Long-time readers of this blog know how much I trust, how often I recommend, and how often I use in my practice the Natural Medicines Comprehensive Database. This trustworthy and evidence-based website (requires subscription) rates natural medications (herbs, vitamins, and supplements) for a wide variety of indications.

If the NMCD rates somethings as “Possibly Effective,” it means:

• This product has some clinical evidence supporting its use for a specific indication; however, the evidence is limited by quantity, quality, or contradictory findings. Products rated “Possibly Effective” might be beneficial, but do not have enough high-quality evidence to recommend for most people.
• To achieve this Effectiveness Rating a product is supported by all of the following:
• One or more randomized clinical trials or meta-analysis (level of evidence = A or B) or two or more population based or epidemiological studies (level of evidence = B).
• Studies have a low to moderate risk of bias and moderate to high level of validity by meeting or partially meeting assessment criteria (quality rating A or B).
• Evidence shows POSITIVE outcomes for a given indication without substantial valid evidence to the contrary. Some contrary evidence may exist; however, valid positive evidence outweighs contrary evidence.

So, what does the NMCD rate as “possibly effective” for the common cold?

ANDROGRAPHIS (Possibly effective for the common cold)

Some clinical research shows that taking a specific andrographis extract, in combination with Siberian ginseng (Kan Jang, Swedish Herbal Institute) orally, significantly improve symptoms of the common cold when started within 72 hours of symptom onset. Some symptoms can improve after 2 days of treatment. It typically takes 4-5 days of treatment before there is maximal symptom relief. Some research suggests this combination of andrographis and Siberian ginseng relieves cold symptoms better than Echinacea or placebo in children.

BIFIDOBACTERIA (Possibly effective for respiratory tract infections)

Some clinical research shows children ages 3 to 5 years who attend day-care centers have significantly fewer influenza-like respiratory symptoms when given milk containing a specific combination of Lactobacillus acidophilus and Bifidobacterium animalis (HOWARU Protect, Danisco). Children taking this product had a 45% lower risk of experiencing fever, cough, rhinorrhea compared to placebo. The duration of symptoms was also 2 days shorter in patients taking this combination. These patients were also significantly less likely to use an antibiotic for their symptoms.

ECHINACEA (See my blog “Echinacea demonstrates little benefit in treating common cold.”)

GINSENG, AMERICAN (Possibly effective for respiratory tract infections)

Some evidence suggests that taking a specific American ginseng extract called CVT-E002 (Cold-FX, Afexa Life Sciences, Canada) 200 mg twice daily over a 3-4 month period during influenza season might modestly decrease the risk of developing symptoms of an upper respiratory tract infection such as the common cold or flu in adults aged 18 to 65 and older. This extract also seems to reduce the symptom severity and duration of symptoms when infections do occur.

GINSENG, SIBERIAN (Possibly effective for the common cold)

Some clinical research shows that taking a specific combination product containing Siberian ginseng plus andrographis (Kan Jang, Swedish Herbal Institute) orally significantly improves symptoms of the common cold when started within 72 hours of symptom onset. Some symptoms can improve after 2 days of treatment. It typically takes 4-5 days of treatment before there is maximal symptom relief. Some research suggests this combination of Siberian ginseng and andrographis relieves cold symptoms better than Echinacea or placebo in children.

LACTOBACILLUS (Possibly effective for respiratory tract infections)

Clinical research shows that children ages 1 to 6 years who attend daycare centers get fewer and less severe respiratory infections when given milk that contains a specific strain of Lactobacillus rhamnosus, Lactobacillus GG (Culturelle). These children also seem to have fewer days of illness-related absence. Additional clinical research shows children ages 3 to 5 years who attend daycare centers have significantly fewer influenza-like respiratory symptoms when given milk containing a specific combination of Lactobacillus acidophilus and Bifidobacterium animalis (HOWARU Protect, Danisco). Children taking this product had a 45% lower risk of experiencing fever, cough, and rhinorrhea compared to placebo. The duration of symptoms was also 2 days shorter in patients taking this combination. These patients were also significantly less likely to use an antibiotic for their symptoms. Patients who took Lactobacillus acidophilus without Bifodobacterium also had significantly reduced fever, cough, and use of antibiotics, but not rhinorrhea.

NASAL IRRIGATION (Possibly effective for upper respiratory tract infection – URTI)

Clinical research shows that isotonic saline nasal irrigation significantly reduces symptoms of the common cold including rhinitis, sore throat, cough, and nasal obstructor and secretion in children with the common cold or flu. Nasal irrigation also reduced the use of other medications including antipyretics, decongestants, mucolytics, and anti-infectives.

THYMUS EXTRACT (Possibly effective for respiratory tract infections)

Taking thymus extract orally may be effective for treating adults and children with recurrent respiratory infections. Thymomodulin (calf thymus extract) treatment seems to reduce the number of infections or coughing attacks in patients with recurrent respiratory infections. Thymomodulin (calf thymus extract) alone, or in combination with vaccine, seems to be more effective than vaccine alone or antibiotics in reducing the number and duration of infections in adults with recurrent respiratory infections.

VITAMIN C (ASCORBIC ACID) (Possibly effective for the common cold)

There is a lot of controversy about the effectiveness of vitamin C for treating the common cold. However, the majority of evidence shows that taking high doses of vitamin C orally might decrease the duration of cold symptoms by 1-1.5 days in some patients. Other studies have found no effect with doses up to 3 grams daily. Some research suggests vitamin C may be more effective for treating cold symptoms in children than in adults. There may also be a dose-dependent response; doses of at least 2 grams per day seem to work better than 1 gram doses. Tell patients that the high doses used for treating the common cold, 1-3 grams daily, can increase the risk of side effects. Some patients might not think the modest benefit is worth the risk. Explain to patients that taking vitamin C supplements prophylactically does not decrease the risk of catching a cold. Dietary intake of vitamin C also doesn’t seem to affect the risk of getting a cold.

ZINC (Possibly effective for the common cold)

Using zinc oral lozenges seems to help decrease the duration of the common cold in adults. The majority of studies show a significant decrease in the duration of symptoms of the common cold when adults take zinc gluconate or acetate lozenges providing 9-24 mg elemental zinc per dose. Lozenges should be taken every 2 hours while awake, starting within 48 hours of symptom onset. However, not all studies have been positive. The reasons for these different findings are not clear, but might be due to differences in zinc formulations and study methodologies. In some cases, flavoring agents such as citric acid, mannitol, and sorbitol might chelate zinc and decrease zinc ionization. Since zinc ionization is thought to be an important step involved in the effectiveness of zinc, a decrease in zinc ionization could decrease effectiveness. Some of the positive studies have also been criticized for inadequately blinding the unpleasant, distinctive taste of zinc. Overall, zinc products seem to be beneficial for reducing the duration of symptoms of the common cold in adults. Zinc from supplements taken prophylactically does not seem to prevent the common cold.