Cold & Flu Season

As we all prepare for the upcoming cold of winter, many of us are also thinking of how to prevent and treat actual colds. Runny noses, red eyes, missed work and family events. Cold and flu season is upon us, and nutrition plays a big role in supporting your immune system.

The intersection of nutrition and immunity is something I could probably write a series of newsletter posts on. Why? Prior to becoming a dietitian, I completed a Bachelor and Master of Science in the field of immunology. Therefore, I am excited to address this topic here, with a focus on the upcoming cold and flu season.

Before I dive into the nutrition, I must acknowledge that personal hygiene and public health safety measures are the biggest things you can do to prevent getting sick in the first place. Washing hands properly, and avoiding touching frequently contacted surfaces such as door handles are number one.

When that fails, enter your immune system, and the dietary components that support it.

Nutrition enhances the ability of your immune system to adapt and protect you from the large amount of potentially harmful microbes you are exposed to over a lifetime, including the many faces of “The Common Cold”.

But what is “The Common Cold”?

The common cold is a term for an infection that causes cold and flu-like symptoms. However, the microbial causes of the infection in the general population are actually diverse. Most frequently the infection is from virus, and less frequently, bacteria.

This is important to differentiate because the way your immune system responds to a bacterial infection is generally different than how it does in a viral infection. Furthermore, remedies commonly used when having a cold may support you in a viral infection, but not a bacterial. And vice versa. The deep dive into the how and why is a discussion that goes beyond the scope of this month’s newsletter. 

However, I’d like to compare and contrast a couple of commonly used remedies, Cold FX and honey, to illustrate why they may or may not be useful, depending on whether or not the infection is bacterial or viral.

Cold FX, for example, is a widely used over the counter drug claiming to prevent or treat the common cold. The main active component is essentially Ginseng, a traditional Chinese medicine. Ginseng has many bioactive molecules, including those that promote defense in the early stage of a viral infection. This is the mechanistic basis for using Cold FX for the common cold.

Despite this, Cold FX is often scrutinized in the general public for not working. But again, it is the context of timing, and type of infection. If not taken prior to, or at the first onset of symptoms, you are unlikely to see much benefit. And if the infection is bacterial, such as strep throat, then it’s also unlikely to be effective. In this latter case, antibiotics, which do work against bacteria, may be indicated.

Also, many people use honey for a sore throat, which may help a bacterial infection due to some anti-bacterial proteins found in honey. But as mentioned, most common cold infections are viral, so this won’t help you in the majority of cases. Also, boiling hot water can break down the anti-bacterial proteins in honey, rendering them less effective, and yet this is the most common delivery method. 

This honey example is not immune system related per se, but I thought I’d mention it since it is a commonly used cold remedy, and the target is bacteria.

Also, by the time laboratories can tell us if it’s a virus or a bacterial infection, it’s likely too late for either honey or ginseng to help. That’s why it’s preferred to avoid this guessing game, and be proactive and preventative. This includes having a healthy diet, rich in nutrients that support immune health.

What nutrients support immune health?

Almost all nutrients support the immune system in one way or another. Specific vitamins of interest include Vitamin A, Vitamin C, Vitamin D, Vitamin E, and several B-vitamins. Some minerals of interest include zinc, selenium, and copper. All of which help support the early and late stages of an immune response, and will work best if already a part of your diet.

In the case of supplementation, the scientific literature often does not show a clear-cut benefit unless your diet is already low in one or more of the vitamins and minerals above. For example, people already deficient in Vitamin C have been shown to benefit from dietary or supplementary intervention to assist in severity and duration of infections. Those who already meet their Vitamin C needs, showed no significant benefit in adding a supplement.

Therefore, if you are already eating a varied and nutritious diet, rich in the above nutrients, you are probably not going to get additional benefit by supplementing. If you are not, then a multivitamin may help. Or better, book an appointment with your resident dietitian to get support optimizing your nutrition status!

What if I’m already sick?

Once sick, it is still important to get the full gamete of nutrition, however, protein needs will increase. When your immune system is actively fending off an infection, it needs building blocks to make all the immune molecules such as antibodies, and other pro- and anti-inflammatory molecules that regulate immune system function. 

Once sick, your protein needs may go up by as much as 20-25%. The tricky part about being sick though is appetite can go down. And in particular, if you have a sore throat, swallowing some foods like meats or other high-quality protein sources can be compromised as well. 

Try to find tolerable ways to ensure adequate protein, particularly if you are already sick. Also, warm liquids such as tea and soup can be comforting and help relieve symptoms. In addition to nutrition, ensuring adequate rest will help you recover faster. 

Is nutrition to “boost” your immune system a thing?

Immune “boosting” is a misleading term commonly found in web-based nutrition misinformation. Your immune system is incredibly intelligent, and nutrition to support immune balance is key. Typically, products advertised as “immune boosting” are not, and are also not written by people with backgrounds in nutrition or immunology. But I digress.

Immune “boosting” may incorrectly imply that the goal is to activate your entire immune system to a high level. Not good. 

For example, one would not want to artificially activate your immune system to fight off bacteria, when the infection is viral. Just as one would not want an overactive immune response causing excessive damage to body tissues, such as your lungs. You want that perfect balance, and only your immune system will know how to do that. You can do your part by eating healthy.

A more appropriate term (and goal) would be “immune supporting” or “immune regulating” nutrition. Also, the nutrients described above, in addition to other components of a healthy diet such as fibre and adequate fluid intake, will do just that.

A note on Covid-19 and Vitamin D

Covid is on the minds of well, everyone. As we know, this is a virus and not bacteria, and so the nutrition that can support defence against viral infections becomes especially important. Vitamin D status has been identified to be of particularly high importance. People with adequate Vitamin D status are better able to fend off infection. Also, fall and winter is when we stop getting it from sun exposure. Therefore, it becomes extra important to take a supplement, and I recommend 2000IU per day or the amount recommended by your Preventous doctor.

In summary

– Ensure you are being proactive in your nutrition, by eating foods rich in vitamins like A, C, and E. Supplement Vitamin D, going with 2000IU or the dosage recommended by your doctor.

– Ensure adequate mineral intake by focusing on a varied diet of whole foods, such as fruits, vegetables, whole grains, nuts and seeds, and legumes. 

Honey may help the early stages of bacterial infection but add to lukewarm beverages to avoid the antimicrobial proteins getting damaged by heat.

– Rather than ColdFX, why not have Ginseng tea!? I always drink this during cold and flu season, and research suggests it can have a bit of a stimulant effect as well so I use it as a substitute for (or in-between) coffee. That said, Ginseng has many bioactive compounds, so if you are taking other medications or have other medical conditions, please check with your doctor before taking it.

– If you get sick, make sure you are getting enough calories, and in particular enough protein. Your immune system will need that added protein to help create molecules to help fend off the infection. 

– Make sure you keep up with good rest, minimize stress, and stay active – all play a role in supporting your immune system.

Stay tuned!

There are more ways in which nutrition impacts immunity that goes beyond this article, including my favourite area – the gut microbiome. Also, how do the above immune-supporting nutrients each specifically impact your immune system? What is the most current evidence? What foods are the best sources?

Dan Neuman
Registered Dietitian


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