Gut health and immunity - what can I eat to support my immune system?
This article was written by The Mission Dietitian intern, Klaudia Sokolowska.
At the start of the autumn season, especially after the last two years of living amidst a global pandemic, it is natural we start to think about how to best support our immunity. Alongside dressing up warm and avoiding obvious exposure to people who are unwell, you may consider how what you’re eating contributes to your health. While the idea of “boosting your immunity” is enticing, the area of nutrition and immunity can be a minefield, with super-foods and supplements peeking from every corner. Let’s look at some of the common ”immunity-boosting” contestants and see what the science says.
Vitamin C
A large number of legitimate research studies show that vitamin C plays an important role in the normal functioning of our immune system. What is more, vitamin C deficiency has been shown to result in impaired immunity and higher susceptibility to infection. However, vitamin C deficiency is uncommon in high income countries such as the UK. Hence, vitamin C supplementation is not routinely recommended at a population level. Instead, aim to get your vitamin C from the diet. Good sources of vitamin C include:
oranges and other citrus fruit,
kiwifruit,
strawberries,
mangoes,
spinach,
tomatoes,
asparagus,
peppers,
or Brussels sprouts.
This said, some studies do suggest that supplementing vitamin C upon the onset of infection may reduce the symptoms and speed up recovery.
Zinc
Zinc is a mineral found in cells throughout the body and is involved in supporting our immune system at multiple levels. Not only does it support our immune cells to fight infections, it was also shown to reduce the ability of viruses and bacteria to linger and grow inside the nose. Similarly to vitamin C, zinc deficiency has been linked to higher susceptibility to infection. This considered, an argument can be made that short-term zinc supplementation in winter months may bring some benefits in preventing infections, particularly in at-risk groups e.g. the elderly. However, long-term use has been associated with unpleasant side effects, including copper deficiency and digestive symptoms. The main dietary sources of zinc include:
seafood (particularly oysters),
meat,
fish,
eggs
and dairy.
Some breakfast cereals are also fortified with zinc. Plant-based sources of zinc include beans and lentils however, phytates also present in these foods impair zinc absorption.
Multivitamins
We now know that some vitamin and mineral deficiencies can impair our immunity - so is it not easier to just take a multivitamin supplement and be covered from all angles? While this may seem like an appealing solution, most micronutrients have safe upper limits. By taking a blanket supplement (often containing high concentrations of these active compounds), especially when taken alongside a balanced diet, we may be exceeding some of those - which can be dangerous. By having a balanced diet, not excluding any major food groups and maintaining diversity, we will more than likely be meeting the recommendations for both vitamins and minerals, with no need for supplementation.
Turmeric
In certain cultures turmeric has been used to treat infections dating centuries back. Recently, it has also made a breakthrough in the Western health and wellness world. Unlike with many health crazes, scientific studies do prove the beneficial anti-inflammatory and antioxidant properties of turmeric, particularly in certain medical conditions such as some forms of arthritis. However, the doses of active compounds from turmeric used in clinical research are much higher than what we can find in our cooking spices. This said, regular inclusion of turmeric in your cooking is likely to contribute to a healthy, immunity-promoting diet. When using turmeric in your kitchen, consider its bioavailability as it is best absorbed when taken alongside black pepper!
Honey
Honey, in some form or another, features as part of cold-cures across most cultures. There are a multitude of research studies, albeit most use small sample sizes and a variety of different types of honey, that prove its antioxidant and antibacterial properties. Research particularly supports the use of honey in upper respiratory tract infections, such as coughs. This has also been recognised by the National Institute for Health and Care Excellence (NICE) who now recommend honey as a first line treatment for cough, before antibiotics. Remember, not all honeys are the same, and it still consists predominantly of sugar and hence should be enjoyed in moderation.
Garlic
Garlic is another example of an ancient medicine which may contribute to building stronger immunity via scientifically-tested, immunity-promoting compounds. Studies have shown its ability to support the immune cells in fighting infections and potentially prevent them in the first place, however, good-quality research is lacking. Importantly, garlic also holds prebiotic properties, which means it supports our good gut bacteria - indirectly benefiting the immunity. Remember, garlic is a high FODMAP food and as such it may exacerbate IBS symptoms in some.
Gut Health
We looked into some single-food heroes often praised in the media. However, it would not be The Mission Dietitian newsletter if we did not spend some time talking about gut health. With 70-80% of immune cells being present in the gut, it seems intuitive that our microbes and general gut health are involved in our immunity to fight infections! In fact, the short chain fatty acids produced by the good gut bacteria in the process of fermenting fibre have been directly shown to improve immunity. For more tips on improving your gut health and microbiome diversity visit @themissiondietitian on Instagram, starting with THIS post!
Take-away Message
Once again, balance and diversity in our diets is the most truthful answer when asked about nutrition for improved immunity. While it is tempting to go for super-foods and quick fixes, having a solid base is always going to bring the biggest benefit. Feel free to include the foods discussed above regularly in your diet (unless contraindicated for other reasons), but most of all work on maintaining plant diversity and do not cut out any food groups unnecessarily!