Raw food diets may appear good at first, but there is a large potential for negative consequences, and they are not as healthy as advocates claim. For one, properly cooking food removes the risk of food-borne illness and subsequent food poisoning, a possibility that is not available to raw food diet practitioners.
Also, cooking actually makes some foods digestible and releases more nutrients than are available in their raw state; cooked tomatoes, for example, offer five times the amount of the antioxidant lycopene compared to when they are consumed uncooked.
As for enzymes, it is true that these are largely destroyed with cooking, but the enzymes available in raw food are mostly destroyed by humans' stomach acid and have a negligible benefit on the digestive process.
Lastly, raw food diets, especially the raw vegan diet, are deficient in many necessary vitamins and minerals, such as vitamin B-12.
So while it is true that some raw foods are healthier, nutritionists largely recommend eating a mix of raw and cooked foods to get the most nutrients possible.
Another challenge presented by raw food diets is that they are hard to maintain over time because they are both demanding and expensive. These diets are highly restrictive and prohibit cooking, cooked foods, and often processed foods as well. Some who have tried a raw diet, such as actress Megan Fox, had to quit not just because of the restrictions that these diets demand but also because of excessive weight loss.
Additionally, many raw recipes require a blender or dehydrator, which are extra expenses that practitioners of these diets must consider.
Overall, there is a reason why raw food diets are referred to as "fad" diets. They are simply not sustainable long-term.