Glycemic Index? 「升糖指數」

Glycemic Index?

The glycemic index or GI describes this difference by ranking carbohydrates according to their effect on our blood glucose levels. Choosing low GI carbs can helps to reducing your risk of heart disease and diabetes and is the key to sustainable weight loss. Low GI food will incread blood glucose levels steadily, whereas high GI food will caused a sharp raises of blood glucose levels and therefore caused the flutuation of glucose levels.

High GI food: > 70
Medium GI food: 56- 69
Low GI food: <55

Other than eating different types of carbohydrate can affects the glucose levels, the structure and processing methods can also affects GI as well:

1. Higher fibre content = lower the GI. I.e. wholegrain bread's GI = 69, white bread's GI = 88. This is one of the reason why white bread is not recommended for diabetic diet.
2. Cooked and uncooked fruit. I.e. Cooked banana's GI = 52, raw banana's GI = 30. As the cooking process helps to release the sugar content of the fruit.
3. Carbohydrat's GI is lower compare to sugary (refined) products. I.e. rice/noodle's GI is lower compare to sweets like candy.
4. Chopped food's GI will be higher than its whole food. I.e. mashed potato & jack potato.

Low GI food can be high in fat content as well, as GI is only an index for carbohydrate fod. So, a low GI foood can be potentially very high in fat content as well. For example, full cream milk's GI is 27, whereas skim milk's GI is 32! Hence, never just choose food containing low GI food without considering the total energy intake, as excessive caloric intake and high cholesterol intake can increase the risk of heart disease.

http://www.glycemicindex.com/

「升糖指數」?

GI值，英文叫Glycemic Index，就是營養學上所說的「升糖指數」，是指食物吃進去後，血糖升高相對於吃進去葡萄糖時的比例。選擇低GI carbs 的食物幫助減少心臟病和糖尿病的風險和是減重策的略. 低GI的食物，吃後令血糖上升的速度及幅度相對較平穩﹔高GI的話，即表示進食後會令血糖快速上升

GI值的3個級別：
高GI值 ： 大過或等如70
中GI值 ： 56至69
低GI值 ： 小過或等如55

除了碳水化合物的含量與種類以外，食物的不同形態及所含的其他營養素，都會影響GI﹕

1. 纖維量愈高GI愈低纖維量較高的全麥麵包，GI為69，屬中升糖指數食物﹔白麵包的則為88，屬高升糖指數食物，怪不得吃白麵包不利血糖控制。
2. 熟生水果GI有差距熟透的水果與未熟透的，GI會有差距。例如熟香蕉與生香蕉，前者GI為52，後者為30，因為熟香蕉糖分較高。
3. 澱粉質GI低 糖類GI高澱粉質消化時間長，GI因而較低，例如粉麵飯﹔相反，糖類很快被身體吸收，GI自然較高，例如甜品糖水。
4. 切碎食物GI較高薯蓉的GI較整個薯仔高，因為稀爛及切碎的食物較易吸收，令血糖快速上升。

低GI食物可以很高脂而且GI只針對食物中的碳水化合物，所以，低GI的食物，可以很低脂，也可以很高脂。例如全脂牛奶和脫脂牛奶都是低GI食物，GI分別為27及32，可是，不要忘記，全脂牛奶的脂肪含量高。盲目崇拜GI飲食，而沒有考慮全脂牛奶的脂肪能影響體內膽固醇水平的話，會攝取很多卡路里，也容易影響心臟健康。