Winter is approaching fast. The weather is turning colder, and the days are getting shorter. With this season change comes an increased susceptibility to cold and flu viruses. Walk into any health food shop at this time of year and you’ll be bombarded with products claiming to ‘boost your immunity’. Now you may be wondering whether any of it really works. This winter, we want to talk a little about the immune system – including the evidence behind vitamins and minerals with immune boosting claims – and what you can do to keep yourself healthy throughout the winter months.
Winter bugs can be particularly challenging for people with cancer.
Having cancer may increase your susceptibility to infection, for example, people with Lymphoma and Leukaemia may be particularly susceptible as these cancers affect the bone marrow where our white blood (immune) cells are made. Also, many chemotherapy drugs adversely affect the immune system, as they temporarily lower the number of infection-fighting white blood cells in your body. In these circumstances, your oncology team will monitor your white blood cell count and advise you if any special dietary and or lifestyle measures need to be taken. Radiation therapy can also cause a decrease in white blood cells (though, in general, radiation effects are milder than those of chemotherapy). Along with this, chemotherapy can also damage oral and intestinal mucosal membranes which are important barriers to infection.
So, what can you do to support your immune system during winter?
We do know there are many nutrients involved in immunity and supplements geared toward immune support often contain the vitamins A, C and D, plus the mineral, Zinc. So, let’s take a closer look at the role of these nutrients in immunity.
Vitamin A is important for the development of immune cells, also for the integrity of the gut lining, our first line of defence against pathogens. The best sources of vitamin A are animal products; eggs, liver, fish and dairy. Many of us rely on foods like carrots, sweet potato and leafy greens for our vitamin A but these foods don’t actually contain Vitamin A, they contain beta-carotene, a pre-cursor which your body must convert into vitamin A. Unfortunately, studies suggest that nearly half of us have a genetic mutation which significantly reduces our ability to complete this conversion. So, unless you’re vegan, we encourage you to regularly include some animal produce in your diet.
Vitamin C is probably the most frequently talked about vitamin when it comes to immunity. Although the evidence for the use of vitamin C in treating infections is weak, it does have a vitally important role in immunity as it stimulates the production of our white blood cells. Eat plenty of vitamin C rich food, to support your immunity this winter. Think peppers, fresh fruits – especially strawberries – citrus fruits and kiwis. Also, broccoli, brussel sprouts and leafy greens.
Vitamin D is crucial to our immune system and studies show it may play an important role in immunity, specifically against winter flu and upper respiratory infection. We can obtain some vitamin D from food sources including oily fish, shellfish, egg yolk, and mushrooms but our main source is exposure to sunshine. When our sun exposure is reduced, we can run low on vitamin D. For this reason, Public Health England (PHE) recommend all adults take a 10 microgram vitamin D supplement during autumn and winter. As vitamin D can be toxic at very high levels, it’s preferable to test your level before supplementing doses higher than that recommended by PHE. If you’re concerned you may be low in vitamin D, ask your GP to refer you for testing. Alternatively, there are reliable and affordable self-tests available via services using NHS trusts.
Zinc is a mineral which your body uses for fighting off infections, making it a super important winter mineral! Zinc is also important for maintaining the integrity of the gut lining. We should be able to obtain sufficient Zinc from our food, since it’s found in a wide range. The best sources generally come from animal origin, and include meat, fish and eggs. Plant based options include sea vegetables, pumpkin seeds and mushrooms, while wholegrains are also good sources. Interestingly, research has shown that Zinc lozenges may reduce the duration of symptoms of the common cold by several days. Larger – higher quality – trials are needed before definitive recommendations can be made, so for now, we recommend focusing on the Zinc rich foods.
Did you know something like 70% of your immune system is in the gut?
Humans have trillions of bacteria living in their gut, mouth and nose, known collectively as the microbiome. Until recently, we thought these bacteria were only important in relation to digestion and the health of the gastro-intestinal tract. But recent research has shown us that some of these bacteria are intricately involved in helping our immune system to function. That’s good reason to look after your gut this winter! Here are some top tips:
- Be sure to eat plenty of soluble fibre, found in oats, flaxseeds, chia seeds, stewed apple and most vegetables.
