How to stay well - and can you REALLY boost immunity?!

By Dr Marissa Kelaher

You wake at 3am with a splitting headache. Then hear your young child coughing in the next room... 

Do you dread the onset of cold weather?

Feel like you and your family are constantly sick?

Wondering what you can do to boost your immunity and avoid all those winter illnesses?

One of the most common questions we're asked as doctors over winter is ‘why am I always getting sick?’

No one wants to get bug after bug, but knowing what really helps can be so confusing, with different advice and opinions everywhere you look. There is a MASSIVE amount of misinformation around these days- from various supplements to ‘boost’ immunity, to promised cures to stop illnesses - despite the fact that these can sometimes just be a clever marketing angle for expensive products…

The good news is, there ARE many evidence backed ways to help optimise your immune system (in addition to recommended public health measures) - and best of all most of them are virtually free 😊

Did you know, your immune system is highly complex and doesn’t have an ‘on/off’ switch as many people think?!

We also don’t actually want to ‘boost’ immunity either, as an overactive immune system is what causes allergies and autoimmune disease.

Ideally we want an immune system that is balanced - can fight off infections quickly when we are exposed to them, and keep us well - but also doesn’t over react to the wrong things and lead to health issues.

Fortunately, what we eat and do really can make a big difference to immune function, so read on for our top evidence based tips!

DIET

A healthy diet does several things.

It maintains gut health (crucial for a healthy immune system), helps control inflammation, and provides the nutrients our immune cells need to function well.

• Research consistently backs a whole food plant focused Mediterranean style diet for health and wellbeing. This diet is high in plant based fibre, fruit and vegetables, whole grains, legumes and omega 3. This is what we teach you in our nutrition focus course, and Reboot course including recipes and meal planners to make it easy!

• We need certain nutrients for optimal immunity too, in particular iron, zinc, selenium, copper, omega 3, and vitamins C, A, D, B6, B12, and E. Deficiency in these can lead to recurrent infections, but a well balanced whole food diet usually contains enough of all of them .

• This means supplements are NOT usually the answer in most situations, as they contain high doses of single micronutrients (which can even be harmful) - it’s always far better to get them from your diet if you can! We only recommend supplementing if you have a confirmed deficiency, or if you have medical conditions that affect your ability to absorb nutrients (please check with your doctor about this)

• Having iron levels in the optimal range (ferritin 50-200 for adults) is important for good immune function, so getting these checked can be helpful if you keep getting sick, or have other symptoms of low iron (such as fatigue, shortness of breath, or hair loss)

• You can also get B12, selenium, vit D and zinc levels checked on a blood test if you are concerned your levels of these are low, although a cost may apply (check with your GP). Testing levels is not usually essential if you are eating a balanced diet, do not have any malabsorption issues, and are otherwise well.

• NZ soils are often deficient in selenium, but a couple of brazil nuts each day provides good levels of selenium. Selenium is also toxic in high levels, so if you do supplement, make sure you follow instructions on the packet and don't take too much!

• Zinc is found in nuts, seeds, whole grains, legumes, and tofu - these also contain lots of vit e and b vitamins as well! You can also get zinc from seafood and some red meat if you choose to eat these

• Brightly coloured fresh fruits and veges are a great way to get vit C and A (orange and yellow ones in particular contain lots of the compound our body needs to make vit A). These contain flavonoid polyphenols, a type of anti-oxidant that seems to decrease how often we catch coughs and colds. Flavonoids are rich in foods such as dark-colored berries, green tea, onions, apples, citrus fruits, and soybeans

• These foods also contain high levels of antioxidants such as quecertin, which help immunity and regulate inflammation.

• Eating a variety of whole, mostly plant based foods is a great way to meet all your nutritional needs for a healthy immune system. This is also called an ‘anti-inflammatory ‘ or Mediterranean dietary pattern, and has been shown to have benefits in many areas of health, including immunity. We also cover anti-inflammatory diets in depth in our nutrition course and Reboot course

• You don’t have to be vegan, just aim for around 80%-90% of your diet to be whole plant foods, and if you choose to you can include some unprocessed animal foods to provide b12 and potentially extra iron

• Whole plant foods are also rich in polyphenols, which help immunity and reduce inflammation. The more plants the better!

