1. What are antioxidants and where do they come from?
Antioxidants are nutrients such as vitamins and minerals or enzymes capable of counteracting the damaging effects of the oxidation-causing free radicals in the body.
Free radicals are the product of oxidative stress and create harmful molecules capable of damaging cells, proteins and DNA. Excesses damage by free radicals is believed to be a major cause of diseases including cancer. Free radical damage is impossible to avoid, as we are constantly exposed to oxidation from pollution, sunlight, smoking, strenuous exercise, x-rays and other external sources as well as internal sources such as normal aerobic respiration, metabolism, and bodily inflammation among other sources.
The paradox is that oxidation reactions are critical for life, but they can also cause damage; thus, plants and animals maintain complex systems of multiple types of antioxidants, such as glutathione, vitamin C, and vitamin E as well as enzymes such as catalase, superoxide dismutase and various peroxidases. Too low levels of antioxidants or inhibition of the antioxidant enzymes causes oxidative stress and may lead to damaged DNA, proteins or cellular-death.
Antioxidants are available from food sources such as fruits and vegetables, as well as in other foods including nuts, grains and some meats, poultry and fish and available in a number of dietary supplements. The list below describes food and supplement sources of common antioxidants.
- Beta-carotene is found in many foods that are orange in color, including sweet potatoes, carrots, cantaloupe, squash, apricots, pumpkin, and mangos. Some green leafy vegetables including collard greens, spinach, and kale are also rich in beta-carotene.
- Lutein, best known for its association with healthy eyes, is abundant in green, leafy vegetables such as collard greens, spinach, and kale.
- Lycopene is a potent antioxidant found in tomatoes, watermelon, guava, papaya, apricots, pink grapefruit, blood oranges, and other foods. Estimates suggest 85 percent of American dietary intake of lycopene comes from tomatoes and tomato products.
- Selenium is a mineral, not an antioxidant nutrient. However, it is a component of antioxidant enzymes. Plant foods like rice and wheat are the major dietary sources of selenium in most countries. The amount of selenium in soil, which varies by region, determines the amount of selenium in the foods grown in that soil. Animals that eat grains or plants grown in selenium-rich soil have higher levels of selenium in their muscle. In the United States, meats and bread are common sources of dietary selenium. Brazil nuts also contain large quantities of selenium.
- Vitamin A is found in three main forms: retinol (Vitamin A1), 3,4-didehydroretinol (Vitamin A2), and 3-hydroxy-retinol (Vitamin A3). Foods rich in vitamin A include liver, sweet potatoes, carrots, milk, egg yolks and mozzarella cheese.
- Vitamin C is also called ascorbic acid, and can be found in high abundance in many fruits and vegetables and is also found in cereals, beef, poultry and fish.
- Vitamin E, also known as alpha-tocopherol, is found in almonds, in many oils including wheat germ, safflower, corn and soybean oils, and also found in mangos, nuts, broccoli and other foods.