Boiling vegetables is a relatively quick and easy technique; however many vegetables lose their nutrients when boiled in water. The boiling water can be saved to make a soup or sauce, but that doesn’t help you on the night you’re serving the vegetables.
Apart from adding extra fat to your meal, frying was found to cause a loss of between 5 and 50 percent of each vegetable’s nutrients.
A Harvard investigation of the impact of various cooking methods on vegetables found microwaving is the best method for retaining nutrients. This was because nutrients weren’t being lost through boiling water and most important, the speedy cooking time that ensures sensitive nutrients affected by heat like vitamin C aren’t destroyed.
While roasting can give vegetables a unique flavour by caramelising natural surface sugars, research has found a number of vegetables like carrots, cauliflower, courgettes and onions, see a decrease in their nutrient levels.
Steaming is widely considered to be one of the healthiest methods of cooking vegetables with a 2008 Italian study finding that it was the best method for preserving antioxidants found in vegetables like broccoli and courgettes.
Frozen vegetables are picked at their best and frozen immediately – because of this they’re considered by many to be superior to fresh vegetables, whose quality can reduce as they are transported and left sitting in supermarkets.