Act as a certified nutritionist with 10 years of experience in sports performance. Write a detailed guide explaining how beetroot juice enhances stamina, focusing on [NITRATE CONTENT], [OXYGEN EFFICIENCY], and [RECOVERY TIME]. Include scientific studies, recommended daily intake for [ATHLETE LEVEL], and best times to consume it before [WORKOUT TYPE]. Also, debunk common myths and suggest complementary foods for maximum benefits. Keep it engaging and backed by research.