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zoom RSS 亜鉛が風邪に効果あり

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 亜鉛が風邪の罹病期間と重傷度を軽減する可能性があり、予防効果もあるらしい。しかし、コクラン・レビューのレポートによれば、こうした報告の質に問題があるという。
 理論上は、亜鉛は風邪のウイルスが鼻咽頭の細胞に付着することを防止し、感染細胞内で増殖するのを妨害するが、その証明が困難だった。
 亜鉛の効果は軽度である。風邪の罹病期間を平均1日減らし、予防服用で罹患リスクが約1/3減らせるが、48個の亜鉛トローチで10.99ドルする。防止するには、1.5〜2時間ごとのトローチが5ヶ月間も必要となる。相当量の亜鉛になる。亜鉛トローチやシロップで亜鉛量は10〜23.7mgと様々だった。亜鉛摂取の基準量は40mgとされており、150〜450mgの摂取で免疫機能を含めた影響が出る。
 2009年6月に亜鉛を含む鼻腔内風邪薬で嗅覚障害をきたした報告があり、警告が出た。
(書きかけ)
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Can Zinc Kill the Common Cold? Doctors Skeptical
Supplement May Reduce Severity of Common Cold; Experts Urge Caution
http://abcnews.go.com/Health/Wellness/zinc-zap-common-cold/story?id=12922238
By KATIE MOISSE ABC News Medical Unit
Feb. 15, 2011

画像How to Stave Off, Treat a Cold

The common cold is more than a mere nuisance. In the United States alone, it prompts up to 100 million doctor's visits, 189 million missed school days and 276 missed work days each year, costing billions of dollars in health care expenses and work losses.

Americans spend $2.9 billion on over-the-counter drugs and another $400 million on prescription drugs to relieve flu symptoms, the authors reported, adding that a medication that is even partially effective could markedly reduce economic losses.

But some experts say evidence for zinc's cold-fighting effects is still lacking.

"I do not recommend zinc, but if asked, I describe the possible benefits and side effects," said Schaffner, adding that the best treatments for a cold are fluids, decongestants and time.

"The current state of the science makes it impossible to say whether zinc works," said Besser. "I am most skeptical of zinc as a means of preventing colds in people who are otherwise well nourished. The evidence is incredibly weak on that question."

Besser said it's also hard to draw conclusions about treating colds with zinc because of the variability in products used across the studies.

"I wouldn't recommend zinc for either the prevention or treatment of colds," Besser said.

For preventing a cold, Besser suggests frequent hand washing or using an alcohol-based hand sanitizer -- especially during cold and flu season and around young children.

For treating a cold, most over-the-counter drugs are ineffective, Besser said. But there are products that can relieve cold symptoms.

"Acetaminophen and ibuprofen are effective pain and fever medications," Besser said. "Some people benefit from a nasal decongestant. And for the uncomfortable nose there are tissues, salt water nose drops and petroleum jelly."

Besser warned against using antibiotics to treat colds, citing the Centers for Disease Control and Prevention motto: "Snort, sniffle, sneeze, no antibiotics please!"

"Colds are caused by viruses and antibiotics treat bacterial infections," Besser said.
The ongoing debate over the role of zinc in combating the common cold was reinvigorated today by a report that suggests the supplement might modestly reduce cold duration and severity -- or maybe even prevent it. But the report, published as a Cochrane Review, raised questions among doctors about the quality of the findings and whether people should start taking zinc for colds.

Drs. Meenu Singh and Rashmi Ranjan Das from the Postgraduate Institute of Medical Education and Research in Chandigarh, India, examined the results from 13 previously therapeutic trials and two preventive trials of zinc in more than 1,300 subjects. Overall, subjects with colds who took zinc were less likely to have symptoms seven days later, and healthy subjects were less likely to get a cold if they took zinc prophylactically.

"This is an important review because many people use zinc products to either treat or prevent common colds," said Dr. William Schaffner, chair of preventive medicine at Vanderbilt University Medical Center in Nashville.

In theory, zinc might prevent the cold virus from attaching to cells in the nose and throat and stop it from replicating in cells that are already infected -- an effect that has been difficult to prove.

All 15 trials reviewed were blinded, meaning the researchers were unaware which subjects were taking zinc. But only six were placebo-controlled, meaning the patients were also unaware of what they were taking -- the gold standard in clinical trials.

Furthermore, zinc lozenges are known to have a bad taste that could be discernable from that of a placebo, Singh and Ranjan Das reported.

Zinc's Modest Benefit

Although the review suggests the effects of zinc in fighting the common cold are positive, they're mild. Promptly treating a cold with zinc reduced its duration by an average of one day, and taking zinc daily for prevention reduced the risk by roughly a third. But these modest pros should be weighed against the cons -- bad taste, nausea and the cost of zinc.