• Particular foods that can help immunity include turmeric, garlic/onion, ginger, cinnamon, berries, nuts and seeds, green tea, flaxseed, and dark green vegetables - try include these regularly, on a daily basis if possible

• Wholegrains, legumes, and fermented foods (kefir, live yoghurt, kombucha,, miso, tempeh etc) also help gut health - 80% of your immune cells are in your gut, so a healthy digestive system is crucial.

• Fibre from foods (especially grains and legumes) feed our ‘good’ gut bacteria, which help immune function and inflammation; and fermented foods have multiple benefits for gut health. To learn more about gut health, checkout our gut health blog, or our nutrition course, or Reboot course where we take a deep dive into how to create a healthy digestive system

• Limit refined carbohydrates (white flour and white rice, processed foods, added sugars), highly processed foods, saturated fats, alcohol, animal protein, and red meat - as these are all associated with higher levels of inflammation in the body, which can negatively affect immune function

EXERCISE

Studies have shown that regular moderate exercise can reduce your chance of catching a cold by up to 50%!!

Exercise:

• Boosts levels of immune cells and anti inflammatory cytokines which help optimise immune function

• Improves the bodies ability to detect and fight infection

• Helps the lymphatic circulation, which ‘flushes’ infection out and circulates immune cells

• Reduces stress hormones (see below)

• Helps the gut to function well and boosts levels of ‘good’ bacteria

• Helps your body clear out damaged immune cells and make new ones

Practices that ‘calm the nervous system’ and include controlled breathing seem to have additional benefits for immunity - these include Qi Gong, Tai Chi, and yoga

Note there is some evidence that very high intensity exercise (ie marathon running /endurance sports) temporarily REDUCES immunity and can actually increase the risk of getting sick during this time.

If adequate rest breaks are allowed over the longer term though, they build the body's defences against infection, the key is building in enough recovery time.

So if you're exercising at at very high level and keep getting sick, it may be your body's way of telling you to rest more often… it’s all about balance!! If you’d like to learn more about how exercise boosts our health (plus tips to get moving!), take a look at our boost your activity mini course or Reboot course

SLEEP AND STRESS

• Lack of sleep and high stress levels play a massive part in immunity

• Our body needs around 7-9 hours of sleep/night to function well - research has shown that consistently getting less than 6h/night increases the risk of catching colds and flu’s by up to 400%! Our body’s immune system is most active at night, when our immune cell function peaks. This means if we aren’t getting enough sleep, our immune system simply can’t do it’s job properly..

• Stress directly affects the immune system as well - it triggers the body to release cortisol (stress hormone), which reduces levels of immune white blood cells in your body, and increases inflammation - limiting the bodies ability to fight off infections.

• If you struggle with stress, we teach you how to take control of your stress with simple practical tips and strategies in our stress course or Reboot course

SOCIAL CONNECTIONS:

Interpersonal relationships are a super important part of our overall well-being. They even impact on how well our immune system works!

Studies have found that things like negative behaviour and discussions (especially if focused on conflict, marital disruption, or the stress of caring for sick relatives) can suppress immune function.

There is also some evidence that having meaningful quality relationships can be protective against these immune changes - ie even if we are under stress, if we have close supportive relationships, this can help our immunity.

And interestingly, patients who feel their doctor is empathetic and cares about their wellbeing during a medical appointment, recover faster from colds!.

SUPPLEMENTS

• Supplements are commonly promoted to help immunity, however for many of them the evidence is still not that clear, despite the marketing….

• Many studies show mixed results, and although they may help some people, this makes it hard to make clear recommendations around what and whether to supplement. To make it more confusing, supplements are often only trialled for specific illnesses (such as colds or flus), and there are many different viruses that cause illness!!!

