By Dr Duane Mellor RD PhD
It seems this year, 2020 has been the year we have learnt more about the importance of our immune system than ever before. This has included being bombarded by what seems to be endless adverts about boosting our immunity or getting our immune system ready for winter. Diet, and how we can improve it to optimise our immune system seems to at the centre of many of these claims.
First, it is important to understand what the immune system can do. In simple terms, there are two parts the non-specific – innate immune system and the adaptive – humoral and cell-mediated immunity. The innate immune system consists of our skin and the lining of our gastrointestinal tract, which act as a barrier to prevent infections getting into our body. This reactive part of the immune system also is responsible for the swelling and high temperature we often see when we are ill. If this works well it can help clear an infection and help with healing. However, this innate response can in some cases overreact causing too high a temperature or perhaps as may be the case with those who are worst affected by COVID-19 that this part of the immune system massively overacts.
A lot of the action when it comes to our immune system happens in our stomach, intestines and bowels. The surface of this part of our body is covered in a protective layer of mucus backed up by immune cells ready to produce antibodies to fight off any bacteria or virus trying that might try and attack. The health of this lining can be influenced by how we eat, along with influencing the balance of potentially health-supporting bacteria which form the microbiome in our intestines. A varied and balanced diet made up of plenty of vegetables, fruit, wholegrains, nuts, seeds and legumes provide the fibre these bacteria can ferment, which in turn provides the fuel which power our intestine’s cells. This helps to keep these healthy and keeps our immune system in ‘balance’.
The maintenance of balance can be seen through the action of the microbiome in our bowels, where as well as what we eat having an impact, the number and type of bacteria in the microbiome also play a vital part. In part what we eat can will help encourage healthy communities of bacteria which in turn produce compounds which nourish the cells in our bowels, and even can help balance inflammatory processes and could even improve our mental health! Another way to change the balance of the population of bacteria, is to take a good bacteria supplement. When choosing a good bacteria supplement it is important to choose one with a good balance of bacteria known to support bowel and general health, these have to be present in adequate numbers and in a formulation that means they are able to get all the way through your digestive tract to be able to colonise the bowel, in order to improve our health.
The concept of balance is key, and it is not in our interests to have a boosted and potentially over active immune system. Although there are a number of supplements that may be marketed with claims of being able to boost your immune system, the only permitted claim in UK (and European) law as approved by the European Food Safety Agency is that it can contribute to normal immune function. A number of nutrients have such a claim approved, including vitamin A, B6, B12, folate, vitamin C, Vitamin D, selenium, copper and zinc. However, to date no such claims have been substantiated for any good bacteria. This is not necessarily because there is no evidence from research that these supplements do not help, in fact there are multiple studies suggesting a benefit. In the case of good bacteria products unlike nutrients, it is hard to identify exactly how the bacteria might be beneficial, so do not meet the criteria needed for a claim to be approved.
So a healthy immune system is all about balance. It is just like keeping our muscles appropriately trained, not being either over-trained or undertrained. The aim therefore is to maintain a normal immune system, not a boosted one in order to help protect us from infection. We can do this, by eating a wide range of healthy foods, maintaining a good sleep routine, engage in regular physical activity and maintain a healthy body weight.