Vitamin A is best known as the vitamin that will protect your eyesight, but scientists have uncovered another reason to keep taking it. According to recent research, when the body is deficient in vitamin A, it is not able to produce energy as quickly. This is important for anyone who calls on explosive energy in their sport, including weightlifters, football players or soccer players — basically, any activity that’s not a marathon or other endurance sport. Ensuring your body is well-stocked with vitamin A can help you last longer on the field or in the gym. Because vitamin A can be toxic in high doses, the best way to get supplemental A is to take 5,000 to 25,000 IU of beta-carotene, which is a nontoxic form of the vitamin, per day with fat-containing meals.