December 5, 2011
The glycemic index (GI) is a numerical system of measuring how much of a rise in circulating blood sugar a carbohydrate triggers–the higher the number, the greater the blood sugar response. So a low GI food will cause a small rise, while a high GI food will trigger a dramatic spike. A list of carbohydrates with their glycemic values is shown below. A GI is 70 or more is high, a GI of 56 to 69 inclusive is medium, and a GI of 55 or less is low.
The glycemic load (GL) is a relatively new way to assess the impact of carbohydrate consumption that takes the glycemic index into account, but gives a fuller picture than does glycemic index alone. A GI value tells you only how rapidly a particular carbohydrate turns into sugar. It doesn’t tell you how much of that carbohydrate is in a serving of a particular food. You need to know both things to understand a food’s effect on blood sugar. That is where glycemic load comes in. The carbohydrate in watermelon, for example, has a high GI. But there isn’t a lot of it, so watermelon’s glycemic load is relatively low. A GL of 20 or more is high, a GL of 11 to 19 inclusive is medium, and a GL of 10 or less is low.
Foods that have a low GL almost always have a low GI. Foods with an intermediate or high GL range from very low to very high GI.
Both GI and GL are listed here. The GI is of foods based on the glucose index–where glucose is set to equal 100. The other is the glycemic load, which is the glycemic index divided by 100 multiplied by its available carbohydrate content (i.e. carbohydrates minus fiber) in grams. (The “Serve size (g)” column is the serving size in grams for calculating the glycemic load; for simplicity of presentation an intermediate column that shows the available carbohydrates in the stated serving sizes has been left out.) Take, watermelon as an example of calculating glycemic load. Its glycemic index is pretty high, about 72. According to the calculations by the people at the University of Sydney’s Human Nutrition Unit, in a serving of 120 grams it has 6 grams of available carbohydrate per serving, so its glycemic load is pretty low, 72/100*6=4.32, rounded to 4.
November 14, 2011
By: Tara Green
One of the most nutritious foods on the traditional Thanksgiving menu is the sweet potato. These orange-skinned root vegetables offer a host of health benefits (especially when cooked without the unnecessary sugar and marshmallows). If you want to raise health consciousness around the dinner table this holiday season, try throwing some of these six sweet potato facts into the conversation:
1. High nutritional value
A 7-ounce (1 cup) serving of sweet potatoes contains 65% of the minimum necessary daily amount of Vitamin C. Sweet potatoes are also high in calcium, folate, potassium and beta-carotene. Beta-carotene is an antioxidant which converts to Vitamin A in the body: one serving of sweet potatoes can provide you with as much as 700% of the US RDA for Vitamin A. The Center for Science in the Public Interest rates sweet potatoes as the number one most nutritious vegetable because they such are so nutritionally rich.
2. Low glycemic index
If you are unfamiliar with this term, the glycemic index indicates the impact a food substance has on blood sugar levels. A high glycemic index means blood sugar levels can spike. Diabetes and others who monitor their blood sugar levels seek to avoid foods with a high glycemic index or load. Sweet potatoes have a glycemic load of only 17. (By way of comparison, a white potato has an index of 29.)
3. Accessing sweet potatoes’ nutritional benefits is easy
To gain the maximum health benefits from eating sweet potatoes, avoid discarding their skins — much of their healing potential resides in this portion of the tubers. Also, following the common dieters’ fallacy of avoiding all fats reduces your ability to access sweet potatoes’ benefits: beta-carotene absorbs more thoroughly into the body when consumed with a small amount of fat. Recent research seems to indicate that steaming or boiling sweet potatoes rather than roasting them helps preserve their low glycemic index.