Cooking methods and vitamin loss

Farm Forum

Cooking methods can limit vitamin intake thus impacting the health value of certain foods essential to human metabolism.

“Cooking foods can reduce the vitamin content because some vitamins are susceptible to loss from heat, air, water, and light,” said Biyi Chen, SDSU Graduate Student in Nutrition and Exercise Science.

Chen explained that currently, 13 vitamins are found and divided into two categories: four fat-soluble which are A, D, E, and K; and nine water-soluble, eight of which are B vitamins and vitamin C.

“Water-soluble vitamins, especially most of the B vitamins and vitamin C, leach into cooking water; as well as fat-soluble vitamins; including vitamins A, D and E, leach into cooking oils,” Chen said. “Only two vitamins, K and B-3, are stable enough to hold up well during cooking.”

Best cooking methods to preserve vitamins

Cooking methods that use only small amounts of fat or water and don’t require long heat exposure preserve nutrients best, Chen explained. “The type of food preparation influences the loss of vitamins. Choose the best cooking methods to help retain the vitamins of food,” Chen said.

Table 1 shows vitamin loss by different cooking methods.

Moist-heat cooking methods

Boiling and poaching will cause a great loss of water-soluble vitamins, such as folate, vitamin B1 and C, so Chen recommends steaming and microwave cooking as good methods to minimize the loss of vitamins.

“Steam can transfer more heat at the same temperature, so the food cooks faster and fewer nutrients are lost,” Chen said. “Stewing/braising can also help with preserving the vitamins, but heat-sensitive vitamins are partially destroyed.”

Chen added that pressure cooking is comparable with steaming and stewing.

Dry-heat cooking methods

With dry-heat cooking methods, heat can be transferred through air or fat. “This method is suitable for foods rich in proteins and where a crust is desired; however, heat-sensitive vitamins are partially destroyed during roasting, grilling, and baking,” Chen said.

Fry-cooking methods

Chen said that correct frying of vegetables preserves vitamins better than boiling or steaming. “Frying does increase the amount of fat and energy,” Chen said.

The advantage of frying cooking includes: no loss of water-soluble vitamins, only a small amount of heat-sensitive vitamins destroyed, and possible increasing of vitamin E based on oil used for cooking.

Tips to help retain the vitamins of food during cooking

• Wash vegetables whole and before peeling under running water.

• Peel thinly or cook with skin on, and cut into large pieces.

• Raw vegetables and fruit salads: add a little lemon juice or vinegar to slow down vitamin C loss.

• Use the smallest amount of water necessary, and cook with the lid on.

• Serve immediately. Keeping food warm causes a vitamin C loss of 4-17% in one hour and 7-34% in two hours.