Mineral Supplements

by Ben Best


  7. ZINC

[Many of the uncited facts below come from MODERN NUTRITION IN HEALTH AND DISEASE by M.E.Shils,et.al, Editors (Eighth Edition, 1994) and TOXICOLOGY LETTERS 102-103:5-18 (1998)]

RDA = Recommended Daily Allowance based on preventing acute nutrient deficiency disease conditions rather than based on amounts producing optimum health.


See Calcium and Adequate Nutrition

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See Chromium and Chromium Picolinate: Health Benefit and Hazard

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Iodine deficiency has been called the world's leading cause of intellectual deficiency [JOURNAL OF CLINICAL ENDOCRINOLOGY AND METABOLISM; Hollowell,JG; 83(10):3401-3408 (1998)]. Iodine deficiency during pregnancy can lead to a form of irreversible hypothyroid mental retardation known as cretinism. Breast tissue highly concentrates iodine for the benefit of the infant such that iodine concentration in human milk is four times greater than that of thyroid tissue (which itself concentrates iodine) [ ALTERNATIVE MEDICINE REVIEW; Patrick,L; 13(2):116-127 (2008)]. Studies of iodine deficiency in children have estimated a loss of at least six IQ points [ENDOCRINE REVIEWS; Zimmerman,MB; 30(4):376-408 (2009)].

The primary nutritional use of iodine by the human body is for synthesis of thyroid hormones by the thyroid gland in response to TSH (Thyroid Stimulating Hormone) secreted by the anterior pituitary gland. Thyroid hormones regulate metabolism and development (particularly of the brain). In adults with low iodine intake, TSH blood levels become elevated, which stimulates thyroid gland growth, while thyroid hormone remains low. An enlarged thyroid gland is termed goiter. Symptoms of hypothyroidism include fatigue, weight gain, cold intolerance, depression and impaired mental function. Excessive dietary iodine can cause hyperthyroidism.

Iodine is highly concentrated in oceans and depleted in mountainous areas. Because the Japanese eat seaweed (kelp) and much seafood, the average Japanese person consumes hundreds of times more iodine daily than the average North American [THYROID; Nagataki,S; 18(6):667-668 (2008)]. Not surprisingly, the addition of iodine to salt for dietary supplementation was begun in mountainous Switzerland in the 1920s. FDA guidelines for iodized salt provide 150 micrograms per half teaspoonful of salt. Most salt used in processed foods is not iodized.

Daily recommended iodine intake is 90-120 micrograms daily for children and 150 micrograms daily for adults. Pregnant and breast-feeding women are advised to take 200 micrograms daily. A number of foods can interfere with iodine uptake, including broccoli, cauliflower, linseed, lima beans and sweet potatoes [ENDOCRINE REVIEWS; Zimmerman,MB; 30(4):376-408 (2009)]. Because of declining salt consumption and increasing vegetarianism, iodine levels in Americans have been declining [JOURNAL OF CLINICAL ENDOCRINOLOGY AND METABOLISM; Hollowell,JG; 83(10):3401-3408 (1998)]. Increasing iodine intake when selenium is deficient can lead to autoimmune disease due to insufficient selenium-based anti-oxidant enzymes in the thyroid to protect against the iodine [JOURNAL OF THE AMERICAN COLLEGE OF NUTRITION; Hoption Cann; 25(1):1-11 (2006)]. Thyroid control of thyroid hormone production and release prevent even very high quantities of ingested iodine from increasing serum thyroid hormone levels [JOURNAL OF CLINICAL ENDOCRINOLOGY AND METABOLISM; Theodoropoulou,A; 92(1):212-214 (2007)]. Selenium supplementation should be an adjunct to iodine supplementation, but excess iodine should nonetheless be avoided because of the potential for thyroid damage and resultant hypothyroidism. A Japanese study of reversible hypothyroid patients found that iodine restriction (avoiding foods such as seaweed products) led to a 50% decrease in serum TSH within one week for those who had no antithyroid antibodies, whereas the same decrease took over two weeks for those with antibodies or who had elevated TSH associated with pregnancy [CLINICAL ENDOCRINOLOGY; Sato,K; 45(5):519-528 (1996)].

