A new study recently published in the British Journal of Sports Medicine found that regular aerobic exercise is a good way to ward off colds and flu. The researchers followed 1002 adults of all ages for 12 weeks during the autumn and winter of 2008. During that time, people who reported doing at least 20 minutes of moderate aerobic exercise-such as jogging, biking or swimming-on five or more days per week were sick with cold or flu symptoms for just five days, on average, compared with about 8.5 days among people who exercised for only one day per week or less. What's more, the regular exercisers tended to have less severe symptoms when they did become ill (Br J Sports Med, 2011; 45: 987-92).
Exercise appears to trigger a temporary rise in immune-system cells circulating about the body, the researchers found. Although these levels return to normal within a few hours, the cumulative effect adds up to improved protection from harm-ful viruses and bacteria, thereby reducing the number and severity of infections such as the common cold.
But don't overdo it-too much intensive exercise may have a paradoxical immune-weakening effect (Amino Acids, 2011; 41: 1165-72).
Ever since two-time Nobel-Prize winner Linus Pauling advocated large doses of vitamin C in his 1970 bestseller, Vitamin C and the Common Cold, interest in the vitamin for preventing and treating colds, and other viral infections, has soared. Although not all studies agree, the weight of the evidence suggests that, when the vitamin is taken prophylactically to prevent colds, it can significantly reduce cold duration and severity.
According to a 2007 meta-analysis (pooled analysis) of 30 placebo-controlled trials involv-ing more than 11,000 participants, vitamin C taken for prevention (200 mg/day or more) was associated with an 8-per-cent reduction in cold duration in adults and a 14-per-cent reduction in children vs a placebo. In addition, regular vitamin C prophylaxis led to a modest decrease in cold severity when measured as days spent indoors, or days off work or school, and by severity scores.
As for reducing the incidence of colds, the meta-analysis could find no significant difference between vitamin C prophylaxis and placebo. However, a sub-group of six studies in which participants were under heavy physical stress because of exer-cise training in cold climates (soldiers, skiers and marathon runners), those taking vitamin C as a just-in-case preventative had a 50-per-cent reduced incidence of the common cold.
The meta-analysis also assess-ed the benefits of vitamin C when taken at the onset of cold symptoms (for treatment rather than prevention), but found no statistically significant benefit for cold duration or severity.
One large trial, however, reported a reduction in cold duration with 8 g of vitamin C taken on the first day of illness (Cochrane Database Syst Rev, 2007; 3: CD000980).
Considerably less research has been conducted on vitamin C and the flu; nevertheless, there is evidence to suggest that it can help with both its prevention and treatment (Altern Med Rev, 2007; 12: 25-48).
In general, at least 1000 mg of vitamin C every day is recommended to fend off colds and flu, with much higher (divided) doses necessary when symptoms strike (take to bowel tolerance).
If you act fast, taking zinc-as a lozenge, syrup or tablet-can reduce the duration and severity of a cold, according to a recent review. The results of 13 trials, involving nearly 1000 people, showed that those who took zinc within 24 hours of their symptoms starting had shorter and milder colds than those who didn't take the mineral. Moreover, taking zinc for five months or longer was associated with significantly reduced cold incidences, school absenteeism and prescriptions for antibiotics in children (Cochrane Database Syst Rev, 2011; 2: CD001364).
Another review looked specifically at zinc lozenges for the treatment of colds and discovered that they are indeed effective, but only at high doses. Trials that used a total daily zinc dose of less than 75 mg found no effect, whereas those using daily doses larger than 75 mg showed a significant reduction in the duration of colds-by 20 to 40 per cent-with zinc acetate proving superior to other zinc salts (Open Respir Med J, 2011; 5: 51-8).
Best known for its role in bone health, the latest evidence suggests that the 'sunshine vitamin' may also be useful for reducing the risk of colds and flu. In a large-scale US study using data from the Third National Health and Nutrition Examination Survey (NHANES III), people with the lowest levels of circulating vitamin D reported having significantly more recent colds or bouts of flu. The risks were highest in those with chronic respiratory disorders, such as asthma and emphysema (Arch Intern Med, 2009; 169: 384-90).
"The findings of our study support an important role for vitamin D in prevention of common respiratory infections, such as colds and the flu," said lead author Adit Ginde. "We are planning clinical trials to test the effectiveness of vitamin D to boost immunity and fight respiratory infection," he added.
In the meantime, consider supplementing with 600-1000 IU/day of vitamin D3 (the natural form) during the winter months. A good source of vitamin D is cod liver oil, which also contains vitamin A, another useful vitamin for fighting infection and illness (Orv Hetil, 2011; 152: 323-30).