• High dose oral vitamin C may help shorten the duration of colds, if taken within 24 hours of symptoms appearing, but taking it regularly does not prevent them. In contrast, high intake of vitamin C from foods DOES help to prevent illness. 

  The main exception to this is in elderly people, or those under extreme physical stress (ie endurance athletes), where vitamin C supplements do appear to help significantly. It is worth noting that Vitamin C from whole foods has additional benefits (such as the flavonoids they contain), and the amount of vitamin C needed to prevent infections (200mg/day) is very easy to get from food.

• Vitamin D is extremely important as it plays a crucial role in our immune system - deficiency is consistently linked to reduced immune function. We get very little vitamin D from our diet, it's produced when sunlight hits our skin. It is best to get this from sensible sun exposure if possible (as this has other health benefits) , but if you are at higher risk of deficiency (darker skin, housebound, mostly indoors, covered skin), or live in cooler climates, then supplementing at recommended doses over winter is sensible. Many people in the south island of New Zealand are vit D deficient over winter. You can also check levels on a blood test (costs normally apply) 

• Zinc MAY help reduce the severity and duration of viral infections if taken at the start of an illness, and can be worth supplementing in this situation even if you are not deficient. There is no evidence for zinc supplements to prevent infections, unless you are deficient in this.

• The main form of zinc studied for respiratory infections are zinc lozenges, in particular zinc acetate. Studies using 75mg/day of this taken at the onset of symptoms show that it can shorten the duration and reduce severity of colds.

• Zinc can be toxic in high doses though, and should only be taken at high doses for short periods, so ensure you follow instructions on the bottle. High dose zinc can also cause anosmia (loss of smell), and interfere with copper absorption, so should not be taken at doses higher than 30mg/day longterm. Some people may need to have zinc levels checked, due to underlying health issues - check with your GP if you think this might apply

• Elderberry, echinacea, olive leaf extract, reishi mushroom, liquorice root and astralgus are all traditionally used to help immune function and fight off infection. The evidence for these is mixed, with some studies showing they help, and others not finding much benefit. In general they are safe to try provided you follow instructions on the packet and some people may find them helpful in addition to the other measures discussed.

• Sage leaf can be used as a gargle for sore throats, steep 1 tsp chopped sage in 1 cup water for 10 minutes, then strain and drink or use as a gargle

• Thyme leaves are traditionally used as cough syrups and can help with calming coughs and clearing mucous. 1-2 tsp dried thyme leaves and flowers can be steeped in 1 cup hot water and taken 3 times daily. Adding honey can increase the cough suppressant effect.

• Probiotics - the research around probiotics is interesting, as we DO know gut health and our gut microbiome plays a huge part in immunity. Yet probiotics do NOT actually colonise our gut when we take them - they pass straight on through. Despite this, they may provide benefits along the way, although the research on this is still in its early days, and again shows mixed results, making it hard to create clear recommendations

  Large studies of adults do NOT show that taking probiotic supplements regularly help to prevent illness, however studies in preschoolers show they may reduce the risk of viral infections and tummy bugs if taken regularly (the strain studied for this is called lactobacillus rhamnosus GG)

  Probiotics are safe to take for most people if you want to try them, but as always, we usually suggest trying to get them from food if possible - fermented foods are great for gut health, and taste good too!!

  HORMETIC STRESS

  This is a slightly off the wall topic, but worth mentioning

  • Hormetic stress is a controlled exposure to small stressors, with the aim of creating a positive reaction in the body - stimulating immune function, healing, and longevity

  • Things like cold water immersion (ice bathing, winter swims), exercise, and fasting all work as hormetic stresses

  • There is some evidence that they can help to improve immune function - we personally find brief cold water showers and time restricted eating (a type of fasting) work well to keep illnesses at bay

  • Find out more about these in our Take control of your stress and Reboot courses

SO WHAT ARE OUR TOP TIPS TO STAY WELL OVER WINTER?!

