Ask someone to imagine the healthiest lunch they can think of and then describe it to you. Chances are, that lunch will be a big salad. If not for the main course, then at least for the side.
Our assumption of what's healthier doesn't always match up with the science. In the case of veggies and fruits, we assume fresh = healthier. Indeed for most that is 100% true. If you take raw broccoli raab it has an ORAC of 3,083. When you cook it, you chop that value in half down to 1,590. The intense 200+ degree heat of boiling or baking breaks down many nutrients. Vitamin C is eviscerated. The chemical compounds of many antioxidants break. Are raw tomatoes better for you than cooked too? There is an exception to this rule.
Thank the lycopene...
Tomatoes are an unusual fruit (yes, they are technically not a vegetable). They contain lycopene which is not found in many plants. You will also find it in guava, watermelon, papaya, grapefruit, and red bell peppers. Aside from these, only minuscule amounts (if any) are in the other fruits and vegetables we eat.
God must have had Italian cooking in mind when creating it. Why? Because when you eat lycopene, rather than breaking down, it actually converts into a more absorbable form (1). With the exception of vitamin A, it's rare for most antioxidants to hold up well in heat. But to become more potent? That's practically unheard of!
There is one reason fresh tomatoes are better than canned... vitamin C. Since that breaks down in heat, you will get significantly higher amounts by eating the tomatoes raw vs. cooked. However since C only represents a minority of its total ORAC, the benefits of cooking and getting more lycopene should outweigh the C you are losing out on.
When processed is worse for you than fresh
Whether it's spaghetti sauce, pizza sauce, salsa, or some other processed tomato product, don't assume they are healthy for you. Even without the high calories from added canola or olive oil, most of these products are loaded with way too much salt. Go to your cupboard and look at the label of a sauce jar if you have any and you will be shocked to see the amount of sodium; often 200 to 500 mg per serving, with 4 to 7 servings per jar. Are processed tomatoes better than fresh in that scenario? Absolutely not! Save your heart and buy the low sodium or no added salt sauces... those are the most nutritious option, providing you the more lycopene without the bad stuff.
USDA Database for the Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2 - Prepared by Nutrient Data Laboratory, Beltsville Human Nutrition Research Center (BHNRC), Agricultural Research Service (ARS), U.S. Department of Agriculture (USDA) - May 2010