Feb 20, 2023 / by Jon Bellis / No Comments

I can’t remember a winter when there were so many malicious viruses. This year’s infections seem to have been far more impactful than those of other recent winters.

One explanation is that having COVID may lower your immunity subsequently. And it could be that, as a population, we are more immunologically naïve after two years of lockdown and lowered exposure to annual pathogens.

Regardless of the explanation, one thing is clear. The stronger your immune system, the less likely you are to be knocked out by an infection.

But how do you build a robust immune system? By adopting the right lifestyle. Do you have a good immune regime? If you’ve been wiped out by a cold or flu this season, then it might not be as effective as it could be.

You might think this isn’t within the remit of a business that specialises in weight loss or conditioning. But consider this: you want to reach your goals in the timeframe you have set for yourself. Can you afford to miss training for two weeks or to be completely inactive for that period? If you’re inactive, bedridden and not eating, you can lose a lot of muscle and strength. That will set you back a lot more than two weeks.

I’m very conscious of exercising and eating in a way that supports my immune system. I haven’t missed a day of training through illness for many years. Perhaps that’s one reason why I became the over 50s British and World natural bodybuilding champion in 2022.

In this post, we take you through nutrition and lifestyle choices you can make to keep your immune system as strong as possible.


Things to help you build a strong immune system

Here’s a list of nutrition and lifestyle factors that will keep your immune system strong.


Vitamin C

All the immune system supplements contain vitamin C and there’s a good reason for that. There is plenty of evidence that it is essential for a well-functioning immune system.


But at what dosage?

To enhance immune cell function to the point where significant infection can be ‘prevented’, saturating plasma doses – 100-200mg per day – have been suggested. And to fight existing infections, significantly more.

It has also been suggested that doses of 1g to 3g per day can effectively prevent the common cold and that at least 1g per day can have a beneficial effect on the severity and duration of cold symptoms.

But you’ll also see the NHS stating that adults need 40mg per day and that 1000mg per day is regarded as a high dose. Doses below 1000mg per day are unlikely to cause any harm, they say.

Their advice is to get all your vitamin requirements from food. This is sound advice. Whether you additionally supplement is your choice, and you should probably read around the subject before deciding to do so. The links above are good starting points.


What foods?

You’ll find plenty of articles on foods containing vitamin C.

I list some good ones here for you: blackberries, blackcurrants, broccoli, cantaloupe, cauliflower, cherries, kale, kiwi, oranges, papaya, peppers, potatoes, raspberries, strawberries, sweet potato, and tomatoes.

There are more, but these are a great start. Spot the common link? Fruit and veg. Fill your boots with the stuff and get plenty of variety.

Blackberries are a great source of vitamin C to help create a strong immune system


Zinc is involved in so many biological processes, including the immune system. It has been shown that supplementation helps with immune system weakness, especially in the elderly. It’s so important for the immune system that you’ll generally see it as a key ingredient in immune system supplements.

That doesn’t mean you should supplement necessarily. It’s just that researchers, when they are trying to isolate the effects of a particular nutrient, tend to administer supplements rather than foods. Other beneficial nutrients in food could cloud the results.

The advice is almost always the same: get your zinc from food.


What foods?

You just have to search to find foods containing zinc. To save you the trouble, here are some foods higher in zinc than others: almonds, baked beans, beef, brown rice, cashews, chicken, chickpeas, dark chocolate, eggs, ham, lentils, nuts in general, oatmeal, pork, seeds, shellfish, shrimp, sunflower seeds, turkey, yoghurt.

Zinc is also an important mineral involved in the maintenance of healthy testosterone levels. That’s another good reason to get plenty of those foods in your diet.

Osters are a great source of zinc to help create a strong immune system


The evidence for selenium is not as widespread as for other nutrients, but you will find it in some immune system supplements. You’ll certainly find papers on selenium’s role in the immune system.

Again, the advice is to get selenium from foods. But note that there is evidence that the selenium content of UK soils is low. That may mean your intake of selenium is low. You could supplement if you’re not sure. Or why not just have one Brazil nut per day – that’ll keep your selenium levels up!


What foods?