Forty-eight zinc lozenges cost as much as $10.99. And according to the review, it takes one lozenge every 1.5 to 2 hours to quash a cold and one daily for at least five months to prevent one.

"That is a lot of zinc," said ABC News chief health and medical editor Dr. Richard Besser. "If you go that route, there is a risk of unwanted side effects including nausea and altered taste. However, the study does not say how frequently these occur."

The dose of zinc used in the studies reviewed varied from 10 to 23.7 mg in lozenge or syrup form. The tolerable upper intake level for zinc is 40 mg, and daily intakes of 150 to 450 mg have been linked to chronic health effects including reduced immune function, according to the National Institutes of Health.

In June 2009 the U.S. Food and Drug Administration warned consumers to stop using Zicam -- a zinc-containing intranasal cold remedy -- after reports that some users lost their sense of smell.

In addition to reducing the duration and severity of colds, Singh and Ranjan Das concluded that zinc can also reduce school absences and antibiotic use.

According to a 2003 study published in Archives of Internal Medicine, more than a third of patients who see a doctor for a cold received an antibiotic prescription.

How to Stave Off, Treat a Cold

The common cold is more than a mere nuisance. In the United States alone, it prompts up to 100 million doctor's visits, 189 million missed school days and 276 missed work days each year, costing billions of dollars in health care expenses and work losses.

Americans spend $2.9 billion on over-the-counter drugs and another $400 million on prescription drugs to relieve flu symptoms, the authors reported, adding that a medication that is even partially effective could markedly reduce economic losses.

But some experts say evidence for zinc's cold-fighting effects is still lacking.

"I do not recommend zinc, but if asked, I describe the possible benefits and side effects," said Schaffner, adding that the best treatments for a cold are fluids, decongestants and time.

"The current state of the science makes it impossible to say whether zinc works," said Besser. "I am most skeptical of zinc as a means of preventing colds in people who are otherwise well nourished. The evidence is incredibly weak on that question."

Besser said it's also hard to draw conclusions about treating colds with zinc because of the variability in products used across the studies.

"I wouldn't recommend zinc for either the prevention or treatment of colds," Besser said.

For preventing a cold, Besser suggests frequent hand washing or using an alcohol-based hand sanitizer -- especially during cold and flu season and around young children.

For treating a cold, most over-the-counter drugs are ineffective, Besser said. But there are products that can relieve cold symptoms.

"Acetaminophen and ibuprofen are effective pain and fever medications," Besser said. "Some people benefit from a nasal decongestant. And for the uncomfortable nose there are tissues, salt water nose drops and petroleum jelly."

Besser warned against using antibiotics to treat colds, citing the Centers for Disease Control and Prevention motto: "Snort, sniffle, sneeze, no antibiotics please!"

"Colds are caused by viruses and antibiotics treat bacterial infections," Besser said.


-----------------------------------------------------
February 15, 2011, 6:07 pm
For Cold Virus, Zinc May Edge Out Even Chicken Soup
By TARA PARKER-POPE

Scientists still haven’t discovered a cure for the common cold, but researchers now say zinc may be the next best thing.

A sweeping new review of the medical research on zinc shows that sniffing, sneezing, coughing and stuffy-headed cold sufferers finally have a better option than just tissue and chicken soup. When taken within 24 hours of the first runny nose or sore throat, zinc lozenges, tablets or syrups can cut colds short by an average of a day or more and sharply reduce the severity of symptoms, according to the Cochrane Database of Systematic Reviews, a respected medical clearinghouse.

In some of the cited studies, the benefits of zinc were significant. A March 2008 report in The Journal of Infectious Diseases, for example, found that zinc lozenges cut the duration of colds to four days from seven days, and reduced coughing to two days from five.

While the findings are certain to send droves of miserable cold sufferers to the drugstore in search of zinc treatments, the study authors offered no guidance on what type of zinc product to buy. The authors declined to make recommendations about the optimal dose, formulation or duration of zinc use, saying that more work was needed before they could make recommendations.

“Over all, it appears that zinc does have an effect in controlling the common cold,” said Dr. Meenu Singh, the review’s lead author and a professor in the department of pediatrics at the Postgraduate Institute of Medical Education and Research in Chandigarh, India. “But there still needs to be consensus about the dose.”

Zinc experts say that many over-the-counter zinc products may not be as effective as those studied by researchers because commercial lozenges and syrups often are made with different formulations of zinc and various flavors and binders that can alter the effectiveness of the treatment.

