7 Supplements for Cold & Flu Season

The cold and flu aisle in your pharmacy is confusing. Here's what to really look for.

woman cold and flu

Adapted from The Supplement Handbook

Every year in the United States, there are more than 1 billion upper respiratory tract infections and colds. In addition, 5 to 25 percent of Americans get the flu, which results in 200,000 hospitalizations and anywhere from 20,000 to 36,000 deaths, depending on the year.

More: 10 Foods That Fight Cold and Flu

When you are otherwise healthy and get sick, your immune system pumps out protein molecules called cytokines, which help battle the virus and lead to many of the symptoms you experience—sneezing, coughing, a runny nose, and puffy eyes. It's the body's immune response to the virus that makes you feel so bad, not the virus itself. That's why it makes no sense when supplements claim they can "boost" your immune system. It's already boosted! (How Healthy Is Your Immune System?)

More: 10 Rules to Know Before You Start Taking Any New Supplement

If you have symptoms that come on gradually and are primarily above the neck—sneezing, sore throat, watery or itchy eyes—you probably have a cold. If you have symptoms that come on quickly, are severe, and are above and below the neck—fever (a key symptom of the flu), shivering, sweating, achy muscles and limbs—you've probably caught the flu. I like to say: "One is a nuisance and the other is a knockout."

Here's what works:

Vitamin C
Vitamin C

250 to 1,000 milligrams a day for prevention during periods of intense exercise and stress and especially for treatment along with conventional cold and flu medicines.

I can hear it already. You're thinking, "I can't believe Moyad made cheap, old vitamin C number 1!" Well, give me a moment to explain. After 30-plus clinical trials involving more than 11,000 individuals, we know that taking 1,000 milligrams a day (2,000 milligrams max) of vitamin C lowers the duration of the common cold in kids and adults by up to 20 percent. So get started with eating these foods that have more vitamin C than oranges

Individuals who have an increased risk of temporary immune suppression due to stress, intense exercise (which is a type of stress), or extreme environments may have the most to benefit in terms of vitamin C: Five clinical studies involving approximately 600 soldiers, runners, and skiers under extreme stress (sub-arctic exercise conditions) showed a more than 50 percent reduction in the risk of getting a cold.

More: 13 Nutrients You Aren't Eating Enough Of

There are only a few very rare circumstances where vitamin C should not be taken, such as with the medical condition hemochromatosis (a genetic defect that leads to too much iron absorption, and vitamin C encourages absorption). Vitamin C is also safe to use during pregnancy, and this speaks volumes about its safety for children and adults.

Pelargonium sidoides
Pelargonium sidoides

30 (1.5 milliliters) three times a day for 10 days for cold treatment.

P. sidoides is a species of South African geranium that's been used for centuries in Zulu medicine and has two randomized trials showing it can improve symptoms of acute bronchitis (which is usually caused by a virus). Its consistent history of effectiveness for respiratory symptoms and safety in kids and adults is what spurred me to include it in my top three for cold treatment (not for prevention).

More: 7 Natural Remedies for Bronchitis

This liquid herbal product is easy to find (look for Umcka ColdCare and follow the dosage instructions on the box), and the side effects are similar to a placebo.

It appears to reduce the duration and severity of common cold symptoms within 5 days, but more commonly 10 days. It worked better for nasal congestion and drainage, sneezing, sore and scratchy throat, hoarseness, and headache than for fever, cough, and muscle aches. Weakness, exhaustion, and fatigue were also improved. By day 10, about 79 percent versus 31 percent (placebo group) felt better, and it reduced days missed from work by about one to one-and-a-half.

It could be argued that since most positive P. sidoides studies have been funded by the company, we should be skeptical. This is fair, but it does not change the fact that the studies had good methodology, efficacy, and safety.

American ginseng (Panax quinquefolius)

200 milligrams twice a day or Panax ginseng 100 milligrams a day for prevention during cold and flu season.

Research has shown that American ginseng can activate some immune cells (macrophages), may increase cytokine and antibody production, and can even help natural killer cells in the body that go after infections.

More: 11 Weird Things Inflaming Your Body

It's been studied against a placebo in at least five different clinical trials, and it reduced the number of colds by 25 percent (not that impressive, but not that bad) and the duration of colds or acute respiratory infections by as much as 6 days (very impressive). In one impressive trial with Panax ginseng (Ginsana), 227 healthy adults who had been vaccinated for the flu took 100 milligrams of a ginseng extract or placebo for 12 weeks. The ginseng group had a 65 percent reduction in colds.

Here's the catch with these products when it comes to colds and flu: While the effective active ingredient in ginseng for improving fatigue is something called ginsenosides, some ginseng products that have shown benefits for colds do not contain them. In other words, it's difficult to say exactly which product is the best to choose, whether it's a supplement like COLD-FX or Ginsana (Panax ginseng), which contains 4 percent ginsenosides. I don't endorse one type of ginseng product over another because the research is unclear (they both may work in a similar fashion).

More: 5 Herbs that Cure The Flu

Side effects reported with American ginseng include gastrointestinal upset, headache, anxiety, and insomnia. So taking it in the late afternoon or evening can increase the odds that you'll have trouble sleeping. But if you're sick and need to keep working, ginseng could play a role in reducing the fatigue and weakness associated with colds or the flu.

Never take ginseng if you're pregnant or breastfeeding because this has not been adequately studied. Similarly, I do not believe kids should take it because it hasn't been well studied in this population either. Also, there have been some case reports of drug interactions (warfarin, phenelzine, and alcohol), so, as always, check with a pharmacist or doctor you trust before taking this supplement. Overall, side effects generally have been similar to a placebo in trials.

