Final answer:
Cooking at high temperatures is a practice that would likely reduce the vitamin content in foods, especially water-soluble vitamins like B and C.
Step-by-step explanation:
The practice that would likely reduce the vitamin content in foods is cooking at high temperatures. When foods are cooked, especially water-soluble vitamins like B and C, they can be destroyed or diminished. This is due to the fact that these vitamins are sensitive to heat, and in the case of boiling vegetables, these vitamins can leach into the water which is often discarded. The loss of vitamins is one of the main reasons to opt for a diet that includes raw fruits and vegetables as they retain more nutrients than their cooked counterparts.