Explain why dietary guidelines for grains changed in 2005? ANSWER IS: Americans eat 41 percent more grains than they did in 1970; this is the result of eating snacks made from grain products such as rice, corn, oat, and barley. Most of these grains are refined and therefore not as healthy as whole grains. The 2005 Dietary Guidelines changed to compensate for this by decreasing consumption levels to six ounces and recommending that half of what someone eats comes from whole grains.