On Nutrition by Ed Blonz

Will Cooking Veggies Make Them Poisonous?

DEAR DR. BLONZ: Is there truth to the “raw foods” movement’s claim that cooking kills the natural living enzymes in foods, including vegetables, and that this creates poisons in our bodies? -- R.V., Berkeley, California

DEAR R.V.: The concept of “living enzymes” is misleading, in that enzymes are not living substances. Rather, they are a type of protein in living cells that speeds up chemical reactions, helping to change other things without being changed themselves.

In our bodies, enzymes not only work on digesting food, but they are involved in most aspects of our metabolism, which can be thought of as the processes associated with life. Enzymes have unique characteristics that determine how and when they become active. For example, if our blood sugar (glucose) is normal, one set of enzymes becomes active to process incoming nutrients. But if blood sugar is elevated, another set of enzymes gets the call. It is a remarkable system, all designed to ensure that things get handled in the most appropriate way for a given situation.

Like us, plants contain enzymes that play a part in their metabolisms. Inside plant seeds, enzymes can remain inactive for years, springing into action when conditions favor a need for their participation in the chemical reactions involved with the development of the new plant. Heat can indeed destroy plant (or any) enzymes, but it is important to appreciate that plant enzymes are there for the plant -- not for us.

A normal, healthy body makes its own enzymes as needed to digest the foods we eat. One of the initial stages of the human digestive process subjects foods to the acid environment in the stomach, which breaks down enzymes, treating them like other proteins that might be in the foods we just swallowed.

The heat of cooking helps make certain foods easier to digest, and it can make certain plant nutrients more bioavailable for our bodies. The idea of cooking being inherently negative because it “kills” anything alive in food is a bogus spin. Eating cooked food does not “poison” our body. Overcooking, the use of excess heat, can destroy some of the nutritive value of food -- and it can, if taken to an extreme, create mutagenic and carcinogenic substances. But that is not what we are talking about here.

By all means, we should enjoy eating fresh, raw, wholesome plant foods as part of a varied, healthful diet. But we should do so because we like the flavors and textures of the foods -- not because we fear that cooking creates poisons.

Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.