Zinc May Shorten Cold But May Cause Side Effects

A new study supports previous findings that suggest zinc may shorten the duration of the common cold in adults; however, side effects may be common.

Zinc is necessary for the functioning of more than 300 different enzymes and plays a vital role in a large number of biological processes. Zinc is a cofactor for the antioxidant enzyme superoxide dismutase (SOD) and is in a number of enzymatic reactions involved in carbohydrate and protein metabolism.

In previous research, there have been conflicting results regarding the effect of zinc formulations in treating the duration and severity of common cold symptoms. Although zinc may be beneficial in the treatment of cold symptoms if taken at the onset of symptoms, more studies are needed to clarify which zinc formulations may be most effective, which rhinoviruses are affected by zinc and if nasal sprays provide a useful alternative application route for zinc treatment. Negative results may be caused by using doses of zinc that are too low, or they may be affected by the presence of compounds like citric or tartaric acid, which may reduce efficacy due to chelating of the zinc ion.

In a new study, researchers conducted a comprehensive literature search for well-designed clinical trials comparing zinc taken by mouth with placebo or no treatment at all. Seventeen trials evaluating a total of 2121 participants were ultimately identified for inclusion.

The researchers found that participants who received zinc experienced cold symptoms for less time than those who received placebo. However, the authors noted that these effects were only significant in adults, not children. Furthermore, side effects, including nausea and bad taste, were more common in participants taking zinc.

The authors concluded that although zinc may shorten the length of a cold, further research is needed to form a firm conclusion and evaluate potential side effects.

Many other integrative therapies have been studied for their potential effects on common cold symptoms. Echinacea taken by mouth is frequently recommended to reduce the duration and severity of upper respiratory tract infections. However, the results of scientific studies are mixed. Scientific studies generally suggest that vitamin C does not prevent the onset of cold symptoms. However, in a subset of studies of people living in extreme climates or under extraordinary conditions, including soldiers in subarctic exercises, skiers and marathon runners, vitamin C significantly reduced the risk of developing colds, by approximately 50 percent.

For more information about integrative therapies for the common cold, please visit Natural Standard's Comparative Effectiveness Database.

For more information about zinc, please visit Natural Standard's Foods, Herbs & Supplements Database.

Comments

[SS]

I know a lot of people who swear by zinc and I never thought of the possibility of side effects. Most people assume since its herbal and over the counter there is not going to be any side effects and they can take as much as they would like. It's articles like this that are great in showing both the benefits an herb or supplement versus the risk (or side effects) that it has.

[ns]

It seems as this study really hits on the concept of risk vs. benefit. I have had colds where I would have gladly taken a substance, such as zinc that could decrease my cold, which could cause other side effects. Because individuals with colds do not have many options I can see many people try zinc as option and see how the side effects affect them. It will be exciting to see future results in this area.

[AB]

Garlic, ginger, black cherry, elderberry, forsythia, onion, anise, ephedra, goldenseal, licorice, marsh mallow and other mallows, mullein, seneca snakeroot, slippery elm, watercress, willow, and garlic-and-onion soup are also thought to help treat colds and the flu.

[mn]

There are Zicam products out there that do not contain zinc, which I feel defies the whole purpose of patients purchasing Zicam for cold and allergy symptoms. It's important for pharmacists to educate their patients about the ingredients and potential side effects of over-the-counter products.

[DLC]

Personally I use the Zicam lozenges when I have a cold and I swear by them. They seem to shorten the time I have a cold and also make them less severe. I have always been plagued by frequent severe colds that will stick around for weeks because they are complicated by my asthma. Finding these zinc lozenges, even if it is a placebo effect, has been great! I am able to recover sooner and able to be more productive and functional during the cold.

[CM]

Zinc has been used for a lot of different conditions. According to Natural Standard it has been used for diarrhea in children, stomach ulcers and even acne. Most recently I have heard about a lot of products containing zinc to help the immune system and decrease the duration of a cold. This article mentioned some of the most common side effects that I’ve heard about like upset stomach. I’ve also heard that taking some zinc products can make you lose your sense of smell. Is this true?

