Some cultures and religions have restrictions concerning what foods are acceptable in their diet. For example, only Kosher foods are permitted by Judaism, and Halal foods by Islam. Although Buddhists are generally vegetarians, the practice varies and meat-eating may be permitted depending on the sects. In Hinduism, vegetarianism is the ideal. Jains are strictly vegetarian and consumption of roots is not permitted.
Sourness is caused by the taste of acids, such as vinegar in alcoholic beverages. Sour foods include citrus, specifically lemons, limes, and to a lesser degree oranges. Sour is evolutionarily significant as it is a sign for a food that may have gone rancid due to bacteria. Many foods, however, are slightly acidic, and help stimulate the taste buds and enhance flavor.
Several studies published since 1990 indicate that cooking meat at high temperature creates heterocyclic amines (HCAs), which are thought to increase cancer risk in humans. Researchers at the National Cancer Institute found that human subjects who ate beef rare or medium-rare had less than one third the risk of stomach cancer than those who ate beef medium-well or well-done. While avoiding meat or eating meat raw may be the only ways to avoid HCAs in meat fully, the National Cancer Institute states that cooking meat below 212 °F (100 °C) creates "negligible amounts" of HCAs. Also, microwaving meat before cooking may reduce HCAs by 90% by reducing the time needed for the meat to be cooked at high heat. Nitrosamines are found in some food, and may be produced by some cooking processes from proteins or from nitrites used as food preservatives; cured meat such as bacon has been found to be carcinogenic, with links to colon cancer. Ascorbate, which is added to cured meat, however, reduces nitrosamine formation.
Seeds of plants are a good source of food for animals, including humans, because they contain the nutrients necessary for the plant's initial growth, including many healthful fats, such as omega fats. In fact, the majority of food consumed by human beings are seed-based foods. Edible seeds include cereals (corn, wheat, rice, et cetera), legumes (beans, peas, lentils, et cetera), and nuts. Oilseeds are often pressed to produce rich oils - sunflower, flaxseed, rapeseed (including canola oil), sesame, et cetera.