Studies have shown that cooking does not always make vegetables less nutritious. It all depends on the specific product and the cooking method. Some vegetables lose water-soluble vitamins, including vitamin C, after heat treatment, while others, on the contrary, become richer in fat-soluble vitamins A, E and K.
Scientists analyzed the effects of blanching, boiling, steaming, and microwaving on the content of vitamins C, E, K, and β-carotene in ten types of vegetables. The greatest losses of vitamin C were observed with prolonged boiling in water, while steaming or microwaving preserved most of the nutrients. Broccoli, spinach, and Swiss chard, after heating, could even increase the content of fat-soluble vitamins due to the destruction of cell walls.
Vitamin K was found to be relatively stable to heat treatment, especially in green leafy vegetables. However, in root vegetables such as carrots and potatoes, a decrease in vitamin E and β-carotene was observed after cooking.
Nutritionists emphasize that it is optimal to combine raw and cooked vegetables. It is worth steaming or microwave-cooking some products to preserve vitamins, and also adding healthy fats to dishes: olive oil, avocado, nuts or seeds for better absorption of fat-soluble vitamins. Such combinations will help make the diet more balanced and healthy.