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Magnesium is the second-most abundant cellular cation after potassium. Magnesium is an essential nutrient for hundreds of diverse biological reactions in the body. Magnesium is required for formation of cyclic ATP (cATP) — the "second messenger" that relays to the cell interior signals received from hormones and neurotransmitters on cell surfaces. The energy molecule ATP itself must be bound to magnesium in order to be biologically active — which means that magnesium is essential for cellular energetics. For that reason, magnesium deficiency is associated with muscle spasm and irregular heartbeat. Low magnesium is associated with age-related diseases and low magnesium can induce cellular senescence in endothelial cells [MAGNESIUM RESEARCH; Killilea,DW; 21(2):77-82 (2008)].

An 18-year epidemiological study of over 4,000 middle-aged men showed a 40% lower all-cause mortality for those with high serum magnesium [EPIDEMIOLOGY; Leone,N; 17(3):308-314 (2006)]. Magnesium depletion results in defective parathyroid hormone secretion and activity. Magnesium depletion is also associated with anxiety disorders, migraine, depression, insomnia, elevated serum lipids, high blood pressure, and reduced immunity. Magnesium depletion causes depletion of calcium and potassium, which is responsible for some of the symptoms. Excess magnesium results in electrocardiogram irregularities and central nervous system depression. Severe magnesium toxicity can cause coma and cardiac arrest.

Increasing magnesium can relax smooth muscle and reduce blood pressure. Coronary artery disease patients given 325 milligrams of magnesium daily showed improved endothelial cell function and reduced exercise-induced angina [CIRCULATION; Shechter,M; 102(19):2353-2358 (2000)]. Evidence for the use of magnesium to prevent artrial fibrillation is not definitive [HEALTH TECHNOLOGY ASSESSMENT; Shepherd,J; 12(28) (2008)]. Rats fed moderately magnesium-deficient diets showed significant increases in blood pressure, oxidation damage, and chronic inflammation, all of which are associated with cardiovascular disease [FREE RADICAL BIOLOGY & MEDICINE; Blache,D; 41(2):277-284 (2006)]. Overweight human subjects who were neither magnesium deficient nor diabetic showed improved insulin sensitivity when given 365 milligrams magnesium-aspartate-hydrochloride daily for six months [DIABETES, OBESITY & METABOLISM; Mooren,FC; 13(3):281-284 (2011)].

Depending mainly on body size, the human requirement for magnesium is estimated to be between 300 to 400 milligrams per day. The average person in the United States does not get this much magnesium. Diabetes and osmotic diuretic drugs can deplete magnesium. Because magnesium (Mg2+) is the coordinating ion in chlorophyll, green vegetables are a good dietary source. Nuts, notably cashews and almonds, are good sources of magnesium. Magnesium sulfate (epsom salts) has been used as a supplement, but the laxative effect can result in diarrhea if too much is ingested.

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See Selenium: AntiOxidant, Anti-Carcinogen and Immune System Booster

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The human body normally contains about 100 μgm (micrograms) of vanadium. Daily intake is in the range of 10 to 160μgm, mainly from black pepper, dill seeds, mushrooms, parsley, shellfish, and spinach. The predominant form of vanadium in the plasma is vanadate (VO43−), although below pH 3.5 vanadyl (VO2+) is common. Supplements sold typically provide 2 to 10 mg (milligrams) of vanadyl sulfate (VOSO4) giving up to 2 mg (milligrams) of elemental vanadium.

In small clinical trials of type 2 diabetic patients vanadium salts have been shown to act as hypoglycemic agents, decreasing fasting blood glucose in doses of 150 mg to 300 mg vanadyl sulfate daily, although all subjects experienced gastrointestinal distress at 300 mg daily [METABOLISM; Goldfine,AB; 49(3):400-410 (2000)]. Vanadium compounds have been shown to increase glucose utilization and insulin sensitivity while reducing glucose production in the liver. Vanadium compounds activate several components of the insulin-signalling pathway [CELL BIOCHEMISTRY AND BIOPHYSICS; Mehdi,MZ; 44(1):73-81 (2006)]. Problems of gastrointestinal distress and poor absorption are being overcome by the use of heterocyclic vanadium compounds [JOURNAL OF INORGANIC BIOCHEMISTRY; Katoh,A; 103(4):567-574 (2009)].

