Tumor or neoplasm represents a cluster of abnormal, uncontrollably growing cells. Tumors occur as a result of DNA mutations or certain epigenetic alterations. Tumors can be benign or malignant according to their possibility of metastasis and possibility to spread into the surrounding tissue. One of the main differences between benign and malignant tumor is that benign tumors does not have the ability to invade the surrounding tissue or spread to other parts of the body. Most benign tumors are not harmful to human health, while cancer is one of the most common causes of death in people. The most common and most deadly cancers worldwide are prostate, breast, lung and colon cancer. Numerous studies point to the growing connection between diet and the development of various types of malignant tumors. In order to maintain the risk of developing cancer to a minimum, WCRF recommends limiting red and processed meat intake and increasing the intake of fruits, vegetables and whole grains, which are important sources of vitamins, minerals and dietary fiber. Alcohol consumption should be kept to a minimum, while the daily moderate consumption of coffee and tea is harmless for the development of malignant tumors.