Does Vitamins in vegetables decrease when we cook them?

A lot of people think that green vegetables are a lot of healthy but their vitamins decline when they are cooked.  This is not true every time. The rate of change in vitamins depends on how they are cooked, whether the vegetables are steamed, stewed in a pressure cooker, boiled in a microwave oven, or deep fried in oil.  When we boil some vegetables their vitamins decrease while some vegetables vitamins increase after boiling. A few years ago when a survey was done on people who only eat raw vegetables are found with high beta carton but they have low lycopene. The reason behind this is that cooked tomato contains more lycopene than raw tomato. Generally in fruits and vegetables the roots and stems are very thick. When we boil them they spread and release their vitamins. But vitamin a, vitamin b and nutrients related to polyphenol dissolve in water and decline.  For example if we boil spinach its vitamins decrease by two times. Moreover the vitamins like A, D, E, K and anti oxidants like carotenoid which dissolve with fats only increase after they are cooked. In a survey it is found that it is healthier to boil vegetables like carrots and broccoli. But we should remember after boiling them the polyphenols present in them also decrease. In the methods of cooking frying is the most dangerous one. Because of frying the nutrients present in the vegetables decrease immensely. Some people say cooking in microwave oven is unhealthy. But surveys have found that it is not true. When broccoli is boiled in water its vitamin C decrease about 22-34 per cent while when we microwave it 90% of vitamin C stays as it was. So, all over none of the methods are totally beneficial for maintaining vegetables nutrients. So it is better to eat some vegetables raw, some steamed, some cooked in microwave oven, and some boiled. But frying is good for none.