We've all experienced it. You dress up for a 3hr Sunday ride, clip your shoes in, roll the pedals and just don't have any power in your legs.
Your mood drops hand in hand with fatigue, as you realize a debilitating cold is on its way. Worse, it could be a pre-cursor to full-blown flu. But what can you do to boost your immune system and get back on track or, better still, prevent these foreigners invading your body? Good question...
Now, before you think you're at less risk from infection than sedentary people, you may be wrong. Increasing evidence reveals that in contrast to moderate physical activity, which appears to have a beneficial effect on the immune system, prolonged and strenuous exercise can compromise immune function. It should also be noted that not overtraining, adequate sleep and maintaining a lifestyle that's not too stressful are also critical to a robust immune system.
But the main area of concern today is nutrition. We'll show you how to give your body a boost and debunk the myths, citing what's real and what's not, from the food you need to whether Echinacea really will stave off colds.
Nutritional deficiencies
Fact: an efficient nutrient intake will help maintain an effective immune system. However, we'll come onto poor diets in a moment. First up, know that this area also covers athletes who consume insufficient amounts of calories and/or protein. This causes a downturn in most aspects of immune function and strongly increases the risk of various types of infections that will lead to colds and sore throats. A test-tube-sized amount of science will explain why...
T-lymphocytes (white blood cells) provide protective immunity, and are vital in defence against bacterial viruses and infections. Triathletes consuming inadequate quantities of protein or calories to cover training demands will reduce the number and function of circulating T-lymphocytes, consequently upping the chance of infection.
That said, most of you will eat enough calories, from a mixture of fat, carbohydrates and protein, although the balance may not be right for peak performance in many athletes. As a general rule, you should aim for 15% protein, 25% fat and 5-10g of carbs per kg of body mass, although this will differ according to the individual and their training needs.
In fact, those most at risk from inadequate protein consumption include vegans and vegetarians who exclude dairy products, though athletes who eat an unbalanced diet can also be affected. For example, individuals who take in too much carbohydrate displacing the protein in the diet and athletes on energy-restricted diets. Regarding that latter point, there?s evidence that losing weight rapidly (more than 1kg per week) will adversely affect the immune system.
Fatty benefits
Little is known about fat and its influence on the immune system, but it's generally accepted that fatty acids from fish oils dampen inflammatory profiles, which can prove useful in countering immune suppression during mental and physical stress.
Triathletes and the public at large should have small amounts of monounsaturated fats in their diet, sources including avocados, olive oil and rapeseed oil. Also, get enough polyunsaturated fats, which include the well-known omega 3 fats, a particular protective type of fat for our hearts and joints.
The best sources of omega 3's are oily fish; mackerel, kippers, pilchards, herring, salmon and trout are great, though smaller amounts can be obtained from plant foods: rapeseed, walnuts, soya, flax and linseed. Adults are advised to eat two portions of fish per week, one of which should be oily.
Carbohydrate intake
Many studies of endurance athletes suggest that carbohydrate ingestion during exercise 30-60g per hour has benefits for immunity, including reduced levels of stress hormones (which can suppress the immune system at high levels), such as cortisol and adrenaline, and fewer negative effects on blood immune count.
Also, exercising with insufficient carbohydrate as fuel has been shown to have a detrimental effect on the immune system. In practice, look at the carbohydrate content on the labels of your sports bar or gel and take in as much as you need to meet your needs. For instance, gels vary between 20-30g so, on average, you'll need to ingest one for every 20-30mins of exercise.
Similarly, dehydration increases stress hormone levels and decreases saliva flow, which is important in the fight against infection because it secretes antibodies that fight infections. Research shows that regular fluid intake maintains secretion of anti-microbe's properties in saliva during prolonged exercise thus helping to fight infection.
Iron and zinc
Iron and zinc are the most common mineral deficiencies seen in triathletes, which is far from ideal as both have a role in a strong immune system.
Iron has numerous functions, but its main requirement in the body concerns the haem part of haemoglobin, needed to carry oxygen around the body. Sadly, low iron levels are common, particularly prevalent in female endurance athletes due to loss of blood during menstruation. Symptoms of deficiency are tiredness and fatigue, breathlessness during exertion, pale skin and poor resistance to infections.
But beware: don't just pop out to your local health shop and purchase iron supplements. Excessive supplementation when not required is toxic and can have serious side-effects. Conversely, unnecessary supplementation can actually increase the chance of infection rather than reduce it.
