There is a strong drive worldwide to use the flu Vaccination each year to prevent colds and flu. However with the current effectiveness ranges from 10% – 67%, the flu shot still falls short of providing an absolute assurance against falling ill this season [1,2]. Whether you decide to get the shot or not is up to you, and as with any medication there are always side effects, so it is important to make an educated decision.
Our assertion is always that a healthy lifestyle that supports your immune system is the best way to prevent the flu. In this article we discuss evidence to support the benefits of eating well, living a healthy lifestyle, and nutrition supplements for the prevention of flu.
When it comes to a healthy lifestyle, adequate sleep is an often overlooked but vitally important factor. Sleep is our bodies chance to rebuild, replenish and detoxify. Inadequate sleep duration or inadequate deep sleep, can lead to changes in your immune profile that is not always rectified by sleep recovery. 
Another factor to consider, in all aspects of health, is the level of stress you are experiencing. Chronic stress leads to a suppressed immune system, thus leaving you exposed to the flu virus. Take note of all of the major stresses in your life, and if they are unavoidable, then make time for things that will decrease your stress (i.e. balance the bad with some good).
The third lifestyle factor is exercise. Exercise can either help with or work against your immune system. Intense exercise can suppress your immune system, whilst moderate exercise can improve it. It is important to find a moderate intensity form of exercise that you enjoy doing and commit to a regular schedule.
Food choices have a powerful effect on the health of your immune system. Some of the main dietary influences include:
- Sugar. Did you know that a high dose of simple sugar (in all forms) can suppress your immune function for up to 5 hours after ingestion? Imagine how much of an effect chronic high consumption of sugar would have!
- Protein. Our immune system relies on a large network of proteins in various forms. These proteins are all made from amino acids which we obtain form our diet. It is important that we get enough healthy protein-rich foods on a daily basis to support immune system functioning. Animal proteins are the richest supply of these amino acids, but there are plenty of vegetarian sources available to us as well.
- Zinc. Chronic zinc deficiency can suppress the immune system. The best dietary sources of zinc are nuts and seeds, grass fed meats and oysters. There are zinc-fortified foods on the market, but these do not necessarily provide immune benefit. Getting zinc from your food or a high quality nutritional supplement is best.
- Fruits and vegetables. Whilst incredibly obvious, these need special mention. These are nature’s richest sources of immune-boosting nutrients such as vitamins C, E, beta-carotene and other phytonutrients. Vitamin C rich foods are particularly important for the immune system, and these include bell peppers, citrus fruits and broccoli. Beta-carotene rich foods include carrots, squash, pumpkins and green leafy vegetables such as spinach.
Whilst a healthy diet and lifestyle can provide the best immune support, there are some nutritional supplements to provide further preventative support through flu season. It is important to consult your healthcare practitioner for nutrient interactions before taking supplements if you are on any prescription medications.
- Probiotics are of course, top of the list. There is solid and significant evidence showing that probiotics support and modulate the immune system. [6,7,8] There are a number of probiotic supplements on the market, but make sure that you get a good quality one with live bacteria for the best support. You can also top up your probiotic intake with fermented foods such as yogurt, kefir and sauerkraut.
- Vitamin D3 will provide benefit to many people. Our immune cells have vitamin D receptors, which suggests that vitamin D3 may play an important role in the immune response to infections. There is also evidence of a link between vitamin D status and influenza risk, with supplementation of vitamin D3 then leading to recovery from influenza. 
- Garlic is another interesting supplement when it comes to colds and flu prevention. Whilst you can ingest garlic in your diet, the recommended intake is 2 – 3 cloves per day (which may lead to tricky conversations with your spouse). You can also get aged garlic in capsule form which might be a bit easier to tolerate. People who take aged garlic capsules (2.56 grams/day) have shown to have reduced duration, severity and incidence of colds and flu. 
- Vitamin C is one nutrient which we are all well aware of. It is probably the most known vitamin when it comes to colds and flu prevention. Vitamin C works to prevent colds and flu, as well as to help you bounce back quickly when you do pick up a cold. The quality of your Vitamin C supplement is vitally important. Commonly, vitamin C supplements contain Ascorbic Acid, which is fine to supplement with, but can irritate the stomach. For improved absorption and less stomach irritation you may look at an Ester-C form. This can be taken in higher dosages. For the best absorption, arguably the Lypospheric form is the best as it delivers high dose vitamin C directly into your bloodstream.
Of course there are many other nutrients well-known to boost your immune system, thus preventing colds and flu. However if you have the above in place you will be well-covered for the flu season of 2018.
- Interim Adjusted Estimates of Seasonal Influenza Vaccine Effectiveness – United States February 2013. Morbidity and Mortality Weekly Report. 2013
- Interim Estimates of 2017-18 Seasonal Influenza Vaccine Effectiveness – United States, February 2018. Morbidity and Mortality Weekly Report. 2018
- Ruiz FS, Andersen ML, Martins RC, Zager A, Lopes JD, Tufik S. Immune alterations after selective rapid eye movement or total sleep deprivation in healthy male volunteers. Innate Immun. 2012;18 (1):44-54.
- Segerstrom SC, Miller GE. Psychological Stress and the Human Immune System: A Meta-Analytic Study of 30 Years of Inquiry. Psychol Bull. 2004;130(4):601-630. doi: 10.1037/0033-2909.130.4.601
- Sanchez A, Reeser JL, Lau HS et al. Role of sugars in human neutrophilic phagocytosis. Am J Clin Nutr. 1973;26 (11):1180-1184.
- Rizzello V, Bonaccorsi I, Dongarrà ML, Fink LN, Ferlazzo G. Role of Natural Killer and Dendritic Cell Crosstalk in Immunomodulation by Commensal Bacteria Probiotics. Journal of Biomedicine and Biotechnology. 2011;2011 1-10.
- Hemarajata P, Versalovic J. Effects of probiotics on gut microbiota: mechanisms of intestinal immunomodulation and neuromodulation. Therapeutic Advances in Gastroenterology. 2012;6 (1):39-51.
- Jeppsson B, Mangell P, Thorlacius H. Use of Probiotics as Prophylaxis for Postoperative Infections. Nutrients. 2011;3 (12):604-612.
- Sundaram ME, Coleman LA. Vitamin D and Influenza. Advances in Nutrition: An International Review Journal. 2012;3 (4):517-525.
- Nantz MP, Rowe CA, Muller CE, Creasy RA, Stanilka JM, Percival SS. Supplementation with aged garlic extract improves both NK and gammadelta-T cell function and reduces the severity of cold and flu symptoms: a randomized, double-blind, placebo-controlled nutrition intervention. Clin Nutr. 2012;31 (3):337-344.