems; labour problems and abnormalities; and spontaneous abortion. Thus it is urgently important to point out that during pregnancy blood and white blood cell concentrations of zinc decline by almost a third, while at the same time, the average pregnant woman consumes significantly less than the recommended daily allowance for zinc. Although the results of various zinc studies in pregnancy are less reliable due to inadequate methods of study design, one well-designed placebo-controlled trial showed that the addition of zinc to a prenatal supplement used by zinc-deficient women markedly improved both birth weights and cranial circumference. The women, who were lower than normal in zinc prior to the study, received 25mg per day.
• Immune support (general)
• Common cold
• Male hormonal health (general)
• Prostate enlargement
• Male fertility (general)
• Low sperm count
• Male pattern baldness
• Polycystic ovaries
• Female infertility
• Excessive facial and body hair (women)
• Skin health (general)
• Dermatitis herpetiformis
• Wound healing
• Macular degeneration
• Mental health (general)
• Learning disorders
• Attention Deficit Disorder
• Hyperactivity Disorder
• Dementia (including Alzheimer’s Disease)
• Foetal growth and development
• Poor appetite
• Copper excess
• Wilson’s Disease
Common Food Sources
• Pumpkin seeds
• Whole grains
Typical Supplemental Dosage Range
• 10-50mg per day
Common Supplement Forms/Sources
• Zinc sulphate
• Zinc oxide
• Zinc gluconate
• Zinc citrate
• Zinc amino acid chelate
• Zinc picolinate
• Zinc glycinate
• Zinc aspartate
• Long-term intake of more than 100-150mg of zinc per day may suppress immune function, lead to irritation or even damage of the stomach lining and reduce levels of HDL (good) cholesterol (potentially increasing the risk of certain cardiovascular problems).
• Intake of more than 200mg per day may cause nausea, diarrhoea, vomiting and digestive pain or irritation.
• Individuals with stomach or duodenal ulcers should only use zinc supplements on the consent and under the strict monitoring of a physician.
• High doses of zinc can interfere with copper utilization. Unless ingesting copper in doses sufficient to maintain an appropriate ratio between the two minerals (see italics below), long-term zinc intake in doses greater than 50mg per day may cause copper deficiency (and associated problems such as microcytic anemia, low neutrophil count and poor iron utilisation).
Although there are differing scientific views on what constitutes an optimal ratio between zinc and copper, it is thought that a ratio for long-term intake of between 7.5:1 and 10:1 (zinc to copper) is probably appropriate.
• Very high doses of zinc may interfere with iron absorption and utilization.
• Zinc supplements should be avoided if taking the drugs amiloride, penicillamine, tetracycline, warfarin or fluoroquinolone antibiotics, unless on the consent and under the strict monitoring of a physician.
|Warfarin Antacids H2 antagonists Proton pump inhibitors ACE inhibitors Ethambutamol Penicillamine Thiazide diuretics Sodium valproate Zidovudine (AZT)|
• When taken on an empty stomach, even moderate doses of zinc can cause nausea in the lozenge form or as zinc sulphate. Thus, zinc lozenges and zinc sulphate should be taken after a meal.
Agents/Factors Which Deplete Levels, Impair Absorption and/or Inhibit Activity
Phytates (i.e. in cereal grains – especially wheat bran) Soy foods
Copper (high intakes) Iron (high intakes) Aspirin
Possible Signs/Symptoms Associated with Deficiency
White spots on nails
Loss of sense of taste and/or smell
Weak immunity/chronic infections
Poor wound healing
Defects in male reproductive maturation
Male infertility/low sperm count
Hair loss (general and male pattern) Polycystic ovaries Female infertility
Excessive facial and body hair (women)
Skin disorders (general)
Dermatitis herpetiformis Diabetes/poor glucose tolerance Macular degeneration Cataracts
Mental dysfunction Psychological dysfunction Behavioural problems Learning disorders
Attention Deficit/Hyperactivity Disorder (ADHD)
Impaired growth and development Poor appetite/anorexia Copper excess Wilson’s Disease Fatigue/lethargy
** What constitutes an optimal intake of potassium depends greatly on one’s intake of sodium, and vice versa. Although there is no official RDA for either potassium or sodium, many experts recommend that