The Effects of Temperature & pH on Vitamins

Vitamin-rich foods are an important part of a healthy diet, but many factors, such as heat and acidity, can decrease the amount of certain vitamins in food. When preparing vitamin-rich foods such as fruits and vegetables, it is important to be aware of these effects.

Temperature and Water-Soluble Vitamins

• Water-soluble vitamins, such as vitamin C and the B vitamins, can be lost when food is heated. Vitamin C is especially susceptible to heat, while some of the B vitamins--riboflavin and niacin, for example--are not affected by heat. In addition, the practice of steaming or boiling vegetables can cause them to leach these vitamins into the water.

Temperature and Fat-Soluble Vitamins

• Vitamins that are fat-soluble, including A, D, E and K, are not affected by heat. Food containing these vitamins, such as spinach, carrots and vitamin-enriched milk, can be cooked without losing nutritional value.

Ph and Vitamins

• Vitamins C, B1 (Thiamin) and B2 (Riboflavin) can be destroyed by alkaline substances, which have a high Ph. Foods cooked in alkaline mediums such as water, soy milk or vegetable broth, lose these vitamins more easily than foods cooked in acidic mediums such as vinegar or soy sauce (Reference 3).