Carbohydrates
carbohydrates, also known as carbs, usually means starches (complex carbohydrates) but can also refer to sugars.
Strictly speaking, carbohydrates are not necessary for human nutrition because proteins can be converted to carbohydrates - the traditional diet of some peoples consists of nearly zero percent carbohydrate, and they are perfectly healthy. However, carbohydrates require (relatively) less water to digest than proteins or fats, and are an important source of energy. Carbohydrates are tasty, cheap, common, and filling.
Problems have been cited for the long term effects of a no-carbohydrate diet. These include reduced athletic performance, possible brain damage, and nephrotoxicity. The brain can only utilize carbohydrates for energy, and protein may not supply enough in many cases. The increase in protein means that more ammonia groups need to be removed from the blood.
Carbohydrates have a high glycemic index, which can promote diabetes.
Carbohydrates can cause farting.