Brazil nuts are the often-cited king of selenium rich foods. But also try these: baked beans, bananas, beef, brown rice, canned tuna, cashews, chicken, cottage cheese, eggs, enriched foods, fish, ham, lentils, mushrooms, oatmeal, pork, salmon, sardines, spinach, sunflower seeds, turkey, yoghurt.



I’m only listing this because it is an ingredient in one or two immune system supplements. It is superb as an anti-inflammatory, and this is likely where most of the benefits come from. The immune system benefits are less well documented.


What foods?

Curry. If you want to avoid too much oil or butter in a commercially made curry then use curry powder and make your own.


Vitamin E

Another ‘mainstream’ vitamin that is important in the immune system. Again you’ll find this in immune system supplements and you’ll find plenty of information on the importance of vitamin E for the immune system, especially in the elderly.


What foods?

You can get all your vitamin E requirements from food. Try these: almonds, avocados, Brazils, broccoli, butternut squash, cashews, corn, fish, kiwi, nuts in general, olive oil, seeds, shellfish, shrimp, soya, spinach, wheatgerm.

Sunflowers are a great source of vitamin E to help create a strong immune system

Probiotics and prebiotics

Probiotics are foods or supplements containing beneficial gut bacteria. They will boost the population of good bacteria and help to make your gut microbiota healthy.

A healthy gut will improve your response to infection and is often referred to as the first line of defence. Probiotics have been shown to reduce the incidence of infection and reduce the duration and severity of symptoms caused by viruses. There are plenty of papers on the topic.

If you want as healthy a gut as possible, you should also eat foods that encourage the growth of good bacteria. These are generally referred to as prebiotics. They are mainly indigestible starches – fibre – that keep the good bacteria well fed. Healthy gut bacteria also thrive on fatty acids and polyphenols.


What foods?

You’ll find plenty of lists that contain both probiotic and prebiotics foods.

Probiotic foods include live yoghurt, kefir, miso, sauerkraut and kimchi.

But you’ll also find prebiotic lists. A healthy consumption of fruit and vegetables should give you plenty of prebiotics, but try the following in particular: peas, brussels sprouts, leeks, onions, garlic, bananas, olive oil, almonds, asparagus, oats, apples, flaxseeds, seaweed.

Live yoghurt is a great source of probiotics to help create a strong immune system

Vitamin D

Have you ever wondered why colds are more prevalent in the winter? A large part of the reason is that there is less sunlight and we tend to cover our entire surface with clothes. That means we manufacture in our skin almost no vitamin D. A large percentage of the population is deficient in vitamin D in the winter. And vitamin D has a vital role in maintaining a strong immune system. A vitamin D deficiency will result in an increased susceptibility to infection.

So significant is the lack of vitamin D in the population during winter, that the government’s official advice is to supplement during the winter. It is the only nutrient that comes with a government recommendation to supplement.

Although you can get vitamin D from some foods, the amounts are relatively low and it may be difficult to get enough.


What foods?

If you don’t want to supplement, then the following foods contain some vitamin D: canned tuna, cod liver oil, eggs, enriched foods, mushrooms, salmon, sardines, red meat, liver. Sunlight is your best option once the days are longer and warmer.



Glutamine is the most abundant amino acid in muscle tissue. But it also plays a crucial role in the immune system. And, when the body is under immunological stress, such as when you’re ill, it will be required in much higher amounts.

Because of the abundance of glutamine in muscle tissue, muscle has a key role as a pool of glutamine for when the body needs a robust immune response, such as when it needs to fight infection. That means, in the absence of a replacement supply, muscle tissue will be broken down to help supply enough glutamine for adequate immune system response. This is not ideal. You should work hard to keep hold of your muscle for numerous reasons.

There are two implications of the above. First, getting enough glutamine in your diet will help you maintain muscle and supply adequate glutamine to support a healthy immune system. Second, it makes sense to build and maintain as much muscle as possible so that, in the event of an emergency, you have a decent pool of glutamine to supply the immune system. Imagine you are in hospital and ‘nil by mouth’. If you have only a small amount of muscle tissue, that could have serious implications for your ability to fight infection whilst in hospital. And let’s be honest, there are plenty of people in hospitals with a variety of infections.

So, build your muscles and get plenty of glutamine in your diet.


What foods?

