The Huddle Cheltenham

Foods to keep your immune system strong

Foods to keep your immune system strong

Jamie Hartnoll

Whilst many are jumping for joy about a return to normality, many are feeling apprehensive given that COVID is still causing havoc across the world. In either case keeping yourself strong, fit and healthy is more important than ever, and part of this means keeping your immune system in tip top shape. 

Whilst there are no foods proven to protect against COVID, here a five key nutritional considerations to give your immune system the best chance to fight anything that comes its way. 

Key Considerations 

  • Energy balance 
  • Give yourself enough carbohydrates and protein
  • Supplement with Vitamin D
  • Probiotics 
  • Eat the rainbow

Energy balance

Energy balance refers to the energy consumed (Kcal through food and drinks) versus the energy that is expended (Kcal burned). If you consume less calories than you burn then you will lose weight and the opposite happens if you over consume. 

If you are under consuming calories you are not giving the body enough fuel to function optimally. Think of filling up a car with only 80% of the petrol needed to get to the destination. You can’t expect the car to reach the destination unless you take out all the seats, reduce the weight and drive very slowly in a high gear. In other words the car is no longer performing optimally. It’s the same for the human body and this means your immune system’s ability to fight infection will be compromised.

Now you may want to lose a bit of weight. You may even NEED to lose a bit of weight. That’s fine, just do it slowly and for short periods of time so you are not constantly under fuelling. This is also likely to be the much more sustainable approach to weight loss and weight maintenance in the long run.

Consume carbohydrates 

If you are trying to lose weight, or if you are training hard/frequently, then make sure you consume at least 50-60% of your calories from carbohydrate. A calorie deficit and/or exercise will deplete glycogen stores, which is what carbohydrate is stored as in the body. Glycogen is the key fuel of our immune cells and with this depleted the immune system will be compromised. Consuming enough carbohydrates during particularly long training sessions (60 min plus) will also help reduce the stress response that comes with exercise. 

Refuelling after an exercise session with a high carbohydrate meal is ideal with foods such as potatoes, pasta, quinoa, lentils and oats for example. Fruits and veg are mostly carbohydrate but also very nutrient dense such as bananas and berries which I will come on to later. These also make excellent foods to refuel on. 

Supplement with Vitamin D

Vitamin D is important for calcium absorption, bone health and muscle function but it is also important in a well oiled immune system. Vitamin D is present in a variety of mechanisms that contribute to a strong immune system but the problem is our main source is sunlight. If we’re living in the UK then a 1000 IU daily dose will help maintain Vitamin D levels particularly during the winter months. If you are deficient (which you can find out from a simple blood test) then you may need a higher dose. 


Probiotics are foods that contain live micro organisms that increase the amount of friendly bacteria and the reduce the amount of unfriendly bacteria within the gut. They are often found in yogurts with the most studied strains typically being Lactobacillus and Bifidobacterium. Fage is a good example of a yogurt that contains Lactobacillus, but you can look for ‘includes live and active cultures’ on the label. 

The evidence is promising but not conclusive that these can help reduce upper respiratory infections, help manage IBS and reduce any issues with foreign food whilst travelling. Given that the 0% fat plain versions such as Fage are low in calories, high in protein and also have no sides effects (provided you are not lactose intolerant) it has made my list! 

Eat the rainbow

There is no magic list of say five foods that you need to eat because there are so many that can provide a benefit. The more nutrient dense the food the better, and an easy way to check this box is to fill your plate with lots of different coloured foods. Anti oxidants such as Vitamin C, E and Beta Carotene are particularly important in immune function as they clear up the free radicals that are caused by stress (both physical and mental). This helps the body protect against potentially damaged cells, enzymes and DNA which would otherwise prevent optimal functioning. 

Red peppers are extremely high in Vitamin C, Almonds are high in Vitamin E and come with lots of healthy fats (monounsaturated) so they can be easily absorbed and berries of all varieties, but in particular blueberries, have very high amounts of anti oxidants. The energy density of fruits and vegetables is usually very low so you can eat a lot of these and still eat within your calorie means whilst staying full. 

BONUS TIP – Multi vitamin 

We should all endeavour to consume a balanced diet full of colour that provides us with nutrient rich foods full of variety. However sometimes this is not possible because of the environment we find ourselves in or because of how busy we may be. Having a multi vitamin to hand in these situations can help plug the gap ensuring you get all the nutrients you need. Look for a multivitamin that contains the recommended daily allowance (RDA) of each vitamin as some may include very high doses which the body does not need. Nutrition X is a good example of such a product. However it should be noted that this should be a Plan B used in times when you know your diet is going to be far from nutrient dense. 

If you need any help with your nutrition then contact us to schedule a free call with our nutritionist Jamie Hartnoll.


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Gleeson, Michael. (2016). Immunological aspects of sport nutrition. Immune Cell Biol 94:117-123