Zinc

Think zinc! This slogan comes to mind as I begin this section. Zinc has so many important functions and potential uses that both doctors and patients should think of zinc more often for handling many day-to-day problems. Zinc deficiency is fairly common now as a result of soil losses and losses in food processing, and this deficiency or depletion can produce a variety of symptoms.

More than 50 years ago, in 1934, zinc essentiality was first suggested. Not until the early 1960s, however, was it known that low intake or low body stores of zinc can cause deficiency symptoms. In recent years, since the discovery that this mineral is becoming less available in our soil and thus in our food chain, zinc has been given more attention, and increased research has produced much new information. We now know that zinc is needed in probably more than 100 enzymes and is probably involved in more body functions than any other mineral. It is important in normal growth and development, the maintenance of body tissues, sexual function, the immune system, and detoxification of chemicals and metabolic irritants. Carbohydrate metabolism is influenced by zinc, and zinc is needed in the synthesis of DNA, which aids our body’s healing process. Zinc is often helpful in reducing healing time after surgery or burns, in many male prostate problems, in skin diseases, and in many other difficulties.

Zinc is found in the body in small amounts, only about 2-2.5 grams total. Of the trace minerals, it is second in concentration to iron, with 33 ppm to iron’s 60 ppm. (Although fluoride is found at 37 ppm in the average human body, it is still questionable whether it is essential. This 37 ppm is also a result of the use of fluoridated water, vitamins, and stannous fluoride toothpaste.) Though zinc is the twenty-fifth most abundant element in the earth’s crust, measuring about 0.01 percent, it is water soluble both in the soil and in food. Rains can wash zinc (as well as iodine, sulfur, and selenium) from our farming soils, as can modern agricultural techniques. When we cook food, much of the zinc may go into the water, as do other minerals and vitamins, so the cooking liquids, especially from vegetables, should be consumed as well. More importantly, when foods are processed, as in the refining of grains, much of the zinc is lost, along with manganese, chromium, molybdenum, and B vitamins. Usually, only iron and sometimes vitamins B1 and B2 are added back in “enriched” foods (and this iron isn’t even in the easily usable form). Adding zinc, manganese, chromium, and more B vitamins such as B6, would be much better and help us avoid common deficiencies.

Zinc absorption may vary from about 20-40 percent of ingested zinc, depending mainly on body needs and stomach acid concentrations. Like iron, zinc from animal foods where it is bound with proteins has been shown to be better absorbed. When bound with the phytates or oxalates found in grains and vegetables, less zinc is absorbed. Calcium, phosphorus, copper, iron, lead, and cadmium all compete with zinc for absoprtion. Milk and eggs reduce zinc absorption. Fiber foods, bran, and phytates, found mainly in the outer covering of grains, may also inhibit zinc absorption. Phytic acid may combine with the zinc in the upper intestine before this mineral can be absorbed.

The zinc-cadmium relationship is interesting. Cadmium is considered a potentially toxic heavy metal. When it contaminates our food, it is found in the center of grain; zinc is found mainly in the grain covering. So eating whole grains, which have a higher amount of zinc than of cadmium, will reduce any possible absorption of cadmium. With refining of grains into flour, the zinc-cadmium ratio is decreased, and cadmium is more likely to be absorbed and cause problems.

In the human body, the 2.5 grams of zinc are stored in a variety of tissues. It is most concentrated in the prostate and semen, which suggests zinc’s tie to male sexual function (impotence can be related to low zinc). The next most concentrated tissues are the retina of the eye, heart, spleen, lungs, brain, and adrenal glands. The skin contains a high amount of zinc, but it is less concentrated than in the organ tissues. Nails, hair, and teeth also have some zinc, and this mineral is important to those tissues as well.

Zinc is eliminated through the gastrointestinal tract in the feces. Some is also eliminated in the urine; alcohol use increases urinary losses of zinc. Zinc is also lost in the sweat, possibly as much as 2-3 mg. in a day. Stress, burns, surgery, and weight loss all seem to increase body losses of zinc.

In evaluating body zinc status, plasma or serum zinc levels may not reflect body stores; however, if they are low, zinc is likely deficient. Low hair levels appear to reflect zinc deficiency, which then should be substantiated through a blood test. High hair zinc levels may also be seen with zinc deficiency, though this is not as correlative as low hair levels. In general, the red blood cell (or white blood cell) measurement of zinc may be most indicative of the body’s true status of zinc nutriture.

