It is best to use Psyllium husk in this recipe. I have tried to replace the psyllium with chia, but the results yielded a denser loaf, less reminiscent of bread, and not nearly as tasty. If you absolutely can't find psyllium, you can replace it with 4 tablespoons chia, soaked in ½ cup water, but be sure to reduce the amount of water used to purée to only ½ cup - ¾ cup. There is also no need to pierce the top of the loaf if using chia, as it won't rise as much as the psyllium.