Is bamboo fabric actually natural?
Mostly no - 'bamboo' clothing is almost always bamboo-derived viscose/rayon, made with the same chemistry as other rayons.
Bamboo grows fast without pesticides, which is where the eco halo comes from. But turning it into soft fabric means dissolving the pulp in chemicals (usually carbon disulfide) and extruding it - the viscose process, identical to rayon from any wood source. The FTC requires such products be labeled 'rayon made from bamboo' precisely because the natural claims are misleading. The fabric itself is fine: soft, breathable, moisture-wicking, comparable to Tencel in use. The only true mechanical-process 'bamboo linen' is rare and feels like regular linen. Buy bamboo viscose if you like how it feels, not because the tag implies environmental virtue - that part is marketing.