Zinc is a trace mineral that plays a broad role in maintaining overall health. It supports the immune system, aids in metabolism, and is involved in protein and DNA synthesis. Zinc also contributes to wound healing and helps maintain the senses of taste and smell. The body cannot produce zinc, making it an essential nutrient that must be obtained through diet or supplementation. It is present in every cell and acts as a cofactor for over 300 enzymes, facilitating numerous biological processes within the body.
Zinc’s Role in Cold Duration
Zinc supplementation can reduce the duration of the common cold. Research indicates that zinc can shorten cold duration by approximately 2.25 days in healthy adults. This effect is thought to occur through several mechanisms, primarily by interfering with the replication of cold viruses.
Zinc ions directly inhibit viral RNA polymerases, enzymes crucial for the replication of RNA viruses like rhinoviruses. By preventing the virus from binding to specific receptors on nasal epithelial cells, zinc can hinder its entry and multiplication. Zinc also modulates the immune response by enhancing the action of interferon-alpha, a protein that helps protect cells from viral infections, and by regulating inflammation.
Effective Zinc Forms for Colds
The effectiveness of zinc for colds largely depends on its form and ability to release free zinc ions in the mouth and throat. Zinc acetate and zinc gluconate are the most studied forms and have shown efficacy in reducing cold duration. Zinc acetate is considered effective because it binds zinc ions less strongly, allowing for better release in the oropharyngeal region. Zinc gluconate also releases free zinc ions, though it binds them more tightly than acetate.
Studies indicate that both zinc acetate and zinc gluconate lozenges can shorten cold duration, with some meta-analyses showing similar efficacy. For instance, zinc acetate lozenges have been observed to shorten colds by about 40%, while zinc gluconate lozenges shortened them by approximately 28%. The difference between these two forms is not statistically significant in many studies, suggesting that properly formulated lozenges of either type can be effective. Conversely, forms like zinc oxide are poorly absorbed orally and are generally not recommended for cold treatment. Lozenges containing ingredients that bind zinc ions tightly, such as citric acid, can also reduce efficacy by preventing the release of free zinc.
Guidance for Zinc Supplementation
For zinc lozenges to be effective in shortening a cold, begin supplementation within 24 hours of symptom onset. The recommended daily dosage for adults using lozenges for cold treatment is typically between 75 mg to 80 mg of elemental zinc per day. This dosage should be divided into multiple doses throughout the day, often administered as lozenges every two hours while awake, until symptoms resolve, which is usually within 4 to 7 days.
While beneficial, zinc is associated with potential side effects. Common side effects of zinc lozenges include a metallic taste, nausea, and mouth or throat discomfort. Gastrointestinal upset, such as stomach pain or diarrhea, can also occur, particularly with higher doses. Avoid taking zinc with food that may interfere with absorption, and do not eat or drink for at least 15 minutes after dissolving a lozenge.
Certain precautions are necessary. Intranasal zinc sprays have been linked to permanent loss of smell, leading to warnings against their use. High doses of zinc over a long period can lead to copper deficiency, low immunity, and reduced “good” cholesterol. Zinc can also interact with certain medications, including antibiotics and diuretics. The tolerable upper intake level for adults is 40 mg of zinc per day for general use, so therapeutic doses for colds should be short-term and discussed with a healthcare professional.