If you suspect that you have low iron levels, ask your doctor to measure your iron stores (not just haemoglobin levels) and follow their advice about supplementation. You should also alter your diet to avoid low levels in the future.
Zinc is required to develop and activate some immune cells, and even a moderate zinc deficiency can adversely affect the immune system, which is a greater threat to endurance athletes because we lose this mineral in sweat, as well as urine. Athletes who train daily should therefore include good regular dietary sources of zinc in their diet.
Is almost become folklore that zinc supplementation will improve conditions such as the common cold. However, its effects on the severity or duration of symptoms remains debatable and additional research is required before zinc supplements could be recommended to treat colds.
That said, if you're convinced of its cold-defying benefits, take it within 24hrs of the symptoms showing themselves. Note: like iron, zinc is toxic at high levels, and can cause severe nausea and vomiting, cramps, hair loss, interference with the absorption of copper and iron, and can actually reduce immunity. So mega dosing is not recommended.
Antioxidants
Under extreme stress – intense exercise, hot/frozen environments – our bodies release free radicals, which have the potential to impair immunity. Our defences against these out-of-control radicals are both the antioxidants manufactured in our bodies and the antioxidants in our diet. (Antioxidant is a classification of several organic substances, including vitamins C and E, vitamin A, selenium and a group known as the carotenoids, which includes beat caretone.)
This is where you'll reap the rewards of being a highly tuned athlete. In theory, you?d think increasing antioxidant intake would be a good strategy for athletes under daily stressful training. But it may not be required, as the antioxidant defence system becomes more efficient in athletes who train regularly.
Like much research about supplementation, a recent study proved inconclusive. Of 41 subjects, who used either vitamin C or a combination of C and E, 20 studies showed antioxidant supplementation reduced exercise production of free radicals, which may be beneficial for athletes; three showed they increased free radical production, so may be more harmful; 18 showed no benefit. A limitation of most research to date is that most have investigated only vitamins E and C. Eating plenty of fruit and vegetables will increase antioxidant levels in your diet.
The International Olympic Committee (IOC) and American College of Medicine in Sport (ACMS) also support the theory that antioxidants should come from food sources rather than supplements. In fact, the only specific recommendation at an international sporting level comes from the Australian Institute of Sport (AIS).
They advise that athletes should have a short-term dose of 500mg of vitamin C and two weeks of 500iu vitamin E during a sudden increase in training, or after a shift to a more stressful environment (heat or altitude). Even in this case they state that evidence is limited and benefits may be short-lived.
Glutamine
Glutamine, an amino acid, is an important fuel for cells of the immune system. Many studies agree that glutamine concentration decreases following prolonged strenuous exercise, the situation being compounded by serious athletes who are likely to keep training during this time when the immune system is already in a weakened state.
However, a plethora of studies show no benefits and question whether low glutamine concentration is actually the cause of impaired post-exercise immunity. Other research has shown that the amount of stored carbohydrate in the body during recovery was increased following consumption of a glutamine and carbohydrate containing drink. Hence, glutamine is added to some commercial recovery drinks. As you can see, the jury remains out.
Echinacea
Who hasn't a friend who'll purport the cold-clearing benefits of Echinacea? Not many, we imagine. Echinacea species are flowering herbs used to treat and prevent upper respiratory infections (colds, sore throats and so on). And several, but not all, clinical trials of Echinacea preparations have reported positive effects in the battle against respiratory infection.
A recent study examined the effect of a daily oral treatment of pressed juice of Echinacea purpurea on 42 triathletes before and after a sprint triathlon. They took the herb for 28 days. The most important finding was that during the 28-day pre-treatment period, none of the athletes in the Echinacea group fell ill compared with seven subjects in other groups.
The World Health Organisation (WHO) has also researched this plant, though didn't produce evidence that it fights colds.
Where studies into Echinacea are let down is inconsistency; different studies look at different species of Echinacea, different parts of the plant and different doses. And inconsistency means doubts remain.
Summary
From research and general common sense, it's clear that you can take nutritional steps to help reduce the risk of many illnesses, though good-quality sleep and managing stress levels are also important.
It's not rocket science – simply get the basics right by eating a well-balanced diet sufficient to meet your energy requirements. This should include adequate protein, iron, zinc and a diet high in antioxidants from food sources. Finally, ensure you're hydrated, as reduced water levels will leave you vulnerable to infection.
What helps you keep colds at bay? Let us know in the comments below!