Technically, rice is a grain, which means it’s not strictly Paleo, but there’s more to the story.
Paleo and Carbohydrates
One of the main reasons we avoid grains is because they tend to be high in carbohydrates and antinutrients. White rice is certainly high in carbs, but it is lacking most of the antinutrients that tend to cause problems. The carbs may still cause problems for some people, but for those who need a little more carbs in their diet, white rice can be a safe way to get those carbs.
The Difference Between Brown Rice and White Rice
White rice has been stripped of the bran (the hard outer layer), whereas brown rice still has the bran on it. Brown rice contains more vitamins than white rice and also more fiber, which can be considered good things. Fiber is effective at mitigating the glycemic load of the carbs (so they cause such a high spike in blood sugar), and it’s a prebiotic (it feeds the beneficial bacteria in our guts). The vitamins come at a price though, because the bran is where the antinutrients are located, and those can cause problems for some people.
For even more information on whether rice belongs in your diet or not, read this article from Mark’s Daily Apple.