Glycemic Index (GI) Calculator
function calculateGlycemicIndex() {
var aucTestFood = parseFloat(document.getElementById(‘aucTestFood’).value);
var aucReferenceFood = parseFloat(document.getElementById(‘aucReferenceFood’).value);
var resultDiv = document.getElementById(‘giResult’);
if (isNaN(aucTestFood) || isNaN(aucReferenceFood) || aucTestFood < 0 || aucReferenceFood < 0) {
resultDiv.innerHTML = 'Please enter valid positive numbers for both AUC values.‘;
return;
}
if (aucReferenceFood === 0) {
resultDiv.innerHTML = ‘Reference Food AUC cannot be zero to avoid division by zero.‘;
return;
}
var glycemicIndex = (aucTestFood / aucReferenceFood) * 100;
var giCategory = ”;
var giColor = ”;
if (glycemicIndex <= 55) {
giCategory = 'Low GI';
giColor = '#28a745'; // Green
} else if (glycemicIndex <= 69) {
giCategory = 'Medium GI';
giColor = '#ffc107'; // Yellow
} else {
giCategory = 'High GI';
giColor = '#dc3545'; // Red
}
resultDiv.innerHTML = 'Your calculated Glycemic Index (GI) is: ‘ + glycemicIndex.toFixed(2) + ‘‘ +
‘This falls into the ‘ + giCategory + ‘ category.’;
}
Understanding the Glycemic Index (GI)
The Glycemic Index (GI) is a ranking system for carbohydrate-containing foods based on their effect on blood glucose levels. It measures how quickly and how much a food raises blood sugar after eating. Foods are ranked on a scale of 0 to 100, with pure glucose typically serving as the reference food with a GI of 100.
How is GI Determined?
The GI of a food is determined by feeding a group of people a specific amount of the test food (usually containing 50 grams of available carbohydrates) and then monitoring their blood glucose response over a two-hour period. The ‘Area Under the Curve’ (AUC) of their blood glucose response is calculated. This is then compared to the AUC of a reference food (like pure glucose or white bread) containing the same amount of available carbohydrates. The formula is:
GI = (AUC of Test Food / AUC of Reference Food) × 100
This calculator allows you to simulate this process by inputting hypothetical AUC values.
GI Categories:
- Low GI: 55 or less (e.g., most fruits, non-starchy vegetables, legumes, whole grains)
- Medium GI: 56-69 (e.g., whole wheat bread, brown rice, sweet potatoes)
- High GI: 70 or more (e.g., white bread, white rice, potatoes, sugary drinks)
Why is GI Important?
Understanding the GI of foods can be beneficial for managing blood sugar levels, which is particularly important for individuals with diabetes. Low GI foods generally lead to a slower and more gradual rise in blood glucose, providing sustained energy and potentially aiding in weight management and reducing the risk of chronic diseases. High GI foods cause a rapid spike in blood sugar, which can be followed by a quick drop, leading to hunger and fatigue.
Limitations of GI:
While useful, the GI has limitations. It doesn’t account for portion size (for which Glycemic Load is more relevant), how foods are prepared, or how different foods are combined in a meal. Individual responses to foods can also vary. Therefore, GI should be used as a guide within a balanced dietary approach.
How to Use This Calculator:
Enter the hypothetical Area Under the Curve (AUC) values for your ‘Test Food’ and a ‘Reference Food’ (e.g., pure glucose). The AUC represents the total increase in blood glucose over a two-hour period after consuming the food. The calculator will then provide the calculated Glycemic Index and its corresponding category.
Example: If a test food results in an AUC of 1500 (mmol·min/L) and the reference glucose results in an AUC of 2000 (mmol·min/L), the GI would be (1500 / 2000) * 100 = 75, which is a High GI food.