Saline nasal irrigation (SNI), whereby a saline solution is used to flush out the nasal passages, also appears to be a useful weapon against colds and flu. In a trial of 401 children with a cold or flu, one randomized group took the standard medication while the other carried out daily SNI (with a saltwater solution) in addition to taking standard medication. The trial consisted of a three-week treatment phase followed by a nine-week preven-tion phase. During both phases, the SNI group reported signifi-cantly reduced nasal secretions, obstructions and medication use. The SNI users also reported fewer illness days (31 per cent vs 75 per cent), school absences (17 per cent vs 35 per cent) and complications (8 per cent vs 32 per cent) compared with the medication-only group (Arch Otolaryngol Head Neck Surg, 2008; 134: 67-74).
For more information on the SNI technique, see WDDTY vol 22 no 3 (pages 22-3).
These friendly bacteria, known to boost immune function, can help stave off colds and reduce the need for antibiotics to treat them, according to a recent review.
Taking prophylactic doses of healthy bacteria through yoghurt and supplements was associated with 12-per-cent fewer acute upper respiratory tract infections (URTIs) compared with a placebo. The study, which reviewed 10 randomized controlled trials and nearly 3500 participants, also found that antibiotic use to treat UTRIs was lower among those taking probiotics compared with those taking a placebo (Cochrane Database Syst Rev, 2011; 9: CD006895).
It's not clear as to what doses and types of probiotic are best for preventing colds and flu, but the evidence suggests that multistrain probiotics are more effective than single-strain preparations (Eur J Nutr, 2011; 50: 1-17).
This gummy substance-collected by honeybees from leaf buds and tree bark-may be helpful for preventing colds and shortening their duration should you catch one. In a trial carried out in Romania, preschool and school-age children were given a water-based preparation of propolis (Nivcrisol) through-out the entire colds season.
The result was that these children had fewer cases of acute or chronic symptoms, as well as a decrease in the numbers of disease-causing microorganisms carried in their upper airways (Rom J Virol, 1995; 46: 115-33).
In another study-this time carried out in Poland-50 ear-nose-throat patients who had been treated with propolis had common-cold symptoms lasting for only one to three days compared with the nearly five days among those who took a placebo (Otolaryngol Pol, 1989; 43: 180-4).
Propolis is rich in bioflavon-oids that may be responsible for its reputed antiviral properties (J Nat Prod, 1992; 55: 294-302).
There is evidence to suggest that people who are psychologically stressed are more susceptible to catching colds and flu (N Engl J Med, 1991; 325: 606-12; Psychosom Med, 2010; 72: 823-32).
This means that making an effort to take the time to relax may be an important way to fight off illnesses. Indeed, controlled studies in children and young adults have shown that stress-management techniques, such as guided imagery, may be effective for reducing cold and flu symptoms (J Psychosom Res, 2001; 51: 369-77, 721-8).
Meditation and yoga can also achieve similar results.
Factfile: Plant preventatives
- Echinacea. The results of clinical trials have been mixed, probably because they used different species and plant parts. However, a recent review reported that Echinacea purpurea is the most consistently useful variety for the common cold; it was effective for reducing symptoms and their duration in five out of six trials (Can Fam Physician, 2011; 57: 31-6). Echinacea appears to be effective for treating flu symptoms, too (J Altern Complement Med, 2000; 6: 327-34). For best results, take Echinacea at the first signs of illness.
- Garlic. In a UK trial of 146 volunteers, one capsule per day of an allicin-containing garlic supplement led to 63-per-cent fewer colds and 70-per-cent fewer sick days compared with those taking a placebo (Adv Ther, 2001; 18: 189-93).
- Ginseng. In a randomized, double-blind placebo-controlled trial of 227 patients vaccinated against the flu, those who took 100 mg/day of a ginseng extract (Panax ginseng) for 12 weeks reduced their frequency of colds and flu while increasing their immune response (Drugs Exp Clin Res, 1996; 22: 65-72).
- Astragalus. This herb has traditionally been used as a tonic and treatment for colds and flu either alone or in combination with other herbs. In one small, double-blind placebo-controlled trial, participants took oral extracts of E. purpurea, Astragalus membranaceus or Glycyrrhiza glabra (liquorice) alone or as a combination of all three, or a placebo, twice daily for a week to determine the effect on immune cells. Astragalus demonstrated the strongest activation and proliferation of immune cells (Altern Med Rev, 2007; 12: 25-48).
Factfile: Heat beats colds
Taking regular saunas may be able to cut your chances of catching a cold, an Austrian study suggests. Fifty volunteers were split into a sauna-bath group and a control group, and followed for six months. At the end of the study, there were significantly fewer episodes of the common cold in the sauna group-particularly in the last three months, when the incidence was roughly halved compared with the controls (Ann Med, 1990; 22: 225-7).
WDDTY VOL 22 NO 10 January 2012