Cold Remedies

"Why do we have Froot Loops in this country that have 18 or 19 ingredients, and you go to Canada and it's got two or three?" Robert F. Kennedy, Jr., November 6, 2024.

Actually, Froot Loops have the same number of ingredients in both countries. (The exact number is 25 to 28, depending on how you parse the ingredient list.)

This may be a trivial mistake, but it's symptomatic. RFK Jr. has also claimed that vaccines cause autism, questioned whether HIV causes AIDS, and attributed the obesity epidemic to seed oils. No surprise that a man who misrepresents the labels on cereal boxes also gets the science wrong.

In this newsletter, I want to share some recent data on treatments for the common cold. Winter is here, colds are more prevalent in colder weather, and Americans spend roughly 3 billion dollars per year on remedies. But how effective are they? Which ones are worth your time and money?

As I looked at the data, I was reminded of RFK Jr.'s bogus health claims. Not just because some cold remedies turn out to be snake oil too, but because some of the ineffective ones are endorsed by the federal agencies that RFK may soon be overseeing.

The most disturbing example is phenylephrine.

You may not recognize the name, but you've probably heard of the decongestants in which it's the active ingredient (Sudafed PE, Vicks Nyquil, Tylenol Cold + Flu Severe Medicine, Benadryl Allergy Plus Congestion, etc.).

Two weeks ago today, the FDA proposed that phenylephrine be removed from over-the-counter products intended to treat nasal congestion. Why? Because, as the agency now acknowledges, "it is not effective as a nasal decongestant."

Three decades have passed since University of Florida pharmacists first raised concerns about phenylephrine's effectiveness. Meanwhile, decongestants that rely on it will be freely sold until the FDA finally orders these products off the market. All consumers can do until then is to read labels and switch products.

RFK Jr. is slated to lead the Department of Health and Human Services, which in turn oversees the FDA and other health-related agencies. Since their inception, these agencies have been a blessing for public health, but the phenylephrine fiasco is one of many signs of their fallibility. Regardless of whether RFK Jr. or someone else runs the HHS, we may need to be especially attentive to what health data tells us.

Unfortunately, scientific data often asks us to set aside simple truths in favor of something more complex but less certain. For instance, this newsletter was inspired by the fact that colds are more prevalent in the autumn and winter months. Why is that?

I had thought the answer was simple.

My mother taught me that we're more prone to colds when our bodies get cold. A bunch of studies seem to prove her wrong. (The details are gross but persuasive. Volunteers who have cold virus pumped into their noses, for instance, aren't more likely to catch colds when they're sitting in icy rooms as opposed to warm ones.)

As it turns out, my mother wasn't completely wrong. A study published last year by Harvard Medical School and Northeastern researchers showed that cold weather inhibits a highly localized immune response. As the cold virus enters our nostrils, tiny sacs called extracellular vesicles (EVs), released from nasal tissue, swarm the virus and prevent it from infecting healthy cells. Cold weather prevents the EVs from being secreted. (Like us, they'd rather not come out when it's cold.)

In short, colds may be more common in cold weather because our noses get cold, regardless of how the rest of our bodies our doing. I find this mildly ironic, given how we dress kids for the chilliest winter days. Practically everything is covered but those little noses.

Still, this isn't the end of the story. Colds also spike during colder weather because we spend more time indoors. This keeps us in closer proximity to others, including contagious people. And, if we're already catching cold, increased exposure to heated air may dry out our nasal passages and increase discomfort. Experts don't agree yet on which of these factors is most influential.

In sum, we know (sort of) why colds and flu peak in the autumn and winter months, but it's a complex story and there's little consensus on the details.

How to prevent a cold

The best remedy for a cold is never catching one in the first place. Here's how I would boil down what the science advises:

1. Avoid contagious people to the extent possible.

2. Wash your hands with soap and warm water, or use hand sanitizer, after coming home (or, if you're out, before touching your face). The cold virus is airborne but also survives on objects, in an infectious state, for as long as 24 hours.

3. Keep your immune system as strong as possible (eat and sleep well, stay active, minimize stress, etc.).

4. Don't take social media tips too seriously. Some of these tips make sense because they support immune system functioning, but so will almost anything that improves your health. There's no evidence of a hack – one magic thing, like fermented garlic honey – that would boost your immune system's ability to ward off cold viruses.

Finally, when your kids start going to daycare, move to a different country and talk to them via Zoom. (Just kidding.)

How to treat a cold

As the saying goes, if you treat a cold, it goes away in seven days, but if you do nothing, it goes away in a week.

