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ABCs of Immuno-nutrition – Potential Strategies to Reduce Infection

A, B, C, D, E, F – Getting to know why and how vitamins aid immunity is worthwhile. Many know that we should get vitamins A, B, C, and so on. But why? How about probiotics? Polyphenols? Emerging research suggests these that are just some nutritional methods might improve immunity. Here is a quick rundown of the ABCs!

ABC Vitamins, Foods and More

Sources of vitamin A include cheese, eggs, and oily fish; to name but a few. Also known as ‘retinol’, it can help improve your sight and skin; as well as immunity. Your body can change a substance called beta-carotene into vitamin A. If you like colourful fruit and vegetables - spinach, carrots, sweet potatoes, mango, apricots – you’re in luck. These are rich in beta-carotene. 

There are many types of beneficial B-vitamins. With immunity in mind, we’ll focus on B6 and B12. Vitamin B6 helps form haemoglobin and allows the body to use and store the energy we eat from carbohydrate and protein foods. Sources include pork, poultry, fish, milk, and vegetables. Vitamin B-12 has similar functions - forming red blood cells, energy release, and maintaining a healthy nervous system. Milk, cheese, salmon, cod, and meat are good sources of this.

Found in plenty of fruit and vegetables, sources of vitamin C include oranges or orange juice, peppers, strawberries, blackcurrants, broccoli, and sprouts. Functions include wound healing and protecting cells, blood vessels, bones, and cartilage (NHS). Finally, vitamin E strengthens our immune system and is found in abundance in nuts and seeds, plant oils (such as olive oil) and wheatgerm seen in cereals.


Broccoli YSN

ABC Supplements and Foods Galore

Adequate carbohydrate (CHO) and protein intake is vital for maintaining immune function. A high-carbohydrate diet with carbohydrate beverage consumption of 30-60 g/kg/hour during intense exercise is associated with lower levels of stress hormones (e.g. cortisol) and inflammatory cytokines (Halson et al., 2004). Post-exercise protein may reduce the negative effects of immune depression, also (Gleeson, 2016).

Vitamin D3 supplementation (1000 IU orally) could reduce the incidence of the common cold and the use of antibiotics (Sa Del Fiol et al., 2015). As our main source of this is sunlight, it might be worth taking a supplement during the winter. Athletes with low levels have shown increased URTI risks and longer-lasting symptoms.

Plant polyphenols, including flavonoids, may boost immune function. Daily supplementation of 1000 mg quercetin (found in capers, lovage leaves, and onions) reduced URTI symptoms in cyclists for two weeks after three days of exhaustive exercise (Nieman et al., 2007). Foods such as apples, citrus fruits, grapes, and green tea contain naturally-occurring polyphenols. High fruit intake has been associated with fewer respiratory illnesses.

Probiotics, commonly known as the ‘gut bacteria’, have shown promise in reducing URTI risk and incidence, as well as gastrointestinal discomfort. Lactobacillus and Bifidobacterium are those for which research exists (Gleeson, 2016).



To support immune-nutrition in athletes, Gleeson (2016) summarises the recommendations as:

  • Energy intake should match energy needs - 50% coming from carbohydrate
  • Ingest 30–60 g of carbohydrate/hour during vigorous training sessions
  • Eat enough protein (1.2–1.6 g/kg/day), with 0.3 g/kg post-exercise
  • Ingest adequate amounts of micronutrients – plenty of fruit and veg, or a multivitamin supplement where necessary

Assess the need, risk, and consequence, and consider taking the following supplements daily:

  • Vitamin D3 (1000 IU), particularly in the winter and when sunlight exposure is limited
  • Probiotics containing at least 10 billion live bacteria
  • Plant polyphenols supplements



Halson S. L, et al. (2004). Effect of carbohydrate supplementation on performance and carbohydrate oxidation following intensified cycling training. J Appl Physiol; 97: 1245–1253.

Gleeson, M., (2016). Immunological aspects of sport nutrition. Immunology and Cell Biology (2016) 94, 117–123. 2016 Australasian Society for Immunology Inc.

Sa Del Fiol, F., et al. (2015). Vitamin D and respiratory infections. J Infect Dev Ctries; 9: 355–361.

Nieman D. C, et al. (2007). Quercetin reduces illness but not immune perturbations after intensive exercise. Med Sci Sports Exerc 2007; 39: 1561–1569


Author credit: Liam Oliver, Performance Nutritionist

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