Winter immunity

Defence against infection has never been more crucial

Why do our immune systems weaken in winter? During these months, we’re unable to get the levels of direct sunlight we get in spring and summer, which provides us with the vitamin D3 we need in order to synthesise 25-hydroxyvitamin D (25-OH) – the active form of vitamin D that helps us fight illness.

While it’s possible to get vitamin D3 through some food sources, such as oily fish and egg yolks, these will not provide you with enough to stay at optimum amounts. As such, supplementation is recommended. Research has shown that consuming 1000 iU or 25 ug of vitamin D3 a day over the winter months can help to keep levels where they should be in order to give you that muchneeded protection. But there are a couple of other tricks you can do to help combat falling ill over the coming months…

PREVENT DRY MOUTH

Within our saliva, there’s an antibody called Immunoglobulin A (IgA), which is our first line of defence against airborne bacteria. Will it stop you getting ill? Not completely, but the potential risk is definitely greater when you have a dry mouth. Having citrus juice in your water on the bike will help you to secrete more saliva and help prevent dry mouth from becoming a problem.

TRAINING IN A LOW-CARBOHYDRATE STATE

During the winter, many of you will be engaging in carbohydrate-restricted riding. Whether this is a good idea or not is an in-depth discussion for another column. However, I can tell you that performing exercise while in a low-glycogen and low-carbohydrate state will increase the cortisol response to that session, which in turn will suppress your immune system, potentially weakening your ability to combat infection.

Will Girling MSc sports and performance nutritionist; willgirling.com

“REDUCED DIRECT SUNLIGHT RESULTS IN A LACK OF THE ACTIVE FORM OF VITAMIN D THAT HELPS FIGHT ILLNESS”