More on raw vs cooked:

http://cebp.aacrjournals.org/cgi/content/full/13/9/1422

Abstract:

This review of the medical literature from 1994 to 2003 summarizes the 
relationship between raw and cooked vegetables and cancer risk and examines 
whether they may affect cancer risk differently. Twenty-eight studies 
examined the relationship between raw and cooked vegetables and risk for 
various cancers. Twenty-one studies assessed raw, but not cooked, vegetables 
and cancer risk. The majority of these assessed risk of oral, pharyngeal, 
laryngeal, esophageal, lung, gastric, and colorectal cancers. Most showed 
that vegetables, raw or cooked, were inversely related to these cancers. 
However, more consistent results were found for oral, pharyngeal, laryngeal, 
esophageal, and gastric cancers. Nine of the 11 studies of raw and cooked 
vegetables showed statistically significant inverse relationships of these 
cancers with raw vegetables, but only 4 with cooked vegetables. The few 
studies of breast, lung, and colorectal cancers also suggested an inverse 
relationship with both raw and cooked vegetables, but these results were 
less consistent. In the two studies of prostate cancer, there was no 
association with either raw or cooked vegetables. One of two bladder cancer 
studies found an inverse relationship with cooked, but not raw, vegetables. 
Possible mechanisms by which cooking affects the relationship between 
vegetables and cancer risk include changes in availability of some 
nutrients, destruction of digestive enzymes, and alteration of the structure 
and digestibility of food. Both raw and cooked vegetable consumption are 
inversely related to epithelial cancers, particularly those of the upper 
gastrointestinal tract, and possibly breast cancer; however, these 
relationships may be stronger for raw vegetables than cooked vegetables.

[...]

Conclusion:

It is clear from this review that both raw and cooked vegetables are 
inversely related to several epithelial cancers, particularly those of the 
upper gastrointestinal tract, and possibly to breast cancer. Although more 
of the studies showed a statistically significant inverse relationship 
between raw vegetables and cancer than either cooked or total vegetables, 
the literature is too varied to compare definitively. Studies on diet and 
cancer need to differentiate between raw and cooked vegetables in their 
methods of food recall and in their analyses. In addition, more consistency 
is needed regarding the types of vegetables assessed in each category. In 
the meantime, the public should be encouraged to increase their vegetable 
intake and to consider eating some of them raw.