Keep colds at bay… with protein

No matter how carefully you plan your training, recovery and nutrition, your cycling fitness will still take a step backwards if you become ill.

So with the season of coughs, colds and flu upon us, it’s your immunity – or lack of – that is most likely to scupper your winter training and preparation for next season.

The link between nutrition, exercise and immunity is undeniable. For example, we know that regular moderate-intensity exercise such as cycling improves your immunity in the longer term. Ironically, however, harder or longer training sessions can temporarily depress your immune system, leaving you more vulnerable to illness and infection in the hours after exercise.

High-quality nutrition, on the other hand, is known to maximise your immunity regardless. That being the case, are there any proven nutritional strategies that could help boost your immunity this winter and minimise the risk of coughs, colds and flu? Well, new research by Scottish scientists suggests that some very simple changes to your diet could do just that.

The science
In the study, the researchers studied whether a high-protein diet could boost the markers of immunity in a group of eight well-trained cyclists undergoing heavy training. Importantly, they set out to also ascertain whether this was reflected in a reduced incidence of upper respiratory tract infections (URTIs, ie coughs, colds, sore throats, flu, sinusitis, etc).

To do this, the cyclists undertook two separate weeks of high-intensity training. In one of these periods, they consumed a high-protein diet containing 3g protein per kilo of their bodyweight. In the other, they consumed exactly the same number of total calories per day but this time the protein intake was a more modest 1.5g per kilo of bodyweight per day (ie less protein, but topped up with more carbohydrate to ensure the same overall energy intake).

Before these high-intensity training weeks, the cyclists performed a week of normal training so that the scientists could see how the cyclists’ immune systems responded when going from normal to heavier training loads. In addition to taking blood samples to measure the activity of important immune cells in the body, the researchers asked the cyclists to fill in daily questionnaires about their health.

In a nutshell
The first finding was that when the cyclists were on the lower-protein diet, upping the training load produced a significant drop in the immune function.

In particular, the activity of cells whose job it is to ‘survey’ the body for viruses and then help trigger an immune response were much less active during the high-intensity training week. When the cyclists were on the high-protein diet, however, their immune function did not suffer in the high-intensity week and remained just as potent as when they were training at normal intensity.

More tellingly, perhaps, when the cyclists consumed a high-protein diet and trained hard, they reported significantly fewer URTI symptoms compared to training hard on the lower-protein diet.

So what?
What’s interesting about this research is that the current consensus on protein intake recommendations for endurance athletes such as cyclists is that just 1.0-1.5g per kilo of body weight per day is all that’s needed, even for elite cyclists.

Yet this study suggests that while 1.5g per kilo per day might be OK in terms of performance, it might not be nearly enough to keep the immune system in tip-top condition, especially during harder periods of training. As always, more studies are needed, but in the meantime the message seems to be ‘don’t skimp on the protein if you want to keep the bugs at bay this winter’!

Brain Behav Immun. 2013 Oct 10. pii: S0889-1591(13)00501-1. doi: 10.1016/j.bbi.2013.10.002. [Epub ahead of print]

This article was first published in the November 28 issue of Cycling Weekly. Read Cycling Weekly magazine on the day of release where ever you are in the world International digital edition, UK digital edition. And if you like us, rate us!