Carbohydrates: Types, Functions, Sources & Requirements
Carbohydrates in Diet: Sources and Allowances
Types of Carbohydrates:
- Monosaccharides (e.g., glucose, fructose)
- Disaccharides (e.g., sucrose, lactose)
- Oligosaccharides (e.g., raffinose, stachyose)
- Polysaccharides (e.g., amylose, glycogen)
In general, monosaccharides and disaccharides, which are smaller carbohydrates, are commonly referred to as sugars. The term carbohydrate often refers to foods rich in complex carbohydrates like starch (cereals, bread, pasta) or simple carbohydrates like sugar (candy, jams, desserts).
Functions of Carbohydrates:
- Polysaccharides store energy (e.g., starch and glycogen) and act as structural components (e.g., cellulose in plants).
- The 5-carbon monosaccharide ribose is a key component of coenzymes (e.g., ATP, FAD, and NAD) and RNA.
- Deoxyribose is a component of DNA.
- Saccharides and their derivatives are important biomolecules in the immune system, fertilization, preventing pathogenesis, blood clotting, and development.
- 1 gram of carbohydrates = 4 kcal
Carbohydrates should account for 60-65% of an adult’s energy requirement, with only 10% directly from sugars (simple carbohydrates).
Carbohydrate Requirements:
- Adults: 5-7g/kg/day
- Children: 10-12g/kg/day
A reduction of sugar intake to under 5% of total energy provides additional health benefits.
Sources of Carbohydrates:
- Foods high in carbohydrates include fruits, sweets, soft drinks, breads, pastas, beans, potatoes, bran, rice, and cereals.
- Carbohydrates are a common energy source, but no carbohydrate is an essential nutrient for humans.
- Carbohydrates are not necessary building blocks; the body can obtain all its energy from protein and fats.
- The brain and neurons generally cannot burn fat for energy, using glucose or ketones instead.
Humans can synthesize some glucose (gluconeogenesis) from specific amino acids, the glycerol backbone in triglycerides, and sometimes from fatty acids.
Glucose is a nearly universal and accessible source of calories.
How to Reduce Sugar Intake:
- Limit consumption of foods and drinks high in sugars (e.g., sugar-sweetened beverages, sugary snacks, and candies).
- Eat fruit and raw vegetables as snacks instead of sugary snacks.