Final answer:
Vitamins, especially water-soluble ones like B and C, are vulnerable to destruction by heat during cooking. Boiling and discarding the water in which vegetables are cooked can result in significant nutrient loss.
Step-by-step explanation:
The statement that vitamins are easily destroyed by heat is generally true. Vitamins can be very sensitive to heat as well as to exposure to air and light, leading to a reduction in their nutritional value when foods are cooked. In particular, water-soluble vitamins like vitamin B (which includes folate or folic acid) and vitamin C are most susceptible. For example, boiling vegetables can cause these vitamins to dissolve into the water, which, if discarded, results in a loss of those nutrients.
Exposure to heat during cooking methods such as boiling, steaming, frying, etc., can thus lead to a loss of essential vitamins. Additionally, some fat-soluble vitamins like A, D, E, and K can accumulate in the body's fat tissue and can lead to toxicity if consumed in excessive amounts. Therefore, it's important to be mindful of the cooking methods used when preparing food to preserve its vitamin content as much as possible.