Nigella seed, also known as Nigella sativa or black seed, has a long history of use in traditional medicine systems. In recent decades, scientific research has begun to explore its potential anticancer properties, primarily attributed to its active compound thymoquinone. Laboratory and animal studies have shown that thymoquinone may have anticancer effects, including the ability to induce apoptosis (programmed cell death) in cancer cells, suppress tumor growth, and reduce inflammation and oxidative stress, which are factors involved in cancer development.

However, the majority of the evidence supporting Nigella seed's use in cancer prevention or treatment comes from in vitro (cell culture) and animal studies. There are a few small-scale human clinical trials and observational studies, but these are limited in number, quality, and scale. No large, high-quality randomized controlled trials have definitively demonstrated that Nigella seed can prevent or treat cancer in humans. As such, while there is promising preliminary scientific evidence, it is not sufficient to recommend Nigella seed as a proven cancer preventive or therapeutic agent.

In summary, Nigella seed has some scientific basis for anticancer activity based on preclinical research, but strong clinical evidence in humans is lacking. Further research, especially well-designed clinical trials, is needed to establish its efficacy and safety for cancer prevention or treatment.