Note: This advice is given by the CAP Executive about non-broadcast advertising. It does not constitute legal advice. It does not bind CAP, CAP advisory panels or the Advertising Standards Authority.
CAP understands that the glycaemic index (GI) is a means of classifying the carbohydrates in food according to their effects on blood sugar levels. A food that has a high GI causes a rapid rise in blood glucose whereas a low GI food causes a slower and more sustained increase in blood glucose.
The international reference method to measure GI compares the blood glucose-raising effect of 50g of available carbohydrate in the test food as a percentage of 50g available carbohydrate from a food with a known GI (usually glucose or white bread, which is given a nominal GI of 100).
The glycaemic load (GL) describes the blood glucose-raising potential as a function of both the amount of carbohydrate found in a typical serving or a specified portion of food and its GI.
Glycemic load (GL) = GI of a food x amount carbohydrate in an average serving (g)
Factual statements of the GI value of a food should be based on that standard methodology, ideally measured in a laboratory that adheres to a suitable Quality Assurance scheme. Published tables list the GI of many commonly consumed foods (for example, Foster-Powell K et al, 2002). CAP and the ASA are likely to use reputable published tables as a substitute for specific testing if the food in question is equivalent in nutritional content and extent or type of processing.
Classifications should be based on these established cut-offs:
Glycaemic index
• High GI: 70 or more
• Medium GI: 56 to 69
• Low GI: 55 or less
Glycaemic load per meal or food
• Low GL: 10 or less
• High GL: 20 or more
Glycaemic load per day
• Low GL for the day: 80 or less
• High GL for the day: 120 or more
CAP believes it is inappropriate to make low GI claims for foods such as meat and unsweetened dairy products that contain few or no carbohydrates.
Some evidence suggests that low GI diets could improve blood glucose profiles, especially in patients with Type 2 diabetes, but evidence to show that low GI diets help to lower LDL cholesterol is inadequate. A Cochrane review on GI and Coronary Heart Disease concluded that there is insufficient evidence to claim a reduction in HDL or LDL cholesterol on low GI diets.
Low GI or low GL diets are not necessarily low in calories. The specific effects of low GI or low GL on weight loss are unproven and marketers should not claim or imply low GI foods will cause weight loss, in the absence of a reduction in calories, unless they hold robust and generally accepted evidence. Low GI foods may be recommended for weight loss only as part of a calorie-controlled eating plan and as part of a balanced diet.
The GI of a standard food can be altered by factors such as combining low GI foods with high GI ones to give a medium GI meal, the pH of the meal (for example, adding lemon juice lowers GI), processing or cooking or the presence or addition of amylose or amylopectins. The addition of ingredients to lower the GI of high-calorie or high-fat foods cannot be used as the basis of weight loss claims.
Last modified : 06 August 2010