Disappointing for vegans perhaps, but it is mainly animal products: meat, poultry, fish, dairy and eggs. But also, in reasonable amounts in beans, lentils and nuts.

And, as with all the nutrients listed in the post, you can also supplement with glutamine.



Polyphenols are micronutrients found in our food – mainly fruit and vegetables – that have numerous beneficial effects on our health. Amongst those effects are various positive influences on the immune system.


What foods?

You’ll be able to find various pages showing lists of foods containing polyphenols. Here are some common foods: apples, artichokes, beans, black grapes, blackberries, blackcurrants, broccoli, cherries, chickpeas, chicory, cloves, curry powder, dark chocolate, ginger, kale, lentils, nuts, olive oil, oregano, peach, peppermint, plums, prunes, raspberries, red onions, rosemary, sage, soya, spinach, star anise, strawberries, tea, thyme.

That’s a long list! And all plant based you’ll notice.

Beans are a great source of polyphenols to help create a strong immune system


Exercise plays an important part in helping you maintain a healthy immune system. In this excellent and comprehensive review of the link between exercise and the immune system, a few points are worth picking out

  • Exercise is particularly important to combat immunosenescence – the tendency for immune function to decline as you get older.
  • There is a J-curve associated with infection risk in response to exercise. The J-curve describes a lowering of infection risk with low to moderate intensity exercise, moving to an increased infection risk at high intensity. This is in line with the commonly held view that overtraining can reduce immunity and leave you vulnerable to viral infection.
  • Athletes are advised to get sufficient carbs and polyphenols to reduce exercise-induced inflammation and improve viral protection.


Things that will weaken your immune system

As well as positive actions you can take to strengthen your immune system, there are things you can stop doing in order to strengthen it. Or looked at another way, you can carry on doing them to weaken it!



Alcohol will definitely blunt your immune system, especially in high doses or through chronic intake. It will leave you vulnerable to infection, especially those of the upper respiratory tract and viruses. If you’re still in two minds, here’s another compelling read.

If you want a strong immune system, don’t drink alcohol!


Lack of sleep

There is a clear connection between circadian rhythms and the efficiency of the body’s processes, including the immune system. If your circadian rhythms are disrupted and you don’t get enough sleep then your immune system will be compromised. This includes international travel and time zone shifts, which will have a similar effect.

Researchers studied twins and found that, all things being equal, those individuals with shorter sleep had a depressed immune response compared to their twin.

Getting the recommended 7 to 8 hours a night should help you to remove any weakening of the immune system due to sleep deprivation.


Chronic stress

People who are chronically stressed can have a persistent weakening of the immune system.

There is a stress response curve describing how stress affects the immune system. At moderate stress levels, it can have a positive effect, but as stress becomes severe and chronic, it will weaken your immune system.

A set of students were studied. Those who practised relaxation techniques such as yoga, deep breathing and meditation were found to be more robust to infection.


Poor food choices

I’ve included this on the back of the evidence regarding diabetes.

It’s been well established that diabetes impairs immunity. But it’s also been found that avoiding high Glycemic Index (GI) foods and taking some exercise can, to a large extent, negate this immunodeficiency. So, better regulation of diabetes improves immunity.

There are clear implications for those without diabetes. If your lifestyle is such that you are encouraging the onset of diabetes, then your immune system will be compromised. That means if you have a diet with lots of high GI refined carbs and you lead a sedentary lifestyle, you’re more at risk of infection. This is an extrapolation of the above cited findings, but it makes sense. Sugar aside, if you have lots of refined foods then you are unlikely to be getting enough unrefined foods – i.e., wholegrains, fruits and vegetables. Those are foods that contribute positively to a strong immune system.


Summary recommendations

There’s a lot of information earlier in this post. To save you working out the complete list, here’s a summary of things you can do or avoid to build a strong immune system.

  • Eat healthy food – see list below.
  • Supplement with vitamin D in the winter.
  • Exercise regularly but avoid overtraining.
  • Don’t drink.
  • Get enough sleep, 7-8 hours a night.
  • If you’re stressed, practise relaxation techniques.


Ok, so you’re thinking that point 1 is rather unsatisfactory. After all, most of the positive actions you can take are about nutrition. That’s why we’ve summarised the nutritional precursors to a strong immune system.


