In my opinion, this additive gets the prize for being the most sneaky of them all. Even when buying organic, always scan labels for this ingredient because it is still allowed in organic products by the FDA.
Studies on animals show a very incriminating linkage between this additive and colon cancer. Although the studies on humans are limited, it is said that this ingredients is not digestible and that, in fact, can be destructive to your digestive system. Your body reacts to it as if it was being attacked by salmonella, causing inflammation leading to ulceration and bleeding.
Research done by the University of Illinois School of Medicine indicates a link between carrageenan and gastrointestinal cancer in lab animals.
This ingredients is widely used due to its thickening and stabilizing properties and can be specially common on non-dairy products such as almond milk, coconut milk, it is also found in yogurts, dietary supplements, etc.
Since this product is naturally sourced from red algae, it is still qualifies as natural and can be added to even organic products.