Consuming a diet high in fruits and vegetables is increasingly seen as a key factor in maintaining a healthy weight and preventing many diseases. The US Department of Agriculture recommends that adults eat between 2.5 to 3 cups of produce every day, but does not specify whether it is best to consume the produce fresh or cooked.
Since many popular diet approaches promote the idea that eating foods in their most natural forms is most nutritious, it might be assumed that cooking fruits and vegetables reduces their dietary value. However, recent research has shown that this is not always the case and some foods actually increase their nutritional value after cooking.
Cooking Effects on Antioxidants
A study published in the British Journal of Nutrition found that a group of 198 research subjects who maintained a raw food diet had low levels of the antioxidant lycopene. Found mainly in tomatoes and other red-hued fruits, lycopene has been linked to lower risks of cancer and heart disease when eaten regularly.
Another study supports these findings. In a 2002 study published in the Journal of Agriculture and Food Chemistry, researchers discovered that the lycopene found in tomatoes increased up to 35% after cooking. The reason from this change was due to heat’s ability to break down cell walls within the tomatoes, releasing more lycopene for consumption.
Lycopene is not the only antioxidant that is increased when cooked. Antioxidant-rich foods like carrots, spinach, and peppers also increase the levels of antioxidants they supply when boiled or steamed before eating.
Vitamin and Mineral Retention After Cooking
Unfortunately, some vitamins and minerals do not benefit from cooking like the antioxidants discussed above. Researchers have found that vitamin C in particular can be destroyed quickly by heating. However, since vitamin C is more abundant than lycopene, it is still recommended to cook lycopene-rich foods and get vitamin C from other sources that do not contain lycopene, like oranges.
Research has found that minerals like potassium, calcium, magnesium, and iron can also be lost after cooking, and lower their levels the most through boiling. To retain the highest amount of minerals, parching, pan-frying, and stewing produce is recommended.