A multifactorial approach to improve immunity

Regina Ford was born and raised in Switzerland where she trained in medicine, graduating from the University of Bern and completing her specialist training in general internal medicine in 2008. Whilst being enthusiastic about medicine she recognises the many limitations which modern medicine is unable to overcome. She moved to the UK and completed a MSc in Ayurveda at Middlesex University in London and now practices simultaneously as a consultant in acute medicine in the UK and as a general medical physician in an Ayurvedic clinic in Germany.

To stay alive and well, especially in the current testing times of the pandemic, a well functioning immune system is key.

The immune system uses two main response pathways: the cellular immune response and the humoral extracellular (antibody related) immune response, which are intricately linked. Many different cells (B and T lymphocytes, natural killer cells, macrophages) and cell subtypes, cytokines, hormones and cell surface antigens are involved in the process, which make the immune system one of the most complex systems in our body. In a system as complex and interlinked as this, you can understand how things can go wrong if only one small part of the system is failing.

What are the requirements for a healthy functioning immune system?

We all know people who hardly ever get ill no matter what they get exposed to and others pick up every cold that goes round. What is the difference between these two groups of people? Is it just genetic or could it be lifestyle also? There are a lot of clinical studies out there showing how lifestyle can improve the function of the immune system but also how certain behaviours can impair it.

Clinical studies …. show how lifestyle can improve the function of the immune system but also how certain behaviours can impair it.

There is also recent evidence about chronic systemic inflammation harming the overall health and impairing the function of the immune system.1

Multiple lifestyle factors affecting the immune system

Scientific studies mostly investigate a single variable factor and assess the outcome once this one factor has been changed. This approach is well established and allows researchers to evaluate the impact of the changes made. In reality, the complex physiology of the human body is impacted by countless influences from the environment and from the lifestyle choices made, voluntarily or involuntarily, every single day. Therefore when attempting to improve the health and immunity of the general population, a multifactorial approach should be chosen. To address a small number of factors only and exclude others is unlikely to provide the best outcome.

The …. human body is impacted by countless influences from the environment and from lifestyle choices.

In this article I will focus on lifestyle changes that have been shown to improve immunity. Most of them should be fairly easy to integrate into daily life, which hopefully would allow more people to adopt them.


Having a healthy diet has been shown to have a huge impact on the immune system and on health in general. Hippocrates famously stated: “Let food be thy medicine and medicine be thy food”. In modern times, nutrition for a healthy immune system has been labelled as immuno-nutrition.2

On the NHS website following a healthy diet is described as “eating a wide variety of foods in the right proportions, and consuming the right amount of food and drink to achieve and maintain a healthy body weight”. The basic principles of a healthy diet, especially the right proportion of carbohydrates, proteins, fats, fibres, fruit and vegetables are explained in an easy way. The “Eat Well Guide” by the British Nutrition Foundation is also very helpful, with colour schemes, drawings and explanations, which can be followed by anyone without any previous knowledge about nutrition.

“Eating a wide variety of foods in the right proportions”

An important part of having a healthy diet also means that the food should be as fresh and unprocessed as possible, allowing nutrients to remain intact. This means that ready meals should be avoided and food cooked from scratch. If possible organic food should be chosen as the soil on organic farms is less nutrient depleted than on conventional farms and contains less harmful pesticide residues.3 Organic food could also be grown in allotments and community gardens, giving people control over where their food is coming from.


Taking vitamin and mineral supplements shouldn’t be necessary for healthy people when following a good diet, except in stages of life with high demand on the body like childhood, pregnancy, lactation, old age and stress.

Taking … supplements shouldn’t be necessary …. when following a good diet …. There are however two exceptions….

There are however two exceptions: Vitamin D and Omega3 fatty acids. In both cases getting a sufficient amount through food to prevent deficiency can be difficult.

Vitamin D

The body can produce its own Vitamin D through sunlight but in the winter month were sun exposure is low in the northern hemisphere, many people have low Vitamin D levels. When it comes to food, Vitamin D is mainly available through oily fish and egg yolks. Covering Vitamin D demand with this small selection of food items can be difficult, so in such cases supplements are a good option.

