5 Tips to Strengthen Your Immune System During “Flu Season”

If we could give every individual the right amount of nourishment and exercise, not too little and not too much, we would have found the safest way to health.
––Hippocrates

Unless you live in Florida or a similar part of the world where it’s always relatively warm and sunny, and unless you’re reading this in the opposite Hemisphere to mine, it’s that time of the year again: flu season.

Fortunately, by working on your fitness, you can whip your immune system into shape, increasing your chances of either staving off common illnesses completely, or at least reducing the severity of any symptoms you may experience.

If, like some of my legendary clients, you’re an athlete following an intense program, work with children or do shift work, or you find yourself getting sick often at this time of year for any other reason, then this article is for you.

These are my top five evidence-based tips to support and enhance your body’s natural defences:

1. Exercise often enough and hard enough.

Research shows that regular, moderate to vigorous exercise can strengthen your immune system, lower the risk of illness, and even potentially increase the effect of vaccines.

So, although any time of the year is excellent to become consistent with a training program, now is a particularly good one!

Of note, the training intensity is as important as the regularity. To make your body fitter, you need to challenge it!
 
While it’s also true that too much and/or excessively intense exercise can have the opposite effect, we’re talking about extremes of training volume and intensity that most people for whom fitness isn’t their career wouldn’t have the time for.

For example, studies reporting a harmful effect of exercise on the immune system are typically conducted on élite-level athletes, like those competing in the Olympics.

Importantly, this research seems to suggest that it’s not their training per se that increases the risk of illness, but rather periods of unusually intense exercise within that program and other contributing factors, such as inadequate nutrition, less-than-great sleep, and international travel across different time zones to take part in high-level competitions.

In other words, if your body is adapted to the training program, you’re fuelling yourself, and taking rest days, then you can tolerate even élite-level training volume and intensity.

It’s when you consistently overshoot your ability to recover from training by going too hard, too often, not eating enough, and not sleeping well that you’re shooting yourself in the foot.

And, since everyone has a different recovery capacity in different seasons of their life, that’s why having a personalised training program and nutrition plan is so valuable.

Bottom line, my view is that you only need to worry about doing “too much” exercise if you absolutely love training and you know that one of your weaknesses is to push yourself too hard, too often, even when you probably shouldn’t.

Furthermore, statistics demonstrate that only one in five adults and adolescents meet the physical activity guidelines for both cardiovascular exercise and resistance training. So, if anything, the majority of us need to focus on exercising enough rather than too much.
 
Besides, the human body is a wondrously resilient and adaptable organism, so don’t be afraid to push yourself in active ways on a regular basis!

It can only make you stronger.

2. Eat a variety of whole foods.

Having a diverse diet that prioritises whole, unprocessed foods over highly processed foods––without excluding either––is likely one of the most beneficial choices you can make for your physical and mental health.

Moreover, there are specific nutrients that can support and enhance your immune system in particular:
 

• Vitamin B6––animal liver and meat, chickpeas, bananas, and dark leafy greens
• Vitamin B9, also known as folate––leafy greens, avocado, and citrus fruit
• Vitamin B12––fish and shellfish, animal liver, red meat, dairy, and some fortified products like cereal
• Vitamin C––green leafy vegetables, tomatoes, liver, whole milk, and oily fish
• Vitamin D––egg yolks, mushrooms, cheese, and soy milk
• Vitamin E––almonds, peanuts, sunflower seeds, pumpkin, and peppers
• Zinc––shellfish, dark chocolate, and pumpkin seeds
• Selenium––Brazil nuts, chicken, beef, eggs, and brown rice
• Copper––shellfish, whole grains, beans, nuts, and potatoes
• Omega-3 fatty acids––oily fish, shellfish, and algae

 
By eating a diverse, omnivorous diet, you can likely get many of these nutrients without supplementation.

The only exceptions for most people include vitamin D and omega-3 fatty acids.

While you can get some vitamin D from food, the ideal option to top up your reserves is sun exposure… which isn’t much of an option in the cold months.

