Fact check: Do natural cold and flu remedies work?

The idea of ​​“boosting” the immune system is popular.

So it’s no surprise that a Google search for “immune boosters” turns up over a billion results. There is no shortage of ads, blogs, and articles promoting certain foods and supplements that contain immune-boosting ingredients.

With the flu, respiratory syncytial virus, and coronavirus circulating, it’s easy to reach for some pill, drink, or superfood that promises to boost your immunity.

Do popular immune supplements and foods really prevent or treat respiratory infections? Science says so.

How the immune system works

Your immune system is constantly working to defend against viruses, bacteria, and other microorganisms that cause infection. When it recognizes a threat, it responds by releasing white blood cells and other immune compounds to destroy the foreign invader.

However, claims that a specific food or supplement can significantly boost your immune system against infection is simplistic and misleading.

That’s because your body’s immune system is a highly complex and finely tuned network made up of many working parts, including organs, cells, and proteins. Researchers still don’t fully understand all the complexities of this system.

Does science support “immune boosters”?

Of the many supplements and foods often recommended to treat or prevent upper respiratory tract infections, here’s the evidence for five of them.

Most studies show that taking a daily supplement of at least 2,000 milligrams of vitamin C in divided doses can shorten the duration of cold symptoms by 24 to 36 hours, with the benefits being greater in children than in adults.

Taking vitamin C supplements has not been proven to prevent colds.

Are you getting enough vitamin C?

Vitamin C supports immune function by protecting immune cells from damage caused by free radicals (unstable oxygen molecules produced during immune reactions). It may also increase the production of immune cells that engulf and kill pathogens.

Many controlled trial studies have shown that zinc gluconate or zinc acetate lozenges reduce the severity and duration of cold symptoms, especially cough, congestion, runny nose, and sore throat. Zinc is thought to prevent cold viruses from replicating.

Cold symptoms should begin within 24 hours of onset, and zinc lozenges should be taken every two to three hours while awake.

Don’t assume that taking high doses of zinc supplements every day will benefit your immunity. The safe upper limit of zinc intake for adults is 40 mg per day from supplements and food. Chronic intake above this level increases the risk of health problems, including impaired immune function.

Adverse health effects from short-term (two weeks) intake of large amounts of zinc from zinc lozenges have not been found.

Probiotics

Many clinical trials have shown that taking probiotics as supplements or fermented dairy products can reduce the risk of respiratory infections (colds, flu, sinusitis, pharyngitis) in infants, children, and adults.

There is also evidence that taking probiotics can shorten the duration of upper respiratory tract infections by about 1.9 days in adults and children.

Most types of probiotics studied belong to the genus Lactobacillus. More research is needed to confirm which strains and doses are most beneficial.

chicken soup

There is no evidence that drinking chicken soup helps treat the common cold. But theory gleaned from laboratory experiments conducted at the University of Nebraska suggests its potential.

The study, published in 2000, showed that bathing volunteers’ blood samples in homemade chicken and vegetable broth slowed the activity of inflammation-causing white blood cells. Supposedly, this reduces mucus flow and helps relieve nasal congestion.

There is nothing to go on. However, there’s no reason not to drink chicken soup when you’re sick. It’s both nutritious and hydrating.

Honey

A 2014 review of three randomized controlled trials concluded that taking two teaspoons of honey before bed can help reduce nighttime coughing in children.

A 2021 review of 14 trials involving children and adults with upper respiratory tract infections found that honey was as effective as, and possibly better than, other treatments for reducing the frequency and severity of coughs.

It’s unclear how honey relieves coughs. Its anti-inflammatory, antioxidant and/or antimicrobial properties may play a role.

Never feed honey to children under one year old due to the risk of infant botulism.

While you technically can’t “boost” your immune system, you can certainly support it by eating a healthy diet that includes plenty of fruits and vegetables. Your immune system relies on a consistent source of nutrients to function optimally.

Exercising regularly, getting enough sleep, and managing stress are other important ways to support a healthy immune system.

Leslie Beck is a private practice nutritionist in Toronto and Director of Food and Nutrition at Medcan.Follow her on Twitter @lesliebeckrd