There is overwhelming evidence that preventing vitamin D deficiency improves immunity and reduces the number and severity of respiratory tract infections.4

Omega 3 Fatty Acids

Omega 3 Fatty acids are available only through a small number of food items like oily fish (sardines, salmon, mackerel) and white fish to a smaller extent, flaxseeds and walnuts. A conscious effort to consume these food items every week needs to be made, otherwise supplements are advisable.


In the last few years a lot of research has been done about a different kind of supplements: probiotics. Probiotics have been shown to improve the function of the immune system through changing the composition of the gut microbiome. However it has also been shown that the gut microbiome can be balanced with a varied healthy diet.5 So one could argue that having a healthy diet makes the intake of probiotics unnecessary.

The gut microbiome can be balanced with a varied healthy diet.


Phytochemicals are a somewhat neglected part of our diet. Phytochemicals are produced by plants to help them resist infection and prevent them from getting eaten by parasites and animals. The effects of phytochemicals have been used over millennia in medical systems all over the world and have recently been rediscovered by modern science.6 Phytochemicals can have anti-inflammatory, antiviral and antibacterial properties and can support the function of the immune system. Some of the best known phytochemicals are carotenoids (in orange fruit and vegetables), Anthocyanins (in dark coloured fruits like blueberries, cranberries, grapes, elderberries), isothiocyanates in cruciferous (mostly green) vegetables, polyphenols in tea and sulphides in garlic and onions to name just a few. The colour of fruit and vegetables can give us an idea about the type of phytochemicals they contain. So to get a good variety of phytochemicals through diet, it is important to choose different coloured fruit and vegetables every day.

Choose different coloured fruit and vegetables every day.

Also herbs and spices are packed full of phytochemicals and can be used to flavour food or to make teas. Medicinal and immune strengthening properties of herbs have been described when used regularly or during an infectious illness. Like fruit and vegetables, herbs could be grown in any garden, allotment or in a plant pot indoors. Even in the cooler climate of the UK, herbs like rosemary, sage, camomile, basil, thyme and mint can grow in abundance and should be used for cooking and teas to harness their beneficial qualities.


The health benefits of exercise are widely accepted. Generally 75 minutes of vigorous aerobic exercise or 150 min of moderate aerobic exercise per week are recommended to stay healthy. In addition to helping to maintain a healthy body weight, improve muscle strength and prevent the occurrence of metabolic syndrome, exercise relieves stress, improves mood and also has been shown to improve immunity.7

Fat tissue has recently been discovered to be an endocrine organ on its own, able to produce inflammatory cytokines.


However human physiology is very complex. Psychoneuroimmunology, a relatively novel area of research, looks at the interactions between the central nervous system, the endocrine system and the immune system. It shows that processes affecting our central nervous system (emotions and stress) can affect our immune response.8 It could be argued that exercise affects immunity by reducing stress levels.

Fat tissue has recently been discovered to be an endocrine organ on its own, able to produce inflammatory cytokines.9 When chronic low grade inflammation is present, with upregulation of the inflammatory response pathways, the immune system tends to react with excessive inflammation when exposed to pathogens. Excessive inflammatory responses have been found to be a problem in severe courses of COVID 19 infection.10 Exercise, by preventing the occurrence of metabolic syndrome with its excess of fat tissue, reduces the chance of the immune system producing an excessive inflammatory response.

Processes affecting our central nervous system …. can affect our immune response.

Sleep and shift work

Good restful sleep helps us to face the demands of daily life, improves concentration and mood and also has been shown to help with regulation of calorie intake and weight control. Poor sleep quality and shift work have been shown to reduce immunity and increase susceptibility to infections.11 The ways in which poor sleep and shift work affect immunity are multifactorial. Sleep affects mental as well as physical health, and both of them are closely linked.

Sleep quality can be improved by exercise, especially outdoors and relaxation techniques/stress management. Trying to go to bed roughly at the same time every day can help. Our bodies are subjected to daily fluctuations of melatonin and cortisol, which makes us sleepy and tired when it gets dark and wakes us in the morning when it gets light. It his helpful to make use of this and sleep when it is dark and when we feel tired rather than staying awake until early morning.

