Blog Archive

Thursday, 1 December 2011

Nutrition and Immunity

It is that time of year again where people are more likely to catch colds and infections therefore, I thought this post would be timely. Getting an upper respiratory tract infection (URTI - mainly known as the common cold) can be detrimental to athletes as it impairs training time, volume and intensity. For team sports, this is a crucial time of year as the season doesn't stop over the winter months. The information regarding nutrition for immune support can be very confusing. Supermarkets and other stores tend to promote certain supplements during this time of year such as Vitamin C, Echinacea, Zinc and various other 'Mickey Mouse' supplements. I have also read quite a few blogs from crank joker nutritionists (I have written about these cowboys and their incompetence here) recommending that you waste your hard earned cash on junk 'immunity stacks' that include up to but not limited to 5 products that will set you back £50! Yes that's right £50! Do you know how many anti-bacterial hand gels you can buy with that sort of money?!

My motivation for writing this blog is to firstly, dispel some of the myths surrounding nutrition and immunity, secondly, give you some sound evidence-based advice that is realistic, practical and hopefully cheap, and finally ensure you have an illness-free winter. The goal of this post is not to write about the mechanisms of the immune system as it is extremely complex and I don't want to send you to sleep! But I will give you some practical tips to help reduce the incidence and possibly the likelihood of getting ill. Endurance athletes who engage in repeated bouts of exhaustive exercise are more susceptible of getting ill however, there are nutrition interventions summarised here that can help.

  • Use antibacterial hand gel often and wash your hands properly

Infectious bacteria can survive on door knobs and other surfaces for longer than you think. Here's an example. Person 1 sneezes on their hand, wipes their hand on their trousers then opens a public door. There may be some bacteria remaining on their hands which has transferred onto the door knob. Person 2 opens the door then itches their nose. Bacteria has then been passed on to Person 2's nose. Similarly when shaking hands, then rubbing your face has the same effect. So by using an antibacterial hand gel after being in contact with public places can help kill some of the bacteria. The worse places are usually public places, crowded areas and being in contact with sick people. Similarly, washing your hands thoroughly has the same effect but is obviously less practical.

  • Make sure you get enough sleep.

There is conflicting evidence regarding sleep and immunity, but from working with elite athletes and my own personal experience, sleep deprivation will suppress the immune system. The evidence indicates that acute bouts of sleep deprivation (i.e. 3 consecutive days) will not increase the incidence of getting an infection but little is known regarding longer term sleep deprivation. I have worked with some athletes who repeatedly get ill from just 2-3 consecutive days of sleep deprivation whereas others cope without major problems. I would recommend that athletes undergoing heavy training need sufficient sleep during that period. Sufficient could be 7 hours for some people but 9 hours for others so know your body. Most of us know when we are sleep deprived. Listen to your body.

  • Commercially Available Probiotics May Help

There is emerging evidence that probiotics may help protect immunity in humans. There has been some research conducted in athletes which has demonstrated promising results but as always, more data is needed. The thing with probiotics is that the effect is strain specific. In other words, not all probiotics have the same effect. This study found that probiotic supplementation reduced the number of episodes, the duration, and severity of infection of 11 weeks supplementation in males but not in females. The sample size did include more males than females so interpret this last point with some caution. Yakult has also funded quite a bit of research recently in athletes and there is some evidence emerging that taking the probiotic strain in Yakult may help. This study found that athletes taking two Yakult servings (one in the morning and one in the evening) over a 4 month period in the winter helped protect the immune system. This was a good study because 84 well trained endurance athletes took part and the group receiving the Yakult had 50% less episodes of infection (probiotic 1.2 ± 1.0, placebo 2.1 ± 1.2). This suggests that taking 2 servings of Yakult over the winter months may be beneficial.       

  • Carbohydrate Definitely Helps

The evidence supporting the use of carbohydrate is convincing. When blood glucose levels fall during exercise our stress hormones rise and this can impair our immune function. By maintaining blood glucose levels during exercise, we can lower stress hormones thus immune dysfunction. When exercising for longer than 45-60 min it is recommended that 60 g of carbohydrate for every hour of exercise should be consumed. This can dampen the immune inflammatory response. Either carbohydrate through a sports drink or solid foods such as cereal bars should be sufficient. Similarly, have your recovery drink immediately after training. For most activities lasting 60 min or longer a 250 mL serving of low fat milk or a low fat milkshake is appropriate. Several athletes in the winter like the idea of having a skinny latté after training which is just as good.

  • Quercetin Supplementation May Help

Quercetin is a plant-derived flavonoid found in fruits, vegetables, leaves and grains. The evidence is mixed as always, however, there are enough well-controlled studies that suggest it could have a positive effect in reducing illness rates during heavy training. This study found that 1000 mg of quercetin with 120 mg of epigallocatechin 3-gallate (EGCG – found in Green Tea) had protective effects in 39 cyclists undergoing 3 days of heavy exertion. A position statement on immunity does recommend that quercetin supplementation can augment some aspects of immune function and reduce illness rates in exercise-stressed athletes. A word of caution when buying quercetin, some quercetin supplements have added ingredient such as Vitamin C. Avoid these as you will read later on this post, Vitamin C is not effective. However, when quercetin is combined with other flavanoids, green tea and fish oil, it can have positive effects in reducing illness rates. Look for quercetin that provides 1000 mg per day and it should be for 2-3 weeks during heavy training or during periods of high susceptibility.
  • Vitamin D