Sources: Most animal foods contain adequate amounts of zinc. Oysters are particularly high, with more than ten times as much as other sources (they are also high in copper and, possibly, in ocean-polluting chemicals and metals). Zinc is added to animal feeds to increase growth rates, so meat usually contains high amounts. Red meats (beef, lamb, and pork) and liver are fairly high; herring is good, as are egg yolks and milk products (though the zinc in eggs and milk products may not be as available to the body as that found in other sources). Other fish and poultry also contain fair zinc levels. As with iron, the zinc in animal foods seems to be better absorbed than that in the vegetable sources, but one can reduce meat foods and eat whole grains and beans and still obtain adequate zinc. Overall, though, in my experience it is not easy for most people eating a relatively healthy diet to obtain the minimum requirement of 15 mg. daily unless they focus on zinc-containing foods.

Whole grains such as whole wheat, rye, and oats are rich in zinc and are good sources for vegetarians. Even though the mineral from these foods is utilized less well because the fiber and phytates in the grain covering bind some zinc in the gastrointestinal tract, much of the zinc in these foods is still available to the body. Nuts are fairly good sources, with pecans and Brazil nuts the highest. Pumpkin seeds contain zinc and are thought to be helpful to the prostate gland. Ginger root is a good zinc source, as are mustard, chili powder, and black pepper. In general, fruits and vegetables are not good zinc sources, although peas, carrots, beets, and cabbage contain some zinc.

The zinc in grains is found mainly in the germ and bran coverings, so refining them will lower the zinc content. Approximately 80 percent of zinc is lost in making white flour from whole wheat. Since zinc is soluble in water, canning foods or cooking in water can cause zinc losses. Zinc losses have also been prevalent in agricultural soils, and it is therefore less available in foods. Chemical fertilizers also decrease zinc soil levels. Many soils-nearly 30 states in the United States-are deficient in zinc. Water, especially from some wells, contains zinc. Water was a better source when some of the water pipes were galvanized (containing zinc), as were some cooking pots. Now, water pipes are more commonly made of copper, which can become toxic at higher levels.

Functions: Zinc is involved in a multitude of human body functions and is part of many enzyme systems. With regard to metabolism, zinc is part of alcohol dehydrogenase, which helps the liver detoxify alcohols, including ethanol (drinking alcohol), methanol, ethylene glycol, and retinol (vitamin A). Zinc is also thought to help utilize and maintain body levels of vitamin A. Through this action, zinc may help maintain healthy skin cells and thus may be helpful in generating new skin after burns or injury. By helping collagen formation, zinc may also improve wound healing. Zinc aids the skin’s oil glands and so may help in acne problems.

Zinc is needed for lactate and malate dehydrogenases, both important in energy production. Zinc is a cofactor for the enzyme alkaline phosphatase, which helps contribute phosphates to bones. Zinc is also part of bone and tooth structure. Zinc is important to male sex organ function and reproductive fluids.
It is in high concentration in the prostate gland as well as in the eye, liver, and muscle tissues suggesting its functions in those areas.

Zinc in carboxypeptidase (a digestive enzyme) helps in protein digestion. Zinc is important for synthesis of nucleic acids, both DNA and RNA. In fact, we are finding that zinc has some antioxidant function. As part of superoxide dismutase (SOD), it helps protect cells from free radicals. Through this antioxidant effect, zinc is also helpful in cell membrane structure and function.

Zinc has also been shown to support immune function. Zinc will improve antibody response to vaccines and can improve cell-mediated immunity by helping regulate the function of the white blood cells. A somewhat higher amount of zinc has caused an increase in production of T lymphocytes, important agents in cell-mediated immunity.

Zinc is important to normal insulin activity and seems related to normal taste sensation. Zinc may have an anti-inflammatory function, especially in the joints and artery linings. It may also be involved in brain function, in maintaining acid-alkaline balance through carbonic anhydrase, another zinc-containing enzyme, and in phosphorus metabolism.

More research is needed on this important mineral. As zinc, due to its function in many enzymes, is so important to chemical detoxification and our ability to handle environmental chemicals and toxins, zinc deficiency may be an underlying factor in those people who become environmentally sensitive. This is just one example of where further zinc research may be valuable.

Uses: Just as it has many functions, zinc has a wide variety of clinical uses. Some of these regularly show very positive results; other uses have variable outcomes, and some new therapeutic trials are under way.