• Eat a rainbow of colorful, mostly plant based foods, with adequate iron, selenium, zinc, vitamin c/a/e/b and omega 3 (if you want to learn how to eat a balanced plant focused diet, and how diet can help inflammation, we explore this in our Nutrition and Reboot courses)

• Limit refined carbohydrates, added sugar, and alcohol

• Avoid cigarette smoke exposure and practice good hand and cough hygiene, and follow all recommended public health advice in other areas

• Try to exercise at least 30 min /day, ideally outdoors

• Aim for 7-9 hours of restorative sleep per night (check out our Sleep course or sleep blog post if you struggle with sleep - simple strategies can really help!)

• Reduce stress as much as possible - things like mindfulness, connecting with others, and deep breathing are all great. Find out more in our Stress and Reboot courses.

• Consider a vitamin D supplement if you are at risk of deficiency

• If you are still getting sick often, talk to your GP about getting some blood tests for iron, folate and potentially zinc and vitamin D

• Zinc lozenges and Vit C can potentially help when taken at the start of symptoms, but ensure not to take high doses of zinc for long periods

• You may wish to try herbal supplements such as echinacea, elderberry, olive leaf, or astralgus, but be aware the evidence for these is still not that clear, although they are generally safe to try

• If you have preschool aged children, a probiotic supplement over winter can potentially help reduce the risk of viral infections and tummy BUGS (lactobacillus rhamnosus GG)

• And remember to smile and be kind!! these are powerful at boosting immunity too ❤️

If you'd like to learn more about how to optimise immunity, energy, health, and overall wellbeing, please check out our Reboot your health course and focus modules! 

In these we cover everything you need to know about to how to improve your wellbeing naturally, using evidence based simple strategies. No dodgy detoxes, expensive supplements, or questionable advice - everything we do is backed by cutting edge science, and best of all, it's sustainable for the long haul!!

REFERENCES:

NUTRITION:

Meydani SN, Erickson KL. Nutrients as regulators of immune function: Introduction. FASEB J. Dec 2001;15(14):2555. doi:10.1096/fj.01-0477com 6.

Somerville VS, Braakhuis AJ, Hopkins WG. Effect of flavonoids on upper respiratory tract infections and immune function: a systematic review and meta-analysis. Adv Nutr. May 2016;7(3):488-97. doi:10.3945/an.115.010538 7.

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Sekirov I, Russell SL, Antunes LC, Finlay BB. Gut microbiota in health and disease. Physiol Rev. Jul 2010;90(3):859-904. doi:10.1152/physrev.00045.2009 3.

Turner JR. Intestinal mucosal barrier function in health and disease. Nat Rev Immunol. Nov 2009;9(11):799-809. doi:10.1038/nri2653

EXERCISE:

Walsh NP, Gleeson M, Shephard RJ, et al. Position statement. Part one: Immune function and exercise. Exerc Immunol Rev. 2011;17:6-63. 4.

Nieman DC. Exercise, upper respiratory tract infection, and the immune system. Med Sci Sports Exerc. Feb 1994;26(2):128-39. 5.

Siedlik JA, Benedict SH, Landes EJ, Weir JP, Vardiman JP, Gallagher PM. Acute bouts of exercise induce a suppressive effect on lymphocyte proliferation in human subjects: A meta-analysis. Brain Behav Immun. Aug 2016;56:343-51. doi:10.1016/j.bbi.2016.04.008 6. Walsh NP,

Oliver SJ. Exercise, immune function and respiratory infection: An update on the influence of training and environmental stress. Immunol Cell Biol. Feb 2016;94(2):132-9. doi:10.1038/icb.2015.99

Wang CW, Ng SM, Ho RT, Ziea ET, Wong VC, Chan CL. The effect of qigong exercise on immunity and infections: a systematic review of controlled trials. Am J Chin Med. 2012;40(6):1143-56. doi:10.1142/s0192415x1250084x 15.

Ho RT, Wang CW, Ng SM, et al. The effect of t'ai chi exercise on immunity and infections: a systematic review of controlled trials. J Altern Complement Med. May 2013;19(5):389-96. doi:10.1089/acm.2011.0593 16.

