The substances consumed by a professional cyclist usually make headlines for all the wrong reasons, but when America's David Zabriskie pedals away from the starting line of the Tour de France this weekend, he will also be starting a unique nutritional experiment.
In a move never before attempted in the 108-year history of his sport's most gruelling event, Zabriskie, who announced his conversion to veganism at the end of last year, will try to complete the 3430km three-week race without consuming any meat, eggs or dairy products.
It's a challenge because cyclists on the Tour need to have roughly 8000 calories a day. They have traditionally scoffed large portions of meat to replace lost protein and aid muscle recovery.
Animal products also replace missing iron, which produces haemoglobin that helps transport oxygen around the body.
Zabriskie, who is 1.8m tall and weighs just over 63kg, began experimenting with his diet last season, after a blood test done by his team chiropractor revealed that he was highly sensitive to certain types of food.
During last year's tour, he began cutting down on meat, believing it required too much energy to digest. Then he cut out milk and cheese, and was pleased with the results.
During the off season, which began in October, he decided that it was time to "make some major changes" to his lifestyle, and announced he would be becoming a vegan.
Since then Zabriskie claims to have been in some of the best form of his career, a fact he attributes directly to the new diet.
"I think a lot of people see food in terms of whether it's going to make them fat or make them skinny," he told the Wall Street Journal.
"I'm seeing food in terms of how it's going to make me think and will it give me clarity."
He said his overall health had improved, and that minor ailments, including canker sores and a persistent saddle rash had all begun to clear up.
Even his eyesight had sharpened, he told the newspaper.
Zabriskie has adopted the new diet for reasons of health, rather than animal welfare, so he takes a pragmatic approach to some of the demands of a true vegan lifestyle.
In a move which might disappoint purists, he has decided to "cheat" by eating small portions of salmon twice a week during the tour, to increase his ability to absorb iron.
The other secret of his daily diet is a brand of vegan energy shake, which contains hefty portions of hemp seeds, flax seeds, and protein from brown rice. He began drinking them after suffering from low energy levels earlier this season, and now consumes at least four a day.
That has been enough to keep his physique more muscular than the vegan stereotype.
But although Zabriskie's animal-friendly diet may be relatively common in his native Los Angeles, it still stands out in professional cycling, where protein shakes tend to be infused with raw egg whites.
Zabriskie's employers, the Garmin-Cervelo team, admit they were initially concerned by his vegan diet.
The team's director, Jonathan Vaughters, insisted he ate extra portions of leafy greens, such as spinach, and took regular blood tests to monitor his level of ferritin, the protein that stores iron.
Their fears dissipated when he hit a run of good form, winning the time trial during this year's Tour of California and then coming first in the US national time trial championships.
On paper, Zabriskie still does not have much chance of winning the Tour de France, which he has entered five times and completed three times.
But he did win the time trial in 2005 and hopes to replicate that feat.
Said Vaughters: "The proof is in the pudding. He's won more time trials this year than he has in his career."
The next three weeks, he added, would be "the ultimate test of the vegan diet".
In a move never before attempted in the 108-year history of his sport's most gruelling event, Zabriskie, who announced his conversion to veganism at the end of last year, will try to complete the 3430km three-week race without consuming any meat, eggs or dairy products.
It's a challenge because cyclists on the Tour need to have roughly 8000 calories a day. They have traditionally scoffed large portions of meat to replace lost protein and aid muscle recovery.
Animal products also replace missing iron, which produces haemoglobin that helps transport oxygen around the body.
Zabriskie, who is 1.8m tall and weighs just over 63kg, began experimenting with his diet last season, after a blood test done by his team chiropractor revealed that he was highly sensitive to certain types of food.
During last year's tour, he began cutting down on meat, believing it required too much energy to digest. Then he cut out milk and cheese, and was pleased with the results.
During the off season, which began in October, he decided that it was time to "make some major changes" to his lifestyle, and announced he would be becoming a vegan.
Since then Zabriskie claims to have been in some of the best form of his career, a fact he attributes directly to the new diet.
"I think a lot of people see food in terms of whether it's going to make them fat or make them skinny," he told the Wall Street Journal.
"I'm seeing food in terms of how it's going to make me think and will it give me clarity."
He said his overall health had improved, and that minor ailments, including canker sores and a persistent saddle rash had all begun to clear up.
Zabriskie has adopted the new diet for reasons of health, rather than animal welfare, so he takes a pragmatic approach to some of the demands of a true vegan lifestyle.
In a move which might disappoint purists, he has decided to "cheat" by eating small portions of salmon twice a week during the tour, to increase his ability to absorb iron.
The other secret of his daily diet is a brand of vegan energy shake, which contains hefty portions of hemp seeds, flax seeds, and protein from brown rice. He began drinking them after suffering from low energy levels earlier this season, and now consumes at least four a day.
That has been enough to keep his physique more muscular than the vegan stereotype.
But although Zabriskie's animal-friendly diet may be relatively common in his native Los Angeles, it still stands out in professional cycling, where protein shakes tend to be infused with raw egg whites.
Zabriskie's employers, the Garmin-Cervelo team, admit they were initially concerned by his vegan diet.
The team's director, Jonathan Vaughters, insisted he ate extra portions of leafy greens, such as spinach, and took regular blood tests to monitor his level of ferritin, the protein that stores iron.
Their fears dissipated when he hit a run of good form, winning the time trial during this year's Tour of California and then coming first in the US national time trial championships.
On paper, Zabriskie still does not have much chance of winning the Tour de France, which he has entered five times and completed three times.
But he did win the time trial in 2005 and hopes to replicate that feat.
Said Vaughters: "The proof is in the pudding. He's won more time trials this year than he has in his career."
The next three weeks, he added, would be "the ultimate test of the vegan diet".
