When I cook vegetables in water, I usually add a little salt to the water. Apparently people a hundred-years-ago wondered whether it was a good idea to add baking soda when cooking vegetables.
Baking Soda in Cooking Vegetables and Fruits
The baking soda will soften the water in cooking beans or cabbage, and the vegetables will cook quicker and more thoroughly, but the alkali has a destructive effect on the vitamins present in these vegetables, and in all fresh foods. Scientists tell us that these vitamins are more important to nutrition than the foods themselves are when deprived of them, and that we lose the good of the food if the vitamins are destroyed. Try adding a little vinegar to the water for beans or cabbage; this will soften them quite as well, and our friends, the vitamins, are not injured by acids, only by alkalis.
Source: American Cookery (February, 1920)