(As a note, the normal internal consumption mentioned here of zinc, copper for balance, lutein and zeaxanthin for eyesight are already included in our Ultimate Foundation multi-vitamin nutrients. Extra supplementation is not needed. Lozenges for colds and sore throats may be advisable – but in small amounts as we mention in the “Additional Supplements”. This article includes excerpts from Consumer Labs, which we subscribe to and recommend to those interested.)
What is It?
Zinc is an essential mineral – and one of the few nutrients for which a number of people are mildly deficient. Zinc deficiency is especially common in adolescents, infants, seniors and women in general, although severe deficiency is rare in developed countries. Certain drugs and nutrients can inhibit zinc absorption and/or increase its excretion. Thus, for many people, increasing the intake of zinc-containing foods or taking a zinc supplement, either alone or as part of a multi-vitamin / mineral, may be a prudent form of nutritional insurance.
As a dietary supplement, zinc is found in many forms. These include zinc gluconate, zinc acetate, zinc citrate, zinc sulfate, zinc chelates, zinc carbonate, zinc orotate, and zinc picolinate. There is no clinical support that one form is better than another.
What It Does
Zinc plays a role in brain function, wound healing, sperm production, and vision maintenance. Zinc in pill or liquid form may be taken in nutritional doses to replenish depleted zinc levels.
In Zinc Deficiency
Among people who are deficient in zinc (especially the elderly), some evidence suggests that such replenishment might help increase immunity. Supplementation is particularly effective in reducing the duration and severity of diarrhea in zinc-deficient individuals.
In a recent Cochrane Review of fifteen clinical trials (Singh, Cochrane Database of Systematic Reviews 2011), the use of zinc is associated with a significant reduction in the duration and severity of symptoms of the common cold. This is when taken as a lozenge or nasal gel, where zinc may act directly in the throat or nose. In children, zinc syrup taken by mouth and swallowed may modestly help prevent and/or treat common colds (including reductions in school absences and prescriptions for antibiotics).
(NOTE: There have been unconfirmed reports of loss of smell resulting from zinc nasal gel.)
Zinc supplementation in high doses alone or along with anti-oxidants (beta-carotene, vitamin C, and vitamin E) slows the progression of advanced age-related macular degeneration (AMD). The combination (but not zinc alone) also reduces the risk of losing visual acuity in this condition. This was demonstrated in the large Age-Related Eye Disease Study (AREDS). In the AREDS study, supplementation failed to prevent the progression of early stage of AMD as well as the progression of cataracts. Studies using smaller amounts of zinc have had mixed results in AMD.
Zinc is helpful in Wilson’s disease, as it reduces copper levels. Other ways in which high-dose zinc may help, include enhancing the effectiveness of antidepressants. It reduces mouth and skin irritation during radiation therapy for head and neck cancer. It also improves symptoms of acne, anorexia nervosa, sickle cell anemia; altered taste sensation (of various origins), attention deficit-hyperactivity disorder (ADHD), and peptic ulcers. However, the evidence that zinc at high dosage levels works for all of these purposes is incomplete at best. Furthermore, such high doses of zinc can have adverse effects.
The balance of current evidence fails to support the use of zinc for cataracts, rheumatoid arthritis or eczema. The use of zinc is highly speculative, in high or low doses, for
benign prostatic hyperplasia (BPH), peptic ulcers,
diabetes, male infertility,
osteoporosis, Crohn’s disease,
tinnitus (ringing in the ear), mouth and skin in radiation therapy.
What to Consider When Buying and Using
Getting Zinc From Food
Oysters have very high zinc content (about 8 mg zinc per oyster). Other forms of shellfish, as well as organ meats, beef, pork and chicken can provide 1-8 mg of elemental zinc per serving. Whole grains, legumes, nuts and seeds provide zinc as well, ranging in amounts from 0.2 to about 3 mg per serving. However, the high phytic acid (phytate) content of these foods may reduce the zinc’s availability. Many breakfast cereals and nutrition bars are also fortified with zinc.
Zinc supplements come in various forms, known as zinc salts or complexes. Zinc sulfate is the least expensive zinc salt, but zinc acetate, gluconate, citrate or picolinate may be better absorbed. Note that there is a difference between the milligrams of pure zinc in a product (“elemental zinc”) and the total amount of the zinc salt. In this article and product list, we use numbers based on the elemental zinc itself, not the salt.
To Prevent or Treat Deficiency
Dose: Mild zinc deficiency is fairly common. The Recommended Dietary Allowance (RDA) of zinc is 3 mg for children ages 1 to 3, 5 mg for those 4 to 8, and 8 mg for those 9 to 13. For males 14 and older the RDA is 11 mg. For females 14 to 18 it is 9 mg, while for those 19 years and older it is 8 mg per day.
The RDA for pregnant women who are 18 years or younger is 13 mg, while it is 11 mg for pregnant women 19 years and older. For lactating women the RDAs are 14 mg if 18 years and younger or 12 mg if 19 years or older. High fiber foods may interfere with zinc supplement absorption if the foods and the supplement are taken at the same time. Certain drugs may increase the need for zinc supplements, such as ACE inhibitors, thiazide diuretics and medications that reduce stomach acid (such as Prilosec or Pepcid).