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Zinc Finger
Zinc Finger

Zinc is an essential component of many enzymes and proteins, including the anti-oxidant enzyme Cu/Zn-SOD (SuperOxide Dismutase) and p53 tumor-suppressor protein. So-called zinc fingers are loops of 12 or 13 amino acids (residues) centered on zinc which is bound to pairs of Cysteine (C) or Histidine (H) residues. Zinc fingers are found on steroid receptors and transcription factors (enabling the factors to bind to DNA). Two zinc fingers are found in the DNA-binding domain of the DNA-repair enzyme PARPPoly (ADP-Ribose) Polymerase. Reduced dietary zinc results in increased DNA damage, at least partly as a result of reduced DNA repair [AMERICAN JOURNAL OF CLINICAL NUTRITION; Song,Y; 90(2):321-328 (2009) and PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES (USA); Ho,E; 99(26):16770-16775 (2002)].

An estimated 10% of the population of the United States gets less than half of the Recommended Daily Allowance (RDA) of zinc, and 50% of the world population may be getting less than half the RDA [CURRENT OPINION IN CLINICAL NUTRITION AND METABOLIC CARE; Cope,EC; 13(6):685-689 (2010)]. An 18-year epidemiological study of over 4,000 middle-aged men showed more than double the all-cause mortality for those with high serum copper and low serum zinc [EPIDEMIOLOGY; Leone,N; 17(3):308-314 (2006)].

Zinc deficiency can lead to impairment of many hormones, including thyroid, corticosterone, growth hormone and sex hormones. Insulin output can be reduced while there is an increase in insulin resistance. Zinc can counteract the inhibition of DNA synthesis by the toxic, carcinogenic metal cadmium [NUCLEIC ACID RESEARCH; Nocentini,S; 15(10):4211-4225 (1987)]. Epidemological evidence indicates a correlation between zinc deficiency and depression, and zinc is known to facilitate synaptic function [CURRENT OPINION IN CLINICAL NUTRITION AND METABOLIC CARE; Cope,EC; 13(6):685-689 (2010)].

The immune system is severely impaired by zinc deficiency, due to both reduction in cell division rate and reduced Cu/Zn-SOD. The thymus & spleen are smaller, and lymphoid tissues show more reduced mass than other tissues. The functions of lymphocytes, neutrophils and natural killer (NK) cells are all impaired. Diabetic patients are often supplemented with zinc to improve immune function. Although excessive zinc can cause copper deficiency, zinc supplementation in the elderly can improve immunity and reduce chronic inflammation [IMMUNITY & AGEING; Haase,H; 6:9 (2009)]. Zinc intake and absorption is reduced with age, which can aggrevate thymic involution and zinc-dependent thymulin & T-lymphocyte development & function [MECHANISMS OF AGEING AND DEVELOPMENT; Mocchegiani,E; 106(1-2):183-204 (1998)].

A randomized, double-blind, placebo-controlled study of human victims of common cold showed that lozenges of 13.3 milligrams of zinc acetate taken every 2-3 hours while awake reduced the overall duration of the cold from about 7 days to 4 days, while also decreasing the severity of cold symptoms (cough, nasal discharge, muscle aches). The beneficial effects of zinc were attributed to antioxidant action and modulation of proinflammatory cytokine release [THE JOURNAL OF INFECTIOUS DISEASES; Prasad,AS; 197(6):795-802 (2008)].

Shellfish and red meats are rich sources of zinc. Nearly 80% of zinc is lost in making flour from wheat during the milling process. Phytate in whole grains binds to zinc thereby aggrevating the risk of zinc deficiency for vegetarians.

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