Can you really ‘boost’ your immune system?
As much as I love basking in the sun, I actually love the Winter. Cosy nights in, wrapping up in Winter woollies and the celebrations of Halloween, bonfire night, Christmas and New Year are all something to enjoy. What I don’t relish is the prospect of Winter bugs and no matter how healthy you are, they always manage to creep their way in.
As the colder months approach, it becomes more important to eat and live well to support a healthy immune system, which helps to protect us against infections. Even the best of us are up against it during the Winter and the challenges these months present can hamper good diet and lifestyle practices. Comfort eating, and the influence of dark mornings and early evenings offer the perfect excuse to lapse on our healthy diet and exercise regimes.
The immunity ‘boost’ conundrum
As Winter approaches, so comes the advice on how we can ‘boost’ our immune system to ward off infectious bugs. The idea that you can ‘boost’ your immune system is a little misleading. This concept conjures up a false expectation of ‘supercharging’ your immune system and in some way making it invincible to anything that attempts to challenge it. The reality is that immunity involves a system and not a single entity. There are many cells of the immune system that have to respond to many different types of microbes. Pinpointing the specific cells and defining to what degree they should be increased is hugely complex and a question that’s yet unanswered by science.
Given the intricacies of the immune response, the science behind the impact of diet and lifestyle on immunity is not definitive, but research is continuing to evolve and it’s clear that maintaining a healthy lifestyle is a key part of keeping your immune system strong and healthy.
Why do we need our immune system?
You couldn’t survive without an efficient immune system, which is made up of special cells, proteins, tissues and organs that defend the body against infectious organisms and other foreign invaders through a series of processes referred to as the immune response.
Foreign invaders in the body are referred to as antigens. These are toxins or other foreign substances that induce an immune response in the body, especially the production of antibodies. One example of an antigen is the common cold virus. What makes the immune system truly remarkable is that once it has encountered an antigen, antibodies are hard coded to fight this invader should it try to attack the body again.
Can the quality of your diet help to maintain a healthy immune system?
The simple answer is yes. Exactly how diet is linked to immunity is not fully understood but is an area of research that continues to evolve. Scientists acknowledge that malnourished people are more vulnerable to infectious diseases, which helps to illustrate the importance of diet on immunity.
Maintaining a healthy balanced diet is key and there are many micronutrients (vitamins and minerals) required to maintain the normal functioning of the immune system. If your diet is compromised in any way through dieting or illness for example, then you may not be eating enough food or the right quality of food that allows you to glean the nutrients required to support your immune system.
Findings from the National Diet and Nutrition Survey (NDNS) have shown that amongst certain groups of the population, intakes of certain vitamins and minerals that support immunity are lacking in the diet (1). Vitamin D plays a key role in immunity and during the Winter months a significant percentage of people have been shown to have low levels of this nutrient, given the lack of sunshine, which is the main supplier. Minerals such as selenium, iron and zinc also play an important role in immunity and have been shown to be lacking the diet of some people as have intakes of vitamin A. This doesn’t necessarily mean your immune system will be compromised but that attention should be paid to eating the right foods to support healthy immunity.
Foods that can support your immune system
Diet is defined by food and not nutrients. Eating a balanced diet consisting of whole foods such as vegetables, wholegrains, lean proteins and healthy fats, will support your immune system. However, for the purposes of this blog I’m going to lay out some of the foods that contain specific nutrients that support good immunity.
Orange and green fruits and vegetables contain a pigment called beta-carotene, which is converted to vitamin A in the body. Vitamin A plays an important role in maintaining a healthy immune system (2). This nutrient helps to maintain the integrity of the mucosal cells of the gastrointestinal tract, eye and respiratory system that function as a first line of defence to infection, forming a barrier between from the environment outside the body. Vitamin A is also important for the normal function of immune cells and the production of antibodies that respond to infections.
