Beet juice has a small effect on athletes. "But the difference between not making the podium at the Olympics and standing on the top step is often only a couple percent," says Andrew Coggan of Washington University in St. Louis. Alastair Bland for NPR hide caption

toggle caption Alastair Bland for NPR

Performance nutrition experts recommend stopping at all the hydration stations for a quick fill-up of a sports drink to replenish the glycogen that's being burned during a marathon. iStockphoto hide caption

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