MadSci Network: Agricultural Sciences

Re: How to find percentage of glucose in foods?

Date: Thu Mar 15 14:38:49 2001
Posted By: Phyllis Stumbo, Staff, Nutrition, University of Iowa
Area of science: Agricultural Sciences
ID: 980049139.Ag

You can figure the percent of glucose in a food by dividing the weight of 
glucose by the weight of the food and multiplying by 100.  For example, ˝ 
cup of grape juice weighs 125 grams and contains 4.3 grams of glucose.  
Therefore it is 3.4% glucose ((4.3/125) X 100 = 3.4).

You can find the glucose content of other foods from an USDA bulletin 
available on the internet at   
Locate and click on “sugars” in the section “Food Composition Products”.  
In the “sugars” section there is an USDA bulletin that can be printed and 
gives the sugar content of approximately 250 foods.

You might be interested in other ways to describe foods by their sugar 
content.  Nutritionists often talk about the percent of Calories that come 
from sugar.  The reason for this calculation is that many foods seem 
deceptively low in sugar, when in fact their only nutrient is sugar.  For 
example, soft drinks are about 10% sugar but 100% of their calories come 
from sugar.  To determine the percent of the calories that come from 
glucose you need to first determine how many calories are provided by 
glucose (there are 4 calories per gram).  Then multiply the grams of 
glucose by 4 (in the case of grape juice there are 17 calories from 
glucose) and divide by the total number of calories in the food.  Total 
number of calories in the ˝ cup grape juice is 64 which means over 25% of 
the calories come from glucose (17/64 X 100 = 26.6).  This makes a very 
different comparison than the 3.4% glucose by weight.  [Note you can find 
the calorie content of foods on the internet.  The URL above also has a 
section called “Search the Nutrient Database”.  This database has the 
calorie value of over 6000 foods.]

Note I have used two terms above, glucose and sugar.  There are several 
sugars in food, and glucose is not the most common.  Table sugar is 
sucrose.  It is good to learn the names of different sugars to help 
understand food labels and other nutrition messages.

Phyllis Stumbo
University of Iowa

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