no, lightly steaming vegatebles do not decrease lycopene levels for example but increase utilization. your argument is that the exact nutrients in which cooking enhances are also destroyed during the same process, this is incorrect. some nutrients are enhanced, and not destroyed hence better utilization. thus eating raw and cooked would give you a mixture of nutrients. its not a 1:1 ratio like you would have us beleive.
things are not equal here and not all of the nutrients that are increased in terms of bioabsorption are damaged, if they are not then cooking is superior for this nutrient, that is why the mix is better.
Heat always destroys nutrients. This is not debatable. Furthermore, several nutrients present in vegetables, like B complex vitamins, are soluble in water. Just by drenching spinach and broccoli in water some of the vitamins B will get lsot. Sure, the loss is minimal in natural room temperature, probably only 1 or 2%. But putting it in hot water causes much greater loss. Why? Because heat is a catalyst, and is used by chemists to speed up reactions. the losss of B vitamins is over 20% when you cook it in hot water.
So the debate is really this: is the increase in bioavailability caused by steaming a vegetable greater than the loss of nutients that heating it causes? If so, then cooking the vegetable is beneficial; if not, then it is detremental. If the same, then it is neutral. As for lycopene, I doubt that cooking tomatoes increases it's bioavailability dramatically. The best way to absorb lycopene from tomatoes is to purée it and put some olive oil in it - because lycopene is liposoluble.
SUCKMYMUSCLE
