What destroys the nutrients in fruits and vegetables?

Vegetables and fruits have the most nutrients when they're harvested, and they begin to lose them as soon as they are harvested. There are other things we can do to fruits and vegetables to hasten this destruction of nutrients after harvest, including:

  • Storage: The longer vegetables and fruits are stored before using, the more nutrients are lost.
  • Cutting: When a plant is cut, it goes on the defensive and activates enzymes that destroys its own nutrients, causing brown discoloration.
  • Cooking: Over-cooking diminishes nutrients by breaking down the cells. When food is fried, barbecued, or baked at high temperatures, toxic compounds such as acrylamides are formed and most important nutrients are lost. Many vitamins are water-soluble, and a significant percent can be lost with cooking, especially overcooking. Boiling makes it easy for nutrients to leach into the water. Many plant enzymes function as phytochemical nutrients in your body and they, too, can be destroyed by overcooking.
  • Freezing. Frozen food is pre-cooked to inactivate the enzymes so that the food won't turn brown, making it easier to over-cook, and diminishing the Vitamin C in particular.
  • Blending or juicing. Juicing breaks down fruits and vegetables into such tiny parts that the nutrient loss begins rapidly. Very few nutrients will be left in the juice or smoothie after 24 hours.

To minimize destruction:

  • Buy the most recently harvested fruits and vegetables you can. Think locally grown produce from farmers markets.
  • Buy whole fruits and vegetables instead of pre-cut and bagged.
  • Enjoy as many as possible whole and raw.
  • If you do store them, don't peel or pre-cut.
  • If you do cook them, cook them whole or cut them into large pieces right before you cook them, and cut them into extra large sizes to cook and cut smaller after cooking.
  • Avoid peeling most fruits and vegetables, as many nutrients are in or just under the skin. If you must peel cooked vegetables, peel them after cooking, as the skin helps keep nutrients in during cooking.
  • Avoid boiling and discarding the water. Use steam so the nutrients won't leach into the water. When food is steamed or made into a soup, the temperature is fixed at 100 degrees Celsius (212 degrees Fahrenheit), the temperature of boiling water. This moisture-based cooking prevents food from browning and forming toxic compounds. Most essential nutrients in vegetables are made more absorbable after being cooked in a soup and water-soluble nutrients are not lost because we eat the liquid portion of the soup too. Only small amounts of nutrients are lost with making a soup, but many more nutrients are made more absorbable. When you heat, soften, and moisturize vegetables and beans, you increase the digestibility and absorption of many nutrients, including protein.
  • Use frozen fruits and vegetables only when fresh are not practical.
  • Drink freshly made smoothies and juice immediately after you make them. Avoid buying bottled juice, which aside from being stored, has also been pasteurized.