Immunonutrition for Athletes

September 5, 2024 Rhys Hanscombe

If you’re not a healthy athlete, your chances of maintaining a successful career are slim. At the root of everything you do should be your health, not performance.

Athletes who are sick cannot train. When athletes don’t train, they miss out on the margins for improvement that is the difference between winning and losing.

I’ve talked about “health first, performance second” before, but this article will focus on the nutritional side. You’ll learn how you can fuel your body to defend against illness so you can be the best athlete you can be.

All information sources are listed at the end of this article, with numbers throughout the text to indicate the source.

Why prioritise Health over Performance?

It should be obvious that you need to be healthy to compete at the highest level of your sport. However, many athletes neglect their physical and mental health to optimise performance.

A study on elite swimmers shows that medal winners at the Olympics experience fewer and shorter upper respiratory infections (URI) than less successful athletes (2).

The pattern shows that the best of the best are also the healthiest.

This prompts a callback to Fergus Connolly’s book, ‘59 Lessons’ where he writes “99% healthy is not 100% injured”. This means that, even if you are suffering from illness, there could still be room to improve on areas. But wouldn’t we all like to avoid illness where possible?!

It can be tempting to train at the beginning or end of a cold, for example. However, athletes need to wait until all symptoms have cleared before returning to exercise after infection to prevent prolonging unnecessary performance dips.

Sickness is part of life. There is no avoiding it, but we can treat our body with the respect it deserves to decrease the risks.

How Nutrition impacts Immunity

Your nutrition affects both your risk of illness and your body’s response to it.

Everything you consume can be put into one of two categories - micronutrients and macronutrients. Both play a big role in several immune processes:

Macronutrients

Macronutrients are involved in immune cell metabolism and protein synthesis.

These include:

Carbohydrates (bread, rice, pasta, etc.)
Protein (chicken, seafood, steak, etc.)
Fats (nuts, eggs, etc.)

Carbohydrates and fats have unfortunately been marketed as the devil in recent years, but all three food groups play a pivotal role in fueling human performance, and preventing illness.

The immune system’s ability to clear viruses, bacteria and other pathogens, termed ‘resistance’, is dependent upon an adequate supply of energy from important fuel sources; including, glucose (sources from carbohydrates), amino acids (protein) and fatty acids (fat).

Micronutrients

Micronutrients are involved in antioxidant defense and play important roles in nucleotide and nucleic acid synthesis.

These include:

Iron, zinc and magnesium - nucleotide and nucleic acid synthesis (supporting your metabolism).

Vitamins C and E - limit tissue damage.

Vitamin D - directly influences immune cell functions by regulating gene expression.

Prebiotics and probiotics - influence immunity indirectly by modifying the gut microbiota.

With all the nutritional facts in place, it is evident that low energy availability is a risk factor for infection in athletes (1). Fuelling appropriately is a large piece of the puzzle that is athlete immunity.

So, caloric-restrictive diets aren’t recommended for athletes who want to perform at their best.

Factors affecting low Immunity in Athletes

There is a lot that goes into your body’s ability to withstand illness. Factors that impact your immune system and put you at higher risk of illness include:

Wintertime - specifically from November to February when temperatures drop and the sun (the biggest source of Vitamin D) hides behind gloomy clouds.

High levels of stress, anxiety, and/ or depression - chronic stress (defined as stress that lasts from days to months) can disrupt the cortisol circadian rhythm and increase glucocorticoid resistance, with harmful effects on immunity, inflammation and infection resistance.

Long-term low energy availability - The key feature of Kwashiorkor, widely recognised to suppress immunity and increase infection incidence, is low protein intake. It is important to note that short-term energy restriction shows only shows subtle changes in immunity (5) and no increase in the immune-modulating hormone, cortisol.

Poor sleep - typically, consistently getting less than 6 hours sleep per night has serious consequences for your day-to-day functioning, let alone your immune system (3).

The facts show that immunity is more than just keeping your distance from people who are sick. Poor mental health, poor sleep, and poor nutrition all play vital roles in maintaining your health.

Nutritional Supplements to improve immunity

It is important to recognise that marketing in the health industry can sometimes be misleading. So-called “Immunity-focused supplements” (11) like glutamine, carbohydrate drinks and gels, echinacea, and caffeine all evident limited, if any, change to immune function.

Tolerogenic supplementation

Zinc Lozenges

Zinc lozenges are an easy and effective way of treating the common cold.

A recent meta-analysis showed that zinc lozenges (75 mg/ day of elemental zinc) reduced URI duration by 3 days when taken 24 hours after the onset of symptoms and for the duration of the illness (4).

Probiotics and Prebiotics

Probiotics are live microorganisms that show health benefits by modulating gut-dwelling bacteria and supporting immunity (7). They can improve immune resistance by reinforcing the intestinal barrier and competing with - and inhibiting the growth of - pathogens for both attachment to the gut epithelium and available nutrients while exerting important anti-inflammatory tolerogenic effects that maintain homeostasis (8).

A study showed that four weeks of supplementation with a multi-species probiotic formulation (Lactobacillus, Bifidobacterium and Streptococcus) reduced markers of gut permeability and symptoms of gastrointestinal discomfort during exercise-induced heat stress (9).

Vitamin D

Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and for many other biological effects. It plays a critical role in calcium and bone homeostasis, let alone in enhancing immunity.

Vitamin D production as a result of sunlight UV radiation penetrating the skin typically provides 80–100% of the body’s Vitamin D requirements.

The rest comes from food sources like:

Oily fish
Egg yolks

The “perfect” measurement of Vitamin D to avoid becoming deficient or overly-sufficient is yet to be pinpointed, but it is typically recommended that ≥50 nmol/L or ≥20 ng/mL is adequate.

This further supports the importance of combatting low sunlight exposure during the wintertime illness with Vitamin D supplementation, with 1000 IU per day.

Vitamin C

Vitamin C is a water-soluble vitamin, meaning that your body doesn't store it. Unlike Vitamin D where you naturally get it through UV radiation, Vitamin C must be consumed through your diet.

Some good sources of Vitamin C are:

Citrus fruits
Broccoli
Tomatoes

You need vitamin C for the growth and repair of tissues in all parts of your body. It helps the body make collagen, an important protein used to make skin, cartilage, tendons, ligaments, and blood vessels. Vitamin C is needed for healing wounds, and for repairing and maintaining bones and teeth. It also helps the body absorb iron from nonheme sources.

The antioxidant levels of vitamin C and the anti-inflammatory effects of Vitamin D may improve tolerance, mitigating excessive tissue damage during infection

Reference nutrient intake for adults is 40 mg/day (UK).

Vitamin C is found in high concentration in leucocytes but the level falls dramatically during a common cold, when oxidative stress increases. As such, Vitamin C supplementation could improve tolerance by mitigating against excessive tissue damage during infection.

Daily doses of more than 200 mg of Vitamin C have prophylactic and therapeutic effects for the common cold (10) Vitamin C supplementation (0.25–1.0 g/day) to reduce URI symptoms in athletes.

Recap

Prioritising your health is the most important thing you can do for long-term success in sports and life.

Proper nutrition and effective supplements, such as zinc lozenges and Vitamin D, can support immune function. By adopting a holistic approach to wellness, athletes can optimise their training and performance, ensuring they're at their best when it matters most.

Hanscombe Performance