So you could get a blood test to ascertain your vitamin D status and take a supplement as needed.

Similarly, since most people don’t eat enough oily fish, shellfish, or algae, you may benefit from fish or algae oil supplements.

If you’re vegetarian or vegan, you have an inherently restricted dietary pattern, so you need to pay closer attention to your food sources to avoid missing out on some of these nutrients.

A well-known example is vitamin B12, which is virtually absent from vegan diets unless you’re eating enough fortified products or supplementing with it.

3. Get at least seven hours of good quality sleep per night.

I wrote an entire article on the importance of sleep for muscle growth and fat loss, but subpar sleep is going to affect your health as a whole, not only your body composition.

Since said article on sleep contains a lot of practical suggestions on how to create or improve upon your sleep routine, I’m going to keep this section short and to the point by mentioning the two suggestions that I and my clients most benefit from.

First off, keep your caffeine consumption under control and do your best to avoid it altogether too late in the day.

Since its half-life is about five hours, this means that about half of the caffeine in your 2 pm coffee could still be in your system by 7 pm, thus potentially impacting sleep.

Secondly, avoid eating an excessively large meal too close to bedtime, as this can also impair your ability to fall asleep and/or affect your sleep quality.

4. Manage your stress.

Too much stress, especially chronic (long-term) stress, can compromise various functions of the immune system.

However, none of us can completely get rid of all the stress in our lives, and you wouldn’t want to, anyway, since a certain degree of stress helps create an adaptation.

For instance, lifting weights with enough volume and intensity of effort is a type of stressor that will help you build muscle and strength.

What I typically recommend to my clients and try to do myself looks like this:
 

• When dealing with stressors I can control, I do my best to identify and respect my personal upper limit, for instance by not overcommitting to too many social events;
• When managing stressors I can’t control, I support myself with stress-relieving activities like guided meditation, leisurely walks, and reading;
• During short-term periods of extremely high stress that I can’t control, I reduce all controllable stressors and temporarily implement supplements like Ashwagandha for extra stress relief.

5. Consider supplementation.

I kept this suggestion for last because supplements have a minor effect compared to lifestyle behaviours like regular exercise, sleep, stress management, and adequate nutrition.

Nevertheless, some of them could be helpful in certain situations, so it would be remiss of me to discard them altogether.

To support your immune system through the winter months, I’d suggest the following:
 
A daily broad-spectrum multivitamin and multimineral
 
This can help you get enough of the micronutrients mentioned previously, especially under certain conditions of restriction, like when you’re in a calorie deficit.
 
A daily vitamin D supplement
 
Among other benefits to your health as a whole, this may reduce the risk of getting acute respiratory tract infections.
 
Fish or algae oil supplements containing at least 500 mg of combined EPA and DHA per day
 
These will provide you with an adequate daily dose of omega-3 fatty acids, which may improve immunity against certain viruses and infections, in addition to having a relatively solid evidence base for a variety of other health benefits.
 
200 to 2000 mg of vitamin C
 
This daily dose range seems to help strengthen the immune system and possibly shorten the duration of the common cold.
 
Zinc acetate lozenges
 
If you start getting cold symptoms, taking 80 to 90 mg per day of zinc acetate for no more than two weeks has also been shown to shorten the duration of symptoms. For best efficacy, let the lozenges dissolve close to the back of your throat.

Before you take any new supplement, I’d strongly encourage you to check with your healthcare team that this is safe and appropriate for you, since some supplements could interfere with certain medications and health conditions.
 
Practical Takeaways
 
1. Exercising regularly, eating a diverse diet, sleeping well, and managing your stress will always make a positive contribution to your health and physique goals, but they’re especially important behaviours to cultivate during the cold months in order to support your immune system.
 
2. Certain supplements may be useful as an extra boost to your immunity, such as vitamin C, D, a multivitamin, and fish or algae oils, among others.
 
Thanks for reading. May you make the best gains.
 
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