Zinc is used commonly to enhance wound healing. Taken before and after surgery, zinc has been shown in numerous studies to speed recovery time and reduce the incidence of postoperative complications, such as wound infections. This use has the potential to greatly cut down on hospital costs. In some studies, the hospital stay has been reduced by more than half. Zinc may be helpful in speeding healing after burns or injury as well. This wound-healing effect is a likely result of zinc’s function in DNA synthesis. The results seem to be particularly pronounced when there is zinc deficiency prior to the treatment. In many of the wound-healing studies, zinc dosages of 150 mg. per day were used. It is possible that lower amounts, even 30-60 mg. per day, would produce these effects.

Zinc may be useful in treating such skin problems as boils, bedsores, general dermatitis, and acne. Research on zinc and acne shows variable results, but many teenagers and others have been helped, especially when zinc deficiency was present; it is likely that other factors and nutrients are also involved in acne. Leg ulcers have healed more rapidly with zinc treatment in a dose of 150 mg. per day. Internally, gastric ulcers have responded favorably to zinc in a similar dosage. Psoriasis is even occasionally responsive to zinc supplementation. White spots on the fingernails, which can be a result of zinc deficiency, may respond also to zinc treatment. Zinc may also be helpful to general nail health, as well as skin and hair health. Cataracts also seem to be associated with zinc deficiency and have been helped by treatment.

My friendly travel agent developed a case of hoarseness that persisted for more than a month. Her otolaryngologist diagnosed chronic inflammation and had suggested long-term quietude and learning to live with it—neither of which was a big hit. In passing (I was quite aware of the foibles of her diet), I suggested zinc lozenges. She began sucking on 3–4 daily and within a week her voice was back. In this case, the $5 bottle of zinc helped more than the $70 office visit. I believe that she was zinc deficient, and that the zinc supplement helped to heal her inflamed tissue.

Zinc is used in a variety of immune problems. It is one of the supportive nutrients used to treat lowered immunity. Zinc has been shown to increase T lymphocyte production and enhance other white blood cell functions. Recent double-blind studies verify that zinc therapy is helpful in reducing the incidence and severity of colds and other infections. Also, infections such as herpes, trichomoniasis, or AIDS may be curtailed some with zinc, especially if it is deficient. Sucking a 25-50 mg. dissolvable zinc lozenge can provide dramatic relief in some cases of sore throat and has been shown to prevent the progression of viral flu symptoms. Individuals with allergies and environmental sensitivities may benefit from zinc supplementation. Measuring zinc status and following it during treatment may be useful in validating its positive effects.

For male prostate problems, there is no scientific evidence that zinc works, though there are a great many anecdotal accounts from men who claim to have been helped by zinc. Mild or persistent nonbacterial infections or congestion have commonly been helped by oral zinc treatments. Of course, when zinc deficiency produces such sexual symptoms as infertility, impotency, or poor sexual development, supplementation of this mineral may have great benefit. There is some suggestion that the prostate enlargement that comes with age, termed benign prostatic hypertrophy (BPH), is related to low zinc (and cadmium toxicity), and that regular zinc supplementation may prevent this common problem. More research is needed to clearly evaluate zinc’s relationship to prostate and sexual health.

Zinc may also be beneficial in rheumatoid arthritis, for which it has been shown to reduce symptoms; in preventing dental caries by strengthening tooth enamel; and with symptoms of heart disease, where the zinc-copper ratio may be important. The use of zinc in cancer prevention and the support of patients with cancers such as Hodgkin’s disease and leukemia has been the subject of some interest.

Zinc therapy can reduce cadmium toxicity from pollution or from cadmium in water or foods. Cadmium toxicity may aggravate hypertension, atherosclerosis, and heart disease and produce complications of hypertension or stroke.

Zinc with vitamin B6 has also been used in the nutritional treatment of schizophrenia and, given along with manganese, has been helpful in some cases of senility. Zinc treatment may help with the loss of taste sensation that comes especially with aging, which is often due to zinc deficiency, and it may help stimulate the taste for food in patients with anorexia nervosa. Menstrual irregularity and female sexual organ difficulties may have some relationship to zinc levels and be helped by zinc therapy, though copper may be more important for these areas in women.

Deficiency and toxicity: Zinc is fairly nontoxic, especially in amounts of less than 100-150 mg. of elemental zinc daily, though this much zinc is probably not really needed and may interfere with the assimilation of other minerals. Zinc salts such as gluconate or sulfate are commonly available in 220 mg. tablets or capsules, each providing 55 mg. of elemental zinc. Taking one of these two or three times daily may cause some gastrointestinal irritation, nausea, or diarrhea but is more likely to have positive effects. Excessive supplementation may cause some immune suppression, premature heartbeats, dizziness, drowsiness, increased sweating, muscular incoordination, alcohol intolerance, hallucinations, and anemia, some of which is due to copper deficiency. More than 2 grams of zinc taken in one dose will usually produce vomiting. If not, it will likely lead to other symptoms until the body clears the excess zinc. Luckily, only a certain amount of it will be absorbed.

