Actually, raw meat and fish can be tremendously beneficial, and are far easier to digest than cooked meat. Raw meat contains naturally rich enzymes and nutrients, as well as hydrophilic colloids that can further facilitate its digestion, absorption and utilization. These are generally destroyed by cooking. Heat denatured protein is naturally harder to digest. I always eat my red meat cooked rare, and occasionally some raw. The USDA states that all one needs to do is make sure it has been frozen solid for two weeks prior to consumption. This ensures elimination of any parasite issues. Properly marinating these foods prior to consumption can also help. Also, supplementary hydrochloric acid is also an excellent defense against food-born parasites (that's what our ancestors relied upon as a first defense). I always bring some HCl caps with me to sushi restaurants. The way I see it, the tremendous benefits of raw animal foods greatly outweighs the risks---especially when reasonable precautions are taken. Raw egg yolks (but not the whites) can also be greatly healthful.
Be careful of over-eating brassica family vegetables raw (broccoli, cauliflower, cabbage, brussels sprouts), as these contain goitrogens which can suppress thyroid function over time.
Animals have teeth, claws, horns/antlers and/or the ability to run away as defenses against predation. Plants have no such advantages and thus must depend upon the production of anti-nutrients (phytates, endocrine disruptors such as trypsin inhibitors, and/or goitrogens, toxic alkaloids, oxalates...etc, etc) in order to deter animals and insects that would otherwise devour them. Some poison outright and others interfere with digetive capacity or endocrine function to reduce the long term capacity of animals/insects to thrive and/or reproduce. Modern agricultural practices have served to breed some of these substances out of modern produce to some degree, but not at all entirely. They can be a real concern. It's OK to eat those salads and greens (easy on the raw spinach, though--heavy on the oxalic acid)....but lightly steaming most vegetables actually enhances nutrient availability in many and can make them more digestible by virtue of helping to break down the cellulose and neutralize many of the anti-nutrients that bind healthy minerals and other substances. We are not herbivores and lack 4 stomachs to naturally ferment our veggies during digestion to accomplish the same thing. Adding a little melted butter or olive oil helps further facilitate absorption of minerals and fat-soluble nutrients (such as carotenoids) from these vegetables. Makes them tastier, too. :)
Grains and legumes are more resistant to these methods and are better avoided. Soy contains the highest levels of phytic acid and trypsin inhibitors (which can inhibit and eventually destroy your ability to digest and absorb protein over time, and cause pancreatic disorders) of any grain or legume and should always be avoided unless fermented. Fermentation helps neutralize the phytic acid and trypsin inhibiting nature of soy, but not the goitrogens, so I would even keep things like miso, natto and tempeh to a minimum. A little once in a while doesn't hurt, though (unless you are sensitive to soy...which an estimated 40% of the population is). I, personally, avoid it....other than the occasional cup of miso (with the tofu picked out) at Japanese restaurants.