We have here a citrus fruit called calamansi. It is small and round but more sour than the lemon. With just 3 to 4 pieces of that citrus can make a glass of lemonade. Calamansi, lemon, lime and other citrus fruits are a good source of vitamin C that can strengthen our body's resistance. Especially for riders and those who are on training and workout, vitamin C is a must. What's good in vitamin C is that there is no risk of overdose. And my suggestion is the fresh fruit juiced instead of the vitamin C tablets or syrup.