All about fruitarianism with a long-term fruitarian, Lena

Leaves and stems of plants, green vegetables or leafy greens, are widely consumed by humans. The protein contents are higher than in fruits, and they contain low amounts of sugar.

Some green vegetables produce secondary metabolites that have bitter or astringent properties and may produce toxic alkaloidal and other compounds such as hemoglutenens. Others produce intestinal enzyme inhibitors, such as lectins, which bind to mucosal surfaces and inhibit digestion, especially that of proteins. 

Plant secondary metabolism produces a large number of specialized compounds (~ 200.000) that do not aid in the growth and development of plants but are required for the plant to survive in its environment. Specialized compounds from secondary metabolism are essential for communicating with other organisms in mutualistic (e.g. attraction of beneficial organisms such as pollinators) or antagonistic interactions (e.g. deterrent against herbivores and pathogens). They further assist in coping with abiotic stress such as increased UV-radiation.

The broad functional spectrum of specialized metabolism is still not fully understood.

Well known specialized compounds include alkaloids, polyphenols including flavonoids, and terpenoids. Humans use quite a lot of these compounds, or the plants from which they originate, for medicinal and nutraceutical purposes.

Leonardo da Vinci

I have from an early age abjured the use of meat, and the time will come when men such as I will look upon the murder of animals as they now look upon the murder of men.

Food Energy

Food energy is chemical energy that animals derive from their food and molecular oxygen through the process of cellular respiration. Humans and other animals need a minimum intake of food energy to sustain their metabolism and to drive their muscles.

Organisms derive food energy from carbohydrates, fats and proteins as well as from organic acids, polyols, and ethanol present in the diet. Some diet components that provide little or no food energy, such as water, minerals, vitamins, cholesterol, and fiber, may still be necessary to health and survival for other reasons. 

Using the International System of Units, researchers measure energy in joules (J) or in its multiples; the kilojoule (kJ) is most often used for food-related quantities. An older metric system unit of energy, still widely used in food-related contexts, is the "food calorie" or kilocalorie (kcal or Cal), equal to 4.184 kilojoules. 

<>Fats and ethanol have the greatest amount of food energy per mass, 37 and 29 kJ/g (8.8 and 6.9 kcal/g), respectively. Proteins and most carbohydrates have about 17 kJ/g (4.1 kcal/g). 

Conventional food energy is based on heats of combustion in a bomb calorimeter and corrections that take into consideration the efficiency of digestion and absorption and the production of urine. Apple