Iron, selenium and zinc
All of these minerals are required for the production of antibodies, which are cells of the immune system that fight infection (3, 4, 5). Findings from the NDNS survey have shown that 27% of adult women and 54% of teenage girls do not get enough iron from their diet and partnered with menstrual blood loss, this puts them at particular risk of deficiency. Selenium intakes are also low with 38% of adults being shown to have inadequate intakes. Zinc is also lacking the diet, with 8% of adults and 17% of teenagers shown to have inadequate intakes of this mineral (1).
You can maintain good intakes of iron by eating foods such as meat, poultry, oily fish and eggs. Plant foods such as beans, pulses, dark green vegetables and dried spices are also a good source and you can increase the uptake of iron from these foods by partnering with foods rich in vitamin C. Selenium is found in Brazil nuts, oily fish and wholegrain foods such as brown pasta, rice and bread. Levels of selenium do vary depending on where the food has been grown and the quality of the soil. Zinc is found in meat, shellfish, eggs, beans, pulses, wholegrains, nuts, seeds and cheese.
This vitamin is the one people most associate with immunity and the common cold, which is backed up by some research suggesting its effectiveness at reducing the risk and length of infection (6). Research has shown how several cells of the immune system accumulate vitamin C and requires this vitamin to perform their task, especially T cells and phagocytes.
Most people get more than enough vitamin C in their diet, but appetite can lesson if you do get ill, which may impact on your intake. You can keep your levels topped up by eating foods such as red peppers, citrus fruits, berries, broccoli and potatoes. Vitamin C is water soluble and easily destroyed so try not to overcook vegetables and avoid soaking before cooking.
Vitamin D has been shown to play an important role in the immune system by increasing the antimicrobial effect of white blood cells that fight infection (7). Low levels of vitamin D can suppress the immune system, putting you at a greater risk of viral infections. Research involving more than 19,000 people found that those with the lowest levels of vitamin D were 36% more likely to develop a common cold than those with higher levels (8).
Findings from the NDNS have shown that 30-40% of all age groups are classed as being deficient in vitamin D due to the lack of sunshine (1). Public Health England recommends everyone takes a supplement providing 10mcg of vitamin D during the Autumn and Winter.
Gut bacteria also play a role
Over 70% of immune cells are located in the gut so it makes that a relationship exists between the two. We’re beginning to understand that it’s quality and not quantity that’s key to gut health and the diversity of microbes in your gut is referred to as your microbiome.
Probiotics are bacteria that have been shown to have a positive health benefit. Well researched strains include those from the Lactobacillus and Bifidobacterium family. Live yoghurt is the most well-known probiotic food and contains strains such as Lactobacillus Acidophilus and Lactobacillus Casei. Fermented foods such as kimchi, kefir and miso also contain strains of bacteria that can support good gut health.
Probiotic supplements offer a way of delivering large doses of specific bacteria to the gut and may be beneficial in the prevention of upper respiratory tract infections (URTI) such as the common cold (9). The effect of probiotics on the immune system has been widely researched and certain strains have been shown to promote the production of antibodies. The same strains have also been shown to stimulate the activity of immune cells such as natural killer cells and T-lymphocytes, which help regulate immune responses. A Cochrane Review showed that probiotics were better than a placebo in reducing the incidence and duration of a URTI (10).
Choose a supplement that contains both Lactobacillus and Bifidobacterium strains in a dose of at least 10 billion bacteria per serving.
Mushrooms are interesting too
The overall quality of your diet is more beneficial than focusing on any single food or nutrient, but mushrooms do appear to be interesting when it comes to immunity. Not only are they one of the few foods to contain a natural source of vitamin D, but they also contain beta-glucan polysaccharides that have been shown by some studies to modulate the immune system (11). Chinese medicine has long considered mushrooms to be medicinal and especially varieties such as shiitake.
Immunity is a hugely complex system that involves many different cells that work together to fight foreign invaders in the body. Your diet is known to have a role to play although exactly how is yet fully understood. Eating a balanced diet is no doubt helpful and there are certain nutrients that play a key role in maintaining the proper function of your immune system. Diet shouldn’t be defined by nutrients as food is what matters but understanding the nutrients that support your immune system help to support the importance of a balanced diet made up of a wide variety of foods.