Türkiye Beslenme Rehberi (TÜBER), Türkiye's national dietary guideline, recommends that between 45 and 60 percent of daily energy come from carbohydrate. For an adult taking in 2000 calories a day, this means the diet holds 225-300 grams of carbohydrate. 1 gram of carbohydrate provides 4 calories of energy; that is why the conversion between percent and grams can be made directly.
The two main types of carbohydrate
Carbohydrates are split into simple and complex according to the number of sugar molecules they carry. The simple ones carry one or two sugar molecules: glucose, fructose, galactose, sucrose, lactose and maltose are in this group. They are found naturally in fruit and in milk, and in candy and fizzy drinks as added sugar.
Starch and dietary fiber go into the complex carbohydrate group. Starch is found in grains, in dried legumes and in root vegetables such as potatoes. Vegetables, fruit, whole grains and dried legumes are the fiber source. Every carbohydrate type other than fiber is broken down into simple sugars during digestion.
How is blood sugar balance built?
When glucose passes into the blood, insulin is released from the pancreas, and the glucose that enters the cell with the help of insulin is turned into energy there. The normal glucose value measured in blood is in the 70-100 mg/100 mL range and changes with the fasting or fed state.
Some foods make this rise fast, some slow. This difference is called the glycemic index, that is, the speed at which a food raises blood sugar. The glycemic index of unrefined whole grains, whose fiber content is high, is low. Carbohydrate taken in excess is first stored as glycogen in the liver and in muscle; once the stores are full, what is left is turned into fat and kept.
Where should daily carbohydrate come from?
The guideline recommends 3-7 portions of grains a day and asks that at least half of that total be whole grain. As one portion grain equivalent it gives 50 grams (2 thin slices) of bread, 75 grams of cooked pasta, 90 grams of cooked bulgur or rice, or about 30 grams of breakfast cereal.
Dried legumes are counted twice in this table: they are both a good carbohydrate source and carriers of plant protein, dietary fiber and oligosaccharides. The energy of cake, pastry and biscuits made from grain flours is high because of the fat and sugar that go into them; these do not stand in the same place as a carbohydrate source.
The lower limit of carbohydrate, and fiber
Next to the percentage range there is also an absolute floor value. The guideline's reference values table gives the recommended adequate intake of carbohydrate for men and women aged 18-50 as 130 grams a day. This floor is independent of energy intake and corresponds first of all to the glucose need of the brain and the nervous system; the guideline states separately that glucose is the essential energy source of the brain and the nervous system.
In the same table there is a value for dietary fiber as well: 25 grams a day in women and men over 18. Fiber is a carbohydrate type, but it is not broken down into simple sugars during digestion, so on the blood sugar side it behaves differently from other carbohydrates. Its main sources are vegetables, fruit, whole grains and dried legumes.
Where does added sugar sit in this table?
Sugar comes into the diet by two routes. The first is the natural sugar in the food's own structure: lactose in milk, fructose in fruit. The second is the sugar added during processing or preparation. The guideline keeps this second group apart; 99.9 percent of sugar is sucrose, that is, it only gives energy and carries no nutrient value.
The different names met on the label most often point to the same thing. Brown sugar, corn syrup, high fructose corn syrup, honey, invert sugar, malt sugar, molasses, dextrose, fructose, glucose, lactose, maltose and sucrose all indicate added sugar. Sugar alcohols are a separate group; substances such as sorbitol, mannitol and xylitol can lead to loose stools in some people when more than 50 grams is consumed.
Where does it turn into a mistake?
The most widespread mistake is seeing carbohydrate as a single item. The same number of grams can come from white bread or from whole grain bread, but their fiber, vitamin and mineral content is different. Refining gives a fine texture and a long shelf life, and in return it reduces the fiber, the iron and most of the B vitamins.
The second mistake is mixing up the carbohydrate amount between the cooked and the raw state. The portion amounts given are cooked weights, and the raw equivalent of the same food is well below that. For an item by item comparison you can look at the carbohydrate tab of the nutrition values table, and for the daily distribution at the macro distribution calculator.