Whether fresh or dried, oregano is high in antioxidants. Indeed, it has the highest level of antioxidant of all herbs. Just one teaspoon of oregano has more antioxidants than a serving of almonds or asparagus, giving it serious disease fighting potential. The specific medicinal effects associated with oregano may include preventing the growth of cancerous cells and fighting the growth of bacteria and parasites that can cause ulcers and other gastrointestinal problems. Oregano is also a good source of lutein and zeaxanthin, phytonutrients that helpprevent eye diseases common in older adults, such as cataracts and age-related macular degeneration.