Final answer:
Garlic compounds are excreted through the breath and urine, while onion compounds are excreted through sweat.
Step-by-step explanation:
Garlic compounds, particularly sulfur-containing molecules, undergo metabolic processes in the body, leading to their release through the lungs during respiration, resulting in the well-known phenomenon of garlic breath. Additionally, these compounds are filtered by the kidneys and excreted in urine. On the contrary, compounds from onions, such as sulfides, are expelled through the skin via sweat glands. The distinctive odor associated with onion consumption manifests itself in perspiration. Therefore, the physiological pathways for excretion differ between garlic and onion, with garlic primarily utilizing breath and urine, while onion relies on the secretion of compounds through sweat glands, supporting the statement that garlic is excreted in breath and onion in sweat.