Are frozen and canned vegetables as good as fresh?

There is a persistent idea that fresh is best and everything else is a sad substitute. For most of what you will cook, it is wrong, and the reason is logistics rather than chemistry.

Frozen vegetables are picked at ripeness and frozen within hours. "Fresh" vegetables are picked, trucked, warehoused, shelved, and then sit in your drawer, and vitamins do not wait. Two studies, one at the University of California and one at the University of Georgia, compared eight fruits and vegetables fresh, fresh after five days in a refrigerator, and frozen. In most comparisons the frozen matched or beat the refrigerated fresh; vitamin C, in particular, fell in the fridge and held in the freezer. That is not an argument against fresh corn in August. It is an argument against the bag of spinach that was going to be a salad on Tuesday and became compost on Sunday.

Canning is harder on vitamin C, because it uses heat, and softer on everything else. Fiber survives, minerals survive, and the beans and tomatoes that are the workhorses of the LP3 kitchen are staples in it, not concessions. A can of beans is cooked, cheap, and ready in the time it takes to open it, which is the difference between eating legumes most days and intending to.

Two things to watch on a can. Salt: rinse canned beans and you remove a good share of it, and no-salt-added versions of most things exist. Sugar: buy tomatoes whole or chopped rather than sauced, because the sauces carry it. That is the whole list.

The practical hierarchy I use is not fresh versus frozen. It is which vegetables survive a week. The workhorses keep for two weeks or more and roast well: carrots, cabbage, onions, potatoes, sweet potatoes, winter squash, beets. They are the cheapest food in the store and they stop the week collapsing on Thursday. The cruciferous group, broccoli, cauliflower, kale, Brussels sprouts, keeps a week or more and carries compounds found nowhere else; roast them hard, because boiled cruciferous vegetables are the reason a generation says it hates them. The leafy group is nutritionally excellent and logistically hopeless: buy less than you think, or buy it frozen. Frozen spinach costs a fraction of fresh, has already been cooked down, and goes straight into egg whites, stews and grain bowls.

Then the finishers, which are the one place I would never economize: herbs, scallions, lemons, chili, garlic, ginger. They are the cheapest things on the list and they do the most work, because their job is making everything else taste like food.

A freezer with vegetables in it is the difference between a plan and a hope, and it removes the single most common reason people fail at eating this way, which is buying vegetables with good intentions and throwing them out. Chapter two of The LP3 Diet is the plant half of the plate, and chapter nine is the kitchen that makes it easy.