In a human epidemiological analysis by Richard Doll and Richard Peto in 1981, diet was estimated to cause a large percentage of cancers. Studies suggest that around 32% of cancer deaths may be avoidable by changes to the diet. Some of these cancers may be caused by carcinogens in food generated during the cooking process, although it is often difficult to identify the specific components in diet that serve to increase cancer risk. Many foods, such as beef steak and broccoli, contain low concentrations of both carcinogens and anticarcinogens.
A negative-calorie food is food that supposedly requires more food energy to be digested than the food provides. Its thermic effect or specific dynamic action – the caloric "cost" of digesting the food – would be greater than its food energy content. Despite its recurring popularity in dieting guides, there is no scientific evidence supporting the idea that any food is calorically negative. While some chilled beverages are calorically negative, the effect is minimal and drinking large amounts of water can be dangerous.
Hybridization is different from grafting. Most of the world's vineyards are planted with European V. vinifera vines that have been grafted onto North American species' rootstock, a common practice due to their resistance to phylloxera, a root louse that eventually kills the vine. In the late 19th century, most of Europe's vineyards (excluding some of the driest in the south) were devastated by the infestation, leading to widespread vine deaths and eventual replanting. Grafting is done in every wine-producing region in the world except in Argentina, the Canary Islands and Chile—the only places not yet exposed to the insect.
In the pre-modern era, the sale of surplus food took place once a week when farmers took their wares on market day into the local village marketplace. Here food was sold to grocers for sale in their local shops for purchase by local consumers. With the onset of industrialization and the development of the food processing industry, a wider range of food could be sold and distributed in distant locations. Typically early grocery shops would be counter-based shops, in which purchasers told the shop-keeper what they wanted, so that the shop-keeper could get it for them.