http://www.direct-ms.org/pdf/EvolutionPaleolithic/Cereal%20Sword.pdf
>Cereal grains represent a biologically novel food for mankind [341, 342], consequently there is considerable genetic discordance between this staple food, and the foods to which our species is genetically adapted. Cereal grains lack a number of nutrients which are essential for human health and well-being; additionally they contain numerous vitamins and minerals with low biological availability. Furthermore, the inability of humans to physiologically overcome cereal grain antinutrients (phytates, alkylresorcinols, protease inhibitors, lectins, etc.) is indicative of the evolutionary novelty of this food for our species. This genetic maladaptation between human nutrient requirements and those nutrients found in cereal grains manifests itself as Cordain 58 vitamin and mineral deficiencies and other nutritionally related disorders, particularly when cereal grains are consumed in excessive quantity. More disturbing is the ability of cereal grain proteins (protease inhibitors, lectins, opioids and storage peptides) to interact with and alter human physiology.
There also seems to be something unique about wheat and heart disease
That said, white rice is probably fine.