There is strong evidence to suggest that very pale, very dark, and indoor-based athletes may have insufficient levels of vitamin D. I don’t want to cover the issue of Vitamin D in too much detail in this post as it could take up the entire topic of immunity. Nonetheless, clinically, there is evidence of the association of vitamin D insufficiency and respiratory tract infections. It is recommended that athletes should get their Vitamin D levels tested and the appropriate supplement dose taken to correct any insufficiencies. Practical advice regarding vitamin D is complex therefore, I suggest you seek professional advice regarding vitamin D.   
  • Zinc

A recent systematic review by Singh and Das (2011) published by Cochrane found that taking zinc syrup, tablets or lozenges can lessen the severity and duration of the common cold. They conducted a systematic review of the available scientific evidence and they found that taking zinc within a day of the onset of cold symptoms speeds recovery. It was also found that zinc could help ward off colds. I'd advise you to be cautious when taking zinc because long-term zinc use can become toxic. One of the conclusions was that the dosage needed was unclear. Now this is a bit of a concern because excessive amounts of zinc can cause nausea, vomiting, abdominal pain and diarrhea. Therefore sensible advice is to take zinc lozenges on the onset of cold symptoms. The amount of zinc added to lozenges is unlikely to be very high. Note that the recommended upper limit of zinc is 11mg per day so check the label. Also note that it is not recommended to take zinc higher than the RDAs so in other words taking more zinc via supplements may not necessarily stop you from getting an infection but could be toxic.

  • Bovine Colostrum Supplementation May Help

Bovine colostrum is the first milk produced by cows during the initial days after giving birth. Scientific research suggests that bovine colostrum supplements have a number of health benefits, including lower risks of upper respiratory illnesses and diarrhea in immune-suppressed children, and a reduced risk of intestinal damage from anti-inflammatory drugs (see refs below). 

Bovine colostrum contains immunoglobulins which are a type of protein involved in promoting the immune system and fighting pathogens. There are also several studies that have found no positive effect of bovine colostrum however, from personal experience I have seen some promising results when used with my athletes. The majority of the studies have used 60 g per day over a 2-3 week period so this dose should be used during heavy training or during periods of high susceptibility.

  • Do not waste your money on these supplements

Vitamin C - No better than a placebo. Not recommended. Save your money!
Vitamin E - Unless there is a deficiency not recommended
Multivitamin - Not recommended. Save your money!
Glutamine - Evidence is conflicting and some researchers don't recommend it.
Branch Chain Amino Acids (BCAA) - Not recommended. Save your money!
Herbal supplements (e.g.,Ginseng, Echinacea) - Not recommended. Evidence is inconsistent but there is more evidence to suggest that it doesn't work. Save your money!
Fish Oils and Omega-3 - Evidence is conflicting and some researchers don't recommend it.
Beta-glucan - Not enough data in my opinion but based on what has been done, not recommended
Unless there is a deficiency present, then the above will not help protect your immune system.  
  • Summary

So as you can see, majority of the supplements we normally associate with immune function and spend our money on don’t actually work! I haven’t really covered other factors such as training, stress and other lifestyle factors. However, it should be noted that large increases in training volume and intensity are also linked to immune dysfunction therefore, consider some of the strategies discussed here when increasing training impulse (volume x intensity). The following is from the immunity position statement by Walsh et al. (2011). This paper is excellent as it summarises most of the available evidence…
“Although there is no single method that completely eliminates the risk of contracting an infection, there are several effective ways of reducing the number of infectious episodes incurred over a given period. These means of reducing infection risk include appropriate management of training loads, use of appropriate recovery strategies, good personal hygiene, avoiding contact with large crowds, young children and sick people, good nutrition, getting adequate good quality sleep and limiting other life stresses to a minimum.”

Hopefully after reading this post you will have a better understanding on how to protect your immune system. If you are an elite/professional athlete, then please seek advice from a qualified professional before buying any supplements. If you are subject to drug testing then the issue of supplement contamination is serious, therefore, ensure the supplement brand screens their products for contamination. A 2 year ban and lifetime ban from the Olympics (if you are a British athlete) is a severe consequence for not taking this issue seriously.   

By Mayur Ranchordas


  1. Any idea if the L. Casei in Yakult is exactly the same L. Casei they use in Greek Yoghurt?

    In the 2011 Yakult study did they actually use Yakult? Or just the L. Casei? If they used Yakult... did they control for the extra 20g of sugar or so the intervention group were consuming?

    Just a thought.

  2. Mac-Nutrition,

    I believe it depends on the brand. I know some Greek yoghurts also have acidophilus and lactobacilus.

    As for your second point, it was Yakult as per their methods quoted below. The authors don't specify the nutritional information of either probiotic or placebo but if I was to have a guess I would think that the only difference was the probiotic.

    "Probiotic and placebo supplements were supplied as fermented milk in sealed pots of 65 ml with date-stamped expiration. The probiotic drink contained a minimum of 6.5 × 109 live cells of LcS in each pot. The placebo was identical in taste and color to the probiotic but contained no LcS. The supplements were stored at 4–7 °C (domestic refrigerator). Subjects returned to the laboratory every 2–3 weeks to receive a fresh supply of supplement. A compliance log of sample collection was taken. Subjects consumed the supplement twice per day, one 65-ml pot taken with breakfast and one with the evening meal, for 16 weeks. They were asked to keep a record of any days when they missed taking the supplement."

    Appreciate comments as always...


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