Nutrition and Immunity
The first gusts of colder weather have hit across Europe, and we are starting to say our goodbyes to summer. The crisp autumn mornings are a beautiful time of year, but along with the lower temperatures comes an increased risk of illness, commonly referred to as ‘flu season’. Nutrition is vital for health all year round, but the importance of good nutrition to support immune function increases at this time of year. Ensuring you consume a wide range of vitamins and minerals won’t guarantee an illness-free winter, and the concept of ‘boosting’ the immune system is incorrect (as it cannot be boosted but can run at optimal levels), but it will increase the chance of getting through the frosty months as healthily as possible.
What is the immune system, and how does nutrition help?
Simply put, the immune system is a network of organs, proteins, and cells that help protect the body from outside invaders, such as bacteria and viruses. It might therefore seem strange that the food we eat can play a part in this, but the nutrients we consume in food are for more than just providing energy and being tasty! A number of different nutrients (vitamins and minerals) are involved in supporting the immune system in a variety of ways.
Vitamins
Vitamin A
Vitamin A helps T-cells, a type of white blood cell that identifies threats to the body, to grow. In foods Vitamin A takes many forms, for example liver and cheese contains retinol, and carotenoids which are found in dark leafy greens and orange-coloured fruit and vegetables, such as sweet potatoes or pumpkin. Pumpkins aren’t just for carving! Our bodies extract the retinol (also called ‘preformed vitamin A’ as it is already in the correct state to be used) and converts the carotenoids into the usable form of vitamin A.
Did you know? Vitamin A plays a role in healthy eye function. One of the components that Vitamin A is broken down into allows cells in our eyes to detect light and colour which sends signals to the brain, which processes these as the images we see. Did you also know that carrots are a good source of Vitamin A? That is why carrots ‘help you see in the dark’!
B vitamins
Vitamin B6, Pyridoxine, and vitamin B12, Cobalamin, are both involved in the production of new immune cells. B6 is found in a wide variety of foods, including cereals and grains, various vegetables such as sprouts, spinach, and broccoli, as well as meat and poultry. B12, however, is exclusively found in products of animal origin, as it is produced in the gut by bacteria. Liver, egg yolk, and fish are all rich sources of vitamin B12. However, fortified foods can provide ample B12 for those avoiding animal products.
Vitamin C
The vitamin most commonly associated with immune function, vitamin C, actually has a wide range of functions such as synthesising collagen and helping the absorption of iron. One of the key roles of vitamin C in immunity is its role in coordinating attacks on foreign bodies by white blood cells called neutrophils. We all know that oranges are a great source of vitamin C, but other fruit such as lemons and guava are also rich in vitamin C, as are berries such as strawberries and blackberries. Did you know that peppers actually contain more vitamin C than oranges?
Vitamin D
Vitamin D, the sunshine vitamin, plays key roles in forming strong bones by helping the absorption of calcium. It is not currently clear how vitamin D is involved in immune function, but we know that deficiencies are linked with compromised immunity; so make sure you are safe in the darker winter months! In the summer months, we synthesise vitamin D from sunlight, but we can also get vitamin D from oily fish, eggs, mushrooms, and fortified foods such as dairy products and cereals. Despite this, for those living in the northern hemisphere, where sunlight is sparse in the late and early parts of the year, it is recommended to take a supplement to ensure deficiency is avoided.
Minerals
Copper
As with other minerals, copper plays an integral part in maintaining the immune system by supporting the growth of healthy immune cells. Copper in abundant in shellfish, seeds and nuts, offal products, wheat-based cereals, and whole grains. Due to it being found in a variety of foods, deficiency in the western world is rare.
Iron
Iron is well known to help produce cells that are integral for immune response, such as B cells which create antibodies which attack bacteria and viruses. Offal is the richest source of iron, such as liver and kidneys, but iron is also found in red meat and non-animal sources such as beans and pulses, nuts and seed, and wholemeal bread.
Zinc
Zinc is another element that has been linked to immune function for a long time, with remedies of supplementing with zinc when cold symptoms appear being well-known. Zinc helps maintain the thymus, the organ which produces T-cells, and people who are deficient have smaller thymuses which produce fewer T-cells. Zinc is present in meat, cheese, some shellfish, wholegrain breakfast cereals, and nuts and seeds.
Staying healthy in winter
Clearly, what we eat can affect the function of our immune system and how we respond to illnesses. What we have highlighted in this article is: the best way to ensure you are getting enough vitamins and minerals to support a strong immune system is by consuming a wide variety of whole foods, including meat and offal, fish and shellfish, a variety of fruit and vegetables (differing in colours), whole grains, nuts and seeds. Whilst there is never a guarantee of avoiding illness, this will give you the best chance of fighting off any colds that come your way!