Brewer's yeast-derived fermentate or beta-glucans from yeast

250 to 500 milligrams a day for prevention and treatment of cold and flu symptoms.

Modified yeast products are essentially yeast that has been placed under some sort of laboratory-induced stress to produce more immune-fighting compounds.

The product EpiCor has the most human research so far. People who took 500 milligrams per day for 12 weeks had fewer cold and flu symptoms and a shorter duration of symptoms than with a placebo. They also reported less nasal stuffiness, hoarseness, and weakness.  Full disclosure: I assisted in the design and research of some of these clinical trials for EpiCor, and our research was given one of the highest awards in the supplement industry. I no longer consult for this company, but I am as convinced of the research today as I was many years ago when these trials were conducted.

More: 9 Ways to Spice Up Your Immunity

The safety of these products has been excellent in trials, with side effects similar to or even less than a placebo. There is some concern that people with inflammatory bowel disease should not use yeast products because the immune response they prompt could theoretically cause a flare-up in symptoms, but this is not definitive so talk to your doctor.

People often ask me if just using brewer's or baker's yeast has the same impact. It is safe but does not have near the amount of research, so I like to stick with what worked in the clinical trials. I believe modified forms of these yeasts provide enhanced immune benefits beyond what the original forms deliver. It's certainly safe to experiment and be your own guinea pig.

Zinc (acetate or gluconate)

10 to 15 milligrams every 2 to 3 hours until cold symptoms disappear or 10 to 20 milligrams a day for cold and flu symptoms (only for treatment).

Zinc is an essential mineral that's used in hundreds of metabolic pathways in the body. There is no doubt that a deficiency of this mineral can increase the risk of infection. Research has shown zinc can block cold viruses from attaching inside the nose and protect cell membranes from toxins produced by these infectious agents.

More: 12 Surprising Immune System Killers

Yet, there is that side effect thing! It is very toxic in large doses. Even when zinc works, many people quit taking it because they feel the benefits do not outweigh the side effects (bad taste and nausea).

One of the largest reviews of past clinical trials of zinc supplements found that they appear to reduce cold symptoms in adults (by 1 to 2 days more than placebo), but not kids, when taken within 24 hours of symptom onset and that zinc acetate impacted symptoms a little more than the gluconate or sulfate forms. Subjects took 10 to 15 milligrams every 2 to 3 hours until symptoms began to disappear.

Overall, more than half of these clinical trials showed efficacy. The acetate and gluconate forms have the most research in general, but they're also less apt to bind to additives in supplements and other products, which could reduce the amount absorbed by the body.

More: How to Repair Your DNA With Dietary Minerals

Do not take zinc to prevent colds or the flu; only take it when you're sick. And avoid zinc inhalers and nasal gels; they can reduce your sense of taste or smell, sometimes permanently. Also, take zinc with food to reduce the risk of stomach upset.


Elderberry has shown promise for the treatment of colds and the flu. In two small studies done more than 20 years ago, up to 4 tablespoons of elderberry extract per day for 3 to 5 days along with conventional treatment cleared up flu symptoms faster than a placebo. (Both studies used the "original formula" Sambucol supplement, with 3.8 percent extract.) While I'm a bit skeptical due to the age of the studies, it appears safe, so I cannot reject it as an option unless some study proves that elderberry extract is clearly ineffective. Throw in a few recent laboratory studies and it still seems that the benefit of these extracts (now there are many) outweighs the risk.

More: 30 Herbs for Cold & Flu Season

Andrographis paniculata
Andrographis paniculata

Andrographis paniculata, or Nees extract, is an herbal extract that's also known as Chiretta, King of Bitters, or Kalmegh, that has been used widely in India (one common brand is Kalmcold). The herb has demonstrated some anti-inflammatory and immune-enhancing benefits, which stem from andrographolide. It has been studied over and over for the treatment of colds, but researchers still haven't been able to identify the exact amount needed of the active ingredients. The most common dosage of andrographolide used in most of the clinical trials was 60 milligrams per day for 3 to 7 days. There is no good research on the potential for allergic reactions to this herbal, and the number of reports has been small. In other words, use at your own risk.

Vitamin D
Vitamin D

Vitamin D might help, but only in cases of extreme deficiency. Let me repeat that: I recommend this for cold and flu prevention and treatment only if your blood test is very low—10 ng/mL or less. If you're deficient, raising blood levels higher (20 ng/mL) or back to normal (30 ng/mL) could have a large impact on your risk of getting colds and the flu as well as pneumonia and other serious infections, such as tuberculosis.

More: Your Vitamin D Cheat Sheet

If you have normal or near-normal levels, vitamin D won't help you fight off viruses. The VIDARIS (Vitamin D and Acute Respiratory Infection Study) randomized trial—one of the best and most rigorous ever conducted—looked at whether healthy individuals can benefit from D supplementation. Compared to a placebo, the D supplementation did not reduce the incidence or severity of an upper respiratory tract infection in healthy adults (332 of them) with near-normal vitamin D levels.

cranberry supplements
Juice concentrate supplements

Juice concentrate supplements, concentrated extracts of fruits and vegetables, can be a convenient way for some people to get their five servings a day. Although these supplements don't contain fiber, they can be helpful for some people who can't tolerate the real thing for whatever reason. Recent research shows that people (health care workers) who took these juice concentrate supplements daily saw a potentially significant reduction in cold-symptom days (fewer colds in general and less severe symptoms) over 8 months compared to placebo. This looks interesting, and I'm hoping we see more research in this area.

For more natural ways to tame symptoms related to cold and flu season, check out these 4 natural ways to soothe sore, scratchy throats.

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