Kulkarni DD, Bera TK. Yogic exercises and health--a psycho-neuro immunological approach. Indian J Physiol Pharmacol. Jan-Mar 2009;53(1):3-15. 17.

Falkenberg RI, Eising C, Peters ML. Yoga and immune system functioning: a systematic review of randomized controlled trials. J Behav Med. Aug 2018;41(4):467-482. doi:10.1007/s10865-018-9914-y

SLEEP AND STRESS:

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Ganz FD. Sleep and immune function. Crit Care Nurse. 2012;32(2):e19-e25.

Nakata A. Psychosocial job stress and immunity: a systematic review. Methods Mol Biol. 2012;934:39-75. doi:10.1007/978-1-62703-071-7_3

SOCIAL CONNECTION:

Kiecolt-Glaser JK, Malarkey WB, Chee M, et al. Negative behavior during marital conflict is associated with immunological down-regulation. Psychosom Med. Sep-Oct 1993;55(5):395-409.

Kennedy S, Kiecolt-Glaser JK, Glaser R. Immunological consequences of acute and chronic stressors: mediating role of interpersonal relationships. Br J Med Psychol. Mar 1988;61 ( Pt 1):77-85.

Uchino BN, Cacioppo JT, Kiecolt-Glaser JK. The relationship between social support and physiological processes: a review with emphasis on underlying mechanisms and implications for health. Psychol Bull. May 1996;119(3):488-531.

Rakel DP, Hoeft TJ, Barrett BP, Chewning BA, Craig BM, Niu M. Practitioner empathy and the duration of the common cold. Fam Med. Jul-Aug 2009;41(7):494-501.

SUPPLEMENTS:

Bucher A, White N. Vitamin c in the prevention and treatment of the common cold. Am J Lifestyle Med. May-Jun 2016;10(3):181-183. doi:10.1177/1559827616629092

Ran L, Zhao W, Wang J, et al. Extra dose of vitamin c based on a daily supplementation shortens the common cold: a meta-analysis of 9 randomized controlled trials. Biomed Res Int. 2018;2018:1837634. doi:10.1155/2018/1837634

Therapeutic Research Center (TRC). Zinc. https://naturalmedicines.therapeuticresearch.com/databases/food,-herbssupplements/professional.aspx?productid=982

Malesker MA, Callahan-Lyon P, Ireland B, Irwin RS. Pharmacologic and nonpharmacologic treatment for acute cough associated with the common cold: chest expert panel report. Chest. Nov 2017;152(5):1021-1037. doi:10.1016/j.chest.2017.08.009

Oduwole O, Meremikwu MM, Oyo-Ita A, Udoh EE. Honey for acute cough in children. Cochrane Database Syst Rev. 2012;3:Cd007094. doi:10.1002/14651858.CD007094.pub3

Johnson RL, Foster S, National Geographic Society. National Geographic Guide to Medicinal Herbs: The World's Most Effective Healing Plants. National Geographic; 2012.

Therapeutic Research Center (TRC). Astragalus https://naturalmedicines.therapeuticresearch.com/databases/food,-herbssupplements/professional.aspx?productid=963

Mousa HA. Prevention and Treatment of Influenza, Influenza-Like Illness, and Common Cold by Herbal, Complementary, and Natural Therapies. J Evid Based Complementary Altern Med. Jan 2017;22(1):166-174. doi:10.1177/2156587216641831

Ross SM. Echinacea purpurea: a proprietary extract of echinacea purpurea is shown to be safe and effective in the prevention of the common cold. Holist Nurs Pract. Jan-Feb 2016;30(1):54-7. doi:10.1097/hnp.0000000000000130

Hao Q, Dong BR, Wu T. Probiotics for preventing acute upper respiratory tract infections. Cochrane Database Syst Rev. Feb 3 2015;(2):Cd006895. doi:10.1002/14651858.CD006895.pub3