Elevated CO2 reduced the concentration of N (protein), S, Mn, and Zn in polished grains by 13.5 percent, 12.6 percent, 20.5 percent, and 5.9 percent, respectively, when compared to ambient conditions (Fig 1A). The equivalent declines in brown rice were 2.0 percent, 3.5 percent, 7.0 percent, and 3.0 percent less than those in polished grains. The effect of elevated CO2 on the concentration of other nutrients in rice was much smaller or not significant at all. The reduction in nutrient concentration due to elevated CO2 would likely have a negative impact on the healthfulness of the diet if these crops were used to make food that requires high concentrations of these nutrients to be edible. Polished grains from elevated CO2 fields had 9 percent more energy than those from ambient conditions because of lower protein concentration under elevated CO2 conditions. This suggests that consumers may want to adjust the amount of rice they eat if it is used as a source of fuel energy. Brown rice from elevated CO2 conditions had higher energy than that from ambient conditions because of higher carbohydrate concentration. However, the difference is small enough that it could be ignored for most applications. The effect of elevated CO2 on the quality of rice depends on the individual nutrient. All nutrients analyzed except for Se showed evidence of degradation under elevated CO2 conditions. For some nutrients, such as Fe and Zn, this degradation was severe enough to affect the quality of the grain. For others, such as Ca and Mg, the effect was minimal.