- Eat prebiotic rich foods such as leeks, onions and garlic. Prebiotics help the beneficial bacteria to colonise the gut.
- Eat probiotic rich foods, such as live yoghurt, kefir and sauerkraut.
The probiotic: Lactobacillus Rhamnosus GG has been shown to decrease the risk of upper respiratory tract infection in children in a daycare setting. Whilst we can’t necessarily extrapolate this data to adults, it’s certainly a good reason to ensure pre- and probiotic rich foods are included in your diet.
In the context of winter immunity and cancer, one of the most important – and oft studied – white blood cells is the Natural Killer (NK) cell. NK cells are best known for detecting and controlling early signs of cancer, as well as for killing virally infected cells. For this reason, many studies have investigated how we might be able to improve NK cell count. To date, the evidence in human studies is limited, though in vitro (test tube) and animal studies are showing promising results.
One human study showed blueberry powder (the equivalent to 250 grams blueberries per day) significantly increased NK cell count in just six weeks. Though promising, eating 250g blueberries per day is probably a little too much for most of us! Another human study, involving a small group of patients with advanced cancer, demonstrated that aged garlic extract significantly increased NK cell activity. A different study – this time animal rather than human – demonstrated selenium may increase NK cell activity in a breast cancer setting. Other natural agents which may promote the health of the immune system – as demonstrated in either in vitro (test tube) or animal studies – include black pepper and cardamom. In general, herbs and spices are known for their antioxidant and antimicrobial activity, so we encourage you to use plenty of these during winter.
For thousands of years, mushrooms, like shitake and maitake, have been used in Eastern medicine for their immune stimulating properties, including their ability to modulate NK cell activity. These mushrooms and – to a lesser extent – oats, brewer’s yeast and seaweed, contain a type of sugar known as beta-glucan. It’s these beta-glucans that are being studied for both their ability to stimulate resistance to infection, and their anti-cancer activity. Though evidence for their use is increasing, overall, human studies are still limited and the anti-cancer effects are mainly based on test tube or animal studies. Still, autumn is the perfect time to up your intake of mushrooms and instead of plumping for your usual white mushrooms, why not seek out some beta-glucan rich shitake mushrooms, which most of the UK’s supermarkets sell at this time of year.
So far, we’ve talked a lot about food and its importance in maintaining a healthy immune system, but having a healthy diet is only part of the picture. Equally important is our lifestyle including sleep, rest, stress levels, exercise and social connectedness.
For many years, research has demonstrated that sleep deprivation suppresses the immune system, making you less able to fend off bugs. The immune system functions best when it gets enough sleep, and most of us need at least seven hours a night for optimal health. Spend a little time this winter working out how many hours sleep you need to feel well. And if you do come down with a winter virus, prioritise your sleep. You’ll feel better for it.
Chronic stress (lasting several days to years) has been shown to suppress the immune system and may make you more susceptible to cold and flu viruses. We can’t avoid stress, but learning how to manage it can be very supportive to our overall health and wellbeing. Spending time with people you love, taking regular exercise, and getting out in nature can also help.
While the research on exercise strengthening the immune system is limited, it’s reasonable to assume that moderate, regular exercise forms part of a holistic approach to healthy living. We also know regular exercise reduces the risk of many different types of cancer. And, if you’re doing lots of exercise, surely you deserve a massage? The good news is that research shows deep tissue massage significantly increases white blood cell count for up to 60 minutes after the massage. I can’t think of a better way to recover from a cold!
Social connection improves physical health and psychological wellbeing, and has been demonstrated to increase longevity and strengthen our immune system. Spending time with people whom you feel a true connection, or perhaps connecting with the local community around you can have a very positive effect on wellbeing.
When it comes to winter immunity, our first line of defence is a healthy lifestyle. What we eat is important, since our immune system needs all sorts of nutrients to function properly. Check out the Penny Brohn UK healthy eating plate which encourages you to include good quality protein, essential fats and plenty of vegetables in your daily diet. But remember, what we eat is only one part of the puzzle. Equally important, is getting enough sleep, managing our stress levels, taking regular exercise, and spending time with people who share similar values and interests to ourselves. What could you do this autumn to best support your body and mind to stay in optimal health this season?