Shift work at night is a situation where these physiological signals have to be forcefully ignored, leading to deranged sleeping patterns long-term and metabolic consequences.12 There are lots of jobs where shift work is mandatory. Would a possible option be that night shifts are only given to the younger workers whereas older age groups, where physical resilience tends to decline, are relieved from this duty?

Stress management

Earlier in the article I touched the effect of stress on the immune system. During stress the sympathetic nervous system starts to take over at the expense of the parasympathetic nervous system. Cortisol levels can be higher than normal during the day. Stress can lead to a state of high alert ready for “fight or flight”. Breaking this pattern can be hard especially when it has been going on for month or even years.

What is experienced as stressful varies highly between individuals. But existential threats like job loss, acute illness and accidents, loss of loved ones, experiencing violence are very likely to affect also the most resilient personalities. Such situations are hard to control but having an easily accessible network of sympathetic support groups and organisations which support individuals in need can make up somewhat for the lack of funding of the public mental health and social security services. Health care professionals should update themselves about charitable organisations in the area they work in, to be able to advise patients where to go. Also, any health care professional, even when not specifically trained in mental health, can take time to listen to somebody in a difficult situation.

During stress the sympathetic nervous system starts to take over …. Cortisol levels can be higher than normal.

In milder forms of stress, simple easily accessible measures like going into nature or the nearby park, enjoyable activities such as yoga, meditation, hobbies, crafts and social activities have all been shown to help ease stress.


A lot of studies have been looking at different ways to improve the immune system. In this article I have attempted to combine the information available to us, and also to raise awareness about the need for a multifactorial approach involving all aspects of health. Being healthy doesn’t just mean to have a body that functions well. It also means being happy and leading a fulfilling life. The environment we live in, the people we meet and the opportunities we get, all have an important influence on our health and immune system.

The measures described in this article help a person to take responsibility for their own health. It is important to see them as a long-term investment. These measures are not a quick fix but rather something that needs to be integrated and maintained throughout a person’s life.


  1. Furman D, Campisi J, Verdin E, et al. Chronic inflammation in the etiology of disease across the lifespan. Nature Medicine 2019; 25: 1822-32
  2. Calder P C, Feeding the immune system. Proc Nutr Soc 2013; 72: 299-309
  3. Crinnion W J, Organic foods contain higher levels of certain nutrients, lower levels of pesticides, and may provide health benefits for the consumers. Altern Med Rev 2010 Apr; 15(1): 4-12
  4. Martineau A R, Joliffe D A, Hooper R L, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic literature review and meta-analysis of individual participant data. British Medical Journal 2017; 356: i6583
  5. Maslowski K M, Mackay C R. Diet, gut microbiota and immune responses. Nature Immunology 2011 Jan; 12(1): 5-9
  6. Craig W J. Phytochemicals guardians of our health. Journal of the American Dietetic Association 1997 Oct; 97(10): 199-204
  7. Nieman DC, Nehlsen-Cannarella SL, Markoff PA, et al. The effects of moderate exercise training on natural killer cells and acute upper respiratory tract infections. Int J of Sports Med 1990 Dec; 11(6): 467-73
  8. Kiecolt-Glaser J K, McGuire L, Robles T F, et al. Psychoneuroimmunology: Psychological Influences on Immune Function and Health. Journal of consulting and clinical psychology 2002; 70(3): 537-47
  9. Coelho M, Oliveira T, Fernandes R. Biochemistry of adipose tissue: an endocrine organ. Arch Med Sci 2013 April; 2: 191-200.
  10. De Lucena T M C, Da Silva Santos A F, De Lima B R, et al. Mechanism of inflammatory response in associated comorbidities in COVID-19.Diabetes and Metabolic Syndrome: Clinical Research and Reviews. 2020; 14: 597-600.
  11. Besedovsky L, Lange T, Haack M. The sleep immune crosstalk in health and disease. Physiol Rev 2019 March; 99: 1325-80
  12. Antunes L C, Levandovski R, Dantas G, et al. Obesity and shift work: chronobiological aspects. Nutrition Research Reviews 2010; 23: 155-68


Featured image by Jamie Brown at Unsplash     

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