The media is full of advice on how to ‘boost’ your immune system, with many claims of certain supplements or foods doing just this. But how much of this is based in science? Rachael Venditti, Registered Nutritionist from allmanhall, looks at how diet can help us remain healthy as we move into the winter months, and whether there is anything to support the mantra that food alone can ‘boost’ the immune system.
How the immune system works
The immune system is one of the most complex bodily systems, made up of a network of cells, molecules, tissues and organs all working together to protect the body.
It defends our body through recognising pathogens which are foreign microorganisms that can cause disease, such as viruses and bacteria. Antigens are proteins that are found on the surface of pathogens and are unique to that pathogen. Antigens trigger an immune response where the body produces antibodies to fight the ‘invader’, the antigen.
Once we have had a disease, our body produces memory cells specific to that antigen. The memory cells remember the microbe which caused the disease and rapidly make the correct antibody so that the pathogen is quickly destroyed preventing symptoms of the disease occurring. Typically, our immune system is stronger in adulthood as we have been exposed to more pathogens and built up our immunity. This can be why children become ill more frequently than teenagers and adults, up to a certain age.
What is the role of nutrition?
The complexity of the immune system means that it cannot be modified acutely by a specific nutritional intervention. There is currently no convincing evidence that any food or dietary pattern can ‘boost’ our immune system and prevent or treat COVID-19. Rather, adhering to a healthy diet provides ongoing support to the immune system and may even delay the process of immunosenescence (the natural gradual deterioration of the immune system as we get older).
What should we be eating this winter to boost our immune systems?
There are many nutrients that are involved with the normal functioning of the immune system, which is why maintaining a healthy balanced diet is the best way to support immune function.
No single, one food is recommended over another. Eating a variety of foods will help to maintain a healthy balanced diet. The immuno-protection of many nutrients is based on their antioxidant capacity (oxidation is a chemical reaction that can damage cells) which is in fact lost if consumed in excess.
In addition to healthy eating, being physically active, reducing stress and getting enough sleep will also all help support immunity function.
Are there any supplements that ‘boost’ or protect us from COVID-19?
There is currently no evidence nor EU approved health claims that any supplement can ‘boost’ our immune system and prevent or treat viral infections, like COVID-19.
Making sure we meet our dietary requirements for many vitamins and minerals is important for good health and normal immune functioning. Eating a healthy balanced diet should provide all the necessary nutrients we need. In case of specific challenges in meeting the dietary requirements, supplements can be used to add nutrients to our diet.
It has been suggested in the media very recently that high doses of Vitamin D supplementation could reduce the risk of COVID-19 and other respiratory illnesses. Some research has shown a link between reduced Vitamin D status and acute respiratory tract infection, such as pneumonia. The National Institute for Health and Care Excellence (NICE) recently conducted a rapid evidence summary did not find a link between vitamin D supplementation and the prevention and treatment of COVID-19. This was also reflected in a joint statement released by The British Dietetic Association, the Royal College of Physicians and the society for endocrinology stating there is no evidence to recommend high doses of Vitamin D for the general population.
Most of our Vitamin D is produced in the skin in sunlight, with some from food sources, but many people do have low levels of Vitamin D which is why the current advice is to take Vitamin D supplements (10 micrograms per day) between October and April and all year round if you have darker skin, little exposure to sunlight or are over 65.
Gut health and the immune system
Another area covered in the media relating to immunity is gut health. Gut microbiota has been a hot health topic for a while now. The gut and its microbiota have been shown to impact metabolism, immunity and even behaviour.
It is thought that the predominance of the beneficial bacteria, referred to as the probiotic bacteria, such as bifidobacteria and lactic acid bacteria, ensure good health and prevent diseases of the gut and other organs in the body. Probiotics fight harmful foreign substances and can prevent the growth of harmful bacteria by producing organic acids that lower the PH in the intestine.
To support good gut health, the advice is to eat a wide range of foods, a diverse microbiota is a healthy one, a diet including different food types can lead to a diverse microbiota. High fibre foods promote microbiome diversity such as fruits and vegetables, beans, legumes, and Wholegrains. Live plain natural yoghurt, and fermented foods, such as kefir, kimchee and kombucha, are also thought to support a healthy gut.
Food and nutrition advice for this winter
To summarise, using a statement recently published from the British Dietetic Association “Simply put, you cannot “boost” your immune system through diet, and no specific food or supplement will prevent you catching COVID-19 / Coronavirus. Although eating a well-balanced diet can help ensure the normal functioning of the immune system, no individual nutrient, food or supplement is going to “boost” it beyond normal levels. Good hygiene practice remains the best means of avoiding infection”. For further advice about nutrient provision in menus, it is important to seek advice from a Registered Dietitian or other healthcare professional and that you follow the current advice set out by the Government, NHS and Public Health England.