The premise of the raw food diet is just that – eating only foods that are uncooked and unprocessed.  This includes raw meat, fish, veggies, fruit, nuts, seeds, eggs, and non pasteurized dairy products.
The philosophy behind this way of eating is that cooking can deplete foods of useful nutrients (which is true eg for veggies, though depending on how they are cooked – boiling veggies brings some of the nutrients into the water, whereas steaming retains the nutrients inside the vegetable). Raw foodists also wish to avoid potential carcinogens that can be present in cooked/processed food (eg heterocyclic amines that are found especially in burned meat (eg BBQ’d), and a long list of environmental pollutants that could make their way into our processed foods (BPA being just one example)). Chemicals and stimulants (such as coffee and tobacco) are also avoided.
Good things about this diet are that one does truly decrease exposure many chemicals that are ubiquitous in our food supply.  Foods that are raw are in their purest form, and highest in nutritive value (especially if wild/organic foods are sourced, as rawists tend to do). 
However, a major risk of eating in this way is food poisoning. There is a reason why we pasteurize our dairy products and cook our eggs and meat.  Processes such as pasteurization have allowed us to function in urban society, enabling us to keep food longer, to feed the masses living in a relatively small space, as we were perhaps not meant to do, but which is a part of modern life for most people.
While some raw foods are very easy to prepare (eg salads), others are very time consuming.  For example, to eat rice or other grains, they have to be sprouted and/or soaked overnight to be digestible. 
And finally, the question that is central to the discussion of any diet:

Is It A Permanent Change?  I would submit that this is very difficult to adhere to over the long term – but this concern is overridden by my greatest fear which is that of the unsafe consumption of uncooked foods and risk of food poisoning that may ensue.

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