What do you have in your bidon? Water? Electrolyte tablets? Sports drink? 

According to legend, the champion Italian cyclist Fausto Coppi filled his bottle with ‘Binda Zabaione’ – a concoction of sugar and twenty beaten egg yolks. As if not to be outdone, Coppi’s famous rival, Gino Bartali, apparently used to break eggs on his handlebars while in the saddle, gulping down the yolk but allowing the white to trickle down onto the tarmac. 

Although downing raw eggs a la Rocky Balboa is ill-advised – for one, there’s the risk of salmonella – there may have been some method to Coppi and Bartali’s madness. Eggs are rich choline: an essential nutrient needed for nerve, muscle and liver function.  

Furthermore, prolonged and strenuous endurance exercise (such as long-distance cycling) can deplete our choline levels, requiring us to get more of the nutrient from our diet. As this article explains, our genetics also significantly influence how much choline we ought to be consuming.  

What is choline and why do I need it?

Choline is a vitamin-like compound found in foods such as liver, eggs and soybeans. It’s used for a variety of functions in the body, including:

  • Making and maintaining the lipid cell membrane that encloses our cells
  • Producing acetylcholine: a nerve signalling molecule needed for muscle contraction and motor control
  • Transporting fats in the bloodstream
  • Making cell-signalling molecules
  • Carrying out metabolic reactions (including key methylationreactions)

While our body is capable of making choline itself, this is typically inadequate to meet our needs. We therefore must obtain choline from our diet. 

A failure to get enough choline can lead to liver damage, reduced nerve function, muscle damage and poorer performance on the bike. You may be at particular risk of this if you’re vegan or vegetarian, as beef, eggs and dairy products tend to contain the highest amounts of choline. 

Why do my genetics matter? 

The exact amount of choline we need from food varies from person-to-person depending on two main factors:

  • How effectively we produce choline – choline synthesis.
  • How much choline we use up during metabolic reactions and in the production of other molecules – choline metabolism.

Our genes influence both of these processes. 

For example, our PEMT geneencodes an enzyme used to produce choline. Some variants of this gene are linked to lower enzyme activity and, consequently, an impaired ability to synthesise choline.  Individuals carrying these variants will therefore need to get more choline from their diet. 

With regards to choline metabolism, variants of our CHDH geneaffect how much choline we convert into another molecule called betaine. As detailed in this FitnessGenes blog, betaine is then used for a key methylation reaction. Some CHDH gene variants enhance the rate of conversion of choline into betaine, while variants of another gene, BHMT, increase the usage of betaine for methylation reactions. If you’re someone who carries these variants, you may need to up your choline intake. 

How does cycling affect my choline requirement?

Research on trained cyclists suggests that long (>2 hours) and intense (>70% of VO2max) rides can significantly reduce levels of choline inside cells and in the bloodstream. 

In turn, a reduction in choline levels can go on to impair exercise performance. There are several reasons for this. One reason is that choline is used to make acetylcholine, the neurotransmitter used to send signals from nerves to muscle fibers, thereby causing them to contract. When choline levels are low, the body is less able to make acetylcholine. This makes it more difficult for a nerve impulse to stimulate muscle contraction (a process called excitation-contraction coupling). 

If choline levels remain low in the long term, our muscles may also become damaged. This is because choline is used to make and maintain cell membranes. When there’s not enough choline available, the cell membranes of muscle cells start to deteriorate, making muscles less able to withstand mechanical stress and more likely to fatigue. 

So, if you’re regularly completing long, tough rides and races, you may need to increase your choline intake. Of course, as explained earlier, your susceptibility to low choline levels will also significantly depend on your genetic make-up. 

From a Coaching Perspective

Knowing how much choline we synthesise and metabolise is a real gift for a coach or nutritionist. Being able to see instantly that an athlete is at risk of muscle damage from low choline levels means that we can take pro-active steps to protect them. This also means that we can pinpoint likely areas in an overall diet plan that might become an issue later, ironing out the process and ensuring that the nutrition plan is even more effective.  

This blog comes courtesy of Dr. Haran Sivapalan, Science Writer at FitnessGenes, with input from the Spokes coach for the ‘Coaching Perspective’.

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