Unfortunately, after the week is up you may catch another cold right away. A 2022 study showed that unlike the COVID-19 and flu viruses, dozens of variants of the rhinovirus (the most common source of colds) circulate in the same geographical area at the same time. As a result, catching cold may not prepare your immune system to ward off other cold viruses already nearby.

Once we've succumbed, we want two things from a cold remedy: Relief from the symptoms, and a reduction in how long we stay sick.

Here are a few thoughts on managing the symptoms:

1. Consider at-home remedies instead of (or along with) commercial products.

Over-the-counter medicines are strong and can have undesirable side effects (drowsiness, excessive dryness, gastrointestinal issues, etc). Meanwhile, honey and warm liquids can soothe a sore throat, warm showers can relieve congestion, ginger and turmeric (dissolved in liquids or foods) may reduce inflammation, and so on.

2. Tailor remedies to symptoms.

At my pharmacy, the Cough, Cold, & Flu section is easily 10 yards long, as it contains medicines for every imaginable type and combination of symptoms. My suggestion is to only take what you need. If you only have a scratchy throat, for instance, a product that also contains a decongestant could only make you more uncomfortable, not to mention drowsy and all the rest.

3. Be careful.

Read ingredient lists (e.g., don't bother taking anything with phenylephrine), follow the directions (for safety reasons), and approach social media tips cautiously. This morning I came across a Tik Tok video of someone heating Vicks VapoRub on a stove top and then covering her head and the pot with a towel while inhaling. This seems like a terrible idea. Vicks is flammable and can easily damage your eyes.

4. Don't take antibiotics (unless you have a bacterial infection too).

Colds are caused by viruses and don't respond to antibiotics.

What reduces the severity and duration of a cold?

Keeping your immune system strong will help, of course. My question is whether there's a hack: Something that's especially good at alleviating symptoms or prompting earlier recovery.

I'll be talking about data on four supplements (elderberry, echinacea, zinc, and vitamin C). I chose these supplements because studies have found each to be beneficial. Unfortunately, most of the data turns out to be unpersuasive.

Elderberry supplements

Elderberry extracts have been studied under the assumption that the anthocyanins they contain boost immune system function.

One of the most recent studies, published by Australian researchers in 2016, compared 158 adults who took elderberry capsules for approximately two weeks to 154 people who took placebo pills during the same time period. (Participants didn't know which group they were in.) The dosage of elderberry (600 to 900 mg per day) was comparable to what's found in commercial products.

I want to say more about this study than others, because it illustrates a problem common to much of the supplement research.

In this study, participants were asked to keep "diaries" in which they responded to questions from the researchers. If they started to experience a cold, they recorded daily notes about their symptoms.

Here are the three main findings:

—no significant differences between groups in number of colds

—shorter duration of colds among the elderberry group

—less severe symptoms among the elderberry group

In sum, elderberry supplements didn't prevent colds, but they made people who had colds more comfortable, and these people recovered more quickly. Amazing, right?

Don't run to the pharmacy just yet.

A fundamental problem here is that over the two-week period, colds were a rare outcome. Only 29 participants developed one. This creates a well-known technical limitation on the credibility of the statistical analyses. Right off the bat, the results are not very trustworthy.

A closer look at the data reveals an example of the problem. Here are the two significant findings:

The figure at the top shows how many days each person with a cold remained sick. The figure at the bottom shows the severity of each person's cold symptoms (the higher the number, the worse the symptoms). Each dot in the figures is data for one person. If you counted, you'd find 29 dots in each figure.

As you can see, the dots for the placebo group extend higher up, meaning that these people experienced more sick days (top figure) and more severe symptoms (bottom figure).

Notice though that the data for most participants is clustered. Look what happens when we remove the few outliers from each figure:

Now you can see that once the few exceptional cases are removed, the two groups look about the same.

The researchers didn't address this problem. With such a small sample of colds, even one or two extreme cases in the placebo group would cause the average to be significantly higher than for the elderberry group.

This illustrates a key challenge for studies on rare events. If the outcomes of just a few people had been different, the conclusions would've been completely different.

(Ultimately, this is a sample size issue. The researchers needed thousands more participants and/or a longer study period in order to have enough colds to make their statistical analyses viable.)

In sum, I see no evidence from this study ­– or others – that elderberry supplements help prevent or treat colds.

As with other supplements, the marketing of elderberry supplements relies on a mishmash of misleading verbiage. The makers of Sambucol, for instance, boast that their elderberry syrup has been "scientifically studied". There's even a check mark next to the phrase, like some requirement has been met. Well, they're not lying. Elderberry products have been "scientifically studied". So has phenylephrine. But the science says they don't seem to work.

Echinacea

Echinacea supplements, derived from coneflowers, have been studied as a means of preventing or alleviating colds, under the assumption that they may boost immune system functioning.

