Most cyclists are taking supplements based on what they read in a forum or watched on a YouTube channel that was selling something. Anthony covers five he actually takes himself, but the bigger point is that without a blood test first, you're guessing.
Key Takeaways
Iron is the one Anthony comes back to most with clients. The recommended daily allowance is set too low for endurance athletes, so almost everyone training hard is running short, and when it gets bad enough you feel it immediately on the bike. He describes it as the worst fatigue you've ever had, legs like concrete, no power. Get tested, and if you're low, pair your iron with vitamin C and avoid tea or coffee around it because the tannins block absorption. B12 matters especially if you're plant-based since it doesn't occur naturally in unfortified plant foods, and oxygen-carrying capacity is the whole game for endurance cycling. Vitamin D at 1000 IU daily is particularly important for cyclists because the low-impact nature of the sport compromises bone density in a way running doesn't.
The antioxidant point is the one most people miss. Vitamin C and vitamin A are useful for immune function, but they work by dampening the free radical stress response, and that stress response is what makes you fitter. If you're popping vitamin C every day through a hard training block, you might be blunting the adaptation you're working for. Anthony periodizes it: closer to events and during recovery phases, fine. Deep in a winter training block, he backs off. The cycling forums and the supplement-of-the-month crowd don't tell you this because they're not thinking about training cycles. They're just telling you antioxidants are good, which is true, but not always and not at every point in the season.
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If you want the full picture on fuelling around training, the Barry Murray episode on World Tour nutrition is the one to listen to next. And if weight management is part of why you're thinking about this stuff, the episode on easy weight loss strategy covers the practical side without the usual calorie-counting nonsense.