Zinc may interfere with copper absorption, so taking regular zinc supplements without copper can cause copper deficiency. This will interfere with iron metabolism and possibly cause anemia, as copper and iron are important in red blood cell formation. We usually need supplemental copper and vitamin A to balance the effect of extra zinc. Some formulas, for example, Nutrilite’s product, A plus Zinc, contain vitamin A and zinc together, which improves the effect of both; additional copper, about 2 mg., might also be supplemented daily, though at another time than the zinc.

• Diet—low in zinc or high in copper; high in fiber, phytates, clay, alcohol, or phosphates, all of which bind zinc in the intestines and reduce absorption; food grown in low-zinc soils.
  
  
• Aging—when zinc absorption and intake are often reduced.
  
  
• Pregnancy—when zinc needs are increased.
  
  
• Growth periods—infancy, especially with increased copper intake levels and for those on low-zinc formulas; puberty, especially in adolescent boys.
  
• Birth control pills—use of these increases copper levels and thus reduces zinc.
  
• Premenstrual symptoms—associated with low zinc.
  
• Increased copper intake—high copper intake in water, food, or supplements will reduce zinc.
  
• Fasting or starvation—causes zinc depletion and increases needs for zinc.
  
• Serious illness or injury—causes zinc depletion and increases needs due to tissue healing.
  
• Hospitalization—stress of illness or treatment, particularly intravenous therapy without zinc supplementation.
  
• Stress—increases zinc use and needs.
  
• Burns—increases needs for tissue healing and dealing with stress.
  
• Acute or chronic infections—greater requirements from stress and for healing.
  
• Surgery—increased requirements for dealing with stress and for healing.
  
• Alcoholism—often associated with low zinc intake and higher needs; alcohol flushes zinc from the liver, causing increased losses.
  
• Diuretic therapy—may cause extra zinc losses.
  
• Psoriasis—rapid skin activity may deplete zinc.
  
• Parasites—cause zinc depletion and poor absorption.
  
• Malabsorption—from pancreatic insufficiency or after gastrointestinal surgery.
  
• Cirrhosis—zinc levels may be half of normal.
  
• Renal disease—causes increased zinc
  
• Chronic disease—metabolic and debilitating disease such as cancer.
  
• Athletics—increased zinc losses in sweat.
  
• Cadmium toxicity—interferes with zinc absorption and utilization.
  

Other problems associated with low zinc levels are peptic ulcers, pernicious anemia, cystic fibrosis, and mongolism.

Zinc deficiency is very likely more common and more complex than previously thought. It was first identified in Iran and Egypt in 1961, in male dwarfs with slow growth and poor sexual development. The unleavened bread that is a staple in the diet there is high in the phytates that bind zinc, and a type of clay used for cooking in Iran also ties up zinc. Zinc treatment was found to help these conditions, stimulating growth and sexual development.

Aging is one of the main factors in zinc deficiency. However, some recent environmental changes have also contributed to the deficiency problem. Soil losses and losses due to food processing are two of the main factors in zinc depletion in foods. With the change from iron- and zinc-containing water pipes to copper ones, not only is zinc intake decreased, but the additional copper interferes further with zinc absorption. The average diet, especially one with low protein intake, supplies only 8-11 mg. daily (the RDA for adults is 15 mg.).

In general, both infants and adolescents have more zinc deficiency, as do the elderly and women, often due to low intake. With the average American diet, we need to eat about 3,400 calories to obtain our 15 mg. of zinc, and most people do not eat that much. Good-quality food is needed, and therefore poor people are more likely to experience zinc shortages.

The subject of our diet and zinc deficiency is an important one. The all-too-typical advanced technology, antinature diet that is high in refined grains, fat, sugar, convenience foods, and fried meats, is often low in zinc and many other important trace minerals and B vitamins. Also, strict vegetarians and consumers of much grain and little animal protein may not obtain sufficient zinc.

There are many symptoms and decreased body functions due to zinc deficiency. It may cause slowed growth or slow sexual development in the pubertal years. Lowered resistance, fatigue, and increased susceptibility to infection may occur with zinc deficiency, which is related to a decreased cellular immune response. Sensitivity and reactions to environmental chemicals may be exaggerated in a state of zinc deficiency as many of the important detoxification enzyme functions may be impaired.

