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  • Writer's pictureDr. Karly McMaster, ND

My 5 Favourite Remedies for Cold & Flu Season

Updated: Dec 28, 2019

Optimizing Immune Function Through Cold & Flu Season Part 2

Aside from the lifestyle modifications you can do to support your immune system through this stressful time of year, read Part 1: The Pillars of Health here, there are several remedies that I love to use to prevent and treat colds & flus. Keep reading to learn more about the my favourite herbs and vitamins to support your immune system!

Disclaimer: Information is empowering but this information is for educational purposes only and not meant to diagnose or prescribe. Please consult your licensed physician before adding to or changing your treatment plan to ensure the changes are safe for you.


1. Allium sativum (Garlic)

While garlic can be a polarizing culinary herb, it has amazing effects on the immune system as a potent anti-microbial (hate to break it to you Grampy). The active agents in garlic, alliin and allicin, are responsible for majority of the antimicrobial benefits that act on bacteria, viruses, fungi, and parasites. It is especially effective in treating lung conditions such as chronic bronchitis, catarrh (phlegm), recurrent colds, and influenza. This is because the volatile oils (the part of the plant that makes it smell) are excreted through the lungs and have antimicrobial properties. The active constituent allicin works by inhibiting the growth of many bacterial strains, including strains that are resistant to antibiotics. It has also been shown to support the good bacteria in your gut while fighting off the bacteria causing infections, unlike conventional antibiotics.

During cold and flu season, increasing the amount of garlic in your cooking can even be beneficial. Studies have shown that raw garlic has 10x more potent antimicrobial effects compared to heated/cooked garlic, however, heated garlic is more stable and the antimicrobial effects only decrease over time with fresh garlic. If you're already fighting an infection, raw garlic cloves, garlic capsules, tinctures (alcohol extractions), or oil infusions (for ear infections) are all great ways to incorporate its medicinal properties into your healing plan.

Garlic is also used medicinally as a blood thinner, so it's important to speak with your licensed physician to see if it's right for you before adding therapeutic amounts in your diet or supplement regime.

Fun fact: When using garlic in cooking, it's important to crush the cloves. This is because the substrate alliin and the enzyme alliinase are stored in different parts of the plant and when crushed, there is a chemical reaction that creates the active constituent allicin. Within 2 minutes, about 80% of the alliin is converted to allicin. This is also how the volatile oils are released which makes the yummy garlic smell! Without crushing the clove, the full medicinal properties aren't achieved!


2. Vitamin D3

Vitamin D is often referred to as the sunshine vitamin because our body makes vitamin D3 in our skin through a series of chemical reactions. It is then activated through two more reactions in the liver and kidneys, but the whole process relies on adequate sun exposure. Since the Northern Hemisphere has lower sun exposure, and we don't absorb a substantial amount of vitamin D from our foods, people are often deficient. People with liver or kidney disease, or a condition that decreases the absorption of nutrients are at even higher risk of vitamin D deficiency.

Vitamin D is important in bone mineralization, neuromuscular function, cellular growth, inflammation, and the immune system. In vitro studies have shown that vitamin D has direct bacteriocidal effects against multiple bacterial strains, in other words it directly kills bacteria. Currently the research has inconsistent conclusions about whether vitamin D prevents the common cold and other upper respiratory tract infections, but its use was more effective in cases of frequent infections and low baseline vitamin D levels. Overall, the rate of vitamin D deficiency, coupled with the cloudy winter months of cold and flu season suggests that supplementation is still beneficial to most people despite inconclusive research.


3. Baptisia tinctoria (Wild Indigo)

Wild Indigo is both an antimicrobial and lymphatic herb, and is very effective in treating infections with excessive mucous production. Therefore, it can be used to treat laryngitis, pharyngitis, tonsillitis, sinusitis, and the common cold. As a lymphatic, it helps to drain enlarge lymph nodes to remove waste products that build up in the body and bring new lymph, which is rich in oxygen and nutrients, that will help to support the healing process.

The constituent "arabinogalactan" is thought to stimulate the immune system by increasing the production of WBCs. These are the cells that recognize infectious agents and either attack or create a memory for that invader so the immune system can easily recognize it if you're exposed again.

Wild indigo works very well as a tincture (alcohol extraction) or a mouthwash/gargle for infections in the oral cavity or pharynx. The constituents that have antimicrobial effects are called alkaloids, and they work directly to kill the microorganism, this is why it can be used as a mouthwash to treat pharyngeal infections, like strep throat. Because of its dual actions of working as an antimicrobial and a lymphatic, Wild Indigo is a great addition to fight most infections!


