Fighting Cold and Flu. Vitamins and Other Supplements to Strengthen Your Immune System


What we need to get better when we’re not feeling well is getting enough sleep, drinking enough fluids, and getting plenty of rest. But what about our diet? How can we change what we eat to get better? And, can what we eat help prevent us from getting sick in the first place? Here is what the literature has to say about what supplements to take to strengthen and maintain a healthy immune system.


Fighting Cold and Flu with Supplements

Vitamin C

Vitamin C stimulates immune system activity to prevent or slow down diseases. Taking vitamin C every day won't necessarily reduce your chances of getting a cold. But it does reduce your chances of catching a cold during times of high physical stress and fatigue. Also, after you exercise intensely, your immune system naturally dips for a couple of hours. There is evidence that athletes who take vitamin C daily catch fewer colds. If you do get a cold, taking vitamin C may reduce your cold’s severity and duration. The vitamin C dosage for adults ranges in the literature from 200 – 1000 mg of vitamin C daily. 


Zinc is involved in fighting infections. There is no evidence that zinc can prevent colds. But it may help you speed up your recovery. Be careful not to take high doses of zinc long term, as too much zinc can interrupt the absorption of other nutrients.


Before we talk about ginseng’s effect on cold and flu, you need to know that there are three different types of ginseng: Panax ginseng (also known as Korean Red), American, and Siberian ginseng. Each has different evidence regarding cold and flu. 

Panax Ginseng: There is preliminary evidence that taking Panax ginseng may reduce the risk of catching a cold or getting the flu. There isn’t evidence for Panax ginseng reducing the duration or severity if you do get sick. 

American Ginseng: American ginseng may help prevent or reduce the severity and duration of upper respiratory tract infections in people who tend to get repeated colds/flu during the season. 

Siberian Ginseng: On the other hand, Siberian ginseng doesn’t have evidence for preventing colds/ flu but it may help reduce the length of time that you are sick with a cold or flu. Especially if you start taking it as soon as you start to feel symptoms. 

Note that ginseng may not be safe (or the safety isn’t known) for kids, during pregnancy or lactation. The exception is that American ginseng has been used safely in kids 3 years and up for periods of 3 days.  


Probiotics can help strengthen the immune system. There is evidence that some strains of lactobacillus can help prevent colds/flu. 


There is evidence that taking echinacea can help prevent colds and reduce their severity and duration when you take it at the first signs of getting sick. Because there are so many different ways to take echinacea (e.g. teas, extracts), there isn’t consistent enough evidence to recommend a specific dose. 


Elderberry may reduce the duration of a cold and flu when you start to take it as soon as you start to feel sick.  


Maintaining Your Immune System

Here are some other vitamins that can help to maintain a healthy immune system.

 Vitamin D

Taking vitamin D can help to maintain overall immune function. Vitamin D may also contain anti-inflammatory properties, but more research is needed. It is recommended that infants get 400IU daily of vitamin D (from drops or formula), children get 600IU daily from supplements and/or food, and adults get 800-4000IU daily from supplements and/or food. However, the food sources of vitamin D are very limited, so most people here in Canada will need a supplement to reach the recommended intake.   

Vitamin E

Studies have shown that vitamin E deficiency is associated with increased infectious diseases, so getting enough of this antioxidant may help to prevent these infections. Most people don’t need a supplement to meet their vitamin E needs. Foods high in vitamin E include avocado, cooked spinach, nuts and seeds (and their butters) and eggs.

Alyssa’s Final Thoughts:

As I was looking into the literature, it seemed like there wasn’t a particular vitamin or mineral that was essential for improving the immune system. The pattern that I was seeing was that a little bit of everything is needed. I think this supports the idea of “eating the rainbow,” meaning that we should eat a variety of fruits and vegetables of different colours to get the various vitamins and minerals into our diet. The ones included above are backed up by research, but I believe that having a variety of fruits and vegetables in our diet can help to improve our overall immune system functioning and wellbeing.

Kristen’s Final Thoughts:

I agree with Alyssa that eating well, including lots of vegetables/fruit and nuts/seeds and being well hydrated and well slept are the foundations for having a strong immune system. So too is taking your vitamin D. 

It’s also reality that we have times of high stress and lack of sleep that make us more vulnerable to getting sick. Taking some vitamin C and probiotics (maybe Panax ginseng too) during these times may help prevent catching a cold or flu. When you do catch something, you’ll notice a theme of the importance of starting to take these remedies at the first sign of getting sick. Note that if you take other medications, are pregnant or breastfeeding, it’s best to find out what’s safe before starting to take a supplement. 

Thank you to co-author and amazing student Alyssa!

Photo credit: Unsplash