Harvard University Anthropologist Richard Wrangham made the news in 2002 with his research into "Cooking as a Biological Trait." Wrangham put forth the possibility that human digestive tracts "no longer allow efficient processing of raw foods," a hypothesis that anyone who has felt the bloating and discomfort that can result from a raw food diet understands all too well. Large amounts of indigestible fiber and food-borne illness can upset your stomach on a raw food diet.
Benefits of Fiber
Your body requires a certain amount of fiber to function. The American Dietetic Association and the U.S. Department of Agriculture recommend that you eat at least 30 grams of fiber a day. That fiber will keep you feeling full after your meals and help you maintain your weight. You'll also regulate your digestive system's functioning and may reduce your chances of developing heart disease or certain types of gastrointestinal cancers. A raw food diet supplies you with ample fiber.
Fiber and Bloating
As vital as fiber is for your digestive health, too much of it can leave you feeling bloated. Your body cannot digest fiber; most of the material passes through your digestive system untouched. The naturally occurring bacteria in your intestinal tract can digest some types of fiber, however. When these bacteria feast, they produce gas as a byproduct of their metabolism, so excess fiber leads directly to excess gas. Until your intestinal flora become used to fiber-rich meals, they may leave you feeling bloated with intestinal gas.
Fiber slows gastric emptying. That makes it easier to control your weight on a raw food diet, especially as most of the foods you eat provide bulk without many calories. However, if you enjoy large meals, you should account for the slow speed at which a raw food meal digests. If you eat a few hours before performing strenuous physical activity, you may still feel uncomfortably full and bloated because the food you've eaten takes longer to process.
After a 2008 outbreak of salmonella food poisoning related to raw produce, the Centers for Disease Control and Prevention prepared a news release which noted that "contaminated produce eaten raw is an increasingly recognized vehicle for transmission of salmonella and other pathogens." Food-borne illness can cause bloating along with other unpleasant or dangerous gastrointestinal symptoms. If you choose a raw food diet and find that your bloating comes with stomach cramps, painful diarrhea, vomiting or fever, you might have a case of food-borne illness and should see your doctor.