Does Reheating Food Destroy Much of Its Nutritional Content?

There are advantages and disadvantages to cooking your food. While heating food may cause some of the nutrients to be lost or lose their potency, cooking is one of the primary ways you make food healthy by killing bacteria. It can be difficult to dissect the mire of information espoused by the raw-food enthusiasts and those who over-cook healthy food. Stick with your doctor or dietitian's advice if you have any doubts about your or your family's health and safety.


Heat-sensitive vitamins such as vitamin C lose their effectiveness when heated, according to Vegetarian Nutrition. Water-soluble vitamins leek out into the water in which you cook them and are destroyed at temperatures exceeding 70 Fahrenheit. Other vitamins that lose their potency in the heating process include the water soluble B-vitamins. According to the Canadian government-sponsored Better Health Channel, in addition to vitamin C, the most unstable vitamins lost through reheating include B-vitamins folate and thiamin 2.


Cooking destroys many of the enzymes in whole grains, beans and legumes that your body needs for many bodily functions, including digestion. At the same time, digesting raw whole grains is difficult and your body loses most of the nutrients anyway when grains don't get digested. While your body produces metabolic enzymes, the food you eat replaces many of those nutrients so that your body doesn't become depleted. According to Lee Berenson, M.D., when you don't produce sufficient enzymes to fully digest your food, the risks increase for free radicals to enter your body and cause:

  • allergies
  • infection
  • disease


Antioxidants are inherent in a number of foods and are important for fighting free radicals in your body that appear naturally or occur from the food you eat, environmental pollutants and ultraviolet sun rays. Lutein and zeaxanthin are two powerful xanthophyllis antioxidants that are naturally present in the phytochemicals found in green vegetables such as kale, broccoli and cabbage. In addition to vitamin A, a fat-soluble vitamin that's usually enhanced by cooking, lutein and zeaxanthina are important nutrients needed for healthy eyes. Reheating foods that contain these nutrients lessens their potency, although, according to the University of Maryland Medical Center, not to a great degree. Food is the most effective source of antioxidants from phytochemicals but you can use supplements to replace nutrients lost from cooking. You should refer to your doctor for guidance however, because some supplements can increase your risks for complications.


While you may lose some of the inherent nutrients in your food by cooking and reheating it, you also reduce the risk of developing a foodborne illness. According to the National Digestive Diseases Information Clearinghouse, about 75 million people get sick in the United States from contaminated food and about 5,000 die. Raw foods are not sterile and pose the greatest risk for developing a foodborne illness. Microorganisms that occur from handling, harvesting and storing can lead to flu-like symptoms that range from vomiting and diarrhea to fever, cramps and dehydration.