It’s true! In fact there have been many population studies that offer much evidence regarding the anti-cancer properties of garlic and onions.
Several population studies show an association between increased intake of garlic and reduced risk of certain cancers, including cancers of the stomach, colon, esophagus, pancreas, and breast. Population studies are multidisciplinary studies of population groups that investigate the cause, incidence, or spread of a disease or examine the effect of health-related interventions, dietary and nutritional intakes, or environmental exposures. An analysis of data from seven population studies showed that the higher the amount of raw and cooked garlic consumed, the lower the risk of stomach and colorectal cancer .