Promising effects have been seen in petri dish-type studies, but there's no credible evidence that these supplements actually help in real-world settings.

Since most studies show no benefits, I decided to focus on the best-case scenario: A Lancet Infectious Diseases review claiming that these supplements reduce the incidence and duration of colds. Unfortunately, the studies reviewed are small (e.g., 40 participants and a total of 7 colds) and plagued by other limitations, such as the combination of echinacea with other treatments, leaving it ambiguous as to what was responsible for the benefits.

My fifth grade math teacher kept a big sign by her blackboard that said "SHOW YOUR WORK!" but I don't want to continue doing that here, because it would just be piling it on. I'll just put it simply: I find no credible evidence that echinacea helps prevent or alleviate colds.

Zinc

Zinc supplements have been explored under the assumption that they might boost immune system function and/or prevent cold viruses from replicating.

This May, a meta-analysis of 34 experimental studies found that zinc supplements neither reduce the risk of catching a cold nor alleviate symptoms once a cold is caught. However, in studies that included measures of duration, people who took zinc recovered from their colds more quickly. The average reduction was around 2 days.

If we could trust this finding, it would be great news. Two fewer days living with a cold would be tremendous, right?

Unfortunately, the authors didn't trust their own finding. Using GRADE, a standard rubric for evaluating health studies, the authors gave the evidence for quicker recovery a "low-certainty" rating. Or, as they put it informally, "we have little confidence in the evidence supporting this conclusion." Problems with the studies included small sample sizes as well as heterogeneity in methods and findings.

You might ask why the authors (and I) even bother to discuss zinc when the best evidence of effectiveness isn't very credible. Well, this is how science is meant to work. Zinc probably doesn't help, but we can't be 100% certain just yet. Perhaps we haven't used the right methods to tease out the specific conditions under which it's beneficial.

At the moment, I wouldn't strongly recommend zinc supplements for colds. (As the researchers noted, minor side effects like upset stomachs and headaches are fairly common. The FDA has also issued a warning about nasal sprays that contain zinc, as they can permanently damage one's sense of smell.)

Vitamin C

Now for the most famous one. For roughly nine decades, scientists have kicked around the possibility that vitamin C supplements could prevent or alleviate colds. In the 1970s, thanks to the proselytizing of Nobel laureate Linus Pauling, the general public began to believe it.

Sadly, current evidence is mixed at best. Dozens of recent studies have ruled out the possibility that vitamin C supplements can prevent colds, reduce their severity, or make them go away more quickly.

Here again, I  tried to look at the best case scenario. In this instance, the most positive and recent statement about the benefits of vitamin C I could find was a 2021 commentary on a 2020 review.

The conclusion of the 2020 review was that apart from exceptional cases, there's no convincing evidence that vitamin C helps prevent or alleviate colds.

The 2021 commentators disagreed, arguing that the data indeed shows benefits for the general population. Their evidence? Three articles published between 1972 and 1975, and a review they themselves contributed to in 2013.

This is very unpersuasive. I only see two clear exceptions to my admittedly gloomy perspective:

1. A person who's deficient in vitamin C would be at greater risk of catching colds (and worse) owing to weakened immune systems that leave them more susceptible to infections. For them, vitamin C supplements would probably reduce the number and severity of their colds. (Most of us get enough vitamin C in our diets; hence taking more is unlikely to be helpful.)

2. Studies suggest that a person who's otherwise healthy but experiencing extreme physical stress (e.g., an elite athlete or military trainee) might lower their risk of catching cold by taking vitamin C supplements. Presumably, doing so would strengthen their immune defenses against infections.

In sum, for most people under ordinary circumstances, vitamin C may not prevent or alleviate colds. (Sorry.)

Conclusion: What should you do?

Sir William Osler, an influential physician, once noted that the best way to treat a cold is with contempt. I think we do that naturally.

Supposedly Osler also advised that one should "Go to bed, hang your hat on the bedpost, and drink whiskey until you see two hats."

I doubt he actually said that. In any case, drinking moderately when you have a cold might temporarily alleviate symptoms, but most experts advise against it, because alcohol can impair immune system functioning and promote dehydration.

As for what else we might do, you're probably familiar with the usual advice: Rest, drink fluids (especially warm ones), and treat your symptoms in a sensible way (see my earlier suggestions). I don't always practice what I preach, but I do try to stay rested and hydrated, at least. I also find it helpful to talk quietly, avoid stress, scale back a bit on exercise, and be as gentle as possible about blowing my nose and coughing. (Of course, you should be cautious about any health advice drawn from a sample of 1.)

Thanks for reading!