Children with zinc deficiency may show poor appetite and slow development, have learning disabilities or poor attention spans, and in later years have acne and decreased sexual development. Dwarfism and a total lack of sexual function may occur with serious zinc deficiency. Fatigue is common.

Acute deficiency may cause hair loss or thinning, dermatitis, and decreased growth. Both poor appetite and digestion are also experienced by adults with zinc deficiency. Loss of taste sensation may occur, as can brittleness of the nails or white spots on the nails, termed leukonykia. These and most other symptoms can be corrected with supplemental zinc. Sulfur may be helpful as well. Skin rashes, dry skin, and delayed healing of skin wounds or ulcers may result from zinc deficiency, and stretch marks, called striae, are also produced by this condition. Zinc and copper are both needed for cross-linking of collagen, and when they are low, the skin tissue may break down.

Zinc deficiency may cause delayed menstruation in teenage females or, in later years, cause menstrual problems. In addition to zinc, vitamin B6 often also helps correct this. Females on birth control pills usually have elevated copper levels and need additional zinc and B6. When zinc is further reduced by the increased copper, depression is more likely, a common side effect of birth control pill use. Morning sickness in pregnancy may result from low zinc and B6 levels, and supplementing these nutrients may help reduce symptoms.

Male teenagers with low zinc have delayed or absent sexual development. Sterility may result from zinc deficiency; when it is caused by testicular degeneration, it may be irreversible. Subtle zinc deficiencies may be responsible for male growth lag in puberty. Even in sexually developed males, low zinc levels have been correlated with a decrease in testosterone levels and a lower sperm count. Prostate problems are more prevalent with zinc deficiency.

Birth defects have been associated with zinc deficiency during pregnancy in experimental animals. The offspring showed reduced growth patterns and learning disabilities. In humans, children with zinc deficiency have decreased intelligence and erratic behavior. With zinc treatment, the IQ and behavior may both improve if the problem is related to zinc deficiency.

Requirements: The RDA for zinc in adults is 15 mg., with additional amounts needed during pregnancy and lactation. Yet the average diet contains only about 10 mg. of zinc. And when zinc needs are considered, we likely need even more than 15 mg. per day to be sure we are meeting our requirements. Adequate amounts can be met by a good diet, especially with good protein and calorie intake. Vegetarians can eat more whole grains; even with some of the zinc binding to grain phytate, we still get a fair share into our body from these zinc-rich foods. Since absorption is about 30-40 percent, our total zinc body tissue needs are about 4-6 mg. per day.

We probably need 15-30 mg. of available (elemental) zinc daily for maintenance and probably about 30-60 mg. for treatment, though more is sometimes used. Fifteen mg. of zinc is often included in general supplement formulas. Separately, zinc gluconate and sulfate in reasonable amounts are used commonly without any side effects, though zinc gluconate is usually a little better tolerated than zinc sulfate. The amino-acid-chelated zinc is probably the best tolerated and absorbed though it is more expensive. Zinc sulfate tablets or capsules of 220 mg. provide 55 mg. of elemental zinc. A supplement labeled “zinc 25 mg. as gluconate” should provide 25 mg. elemental zinc. In medical treatment or research, zinc sulfate 220 mg. may be used two to three times daily, supplying about 100-150 mg. of available zinc for absorption. This dosage is usually tolerated fairly well.

Although 30-60 mg. of elemental zinc per day is the usual therapeutic level, more may be needed to correct zinc deficiency. Taking zinc alone two hours after meals or first thing in the morning will increase absorption by reducing the competition with other nutrients, such as calcium and copper, or food constituents such as the phytates and fibers in grains. With infections, burns, before or after surgery, in pregnancy, or with aging (often accompanied with lower absorption), 50-75 mg. per day is suggested as a therapeutic dose.

When taking higher amounts of zinc, we must make sure we get adequate amounts of copper-at least 2-3 mg. supplemented, and possibly more with higher zinc intakes-so copper deficiency does not occur. The suggested zinc to copper ratio is about 15:1. About 200 mcg. per day of selenium should also be taken, to prevent depletion by supplemental zinc. Zinc may be taken with magnesium, vitamin C, and B complex vitamins, but it is best to take a regular vitamin-mineral combination with 15-30 mg. of zinc in proper proportion to other minerals, so that deficiencies of zinc or imbalances of the other minerals do not occur.