Nutrition and Immunity

Nutrition and Immunity

By Helen Phadnis, BSc MSc PgDip MBDA, Consultant Dietitian

In the current environment more than ever, its important to maximise your immunity and fight off disease. In this article I’d like to give you some commonsense advice, dispel some immunity myths, and share whats on the horizon for personalised nutrition to optimise your immunity.  I have a strong belief in the power of nutrition, having witnessed time and again the positive impact that dietary change can have on health and well-being.  At times we can feel helpless when exposed to disease risk or the disease process itself, but our ability to choose how we nourish our bodies on a daily basis can have far-reaching effects on our immune system and empower us to take control of our health.

Healthy Eating

It’s well known that a Mediterranean style diet has been proven to be the healthiest way of eating in terms of preventing disease, and this also applies to optimising immunity. But what can we do beyond the Mediterranean diet, and why is it important for our immune system? 


The moisture barrier in our noses and our mouths (saliva) is reduced if we are dehydrated. Staying hydrated maintains that barrier. General advice is to drink 2 litres of fluid daily, which equates to about eight glasses. This can include tea and coffee, which are not dehydrating as previously thought. However fluid requirements vary substantially from person to person. In my work with athletes I see a variation in sweat rates when exercising from 200ml/hour to 2L/hour. In this case it’s important to monitor your own hydration via following thirst cues, and regularly checking your urine colour to ensure it is at least the colour of straw. 

Alcohol does not need to be eliminated, but avoid more than 14 units a week for men and women, and limit to no more than 2 alcoholic drinks at a time e.g. 2 pints of beer or 2 glasses of wine, and keep 2 alcohol free days a week. Excessive alcohol intake not only causes dehydration, it also disturbs your quality of sleep, which in turn has a negative impact on the immune system. 

It’s all in the detail

Healthy nutrition goes far beyond calorie counting and knowing your ‘macro’s’ – the popular practice of calculating how much fluid, carbohydrate, protein and fats our bodies require. Of equal importance in my opinion are to nurture the more detailed aspects of your nutrition:


  • By eating a balanced Mediterranean style diet, you will be ensuring you meet all your vitamin and mineral micronutrient requirements. If there are barriers to this for you (e.g. reduced appetite and diet intake during illness) it may be pertinent to take a multivitamin and mineral supplement. Take this with your biggest meal of the day to ensure the best absorption – try keeping them in your cutlery drawer to make sure you don’t forget. 
  • The one vitamin supplement I recommend everyone to take regularly is Vitamin D 10ug  per day (5ug  for children) especially between October – March when we do not receive enough sunlight. This prevents deficiency which has a proven negative effect on immune function. 
  • Avoid high dose vitamin C supplements. This is a common supplement people take to try and boost immune function, however unnecessary excessive intake can cause your body to downregulate its uptake, and high doses of vitamin C can cause nausea, diarrhoea, and abdominal pain, all of which have a negative impact on immunity. Your daily requirements can be met via eating one orange or kiwifruit for instance. 


There is good scientific evidence to show that maintaining a healthy number and variety of gut microbes (bacteria and fungi) confers a health benefit. Probiotic foods come in the form of live yoghurts, mould ripened cheeses, kefir, and fermented foods such as kimchee and sauerkraut. I encourage my clients to ‘eat something living every day’. 

Fibre acts as a prebiotic, which means it provides food for these beneficial microbes to feed of, and helps them flourish. Aim for 30g fibre a day via wholegrains, fruit and veg, nuts and seeds. Also aim for variety in your fibre – try to include 30 different types of plant-based foods a week. Avoiding emulsifiers and sweeteners also helps our gut microbiome to thrive


Phytonutrients are biologically active chemical compounds found in plants. They help protect plants from predators, and then in turn help prevent us from getting sick. They are not only found in fruit and vegetables, but also in pulses, tea, coffee, red wine, cacao, herbs, spices and olive oil. 

Wider lifestyle advice

Remember that nutrition does not act in isolation and that the other ‘pillars of health’ must be present to prevent the roof collapsing. Expert immunologist Dr Jenna Macciochi states that lack of sleep lowers our immune system by over 60%. Smoking also has a negative effect. Moderate exercise is immune protecting, whereas intense exercise can be an immune depressant – listen to what your body is telling you and avoid over-training. 

Exercise nutrition

Timing of nutrition around exercise can help negate this dampening of the immune system immediately post-exercise. Eating within your ‘recovery window’ of an hour, or ideally as soon as possible after exercise can maintain healthy immunity.  This should ideally contain carbohydrates, proteins, vitamins and healthy fats to help you Refuel, Rebuild, and Rehydrate, the ‘3 R’s’ of recovery. 

Beware of misinformation

There is always interesting nutrition advice out there – remember to check the credentials of anyone handing out this advice to ensure they are either a Registered Dietitian such as myself, or an Accredited Nutritionist. Let me dispel some common myths. 

  • Milk does not cause excess mucus. Dairy is not ‘inflammatory’ and does not dampen our immune systems. 
  • Celery juice, garlic and elderberry supplements will not ‘boost your immunity’. It is tempting to take a supplement or pill to help with your health, but don’t ignore the power of something so simple as eating healthily, and remember supplements can cause more damage than good. 
  • You cannot ‘flush out’ an infection within your body. It is important to stay hydrated, but excessive fluid intake will not help your body’s ability to fight off infection. 

Personalised nutrition 

Although there are general rules about nutrition we now know that a ‘one size fits all’ approach to nutrition is not the best approach to optimising health. Our genetics differs from person to person, which means our bodies differ in how we absorb, digest, and excrete nutrients. Genes also affect our appetite, taste and smell. This all means some blanket nutrition advice is more relevant to certain members of the population than others. I use DNA testing in my own clinics to provide a completely bespoke service when forming nutrition plans, so clients can focus on what health risks are most relevant to them and how they can mitigate these risks through diet. 

When there is so much in life you have no control over, I hope this article leaves you feeling empowered with the knowledge that the diet choices you make several times a day can optimise your health and well-being. 

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