Fighting colds and flu: The cold facts

Today is the official start of our flu season, which in the Philippines begins in June and ends in September. And every year, health-conscious folks are looking for every possible edge to reduce the odds of getting sick.

Unfortunately, despite what you may read in ads and articles touting purported breakthroughs, current science offers insight but no “magic bullet” to boost your immune system against colds and the flu. It’s probably because the body’s immune system is too complex for any single treatment to “supercharge.” For example, the evidence that antioxidants Ñ or any other specific nutrient — significantly improve immune function is mixed at best.

Instead, experts emphasize the importance of eating a balanced diet, since all nutrients contribute to maintaining your body’s maximum disease-fighting capability. Other healthy habits that are a good idea anyway can help fight colds and flu. Regular exercise has been shown to improve immune function — although intense, exhausting exercise can temporarily suppress the body’s immune response, so don’t overdo it. Getting adequate sleep is also important for a healthy immune system. And drink plenty of fluids.

Stress, on the other hand, can weaken your body’s natural defenses. Smoking — or being exposed to secondhand smoke — makes you more prone to respiratory illnesses and more severe complications.

The number one healthy habit to cultivate this cold and flu season is washing your hands. Other than getting both a seasonal flu and H1N1 vaccination, public health officials agree that basic personal hygiene is the best protection against infection. Even if you’re a regular hand-washer, chances are you’re not washing often enough or long enough. The Alliance for the Prudent Use of Antibiotics cites research that antibacterial soaps are no more effective than ordinary soaps for fighting infection — if you wash your hands right. Here’s what the organization recommends:

• Use soap and warm, running water.

• Wash all surfaces thoroughly, including wrists, palms, back of hands, fingers, and under the fingernails.

• Rub hands together for at least 10-15 seconds.

• When drying, use a clean disposable towel if possible, and pat your skin rather than rubbing to avoid chapping and cracking.

Vitamins, Minerals, Herbs And Supplements

But what about vitamins, minerals, herbs, and supplements that fall in the gray area of science, promising but unproven? Given the ubiquity of the common cold and the dangers of influenza, researchers keep looking for, if not exactly magic bullets, at least new weapons in the anti-infection arsenal.

Here’s an A to Z rundown of the latest findings on possible cold and flu fighters, according to the US National Library of Medicine (NLM) and the National Institutes of Health (NIH). The NLM/NIH’s Medline Plus rates the evidence for each, using this scale:

A = Strong scientific evidence for this use.

B = Good scientific evidence for this use.

C = Unclear scientific evidence for this use.

D = Fair scientific evidence against this use.

E = Strong scientific evidence against this use.

• Arginine. Some research suggests that this amino acid may decrease the risk of respiratory infections and boost immune response in older people receiving the pneumonia vaccine. The NLM/NIH, however, rates the evidence for these uses only a “C.”

• Echinacea. Probably the best known herbal treatment against colds and other respiratory infections, echinacea has been the subject of several recent, hotly debated studies. For treatment of upper respiratory tract infections, according to the NLM/NIH, numerous human trials have found echinacea to reduce duration and severity, particularly when initiated at the earliest symptoms. But the majority of trials, largely conducted in Europe, have been small or of weak design, while two US trials have negative results. A 2006 meta-analysis of three trials, however, found that the likelihood of experiencing a clinical cold was 55 percent higher with placebo than with echinacea. The bottom line? “The sum of the current evidence is conflicting and further well-designed studies are needed before a definitive conclusion can be drawn.” For preventing infections, the evidence is more clear-cut: “Daily echinacea has not been shown effective in human trials.”

• Garlic. Preliminary evidence suggests that the “stinking rose” may help reduce the severity of upper respiratory tract infections, but this benefit has not been demonstrated in well-designed human studies (“C”).

• Ginseng. Several studies indicate that ginseng may boost immune-system function, enhance the body’s response to flu vaccines, and improve the effectiveness of antibiotics against acute bronchitis. The NLM/NIH rates the evidence for this benefit a “B,” but cautions that additional research is needed. Ginseng may also be safe, well tolerated, and potentially effective for preventing acute respiratory illnesses caused by flu. But the evidence to date rates only a “C.”

• Green tea. In addition to its myriad other emerging benefits, preliminary data suggests that a specific formulation of green tea may help prevent cold and flu symptoms. A new study also finds an association between green tea and protection against pneumonia deaths in women. Further research is needed, however, and the evidence for green tea to date rates only a “C.”

• Licorice root. A traditional expectorant and anti-cough treatment, licorice has also been studied as a treatment for simple upper respiratory tract infections. Results are mixed and overall, the scientific evidence for its use remains unclear (“C”).

• Selenium. Because of selenium’s apparent role in immune function, selenium supplementation has been studied against a variety of infections. Some evidence suggests selenium may promote recovery from bronchitis and pneumonia caused by Respiratory Syncitial Virus (RSV). More studies are needed to show its effectiveness in treating respiratory infections (“C”).

• Vitamin C. Who hasn’t heard that vitamin C combats the common cold? Despite popular beliefs and prominent promoters, however, the effectiveness of vitamin C in the prevention/treatment of the common cold and respiratory infections remains controversial. More than 30 clinical trials totaling over 10,000 participants have examined the effects of taking daily vitamin C to prevent colds; overall, no significant reduction in the risk of developing colds has been observed. The only research to clearly show a cold-prevention benefit involved a subset of subjects in extreme circumstances — soldiers in subarctic exercises, skiers, marathon runners — who did cut their risks in half. Except for extreme cases, the NLM/NIH rates the evidence that vitamin C prevents colds as “D.”

In people who developed colds while taking vitamin C, no difference in severity of symptoms was seen overall, although a small but significant reduction in the duration of colds has been reported (approximately 10 percent in adults and 15 percent in children).

For cold treatment, numerous studies have examined the effects of starting vitamin C after the onset of cold symptoms. To date, no significant benefits have been observed, and its use also rates a “D.”

• Zinc. In a study published in 2007, Meydani and colleagues found that nursing home residents, ages 65 and up, with normal zinc levels in their blood reduced their risk of developing pneumonia by about 50 percent. Meydani adds, “Those participants with normal serum zinc concentrations in their blood were more likely to spend fewer days on antibiotics and recover quickly.”

Overall, the NLM/NIH rates evidence that zinc benefits the immune system a “B,” noting that zinc gluconate appears to have beneficial effects on immune cells. Relatively few studies, however, have examined zinc levels and the effects of zinc supplementation on the elderly.

Despite the popularity of zinc-based products to treat cold symptoms, the evidence is contradictory and more research is needed (“C”). One recent study found no significant differences between zinc nasal spray and placebo. And the US FDA recently warned consumers to stop using Zicam intranasal cold-remedy products because of more than 130 reports of users who’ve lost their sense of smell.

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To learn more: Flu Prevention & Treatment, www.flu.gov: The Common Cold, www3.niaid.nih.gov/topics/commonCold; and The Alliance for the Prudent Use of Antibiotics, www.tufts.edu/med/apua.