Spice up your food for cancer prevention: Cancer chemo-prevention by natural compounds from common dietary spices

Spices play a unique role in food preparation and provide ethnic identity to cuisines. Spices are appreciated not only for their flavor but also known for their healing effects on both chronic or lethal diseases such as diabetes and cancer. A large corpus of scientific studies supports the cancer-preventive properties of spices, such as garlic, ginger, chili pepper, turmeric, cloves, cinnamon, saffron, and cardamom, the most common flavoring food items used globally. The focus of this review is on these spices that contain multiple bioactive compounds, some of which, in experimental models and human clinical studies, have shown significant anticancer and cancer preventive activities. The presence of high amounts of bioactive compounds such as alkaloids, flavones, polyphenols, triterpenes, and saponins in common spices have the potential to function as medicines that can prevent chronic metabolic diseases and even cancer. As anti-oxidants, anti-inflammatory, immune function modulators, and inducers of apoptosis in tumor cells, the bioactive compounds may be useful as single agents or as adjuvants. The molecular mechanisms of their biological action are their abilities to induce epigenetic modifications such as methylation, acetylation, ubiquitination, and suppression of lipid peroxidation. The low toxicity of these spices makes them favorable as chemopreventive agents. However, the significant therapeutic efficacy of these compounds in scientific clinical trials is still equivocal. Rigorous studies on human subjects are required to improve their bioavailability and standardize their clinical effectiveness. Such studies could define appropriate intervention strategies for maximum benefits from the dietary spices.