“A lot of preparations have added so many things that they aren’t releasing zinc properly,” said Dr. Ananda Prasad, professor in the department of oncology at Wayne State University School of Medicine in Detroit and an early pioneer of research into zinc as an essential mineral. Two of Dr. Prasad’s studies were included in the Cochrane report.

“The public is confused because people have used the wrong dose, they have used the wrong sort of zinc or they have not started the treatment within 24 hours of onset,” he said.

Even so, the new report gives credence to the long-debated theory that zinc can be an effective treatment for colds. While it’s not certain how the mineral curbs colds, it appears to have antiviral properties that prevent the cold virus from replicating or attaching to nasal membranes.

The first study to show that zinc might be a useful treatment for the common cold was published in 1984, but the research was criticized for its poor methods. Since that study, 18 more trials of zinc for colds have been conducted: 11 of them showed it to be a useful treatment, while seven of them showed no benefit, according to the review.

Although a majority of trials have shown some benefit from zinc, many of them have been criticized for failing to “mask” the treatment, meaning the participants most likely knew they were using zinc, which may have skewed the results. At the same time, many of the trials that showed no benefit from zinc have been criticized for using formulations that may have contained ingredients that blunted the effectiveness of zinc.

The Cochrane reviewers selected 15 studies that enrolled a combined 1,360 participants. The studies were all considered to have good methodological quality with a low risk of bias, but they were far from perfect. All the studies compared zinc use with a placebo, but in several studies the zinc users complained about the taste of lozenges, suggesting that some people may have known that they were using zinc rather than a placebo.

Even so, when the data was pooled, the effect shown was strong. The review found that not only did zinc reduce the duration and severity of common cold symptoms, but regular zinc use also worked to prevent colds, leading to fewer school absences and less antibiotic use in children. People who used zinc were also far less likely to have a cold that lasted more than seven days.

The studies used various forms and doses of zinc, including zinc gluconate or zinc acetate lozenges and zinc sulfate syrup, and the dose ranged from 30 to 160 milligrams a day. Several studies in the Cochrane review used zinc acetate lozenges from the Web site ColdCure.com, created by George Eby, the researcher who wrote the first zinc study in 1984.

Dr. Prasad said his studies have used zinc acetate lozenges from ColdCure.com that contained about 13 milligrams of zinc. Study participants took a lozenge every three to four hours during the day for four consecutive days, resulting in a daily dose of 50 to 65 milligrams a day, he said.

Some cold sufferers have been wary about using zinc since the Food and Drug Administration warned consumers to stop using Zicam nasal sprays and swabs, which contain zinc, after numerous reports that some users lost their sense of smell after using the product. The Cochrane report did not review any studies of nasal zinc products.

----------------------------------------------------
J Infect Dis. 2008 Mar 15;197(6):795-802.

Duration and severity of symptoms and levels of plasma interleukin-1 receptor antagonist, soluble tumor necrosis factor receptor, and adhesion molecules in patients with common cold treated with zinc acetate.

Prasad AS, Beck FW, Bao B, Snell D, Fitzgerald JT.

Department of Internal Medicine, Wayne State University School of Medicine, Detroit, MI 48201, USA. prasada@karmanos.org
Abstract

BACKGROUND: Zinc lozenges have been used for treatment of the common cold; however, the results remain controversial.

METHODS: Fifty ambulatory volunteers were recruited within 24 h of developing symptoms of the common cold for a randomized, double-blind, placebo-controlled trial of zinc. Participants took 1 lozenge containing 13.3 mg of zinc (as zinc acetate) or placebo every 2-3 h while awake. The subjective scores for common cold symptoms were recorded daily. Plasma zinc, soluble interleukin (IL)-1 receptor antagonist (sIL-1ra), soluble tumor necrosis factor receptor 1, soluble vascular endothelial cell adhesion molecule, and soluble intercellular adhesion molecule (sICAM)-1 were assayed on days 1 and 5.

RESULTS: Compared with the placebo group, the zinc group had a shorter mean overall duration of cold (4.0 vs. 7.1 days; P < .0001) and shorter durations of cough (2.1 vs. 5.0 days; P < .0001) and nasal discharge (3.0 vs. 4.5 days, P = .02) Blinding of subjects was adequate, and adverse effects were comparable in the 2 groups. Symptom severity scores were decreased significantly in the zinc group. Mean changes in plasma levels of zinc, sIL-1ra, and ICAM-1 differed significantly between groups.

CONCLUSION: Administration of zinc lozenges was associated with reduced duration and severity of cold symptoms. We related the improvement in cold symptoms to the antioxidant and anti-inflammatory properties of zinc.

PMID: 18279051 [PubMed - indexed for MEDLINE]


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