Summary of food choices

We’ve picked out from the information above the top 10 ‘food groups’. Here they are:

  1. Beans, lentils and chickpeas.
  2. Nuts and seeds.
  3. Broccoli, spinach, kale, mushrooms.
  4. Eggs.
  5. Live yoghurt.
  6. Meat and poultry.
  7. Berries and cherries.
  8. Fish, including oily varieties.
  9. Wholegrains such as brown rice and oats.
  10. Olive oil.

You’ll notice we’ve singled out certain vegetables and certain fruits, simply because they are most cited within the immune system studies. In reality, the more variety you can get into your diet, the better. Other great choices are apples, kiwi, bananas, artichokes, Brussels sprouts, black grapes, butternut squash, cauliflower, chicory, peppers….. The list could go on.

If you’re a vegan or vegetarian, there are still choices you can make to get all the nutrients you need. You’ll just need to be a little more conscious of the choices you are making and ensure you’re getting everything you need. Check the lists in the individual sections for vegan options.

Do you notice anything about the food list above? It’s the same as the list you’d come up with if you were looking for weight loss, muscle gain, diabetes regulation, blood pressure regulation and so on. It’s basically a healthy diet, devoid of processed foods and additives. Buy and cook unprocessed food, and you’ll not only be a lot healthier for it, but you’ll have a more robust immune system.



What do I do?

You may be interested to know that in the last 10 years I haven’t really been ill.

I’m pretty sure that I still get infections. I’ll sometimes wonder if I have a cold. If I’m feeling a bit tired or my energy levels are low, then I start suspecting that I have a bug. But that’s as far as it goes. I never get symptoms that I can identify as a cold. And if I think I have a cold because I’m a bit sluggish, I’m always fine after a kip.

I can only assume my immune system is very efficient and it kicks any invaders into touch pretty sharpish.

It would make sense if I had a robust immune system because I do consciously eat and supplement to maintain it. Below I list my ‘immune regime’. I want to be clear: I am not recommending this. If you asked a government health adviser, some of this would be deemed unnecessary or even outside of safe limits. Almost certainly I could pare this back and still enjoy the same robust immune system. I just don’t want to do the experiment to find out!


My ‘immune regime’

  • A diet that includes, in abundance, all of the ‘top 10’ shown above. It has a bucket load of polyphenols and almost nothing that is high GI.
  • Supplements:
    • Vitamin C
    • Vitamin E once a week
    • Vitamin D
    • Zinc
    • Probiotic and prebiotic
    • Glutamine in powder form. Any time I have a ‘sports drink’ or ‘health drink’, I’ll put glutamine in it. Pre-workout, post-workout, super-greens, pre-cardio, casein meal replacement. I’ve done this for years as an athlete – the immune benefits were initially just an additional benefit, but now I take glutamine for its immunity benefits.
  • I exercise daily. Most days it’s proper exercise, but even if I don’t do that, it’ll be a decent walk.
  • I don’t drink.
  • I’m not chronically stressed, not like I used to be in the corporate world. These days my stressors are positive and healthy.

Some of these supplements are useful in a sporting sense. For example, zinc and vitamin D help with testosterone support. I’ve always trained hard and felt that I need a little more micronutrient support than I can derive from my diet. Given how good my diet is, I probably don’t in reality. But, as I mentioned, I just don’t want to do the experiment.

Probably the one thing that lets me down is my sleep. I’m probably averaging six and a half hours, and I do get tired. But I regard this as temporary whilst I build a business that can support me working fewer hours.


The wrap-up

It’s the same advice that you’ll see in many of our posts. Get a healthy, varied, unprocessed diet consisting of lean protein, pulses, nuts and seeds, healthy fats, whole grains, fruits, vegetables and low-fat dairy.

That said, if a strong immune system is your goal, you might want to pay more careful attention to what you are eating. Even if you regard your current diet as healthy, make sure you take care of each of the above nutrient requirements and lifestyle factors. Take a look at the foods listed in each section and check that your diet contains a decent amount of some of the foods in each list. Make exercise a lifestyle choice and a habit. Make these changes, and you’ll significantly reduce your infection risk or at least the severity and duration of any symptoms.

So, stay healthy, and stay on track. Keep your immune system in good health, and you stand the best chance of reaching your health and fitness goals.


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