8 Ways Your Diet Could Be Weakening Your Immune System

No food or pill can make you invincible. However… 

…that isn’t the end of the story.

You have to love the world we live in. “Never let a good crisis go to waste” is alive and well in the nutrition and fitness world.

Every single fitness trainer’s business is on life support while trying to help as many clients as possible from a computer or cell phone via Zoom. Coming up with bodyweight and minimal equipment workouts to try and best serve clients, and pivoting to full force online coaching, for the time being, is a move that everyone in the fitness industry is (should) be doing.

And then you have the nutrition people...

Ads popping up for “Immune Boosting Supplements”, “Immune Boosting Smoothies”, and “Anti-Viral Concoctions” … or people telling you to just drink straight ethanol...

I get it – there is still money to be made… but this is slimy because it’s bogus (and dangerous).

As I say with fat loss supplements – if they worked – I’d be selling them left and right!

In alignment with this statement is the official statement by the Dietitian’s of Canada (couldn’t find one from the USA, so we will have to settle for Canada) –  which I saw on Instagram:

100% spot on. Well done Canada! But wait…are they 100% right?

While there is no magic food that can prevent you from getting any virus, or totally bulletproof your immune system, there are plenty of ways you can WEAKEN it through diet/lifestyle choices.

If you can’t boost your immune system past optimal, you can boost your immune system above terrible.

So what weakens your immune system directly?

Sugary Foods 

Think soda, candy, cookies, cakes…yup, all the comfort foods that so many of us want in times of stress. High doses of sugar can temporarily suppress your immune fighting cells by essentially slowing down their reaction time to “catch” a bug.

It is a temporary suppression – so if you are going to have some treats, don’t do it all day – and focus hard to minimize them right now. Short term “sacrifices” for short term and long term health and safety.

Low-Quality Processed Foods

Did it grow in the ground, on a plant, or once walk or swim around? If not, it’s processed.

Now, this is still a broad term and needs to be taken with a grain of salt. When I say processed food, I’m talking about the kind of food you may have lived on in college, or while you were a single grad living in a studio apartment, or the foods that your 8-year-old wants to eat all day.

Heavily processed foods are usually void of micronutrients, protein, and fiber – all essential things for an optimal immune system.

They are also usually high in added sugars, sodium, and pro-inflammatory fats. All things that will stress your body out even more – and who needs MORE stress right now?


We all know that excessive alcohol consumption can lead to liver disease, cancers, and mental health issues of addiction – but alcohol also weakens your immune system. According to a 2015 study, “the function of alveolar macrophages is impaired because of alcohol-induced changes in cytokine profiles as well as in the levels of ROS and antioxidants that result in oxidative stress”

In English, this means – alcohol temporarily impairs your cellular defense system in your lungs and makes it easier to catch respiratory viruses. Not the best thing to be dealing with right now!

What can weaken the immune system indirectly?

Person to Person Specific Intolerances 

Does dairy go straight through you? Every time you eat gluten getting you stuffed up? Well then listen to your body and maybe consider trying to cut it out. Any form of added stress to your system is not something you need right now.

Listen to your body. It will tell you more than you think.

Alcohol (again)

People think they sleep great after a couple of drinks. I get it – it helps to unwind. But if you look deeper, you might realize that even one drink can suppress your sleep quality, and in turn, your immune system.

You may think you sleep hard – but alcohol prevents the body from fully recovering – mentally and physically by limiting your deep and REM sleep. So even if you get 7-8 hours, it likely wasn’t a restful sleep. Also, if you can monitor your resting heart rate, you will see that your RHR is elevated while you sleep after drinking, another pro-inflammatory response.

High Fat/Greasy/Sugar Foods before Bed

Again, certain foods that can directly weaken your immune system, can also indirectly suppress it by affecting your sleep. High grease, salt, sugar or process crap foods before bed can keep you tossing turning while you sleep – thus limiting your recovery.

Try to limit your junk food consumption as much as possible, but especially before bed if you know it affects you!


Caffeine is great. But too much or at the wrong time can be not so great. Caffeine is a powerful stimulant, thus putting a person into a sympathetic state – fight or flight baby! With excessive intake comes elevated levels of cortisol, the stress hormone. I think we all have enough of that right now.

Excessive cortisol leads to immune suppression and an inflamed and broken down system, thus sending your body into a fat-storing, energy-sucking, demotivated state.

Also, caffeine too late in the day will prevent you from getting quality sleep, which was covered above.

Crash Dieting

Now is not the time to be starving yourself, or trying a 600 calorie juice cleanse. Undereating, especially if following a fad diet, leads to many potential micro and macronutrient deficiencies. In the bodybuilding world, it is often known that many competitors get sick during contest prep, because of suppressed immune systems.

Now – if you have a significant amount of weight to lose, trying to do so right now might be a good idea – if you do it responsibly, without starving yourself, crash dieting, or over-exercising.

Can you still lose weight?

Being that obesity is linked to numerous underlying health conditions (diabetes, hypertension, heart disease, sleep apnea) losing some body fat will be beneficial – maybe not now, but definitely in the future.

If you are relatively lean and healthy, just hold tight and maintain – it’s NOT to time to try and diet down for your potential beach vacation – maintenance practice is a great thing to focus on during high times of stress.

But I Need Comfort Food!

I get it. I just baked 12 hot cross bun rolls yesterday (who am I?) and my wife recently made a red velvet cake. Do we need to be eating “100% Clean” right now… no.

If you are seriously concerned about getting sick or beating up your immune system though – you need to take a hard look at what you are currently using as a stress relief source right now. While it may make you feel “better” in the short term, we need to remember LONG term benefit or risk – and make sure your actions match your goals/concerns.

If you find yourself reaching for junk and more junk I recommend writing out your goals and your “why” of your goals – and sitting down and having a discussion with yourself on how your current actions could be benefiting or hurting them.

It’s not the time to try and be perfect – but it’s also not the time to eat like an unsupervised 9 year old.

BONUS: Want to throw gas on this fire? Then Overtrain! 

Doing all or some of the above, AND beating your body into the ground with bodyweight HIIT challenges 3 times a day (because we all have more time, right? ;), running 10 miles per day when your body is used to ZERO, or constantly trying to crush your soul in your home gym that you just spent your stimulus check on is a great way to weaken your immune system even more.

Most exercise in itself boosts your immunity – as long as you are properly recovering from it.

…but not when you’re living like a frat bro!

However, if you are putting your body into a stressed state, fueling it with junk and booze, then you might be better of doing a little strength training and going for a walk (always a good choice, honestly).

High-intensity circuit type and traditional cardio (think jogging) raise your hunger levels and the stress hormone cortisol. While walking lowers your cortisol, and strength training elevates multiple other positive hormones that strengthen your immunity.

What is the main takeaway here?

All the things that weaken or suppress your immune system are the things that I and many nutrition professionals have been preaching for much longer than that last 3 months or so.

I am not here to tell you “I told you so” – I am here to tell you to beware of scammers, gurus, and charlatans selling bogus pills and drinks.

If you haven’t taken time to care about your health from a dietary perspective until now, it’s a great time to start!

Stay healthy and safe my friends,

If you want more daily guidance through this crazy time we are in, look no further than online coaching – training and nutrition – let me help you find the best plan for you!

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Stay healthy my friends,


Published by Mike Gorski

Registered Dietitian and Fitness Coach OWNER OF MG FIT LIFE LLC