[MW]

For every study that says that Zinc helps with a cold there is another study disproving it. It would be nice if we could finally get a consensus on the issue. I sometimes struggle with recommending Zinc or any other product claiming to shorten colds. This is a common question that gets ask at the pharmacy all the time. Generally I recommend if they had a cold for a few days already to just treat the symptoms, but if they feel it starting to come on then I recommend one of the products.

[EM]

I have always wondered the best therapy to recommend to patients trying to rid themselves of a common cold. Based on the data here, it doesn't seem that zinc is what they're looking for. I've had more than one patient mention the Zicam nasal spray incident when I suggest zinc lozenges, and the side effects don't always outweigh the benefits with this formulation either. I look forward to reviewing the comparative effectiveness data on integrative therapies for the common cold.

[JW]

This article is right, there has been many many studies over the last couple decades on whether zinc decreases the length of the common cold. From what I can remember, many meta-analysis showed benefits in zinc helping reduce the cold by 2-3 days. Although, I do agree that more research is needed to correctly identify which agents or formulations help with this reduction and if there is a difference between them. I do know that it is important to start zinc at the onset of feeling a cold come on. I do not believe that having a bad taste is worse than feeling gross and run down for a week or more. I will take some of those side effects over feeling miserable.

[Emily]

A recent article on Pub Med documents the success of vitamin C plus zinc as an collaborative intervention against the common cold. Prior to the study, a literature review was conducted on the effectiveness of zinc and vitamin C when used separately to combat the common cold. Their findings indicate that the combination intervention is the most effective in symptom alleviation and product toleration across the literature review and two randomized, placebo-controlled trials. These findings are worth considering before discounting vitamin C as an effective intervention against the common cold, as it seemed to supplement the effects of zinc supplementation on its own.

[KM]

I actually use zinc supplements frequently if I feel myself coming down with a cold. However, I agree with fact about side effects being present. I usually use the zinc lozenges, and always notice a metallic taste. I couldn't use the Zicam oral spray because I felt this metallic taste was worse with the spray than with the lozenges. It would be interesting to see if there was a side by side analysis of the adverse effects of the different dosage forms of zinc containing products.

[Maha Islami]

I think zinc did not seem to make much of difference in cold duration in children duo to adults tended to use a different form of zinc than the children. Experts recommend that zinc should not be taken for more than five days. Long term use of zinc for more than six weeks can lead to copper deficiency.

[LB]

It's interesting, certain rhino viruses will be more susceptible to zinc which makes me question how practical it will be with over 100 different serotypes of the rhino virus.

[CL]

As an alternative to zinc, I would also recommend echinacea for treating a cold. However, this plant is in the same family as ragweed and is a common cause of allergic reactions. A guest lecturer in one of my classes mentioned that fresh echinacea would make your mouth tingle when taken, so perhaps the products off the shelf may not be as effective as the fresh herb made as a tea, for example.

[LT]

This is an interesting topic that may be applied to a retail pharmacy setting. The use of zinc in children does warrant further research. The study that the blog talks about shows that the pediatric population that was in the trials was treated with a lower dose of zinc. This may suggests that the therapeutic effects of zinc in the common cold may be dose-dependent.

[Fariza]

Individuals should consult their physician or pharmacist prior to taking zinc. Although zinc may shorten the duration of a cold it is usually only by a day or two. I do not believe the severity of the cold is reduced with the use of zinc. Personally I would not want to experience the adverse effects associated with zinc such as metallic taste in order to shorten a cold by only a day or two. For others a cold may be disruptive to their work and quite bothersome.

[CL]

I'm wondering, is the loss of taste permanent? As stated in the article, cold symptoms had a shorter duration if zinc was taken, but generally cold last about 10-14 days anyways. Having the cold may be inconvenient, but it may be worth it to avoid taking zinc during a cold. Perhaps lower amounts as a preventative measure would be better?

[Jared]

I remembered there being a recall of a Zicam zinc-containing product a while back. In your zinc monograph it says that it was an intranasal spray Zicam, and that it caused permanent loss of smell in over 100 people. Luckily it seems like oral zinc products don't have this problem.