With winter well and truly here it seems people are getting struck down with the flu left right and centre. The best way to avoid getting sick this winter is by supporting your immune system and there are many ways this can be done through a healthy diet/lifestyle.
Not only is sugar bad for your waistline, but it has also been shown to negatively affect immunity. One study in the American Journal of Clinical Nutrition found that oral 100-g portions of carbohydrate from glucose, fructose, sucrose, honey, or orange juice all significantly decreased the capacity of neutrophils to engulf bacteria meaning the ability to fight infection was reduced. Starch ingestion did not have this effect. The decrease in phagocytic index was rapid following the ingestion of simple carbohydrates (1). Therefore it is important to be mindful of your sugar intake in order to maximise your immunity.
The nutritional importance of Zinc has been known for a long time however recently it has been discovered that Zinc could play a central role in the immune system, with zinc-deficient persons experiencing increased susceptibility to a variety of pathogens (2). One study in particular found that zinc administered within 24 hours of onset of symptoms reduces the duration of common cold symptoms in healthy people (3). So dosing up on Zinc when you feel a cold coming on could be a good way to reduce your downtime!
The old famous immune boosting vitamin! Vitamin C functions as an antioxidant to neutralise free radicals as well as supporting a healthy immune system. Studies have suggested that a Vitamin C deficiency can result in reduced resistance against certain pathogens whilst a higher supply enhances several immune system parameters (4). It should be noted however that these results have been found when Vitamin C intake was consistently adequate- not just dosing up when you feel a cold coming on (5). So in the case of Vitamin C- consistency is key!
Get enough micronutrients
Many people nowadays are just not getting enough micronutrients. This is usually from a diet high in processed food and not enough vegetables. There is some evidence that suggests that deficiencies in certain micronutrients (such as zinc, selenium and iron) can alter immune response in animals. Although the effect on human immune response is yet to be assessed the research at this stage is promising and there is no harm in ensuring that you get enough micronutrients!! This is where ensuring you are getting at least 6 servings of vegetables per day and even supplementing with a good quality greens powder can be awesome.
Vitamin D is an important factor in immune status. Some studies have shown that there is a link between vitamin D status and the risk of developing influenza. People who have low vitamin D levels may have an increased risk of developing influenza (6). The best way to get Vitamin D is from sun exposure so even sitting out in the sun for 15 minutes during your lunch break can work wonders for your health and everyday performance. However in winter this can be difficult so if you think that you may not be getting enough, it is definitely important to consider a supplement.
1. Sanchez A, Reeser JL, Lau HS, Yahiku PY, Willard RE, McMillan PJ, et al. Role of sugars in human neutrophilic phagocytosis. The American Journal of Clinical Nutrition. 1973;26(11):1180-4.
2. Shankar AH, Prasad AS. Zinc and immune function: the biological basis of altered resistance to infection. The American Journal of Clinical Nutrition. 1998;68(2):447S-63S.
3. Singh M, Das RR. Zinc for the common cold. Cochrane Database Syst Rev. 2013(6):CD001364.
4. Strohle A, Hahn A. [Vitamin C and immune function]. Med Monatsschr Pharm. 2009;32(2):49-54; quiz 5-6.
5. Wintergerst ES, Maggini S, Hornig DH. Immune-enhancing role of vitamin C and zinc and effect on clinical conditions. Ann Nutr Metab. 2006;50(2):85-94.
6. Laaksi I, Ruohola JP, Tuohimaa P, Auvinen A, Haataja R, Pihlajamaki H, et al. An association of serum vitamin D concentrations < 40 nmol/L with acute respiratory tract infection in young Finnish men. Am J Clin Nutr. 2007;86(3):714-7.