Gluten and Wheat. It’s really a problem. For people who are slim and who love bread, it’s easy to wave off concerns about gluten as ridiculous. On the other hand, some health bloggers barely consider grains to be a food—perhaps for good reason. First of all, almost 1 percent of us have Celiac disease—a disorder that destroys the gut lining in the presence of the wheat protein gluten. At least another 6 percent of us have non-allergic reactions to gluten that show up as symptoms as diverse as abdominal pain, eczema, headache, foggy brain, fatigue, diarrhea, depression, anemia, numbness in legs, and joint pain.

Cheese and Dairy. By now perhaps everybody has heard the news that dairy is getting a second look as a possible source of good fats. But even so, many people do poorly on dairy. The symptoms can show up as a wide array of intractable health problems. Indeed, The New York Times food writer Mark Bittman describes fruitlessly attempting to stop taking antacids for seven years (seven years!) only to find that his chronic heartburn resolved immediately after quitting dairy. Besides an improvement in stomach pain, many people find that without dairy their sinuses open and their energy levels rise. Even acne clears up, no matter what some smart conventional physicians may say about not being any evidence.