Lozenges – For Colds
More research is needed to determine optimal dose and formulation. However, most (but not all) studies suggest that when zinc is taken in the form of a lozenge or nasal gel (as opposed to an oral supplement), it can directly kill cold viruses and thereby shorten the duration of a cold. Only zinc gluconate and zinc acetate have been shown to be effective for this purpose – although other forms of zinc are available on the market in lozenges.
It is thought that certain flavorings that may be added to lozenges, such as citric acid and tartaric acid, can interfere with zinc’s antiviral action. The flavorings (sweeteners) dextrose, sucrose, sorbitol and mannitol are thought not to interfere. Products are available in which zinc is mixed with a great variety of other substances, such as herbs or vitamin C, but these have not been tested for their combined efficacy.
A typical dose of the lozenge form of zinc is 13.3 to 23 mg of zinc given every 2 hours during the day while symptoms persist. It is important not to take this much zinc for more than a week or so, as the amount greatly exceeds the tolerable intake levels discussed below (see Concerns and Cautions below).
It is possible that concern over excess zinc is the reason why several products on the market provide only 5 mg per lozenge and suggest a dose of only one or two lozenges per day. However, zinc lozenges are not likely to help a cold if taken this way, so you may need to use these more frequently. Some people get an upset stomach from the lozenges.
Because zinc needs to act in the throat, let the lozenge dissolve fully — do not chew it or swallow it whole. Our recommended source for zinc lozenges is Quantum Thera-zinc in the Additional Supplements. We like it because its 14 mg dosage allows it to be taken more often a day than the higher dosage lozenges.
In children, zinc sulfate syrup in a dose of 15 mg of zinc per day may help prevent colds. 30 mg of zinc per day at the first onset of symptoms may help treat a cold, although the benefits appear to be modest. In the seven-month study from which these results were reported, side effects were minor and similar among the zinc-treated kids and those treated with placebo (sugar pills). However, the kids in the study were not monitored for signs of zinc overload or other potentially serious side effects of taking high doses of zinc for many months. Doses exceeding the UL for children should only be used under physician supervision.
To Prevent Macular Degeneration:
As noted earlier, the Age-Related Eye Disease Study (AREDS) found that zinc alone or with anti-oxidants can slow the progression of age-related macular degeneration when taken on a daily basis. The tablets used in AREDS were manufactured to contain the following minimum contents throughout their shelf-life:
7160 IU of vitamin A (beta carotene),
113 mg of vitamin C (ascorbic acid),
100 IU of vitamin E (dl-alpha tocopheryl acetate),
17.4 mg of zinc (zinc oxide),
and 0.4 mg of copper (cupric oxide).
Four tablets were taken daily, providing a total of:
28,640 IU of vitamin A,
452 mg of vitamin C,
400 IU of vitamin E,
69.6 mg of zinc, and
1.6 mg of copper.
(The copper in the formula was included to prevent zinc-induced copper deficiency — see Concerns and Cautions below.) These are the same amounts provided by the Ocuvite and ICAPS products in this review.
[NOTE: Some articles about AREDS report suggest that the supplement used contained slightly higher amounts of ingredients, such as 80 mg of zinc per day, but the actual specifications for the product are those described above.]
Other compounds that may improve eye health are lutein and zeaxanthin — (included in the Ultimate Foundation).
To Treat Acne:
Some evidence suggests that 30 mg of zinc taken orally each day may be helpful for acne. This is a safe dose for most people. However, in many studies of zinc for acne, a much higher dose was used: 90 mg daily or more. Doses this high should only be used under physician supervision (see Concerns and Cautions below).
Concerns and Cautions
Zinc supplements cause few immediate side effects other than occasional stomach upset or unpleasant taste. The established tolerable upper intake levels (UL) for daily intake (amounts that should be safe when taken long term by almost anyone who is in good health) for zinc are:
7 mg for children ages 1 to 3,
12 mg for those 4 to 8,
23 mg for those 9 to 13,
34 mg for those 14 to 18, and
40 mg for individuals 19 years and older.
Excessive intake of zinc can interfere with the absorption of copper, leading to copper deficiency. The combination of excess zinc and deficient copper can dangerously suppress the immune system and also cause anemia and heart problems. In order to partially offset these risks, it is generally considered advisable to take copper at a dose of 1 – 3 mg daily when taking zinc supplements long term (also in our Ultimate Foundation).
As noted earlier, when using zinc lozenges for the treatment of the common cold, one is taking zinc at doses exceeding the UL. Such short-term use should be safe, but should be limited to no more than one to two weeks. Doses exceeding the UL for more than a week or two should only be used under physician supervision.
Long-term zinc supplementation at very high doses (over 100 mg per day) has been associated with a decrease in HDL (“good”) cholesterol, reduced immune function, and an increased risk of prostate cancer. Zinc’s overall role in prostate cancer, however, is unclear as there is also research indicating that zinc may suppress prostate cancer cell growth.
Zinc nasal gel has been linked in reports to permanent or temporary loss of smell, as well as pain in the nose immediately after use. This has been known for several years. By June 2009, a sufficient number of cases (over 130) had been reported to apparently cause the FDA to issue a warning to consumers and health care professionals to discontinue use of three Zicam Nasal Gel/Nasal Swab products.
Zinc can impair the absorption of antibiotics in the tetracycline or fluoroquinolone families (e.g., doxycycline, tetracycline, ciprofloxacin, Cipro, Noroxin), as well as the drug penicillamine. In addition, combined use of zinc supplements and the drug amiloride might lead to excess zinc in the body.