When there are more free radicals present than can be kept in balance by antioxidants, the free radicals can start doing damage to fatty tissue, DNA, and proteins in your body. Proteins, lipids, and DNA make up a large part of your body, so that damage can lead to a vast number of diseases over time. These include:

diabetes
atherosclerosis, or the hardening of the blood vessels
inflammatory conditions
high blood pressure, which is also known as hypertension
heart disease
neurodegenerative diseases, such as Parkinson’s and Alzheimer’s
cancer