4. Vitamin C

Vitamin C has multiple different mechanisms in improving immune response. Firstly, it is inherently antiviral and has shown to be effective at inactivating majority of viral infections, in vitro, by disrupting the DNA or RNA strands. Also, vitamin C stimulates the production of an immune signalling protein called interferon, which alarms other immune cells to attack invading viruses. Vitamin C also has antibacterial effects against certain strains, as well as, potentiating the effects of exogenous antibiotics. Lastly, vitamin C works as an antioxidant to protect the body against free radical damage from bacterial toxins. In other words, vitamin C is a powerhouse when it comes to fighting off infections!

Multiple studies have shown that vitamin C given alongside conventional treatments greatly improved recovery time in whooping cough, bronchitis, and recurrent upper respiratory tract infections (URTIs) with relatively low therapeutic dosing. When used in high doses for acute illness, vitamin C often showed rapid improvement of symptoms in a variety of viral illnesses including chronic bronchitis, sinusitis, tonsillitis, chickenpox, mononucleosis, and viral pneumonia.

Other than dosing vitamin C orally, it can also be administered intravenously in high doses for acute illnesses. That way we can bypass your body's intestinal absorption and the liver, and the vitamin goes straight into your blood stream!

Have you ever tried IV nutrient therapy? This is a therapy I use often for patients with recurrent infections and poor absorption of nutrients.


5. Sambucus nigra (Elderberry)

Elderberry acts primarily as an antiviral agent and is effective at treating rhinovirus, influenza, and Herpes virus. The berries are also rich in bioflavonoids such as rutin and quercitin that also work to modulate the immune response. These active constituents work by deactivating the proteins on the surface of viruses to block them from landing and entering the host's cells. The flowers are also useful in treating conditions of excess mucus and help to support fever!

Elderberry has shown positive results in the prevention and treatment of the common cold as well as influenza A and B. When studied for the effectiveness of treating H1N1, elderberry groups had a 56.3% reduction in the duration of symptoms with no side effects of treatment (3.1 vs 7.1 days compared to placebo).

Elderberry is also high in vitamin C (bonus!) and super delicious as a tea/decoction, tincture, or syrup. My favourite ways to incorporate Elderberry is as a tea or as an extract to make immune gummies!

Stay tuned for my next blog post to get my

Elderberry Immune Gummy recipe!


As a naturopathic doctor, I'm always looking at the whole picture of what's causing you to get sick and what obstacles are preventing you from making a full recovery. That's why it's important to create a treatment plan that addresses your lifestyle factors that contribute to the Pillars of Health and natural remedies to help support your body's innate ability to heal. If you feel like you are always getting sick or never fully recovering from illness, naturopathic medicine provides a huge toolkit that can help optimize your immune system!

"The uniqueness of naturopathic medicine is not in its therapeutic modalities,

‘natural’ alternatives to the drugs and surgeries of standard medicine.

It is in the clinical theory that governs the selection and application of these modalities... That is, it is the way the naturopath thinks about illness and healing."

- Jared Zeff, Pamela Sniders, Stephen Myers



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  2. Gaby, A. (2017). Nutritional medicine, second edition. Concord: Fritz Perlberg Publishing.

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  5. Rahman, M. S. (2007). Allicin and Other Functional Active Components in Garlic: Health Benefits and Bioavailability. International Journal of Food Properties, 10(2), 245–268. doi: 10.1080/10942910601113327

  6. Ran, L., Zhao, W., Wang, J., Wang, H., Zhao, Y., Tseng, Y., & Bu, H. (2018). Extra Dose of Vitamin C Based on a Daily Supplementation Shortens the Common Cold: A Meta-Analysis of 9 Randomized Controlled Trials. BioMed Research International, 2018, 1–12. doi: 10.1155/2018/1837634

  7. Sabetta, J. R., Depetrillo, P., Cipriani, R. J., Smardin, J., Burns, L. A., & Landry, M. L. (2010). Serum 25-Hydroxyvitamin D and the Incidence of Acute Viral Respiratory Tract Infections in Healthy Adults. PLoS ONE, 5(6). doi: 10.1371/journal.pone.0011088

  8. Splunter, M. V. (n.d.). Immunomodulation by raw bovine milk and its ingredients: effects in nutritional intervention, oral vaccination and trained immunity. doi: 10.18174/453828

  9. Torabian, G., Valtchev, P., Adil, Q., & Dehghani, F. (2019). Anti-influenza activity of elderberry (Sambucus nigra). Journal of Functional Foods, 54, 353–360. doi: 10.1016/j.jff.2019.01.031

  10. Vorilhon, P., Arpajou, B., Roussel, H. V., Merlin, É., Pereira, B., & Cabaillot, A. (2018). Efficacy of vitamin C for the prevention and treatment of upper respiratory tract infection. A meta-analysis in children. European Journal of Clinical Pharmacology, 75(3), 303–311. doi: 10.1007/s00228-018-2601-7

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